Whitepapers
NuSil Technology's commitment to silicone education is manifested in part by our investment in
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resources like a Terms & Definitions document and an Adhesive / Primer study. While some papers are
broad in scope, others are industry specific. Papers are typically added monthly. Registering with
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For further reading, please see our Technical Resources section.
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Oct 9, 2012
Versatility of Silicone Chemistry for Electronics in Medical Device
Since the first use of silicone for medical applications in the 1950s, this material’s chemical stability, physical strengths, and bioinertness have proven it a valuable candidate for medical device applications. Best of all, silicones are so dynamic they can be formulated to achieve specific performance, aesthetic, or therapeutic properties...
Since the first use of silicone for medical applications in the 1950s, this material’s chemical stability, physical strengths, and bioinertness have proven it a valuable candidate for medical device applications. Best of all, silicones are so dynamic they can be formulated to achieve specific performance, aesthetic, or therapeutic properties that aren’t inherently available with silicone elastomer chemistry alone. Additionally, traditional applications such as pacemakers, cochlear implants or other devices that rely on electronics or battery use may benefit from a silicone component with a conductive feature. While the use of fillers is not new to silicone chemistry, the quality and grade of fillers used for customizing silicone are collectively subjected to numerous biological tests to prove biocompatibility. This presentation will cover all of these examples in greater detail in order convey how versatile silicone is, namely as regards using electronics in medical device applications.
Aug 27, 2012
Needle Coatings to Relieve Penetration and Drag Forces of Needles
A study comparing penetration forces of uncoated and coated needles was performed to analyze and compare the
efficacy of specific NuSil needle coating materials in lowering the force required to penetrate and pass through a substrate. Testing was performed on a TA.XT.plus Texture Analyzer with a 5-kg load cell. Needles coated...
A study comparing penetration forces of uncoated and coated needles was performed to analyze and compare the
efficacy of specific NuSil needle coating materials in lowering the force required to penetrate and pass through a substrate. Testing was performed on a TA.XT.plus Texture Analyzer with a 5-kg load cell. Needles coated with MED-4162 proved to have the largest decrease in penetration and drag forces.
Jul 10, 2012
The Effect of Infrared Spot Curing on the Cure Times of Silicone Materials for the Healthcare Industry
Utilized in a wide variety of adhesion applications — from urinary catheters to cardiac pacemakers — one-part condensation-cure adhesives have traditionally been the most commonly used silicone adhesives in the healthcare industry. Despite their acclaimed and proven effectiveness, the downside to using these adhesive systems is their long cure time...
Utilized in a wide variety of adhesion applications — from urinary catheters to cardiac pacemakers — one-part condensation-cure adhesives have traditionally been the most commonly used silicone adhesives in the healthcare industry. Despite their acclaimed and proven effectiveness, the downside to using these adhesive systems is their long cure time (many hours or even days at room temperature) and inability to be accelerated with heat. Alternatively, using a two-part, addition-cure silicone adhesive — also known as a fast-cure adhesive — is often helpful or even necessary, depending on the application at hand.
An adhesive is considered a fast-cure adhesive if it fully cures in less than 10 minutes using heat, or if it partially cures for handling in less than five minutes and fully cures at room temperature in eight hours. Fast cures as defined here are induced by bringing the adhesive into contact with heat, usually via an air-circulating oven.
May 22, 2012
Characterization of Fuel Resistant Fluorosilicones
Silicones are commonly used in automotive applications as potting compounds, adhesives, gaskets, seals and encapsulants due to their ability to remain elastic at low temperatures and resist breakdown at high temperatures or in UV light. In addition to a broad operating temperature range, silicones inherently possess high dielectric strength (=...
Silicones are commonly used in automotive applications as potting compounds, adhesives, gaskets, seals and encapsulants due to their ability to remain elastic at low temperatures and resist breakdown at high temperatures or in UV light. In addition to a broad operating temperature range, silicones inherently possess high dielectric strength (= 500 V/mil), low modulus and a low glass transition point (Tg), as compared to organic-based rubbers. These characteristics make silicones ideal for use in high-power electronic applications, yet gentle enough for delicate wire bond encapsulation and other applications in which thermal cycling is a concern. Ultimately, the quality that contributes most to silicone’s wide use in the automotive and other industries is the opportunity for formulation flexibility.
May 21, 2012
Non-toxic novel silicone foul-release marine coatings
This study evaluates modified silicone elastomers as foul-release coatings. The coatings are easy to apply, cure rapidly and relatively tough materials. They are non-toxic and biologically inert but still prevent the adhesion of marine life. The coatings were tested by a novel barnacle adhesion test with adhesion results in two...
This study evaluates modified silicone elastomers as foul-release coatings. The coatings are easy to apply, cure rapidly and relatively tough materials. They are non-toxic and biologically inert but still prevent the adhesion of marine life. The coatings were tested by a novel barnacle adhesion test with adhesion results in two weeks. The test consisted of coated glass slides upon which a barnacle was transferred from one substrate and re-attached to the test slide. After the barnacle re-attached, the adhesion was directly measured by a force displacement tester. Results are measured in psi.
