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Silicones having improved chemical resistance and curable silicone compositions having improved migration resistance

a technology of curable silicone and composition, applied in the field of curable silicone composition and silicone, can solve the problems of high cost of fluorosilicone elastomers, solvents and engine oils, and poor resistance of polyorganosiloxane elastomers to some organic chemicals, and achieve the effect of improving resistance to bleed

Inactive Publication Date: 2005-02-17
DOW CORNING CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

“Chemical resistance” means reduced tendency of a silicone to swell, or degrade, or both, when exposed to solvents and oils.
A tilt of 25-35 degrees will enhance the halo of the bleeding layer on the image captured. The microscope zoom is adjusted from 1 to 4.9X, with the latter giving the best optical reference to measure or quantify the bleed from a nubbin. Once focused on a nubbin at the correct zoom, a picture is taken and the image saved to a file. This process is then repeated after 24 hours.

Problems solved by technology

However, these polyorganosiloxane elastomers may suffer from the drawback of poor resistance to some organic chemicals, such as solvents and engine oils.
However, fluorosilicone elastomers suffer from the drawback of having higher cost than polyorganosiloxane elastomers (that are non-fluorinated).
However, proposed approach has generally not been used due to concerns that the fluorosilicone and non-fluorinated organosilicone components would phase separate, resulting in unstable properties.
Silicone compositions that cure to form elastomers may also suffer from the drawback of poor resistance to Bleed.
Bleed can be problematic in applications in which the composition is applied to a portion of a substrate before curing.
The species that Bleed (out of the silicone composition) may contaminate the substrate.
This tends to be particularly problematic for adhesives, such as die attach adhesives used in electronics applications, because the addition of adhesion promoters to hydrosilylation-reaction curable polyorganosiloxane elastomer compositions has been found to increase Bleed.
Organic elastomers may suffer from the drawback of having insufficient flexibility or bulk thermal properties.

Method used

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  • Silicones having improved chemical resistance and curable silicone compositions having improved migration resistance
  • Silicones having improved chemical resistance and curable silicone compositions having improved migration resistance
  • Silicones having improved chemical resistance and curable silicone compositions having improved migration resistance

Examples

Experimental program
Comparison scheme
Effect test

reference example 1

Sample Preparation and Analysis

A base is prepared by milling the following components in a 1 quart Ross mixer: Filler 1, Filler 2, Pigment, and the Polymer or Polymers selected for each example.

A blend is prepared by blending Cure Modifier and Organohydrogenpolysiloxane or Fluoroorganosilicone, or both, and heating for at least 30 minutes at 70 ° C.

The base, the blend, and any additional Polymer or Polymers are combined in a 20 gram dental mixer cup and are mixed at 3,500 revolutions per minute for 30 seconds. The resulting mixture is allowed to cool and Catalyst is added and is hand mixed for 10 seconds. The resulting mixture is again mixed at 3,500 revolutions per minute for 10 seconds with the dental mixer.

Rate of Bleed is measured as follows. A sample is allowed to equilibrate to room temperature. A 9 mm (length) piece of Continuous Au / Cu PI TAB tape purchased from Hitachi Cable is cut and taped to the middle section of a stainless steel print frame that fits in a vacuu...

examples 6-8

Compositions Containing Component (II)

Samples are prepared according to the method of Reference Example 1. The components and amounts for examples 6-8 are in Table 3. Extent of Bleed is measured as % change after 24 hours. The results are in Table 3.

TABLE 3Example #678Polymer 133.2632.9632.83Adhesion Promoter0.80.80.8Pigment0.40.40.4Filler 1111Filler 2606060Organohydrogenpolysiloxane0.80.40.21Fluoroorganosilicone 12.423.123.45Cure Modifier0.050.050.05Catalyst 11.271.271.27Extent of Bleed13.2%17.8%16.6%SiHtot / Vitot1.501.501.50

As shown in the examples and comparative examples above, compositions containing adhesion promoters but no fluoroorganosilicones exhibit greater Bleed than the compositions that contain neither adhesion promoters nor fluoroorganosilicones and the compositions that contain fluoroorganosilicones but no adhesion promoters. However, it was surprisingly found that the compositions containing both adhesion promoters and fluoroorganosilicones exhibit less Bleed t...

reference example 2

Sample Preparation and Analysis

Samples are prepared by combining Polymer 2, Pigment, Spacer, filler 2, Crosslinker 1, Adhesion Promoter, Catalyst 2, Adhesion Promoter, and any Phenylsiloxanes and Crosslinkers.

