Whitepapers - Electronics
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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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
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 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.
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 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.
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.
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
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 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.
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
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.
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.