May 21, 2012
Novel Adhesions Methods for Solar Cell Assemblies
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can...
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can serve the same purpose as liquid adhesives but eliminate long wait times for room temperature cures or additional equipment, such as ovens, required to heat accelerate the cure process. Moreover, the processing these low outgassing materials undergo allows them to be used on extraterrestrial applications like satellites as mentioned above.
Apr 2, 2012
LED Packaging with Silicone Encapsulants
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically.
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically. It is for this reason that a relationship needs to be maintained between the LED packager and material supplier. In most cases, the material of choice for LED packagers is silicone. To accommodate the various needs of the LED packager, silicone has become widely used due to its flexibility. Some attributes of silicone that lend themselves well to the LED industry are a high transparency in the UV-visible spectrum, thermal stability, mechanical and optical properties and an ability to control the Refractive Index (RI).
Jan 26, 2012
Designing low permeability, optical-grade silicone systems – Guidelines for choosing a silicone based on transmission rates for barrier applications
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such...
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such as phosphor, used to make white LEDs for back-lighting applications and decrease or change the light output and color over time. Of the polymeric adhesives and sealants commercially available, silicones are used for their thermal stability, clarity, and comparably low modulus that provides stress relief during thermal cycling. In addition, silicones are also known to be very permeable to low molecular weight gases such as water vapor and oxygen. Recently, several types of silicones were tested for the oxygen and water vapor transmission rates, and it was found that they can have drastically different results. Silicone properties strongly affecting permeability are polymer backbone chemistry, crosslink density and fillers. Phenyl (C6H5) and trifluoropropyl (CF3CH2) groups are used to optimize the refractive index of optically clear silicones. The effect of chemical composition on the water vapor transfer rate (WVTR) and the oxygen transfer rate (OTR) at 400 C and 90% Relative Humidity was investigated on several silicones with various refractive indices and compared to polydimethylsiloxane (PDMS) with similar durometers. It was found that polymer backbone chemistry had a significant influence on the permeation rates and will assist in material selection when designing for low-permeable barriers to improve package reliability.
Jan 9, 2012
Choosing a Silicone for Joining Technologies
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges...
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges they face. The advantages of silicone lie in the chemistry of the polymer chain, which can be modified to achieve desired mechanical properties.
Jan 9, 2012
Increasing Hair Manageability Using Silicone for Moisture Control
When considering hair, moisture is a double-edge sword. Everyone strives to achieve healthy looking, moisturized hair; shiny and strong. Dry hair, on the other hand, is associated with damage and brittleness. Why is it then that a humid or rainy day — full of moisture in the air — concerns...
When considering hair, moisture is a double-edge sword. Everyone strives to achieve healthy looking, moisturized hair; shiny and strong. Dry hair, on the other hand, is associated with damage and brittleness. Why is it then that a humid or rainy day — full of moisture in the air — concerns so many? To keep hair manageable, moisture must be controlled. A study was recently conducted to determine the best silicone for moisture control. With a general knowledge of silicone, the anatomy of hair and the results uncovered during the study, determining methods to treat hair to increase manageability becomes easier to establish.
Oct 21, 2011
Fluorosilicones in the Aerospace Industry
Fluorosilicone’s advent into the commercial marketplace offers opportunities for manufacturers to pursue new applications for silicones in the automotive, aircraft and general markets. The unique properties of fluorosilicones provide a solution for products that need broad operating temperatures, fuel resistance and long-term reliability. Conventional dimethyl silicones cannot survive the harsh...
Fluorosilicone’s advent into the commercial marketplace offers opportunities for manufacturers to pursue new applications for silicones in the automotive, aircraft and general markets. The unique properties of fluorosilicones provide a solution for products that need broad operating temperatures, fuel resistance and long-term reliability. Conventional dimethyl silicones cannot survive the harsh environments that fluorosilicones can endure. Similar to other silicones, fluorosilicones can be provided as high consistency rubbers (HCRs), liquid silicone rubbers (LSRs), dispersions, gels and even foams. Silicone manufacturers offer a variety of fluorosilicone solutions that fit the unique processes of any end-user. Whether fluorosilicones are used as adhesives, molded parts or protective coatings, flexibility of application is possible.
Apr 4, 2011
Choosing a Silicone Encapsulant for Photovoltaic Applications
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when...
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when using a RI matching silicone to minimize light loss versus a non-phenyl containing silicone.
Dec 22, 2009
Using Optical Index Matching Silicone Gels to Improve Outdoor Viewing and Ruggedness of Displays
Portable computing, military environments, and demanding outdoor activities like fire rescue require a reliable and accurate display. The bright ambient light outdoors can cause high reflection losses and subsequently “display washout.” A growing trend is use of optical index matching silicone gels to reduce reflection losses and also aid in...
Portable computing, military environments, and demanding outdoor activities like fire rescue require a reliable and accurate display. The bright ambient light outdoors can cause high reflection losses and subsequently “display washout.” A growing trend is use of optical index matching silicone gels to reduce reflection losses and also aid in durability.