Bleed is measured as the percent increase in diameter of a dot of sample placed on an electronic circuit tape. The circuit tape is Hitachi polyimide TAB Tape LC-TAB μBGA 220A14, which consists of gold plated copper circuit traces with Tomoegawa X epoxy laminate adhesive between the traces. Dots of sample with diameters ranging from 0.914 mm to 1.953 mm are placed on to the epoxy surface on this circuit tape. Immediately after the dots are applied to the epoxy surface, pictures of the dots are taken and the time of placement is recorded along with the picture.

As time passes, subsequent pictures of the dots are taken using identical magnifications. All pictures are taken with a Nikon sMZ-10A microscope, a Diagnostic Instruments, Inc. Spot Jr Model 1.5.0 digital camera, and...

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Abstract

A composition is prepared by mixing components including: (I) a polyorganosiloxane having an average of at least two unsaturated organic groups per molecule, with the proviso that component (I) is free of fluorine atoms; optionally (II) an organohydrogenpolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule, with the proviso that component (II) is free of fluorine atoms; (III) a hydrosilylation catalyst; (IV) a fluoroorganosilicone, with the provisos that (1) component (IV) has at least one functional group reactive with component (I), component (II), or both, (2) when component (II) is not present, then component (IV) has an average of at least two silicon-bonded hydrogen atoms per molecule, and (3) component (IV) is added to the composition in an amount sufficient to provide chemical resistance to a cured product of the composition; and (V) an adhesion promoter.

Description

TECHNICAL FIELD This invention relates to curable silicone compositions and silicones formed by curing the curable silicone compositions. More particularly, this invention relates to hydrosilylation-curable compositions having improved resistance to Bleed. The curable silicone compositions cure to form products having improved chemical resistance and resistance to Bleed. BACKGROUND OF THE INVENTION Polyorganosiloxane elastomers, such as polydimethylsiloxane-based elastomers, are frequently used in the electronics industry for properties such as their thermal stability and ability to relieve stresses over a broad thermal range. However, these polyorganosiloxane elastomers may suffer from the drawback of poor resistance to some organic chemicals, such as solvents and engine oils. Fluorosilicone elastomers and organic elastomers have been used to improve chemical resistance. However, fluorosilicone elastomers suffer from the drawback of having higher cost than polyorganosiloxane ela...

Claims

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Application Information

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IPC IPC(8): C08L83/04C08L83/08C09D183/05C09D183/07C09J183/04H01L23/29H01L23/31
CPCC08G77/12H01L24/48C08G77/18C08G77/20C08G77/70C08G77/80C08L83/04C08L83/08C09J183/04H01L23/293H01L23/3114H01L23/3128H01L2224/32145H01L2224/32225H01L2224/48091H01L2224/48227H01L2224/73265H01L2924/01004H01L2924/01012H01L2924/0102H01L2924/01046H01L2924/01057H01L2924/01077H01L2924/01078H01L2924/01079H01L2924/15311C08G77/16H01L2924/01019C08L83/00H01L2924/00014H01L2924/00H01L2924/00012H01L2924/12044H01L24/73H01L2924/181C09D183/04C09D183/08C08G77/24Y10T428/31663C09J183/08H01L2224/45099H01L2224/45015H01L2924/207C08L83/06
Inventor AHN, DONGCHANHUEY, PAMELA JEANSHEPHARD, NICK EVANWATSON, MICHAEL JOHN
Owner DOW CORNING CORP
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