Whitepapers

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.

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:

1. do everything possible to get the heat out
2. be aware that effect of material incompatibilities will be accelerated at elevated temperatures
3. use the lowest cure temperatures needed to accomplish the curing of the silicone

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

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.

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.