Dec 15, 2009
Versatility and Flexibility from Low Outgassing Silicones
Miniaturization of electronic packages has led to using thinner and more fragile materials. This, in combination with the use of lead-free solder with solder reflow temperatures up to 260°C, can cause high shear stress during heating and cooling that can damage a device. Subsequently, there is growing interest in...
Miniaturization of electronic packages has led to using thinner and more fragile materials. This, in combination with the use of lead-free solder with solder reflow temperatures up to 260°C, can cause high shear stress during heating and cooling that can damage a device. Subsequently, there is growing interest in silicone adhesives and encapsulants for terrestrial electronic packaging applications.
Dec 1, 2009
Understanding the Role of Silicones in Controlled Release Applications
Silicones possess certain dynamic characteristics which allow them to be compounded in with a host of actives. These same unique characteristics also allow them to release those actives from a molded/extruded device in a predictable way – whether that application is for transdermal, transmucosal, short or long-term human implantation.
Silicones possess certain dynamic characteristics which allow them to be compounded in with a host of actives. These same unique characteristics also allow them to release those actives from a molded/extruded device in a predictable way – whether that application is for transdermal, transmucosal, short or long-term human implantation. This article will highlight key attributes of certain silicones as well as key considerations when selecting a silicone.
Nov 25, 2009
Recent Developments in Ultra Low Outgassing Silicones for Space Application
In this study, these 2-part, platinum cure, RTV silicones are compared to standard low outgassing materials, CV-2289 and CV10-2568. The physical properties are compared looking for any property losses, and the TML’s and CVCM’s are compared and analyzed according to ASTM E 595 standards and the outgassing kinetics from ASTM...
In this study, these 2-part, platinum cure, RTV silicones are compared to standard low outgassing materials, CV-2289 and CV10-2568. The physical properties are compared looking for any property losses, and the TML’s and CVCM’s are compared and analyzed according to ASTM E 595 standards and the outgassing kinetics from ASTM 15592 experiments.
Jun 8, 2009
Controlled Volatility Silicone Materials: Development and Analysis of Ultra Low Outgassing Elastomer For Space
In this paper, we compare a standard controlled volatility silica reinforced silicone adhesive that has a history of use in aerospace applications with a newly developed equivalent Ultra Low OutgassingTM version that exceeds typical ASTM E 595 requirements achieving < 0.1 % TMLs and < 0.01% CVCMs. We will...
In this paper, we compare a standard controlled volatility silica reinforced silicone adhesive that has a history of use in aerospace applications with a newly developed equivalent Ultra Low OutgassingTM version that exceeds typical ASTM E 595 requirements achieving < 0.1 % TMLs and < 0.01% CVCMs. We will compare the cured physical properties and monitor the outgassing profiles of each material based on ASTM E 1559 test method. We will also examine how different reinforcing and functional fillers can be incorporated into silicone materials while continuing to achieve low outgassing characteristics.
Jan 1, 2009
Silicones for Drug Delivery Combination Devices: Interview with Brian Nash
Recently, NuSil launched a comprehensive line of silicone materials and services intended specifically for use in drug delivery combination medical device applications. Drug Delivery Technology recently sat down with Brian Nash, Vice President of Marketing and Sales at NuSil Technology, for an exclusive interview to discuss how they are providing...
Recently, NuSil launched a comprehensive line of silicone materials and services intended specifically for use in drug delivery combination medical device applications. Drug Delivery Technology recently sat down with Brian Nash, Vice President of Marketing and Sales at NuSil Technology, for an exclusive interview to discuss how they are providing solutions and meeting the challenges in this competitive and global marketplace.
Oct 9, 2008
Adding Color to Medical Devices
Medical device companies continue to support the healthcare community by distinguishing models, sizes and improving the aesthetics of the device with the addition of color. Color in medical devices offers a number of benefits in marketing the device. Adding color can help differentiate the product in a competitive marketplace, and...
Medical device companies continue to support the healthcare community by distinguishing models, sizes and improving the aesthetics of the device with the addition of color. Color in medical devices offers a number of benefits in marketing the device. Adding color can help differentiate the product in a competitive marketplace, and the addition of corporate colors can also create a strong tie to the company's brand.
May 18, 2008
Material and Process Innovations with Filled Silicone Elastomers
Today the technological progress of modern military aircraft design has been greatly influenced by the use of advanced composite materials. These materials permit design of lighter stronger more flexible aircraft yet offers a new set of challenges in design, production and quality.
Today the technological progress of modern military aircraft design has been greatly influenced by the use of advanced composite materials. These materials permit design of lighter stronger more flexible aircraft yet offers a new set of challenges in design, production and quality.
Apr 30, 2008
Evaluation of Phosphor Settling Rate in Silicone Encapsulant
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing...
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing and production of white light emitting diodes. The phosphor dispersions
were evaluated over a large temperature range, -40 to 150°C, to attempt to understand the
material in the most broad and general way. This temperature range was subsequently
divided into storage, -40°C to –20°C, dispensing, 15°C to 35°C, and curing, > 40°C,
recognizing these portions of the range have unique requirements for production
applications.
Feb 13, 2008
A Characterization of Yellowing Caused by UV Radiation on Silicone Encapsulants, and Improvements in Future Materials
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage...
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage of UV, silicones perform better than UV
curing acrylates, which perform better than epoxies.
Jan 18, 2008
A Silicone-Based Ice-Phobic Coating for Aircraft
The problem of ice build-up in an engine or on the leading edges of a plane is a significant
problem in the aircraft industry. Ice build up can affect many aspects of flying such as lift, drag,
and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the...
The problem of ice build-up in an engine or on the leading edges of a plane is a significant
problem in the aircraft industry. Ice build up can affect many aspects of flying such as lift, drag,
and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the Army,
Engineer Research and Development Center, Cold Regions Research and Engineering
Laboratory (CRREL) in Hanover, NH, U.S, performed adhesion strength tests designed to
measure the adhesion strength of ice to several different commercially available ice-phobic
coatings. The results show that the silicone material, R-2180, dropped the adhesion strength by a
factor of 40 over bare steel and aluminum surfaces. These results were the lowest mean failure
stress that CRREL has ever seen at 37 kPa while Teflon was previously the lowest tested value
measured at 238 kPa.
Jan 18, 2008
Evaluation of Removal Rate of Cured Silicone Adhesive from Various
Electronic Packaging Substrates by Solvent and Silicone Digesters for
Rework Applications
Reworking electronic packages is an integral process related to diagnostics and
salvaging valuable materials. It is a meticulous and time-consuming procedure that
requires some knowledge of the package material composition to determine compatible
cleaning solutions and processes. Silicone adhesives are being used more frequently due
to their ability to minimize shear stress during temperature...
Reworking electronic packages is an integral process related to diagnostics and
salvaging valuable materials. It is a meticulous and time-consuming procedure that
requires some knowledge of the package material composition to determine compatible
cleaning solutions and processes. Silicone adhesives are being used more frequently due
to their ability to minimize shear stress during temperature cycling. A common method
for removing silicone adhesive is by swelling in solvent and removing by mechanical
methods taking care not to damage fragile materials and leave minimal residue. Silicone
digesters (emulsifiers) are another means of removing cured silicone. They are
comprised of weak acids or bases and remove silicone by breaking the siloxane bonds
that make up the polymer matrix. They are able to penetrate into areas that are difficult,
or impossible to reach, greatly reducing the risk of causing damage due to mechanical
removal. The purpose of this study is to evaluate the rate of silicone removal by solvents
and silicone digesters on silicones bonded to copper and aluminum. The removal rate
was determined by developing a rating system based on time intervals where silicone was
observed to delaminate or dissolve. Silicone adhesives and Thermal Interface Materials
(TIMs) were used in the evaluation of two commonly used solvents and two commercially
available silicone digesters. Copper and aluminum panels were evaluated by using a ~
0.5 mm thick layer of silicone to bond 2 panels together. The samples were placed in
cleaning solution for 24 hours at 40 degree Celsius and evaluated at specific intervals for
any changes in appearance of silicone. Based on the performance of combinations of
silicone, substrate and cleaner, the engineer can chose which method is best for
reworking based on their own assembly configuration and materials.
Nov 8, 2007
A Silicone-Based Ice-Phobic Coating for Aircraft
The problem of ice build-up in an engine or on the leading edges of a plane is a significant
problem in the aircraft industry. Ice build-up can affect many aspects of flying such as lift, drag,
and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the Army,
Engineer...
The problem of ice build-up in an engine or on the leading edges of a plane is a significant
problem in the aircraft industry. Ice build-up can affect many aspects of flying such as lift, drag,
and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the Army,
Engineer Research and Development Center, Cold Regions Research and Engineering
Laboratory (CRREL) in Hanover, NH, U.S, performed adhesion strength tests designed to
measure the adhesion strength of ice to several different commercially available ice-phobic
coatings. The results show that the silicone material, R-2180, dropped the adhesion strength by a
factor of 40 over bare steel and aluminum surfaces. These results were the lowest mean failure
stress that CRREL has ever seen at 37 kPa while Teflon® was previously the lowest tested value
measured at 238 kPa.
Jun 28, 2007
Processing Silicone Polymers: A Foundation for Creating Consistent Silicone Systems
The unique chemistry of silicone polymers are customizable to create a variety of material types with a specific properties. The polymer properties have proved useful in a number of applications, including drug delivery. Silicone polymers represent the basis of all silicone systems, adhesives, gels, elastomers, and resins. Silicone polymers are...
The unique chemistry of silicone polymers are customizable to create a variety of material types with a specific properties. The polymer properties have proved useful in a number of applications, including drug delivery. Silicone polymers represent the basis of all silicone systems, adhesives, gels, elastomers, and resins. Silicone polymers are created via acid or base catalyzed polymerizations of silicone cyclics and endblocking silicone molecules. The polymerization process is an equilibrium reaction that yields both starting materials and a polymer distribution of varying molecular weight. The subsequent processing and testing of these polymers is critical to their performance in silicone systems. Lack of proper processing may lead to variable physical properties in elastomer systems. These variations may, in turn, affect the system’s function in drug delivery systems, influencing factors like drug permeation rates. The paper critically evaluates the polymerization process and subsequent purification processes that are critical to producing consistent silicone systems.
Jun 11, 2007
Characterization of Ultra Low Outgassing™ Silicone Materials for Aerospace Applications
The Aerospace Industry has used silicone adhesives and coatings for over five decades. Silicones ability to maintain its elasticity and low modulus over a broad temperature range, –130 to 260°C, provides excellent utility in space, where spacecraft are often exposed to these extreme temperatures. The National Aeronautics & Space Administration...
The Aerospace Industry has used silicone adhesives and coatings for over five decades. Silicones ability to maintain its elasticity and low modulus over a broad temperature range, –130 to 260°C, provides excellent utility in space, where spacecraft are often exposed to these extreme temperatures. The National Aeronautics & Space Administration (NASA) and the European Space Agency (ESA) recommend testing low outgassing materials per ASTM E-595 prior to use in space. These materials should meet the specifications outlined in NASA SP-R-0022A and ESA PSS-014-702, which require a maximum Total Mass Loss (TML) of 1% and Collected Volatile Condensable Material (CVCM) of 0.1%. TML and CVCM levels higher than this specification can cause outgassing and subsequent contamination of expensive equipment. Although a standard for many years, many in the industry question whether these specifications are low enough.
Jan 23, 2007
A Characterization of UV Effects on Optical Silicones used in Opto-electronic Devices and New Developments in Resistant Materials
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been...
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been used throughout the last decade1, 2. The high light flux and associated heat proved too much for the traditional epoxies. Data confirms silicone encapsulants/adhesives provide longer optical transmission life than epoxy encapsulants 3. Almost all optical devices have some interaction with UV wavelengths. Manufacturers of Blue LEDs with wavelengths near 405nm, and other LEDs that emit wavelengths deeper into the UV (365-399nm), have concerns about the effects of this radiation on the light transmission of the encapsulant over time. LCD and sensor devices may have UV radiation from the sun to contend with. This paper looks at many different encapsulants/adhesives, silicone, epoxy and acrylate, for their change in optical transmission due to a 680- 68000J/cm2 dose of radiation with the following spectral output: 34% in the UVA (320-399nm), 17% in the UVB (280-319nm), and 49% concentrated at 405nm and 450nm. All samples were prepped and exposed the same way so that comparisons between the samples would be meaningful. Results show that silicones perform better than acrylates, which perform better than epoxies, and not all silicones perform equally. Data will be provided of the best performing materials and a discussion of future work given the understanding of the chemistry.
Nov 28, 2006
Solvent Resistance of Silicones used for Electronic Packaging Applications
Silicones are becoming more popular in advanced packaging for their thermal stability above 200oC and ability to protect the electronic package from environmental factors. The electronic package may be exposed to a variety of different solvents by fabricators in the cleaning process. Problems arise when the silicone swells with solvent.
Silicones are becoming more popular in advanced packaging for their thermal stability above 200oC and ability to protect the electronic package from environmental factors. The electronic package may be exposed to a variety of different solvents by fabricators in the cleaning process. Problems arise when the silicone swells with solvent. When the solvent evaporates, the silicone will become harder and put stress on the metal bonds, potentially bending and even shearing them. Fundamentals of silicone manufacturing allow silicones to have different chemical characteristics that can respond differently to various solvents. For example, some silicones are more resistant to hydrocarbon solvents, whereas others are more resistant to halogenated solvents. The purpose of this study is to evaluate the solvent resistance of silicone materials that can be used for electronic packaging. The solvents chosen for this study are commonly used solvents used in the electronics industry and the silicone materials chosen were based on the chemical composition. The change in thickness and specific gravity (% Swell) was measured over time after silicone was exposed to various solvents. By understanding how the electronic package is affected by different solvents, the appropriate solvent and silicone system can be chosen.
Sep 28, 2006
How Temperature Effects Transmission of Silicone Encapsulants
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by...
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by the 150°C temperature exposure and the juxtaposition of dissimilar materials leads us to the following recommendations for working with optically clear silicones at high temperature:
- do everything possible to get the heat out
- be aware that effect of material incompatibilities will be accelerated at elevated temperatures
- use the lowest cure temperatures needed to accomplish the curing of the silicone
Jul 31, 2006
Overcoming Package Stress in Flip Chips with Low Outgassed Silicone Materials to Reduce Contamination
The EU mandates for lead free solders are often soldered at higher temperatures than lead and have created a need for electronic packaging materials that can handle these thermal cycling extremes. Thermal Interface Materials (TIMs) and Underfills based on low outgassed silicone chemistry can aid the designer in overcoming thermal...
The EU mandates for lead free solders are often soldered at higher temperatures than lead and have created a need for electronic packaging materials that can handle these thermal cycling extremes. Thermal Interface Materials (TIMs) and Underfills based on low outgassed silicone chemistry can aid the designer in overcoming thermal cycling stress while maintaining minimal contamination due to low levels of contaminates from mobile polymer chains that have been known to cause fogging. The low modulus of silicones as compared to epoxies overcomes the stress due to large CTE differences in the package with the heat sink, heat spreader, die and substrate. The lap shear, bulk conductivity (W/mK) and ionic content of three TIM materials were tested and compared to each other. The TIM materials used were a low outgassing silicone, standard silicone, and an epoxy. Both the standard silicone and epoxy materials tested had higher weight loss at 275ºC for 1 hour than the low outgassing silicone. The results for
Jul 26, 2006
Comparing Silicone Pressure-Sensitive Adhesives to Silicone Gels for Transdermal Drug Delivery
Transdermal, drug-delivery applications mandate the use of adequate adhesive systems to not only keep the pharmaceutical agent in contact with the intended surface, but to facilitate sustained, controlled delivery. An engineer who must determine which silicone chemistry is optimal for their device has a few options. This paper will investigate...
Transdermal, drug-delivery applications mandate the use of adequate adhesive systems to not only keep the pharmaceutical agent in contact with the intended surface, but to facilitate sustained, controlled delivery. An engineer who must determine which silicone chemistry is optimal for their device has a few options. This paper will investigate the differences in silicone pressure sensitive adhesives (PSAs) and silicone gels for transdermal drug delivery applications. The paper begins with analysis of the chemistry of silicone and silicone materials. The many variations of the chemistry demonstrate the versatility of using silicone in drug delivery applications. Further exploration of the materials demonstrates fundamental differences between silicone PSAs and silicone gels and the advantages and disadvantages of these materials in use. The findings of the study suggest that silicone gels can offer a compelling alternative to the more traditionally used silicone pressure sensitive adhesives. The paper does recognize that the tradeoffs between ease of use and physical properties need to be considered when evaluating both materials for transdermal drug delivery applications.
May 1, 2006
New Low Stress Film Adhesive for Aerospace Applications Requiring Low Outgassing
Low stress liquid adhesives based on silicone chemistry have been used for years in the aerospace industry requiring low outgas, ASTM E-595 requirements (1). The applications include coverglass adhesives, mirror bonding, potting of electronic parts and many more. Silicones are valued for their dependability during extreme temperature cycling and inherently...
Low stress liquid adhesives based on silicone chemistry have been used for years in the aerospace industry requiring low outgas, ASTM E-595 requirements (1). The applications include coverglass adhesives, mirror bonding, potting of electronic parts and many more. Silicones are valued for their dependability during extreme temperature cycling and inherently low modulus characteristics. Aerospace Engineers working on applications that require precision bond lines for adhesion or sealing applications have struggled with liquid silicone systems. The lack of uniform bond thickness and mess/ clean-up issues result in significant process inefficiencies. Film adhesive technology solves many of these problems. Films can be produced to an exact thickness specified by the customer. If many of the same components are going to be adhered to, a die cut of the film could be obtained and reproduced to improve the efficiency of applying adhesive. Mess and clean-up are non-existent. The problem until recently is that low stress, low outgassing silicone film adhesive versions were not available. This paper will characterize new film adhesives and compare with similar liquid materials; CTE, High/low temperature resistance, adhesion, etc. The possibility for future novel applications will also be discussed.
Dec 19, 2005
Low Outgas Silicone Pressure Sensitive Adhesive for Aerospace Applications II
The aerospace industry, primarily satellite manufacturers, have expressed the need for a low outgas, thermally stable, adhesive tape. The current products in the marketplace have limitations at both high, 175ºC, and low, -100ºC, temperatures. A new silicone Pressure Sensitive Adhesive (PSA) was developed to pass ASTM E-595(1), low outgassing requirements...
The aerospace industry, primarily satellite manufacturers, have expressed the need for a low outgas, thermally stable, adhesive tape. The current products in the marketplace have limitations at both high, 175ºC, and low, -100ºC, temperatures. A new silicone Pressure Sensitive Adhesive (PSA) was developed to pass ASTM E-595(1), low outgassing requirements of 1% or less Total Mass Loss (TML) and 0.1% or less Collectable Volatile Condensable Materials (CVCM). This PSA was then fabricated into a tape and measured for performance and compared to other non-low outgassing silicone PSAs. The basics were outlined in a presentation presented at the SAMPE technical conference in Long Beach, CA, May 2004(2). This paper will expand on this technology by providing testing data at both high and low temperatures, comparative testing under different conditions with industry standard acrylate tapes, and more details on the fabrication of the tape.
Mar 18, 2005
Index Matching Silicone for High Brightness LED Packaging
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease.
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease. This paper will examine various silicones as effective encapsulants and lenses for High Brightness LEDs (HB LEDs). Physical and optical characteristics will be tested to determine which materials may prove to be the best.
Mar 18, 2005
Low Outgassing Materials for Electro-Optic and Electronic Systems
This paper explores the need for low outgassing, thermally stable, high performance materials for electrooptic and electronic systems, citing various applications of low outgassing materials in electro-optic and electronic systems. This paper also describes the chemistry of silicone polymerization, identifying the source of outgassing components in silicones as well as...
This paper explores the need for low outgassing, thermally stable, high performance materials for electrooptic and electronic systems, citing various applications of low outgassing materials in electro-optic and electronic systems. This paper also describes the chemistry of silicone polymerization, identifying the source of outgassing components in silicones as well as the procedures for eliminating these volatile materials—solvent washing or wipe film evaporating. Finally, a comparison of low-outgassing versus nonoutgassing materials verifies low outgassing materials performance quality, even after additional processing.
Mar 2, 2005
Phosphors and Silicone Dispersions
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the...
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the chemistry of silicone, the multiple material composition options and various cure chemistries demonstrates how silicone can be tailored to fit specific applications. A brief discussion of both physical and optical properties of two types of material compositions, Cured Gels and Thermosets, the most common types used in HB LED packaging. Then, a general investigation of the way a silicone interacts with a phosphor, in regards to compatibility, particle size and potential interactions. The paper will also review methods of dispersion, processing considerations and equipment.
Nov 4, 2004
Optical Silicones for use in Harsh Operating Environments
The optics industry widely uses silicones for various fiber optic cable potting applications and light emitting diode protection. Optics manufacturers know traditional silicone elastomers, gels, thixotropic gels, and fluids not only perform extremely well in high temperature applications, but also offer refractive index matching so that silicones can transmit light...
The optics industry widely uses silicones for various fiber optic cable potting applications and light emitting diode protection. Optics manufacturers know traditional silicone elastomers, gels, thixotropic gels, and fluids not only perform extremely well in high temperature applications, but also offer refractive index matching so that silicones can transmit light with admirable efficiency. However, because environmental conditions may affect a material’s performance over time, one must also consider the conditions the device operates in to ensure long-term reliability. External environments may include exposure to a combination of UV light and temperature, while other environments may expose devices to hydrocarbon based fuels. This paper will delve into the chemistry of silicones and functional groups that lend themselves to properties such as temperature, fuel, and radiation resistance to show why silicone is the material of choice for optic applications under normally harmful forms of exposure. Data will be presented to examine silicone’s performance in these environments.
Jul 1, 2004
Choosing a Silicone Adhesive & Treatment System
As devices become smaller and bonds more critical, choosing the right adhesive system may be essential to the success of the device.This article investigates some adhesives and primers used to adhere difficult substrates.
As devices become smaller and bonds more critical, choosing the right adhesive system may be essential to the success of the device.This article investigates some adhesives and primers used to adhere difficult substrates.
Jun 25, 2004
Drug Delivery Market Summary
Silicones have been cited as materials regularly used in drug delivery devices. These drug delivery devices incorporating silicones primarily fall into three major categories:
- Implanted delivery devices
- Mucosal delivery devices
- Transdermal delivery devices
Implanted drug delivery devices include spinal treatment devices, ocular treatment devices and contraceptive devices. These delivery configurations typical utilize silicone...
Silicones have been cited as materials regularly used in drug delivery devices. These drug delivery devices incorporating silicones primarily fall into three major categories:
- Implanted delivery devices
- Mucosal delivery devices
- Transdermal delivery devices
Implanted drug delivery devices include spinal treatment devices, ocular treatment devices and contraceptive devices. These delivery configurations typical utilize silicone tubing or molded configurations. The silicone is used to either hold or precisely deliver the drug to a specific location. Liquid silicone rubbers or high consistency silicone rubbers can be molded into precise configurations required by these applications. Transmucosal drug delivery devices can include silicone elastomer systems with the drug incorporated into the silicone matrix. After the device is placed in contact with the mucosal membrane, the drug elutes from the device at a controlled rate. A non-medicated sheath is cited (References 12,11,7) as a means to control the initial burst of drug from the device. Drugs can be incorporated into liquid silicone rubbers and molded into various configurations. Transdermal delivery devices are primarily skin patches in configuration. The drug may be incorporated directly into the adhesive of the patch or may exist as a separate layer. Silicone pressure sensitive adhesives have been used in these applications because of the low skin sensitization, oxygen and drug permeability properties they offer. Silicone materials used in medical device configurations can also be treated with drug infused coatings.
Jun 24, 2004
Silicone Adhesives and Primers on Low Surface Energy Plastics and High Strength Metals for Medical Devices
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, flame treatment, or plasma treatment, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and...
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, flame treatment, or plasma treatment, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and chemical interaction. Most plastic have a surface energy under 50 dynes/cm while aluminum, an easier substrate to adhere to, is closer to 825 dynes/cm. Surface energy is a thermodynamic effect of how a liquid will ‘wet out’ on a surface. Low surface energy materials, like plastics, do not allow a liquid, like an adhesive, to ‘wet out’ on its surface. Adhesion chemistry tells us that the better an adhesive can ‘wet out’ on a substrate, the more surface area it can cover and allow more reactive groups to bond, making a stronger bond. Several low surface energy plastics and high strength metals were tested with silicone adhesives and primers, as well as with plasma treatment, to achieve cohesive bond failure when performing lap-shear testing. This list of substrates evaluated include polycarbonate, polyetherimide, polyamide, polyurethane, polymethylmethacrylate, polysulphone, titanium, stainless steel, and aluminum.
Jun 16, 2004
Low Outgas Silicone Pressure Sensitive Adhesive for Aerospace Applications
The need for a low outgas, thermally stable, high performance adhesive has initiated the development of a new experimental silicone Pressure Sensitive Adhesive (PSA) able to pass ASTM E-595, low outgassing requirements of 1% or less Total Mass Loss (TML) and 0.1% or less Collectable Volatile Condensable Materials (CVCM). The...
The need for a low outgas, thermally stable, high performance adhesive has initiated the development of a new experimental silicone Pressure Sensitive Adhesive (PSA) able to pass ASTM E-595, low outgassing requirements of 1% or less Total Mass Loss (TML) and 0.1% or less Collectable Volatile Condensable Materials (CVCM). The performance goals were to maintain performance under load at temperatures above 175°C and have similar properties to other low outgassed silicone PSA’s as tested by peel, loop tack, shear, release force and Blunt probe tack.
Jun 14, 2004
Silicones as a Material of Choice for Drug Delivery Applications
This paper will investigate the benefits of using silicone in drug delivery applications. This investigation first provides an overview of how versatile of a material silicone can be to the drug delivery industry. An examination of the chemistry of silicone, the multiple material composition options and various cure chemistries demonstrates...
This paper will investigate the benefits of using silicone in drug delivery applications. This investigation first provides an overview of how versatile of a material silicone can be to the drug delivery industry. An examination of the chemistry of silicone, the multiple material composition options and various cure chemistries demonstrates how silicone can be tailored to fit specific drug delivery applications. Then, a general investigation of the way a silicone interacts with a drug, in regards to compatibility and potential interactions, exhibits silicone’s ability to deliver pharmaceutical agents. The paper will also review factors that have made silicones the materials of choice in the medical device industry, particularly for long-term implantable devices. Examples of applications demonstrate the reasons for choosing silicone over a different material. The paper will finish with real world examples of current drug delivery applications incorporating a silicone, such as hormone replacement therapies, to manifest the benefits of using silicone in drug delivery applications.
Jun 8, 2004
Adhering to Difficult Substrates
Adhesive echnology is equal parts chemistry and ‘black magic’. Because there are so many different substrates, each adhesive can not be actually tested before hand on each and everyone. However, by testing on some novel substrates, or difficult to adhere to, inferences can be made which can narrow the choices...
Adhesive echnology is equal parts chemistry and ‘black magic’. Because there are so many different substrates, each adhesive can not be actually tested before hand on each and everyone. However, by testing on some novel substrates, or difficult to adhere to, inferences can be made which can narrow the choices of adhesives. We can define adhesion as the chemical bonding of two substrates. Substrates that have reactive groups available for bonding like OH groups on glass and aluminum make this chemical bond easier. Substrates with nothing to react to make adhesion difficult; graphite and PTFE. Multiple other substrates fit somewhere in-between.
Sep 25, 2003
Silicone Adhesives and Primers on Low Surface Energy Plastics and High Strength Metals
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and chemical interaction. Most plastic have...
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and chemical interaction. Most plastic have a surface energy under 50 dynes/cm while aluminum, an easier substrate to adhere to, is closer to 825 dynes/cm. Surface energy is a thermodynamic effect of how a liquid will ‘wet out’ on a surface. Low surface energy materials, like plastics, do not allow a liquid, like an adhesive, to ‘wet out’ on its surface. Adhesion chemistry tells us that the better an adhesive can ‘wet out’ on a substrate, the more surface area it can cover and allow more reactive groups to bond, making a stronger bond. Several low surface energy plastics and high strength metals were tested with silicone adhesives and primers to achieve cohesive bond failure when performing lap-shear testing. This list of substrates evaluated include polycarbonate, polyetherimide, polyamide, polyurethane, polymethylmethacrylate, polysulphone, titanium, stainless steel, and aluminum.
Feb 17, 2003
Accelerating Cure of Silicone Adhesives
This paper will demonstrate the availability of dramatically accelerating the cure of certain silicone adhesives and their advantage to the manufacturing process. A ‘fast cure’ adhesive is defined as full cure in less than ten minutes—or partial cure for handling under five minutes and full cure at room temperature in...
This paper will demonstrate the availability of dramatically accelerating the cure of certain silicone adhesives and their advantage to the manufacturing process. A ‘fast cure’ adhesive is defined as full cure in less than ten minutes—or partial cure for handling under five minutes and full cure at room temperature in 8 hours or one shift. Using a specific cure system and materials that have been developed to obtain fast-cure with heat acceleration, an experiment was performed to determine how fast, and at what temperatures these adhesives will cure. In conclusion, to obtain fast-cure at low temperature, 65ºC, R31-2186 can be fully cured in one minute. When adhering to temperature sensitive substrates, this provides a fast-cure choice. Although needing a higher temperature to obtain ‘fast-cure’, R32-2186 fully cures in 2 minutes at 100ºC. This can be useful because of R32-2186’s extended worktime. LSR-9820-20 proves the best choice for high temperature cure, 185ºC. In just 30 seconds it has a 300psi lap shear. Although this figure reaches optimum over time, for many applications this is a great partial cure.