Addition-Crosslinked Silicone Press Pads for PCB Manufacturing
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Solution Overview
Problem
Existing press cushions for high-pressure heating presses cause quality defects and contamination in the production of printed circuit boards and circuit boards due to outgassing of peroxide by-products during the crosslinking process, leading to electrical faults and failure to meet high purity requirements.
Innovation Solution
The use of addition-crosslinked silicone elastomer and copolymers, which are crosslinked using vinyl groups and a crosslinking agent with Si-H groups in the presence of platinum, palladium, or rhodium catalysts, eliminating outgassing and providing enhanced temperature resistance and reduced shrinkage, and incorporating metal threads for improved heat transfer and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If peroxide crosslinking is used to achieve heat resistance and elasticity, then the press pad can withstand high temperatures up to 250°C, but outgassing of peroxide by-products causes contamination and quality defects in printed circuit board production
Solution Approach 1:
The patent changes the crosslinking chemistry from peroxide-based to addition-crosslinking based on vinyl and Si-H groups. This parameter change in the chemical reaction mechanism eliminates outgassing while maintaining heat resistance, directly resolving the contradiction between thermal stability and contamination-free operation
Solution Approach 2:
The patent converts the harmful outgassing effect into a beneficial outcome by selecting a crosslinking system that inherently produces no volatile by-products. The addition-crosslinking reaction between vinyl-containing silicone polymers and Si-H crosslinking agents provides a clean curing process that benefits high-purity electronic industry applications
2Manufacturing precision
If press pads are made with high elasticity to compensate for thickness tolerances, then pressing uniformity is improved, but the press pads require frequent replacement due to poor resilience after pressure relief
Solution Approach 1:
The patent uses composite construction with a fabric core (providing structural stability) covered with crosslinked silicone elastomer (providing elasticity and resilience). This composite structure allows the press pad to maintain high elasticity for thickness compensation while the crosslinked elastomer layer provides exceptional resilience for extended service life
Solution Approach 2:
The patent changes the elastomer properties through addition-crosslinking, which creates a three-dimensional network structure that dramatically improves resilience and elastic recovery. This parameter change in the material structure allows the press pad to withstand repeated compression cycles without permanent deformation, extending service life while maintaining compensation capability
3Temperature
If metal threads are added to improve thermal conductivity, then heat transfer from heating plate to press plate is enhanced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent creates a composite fabric structure combining metal threads (for thermal conduction) with elastomer-coated core threads (for elasticity and structural integrity). This composite approach enhances heat transfer while the elastomer coating integrates the metal threads into the fabric matrix, managing the complexity through material integration
Solution Approach 2:
The metal threads serve multiple functions: they provide thermal conductivity pathways, maintain fabric structural stability, and contribute to the overall mechanical strength. This multi-functionality reduces the need for separate components, managing device complexity while achieving improved heat transfer
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution prevents contamination and quality defects, meets high purity requirements, and extends the lifespan of press pads by reducing permanent dynamic load and shrinkage, ensuring effective compensation of thickness tolerances and improved heat transfer properties.
Implementation Method 1
the silicone elastomer and/or the copolymer are addition-crosslinked, with addition-crosslinking using both silicone polymers containing vinyl groups, a crosslinking agent, the Si-H Contains groups, and a platinum, palladium or rhodium catalyst are present
Implementation Method 2
press cushions must have sufficient elasticity, i.e. flexibility, in order to be able to compensate for the thickness tolerances during the pressing process
Implementation Method 3
The metal threads are used to transfer heat from the heating plate to the press plate
Data Source
Figure 1~2
AI summary
The press cushion comprises a flat contexture (8) made from threads or fibers, and a silicon elastomeric material made by crosslinking silicon rubber or a copolymer made by crosslinking silicon rubber and fluor silicon rubber or a copolymer made by crosslinking silicon rubber and fluor rubber. The silicon elastomeric material and the copolymer are addition crosslinked. The flat contexture is a woven material or a knitted material. The silicon elastomeric material or the copolymer is provided in the press cushion as a coherent layer or included in threads. The press cushion comprises a flat contexture (8) made from threads or fibers, and a silicon elastomeric material made by crosslinking silicon rubber or a copolymer made by crosslinking silicon rubber and fluor silicon rubber or a copolymer made by crosslinking silicon rubber and fluor rubber. The silicon elastomeric material and the copolymer are addition crosslinked. The flat contexture is a woven material or a knitted material. The silicon elastomeric material or the copolymer is provided in the press cushion as a coherent layer or included in threads that are in particular provided as warp threads (11) or weft threads of a fabric. The threads of the flat contexture include: a core made from monofilament or multifilament metal threads or made from monofilament or multifilament high temperature resistant plastic laminates; a jacket made from silicon elastomeric material or a copolymer; and monofilament or multifilament metal threads at their outer enveloping surface. The threads of the flat contexture are partially embedded in the silicon elastomeric material or the copolymer and connected with the silicon elastomeric material or the copolymer in a force transmitting manner. The silicon elastomeric material or the copolymer includes a metal portion, which is provided as a metal powder that is homogeneously distributed in the silicon elastomeric material or in the copolymer. The woven material includes: a thread system comprising threads including the silicone elastomeric material or the copolymer; and another thread system including monofilament or multifilament metal threads, preferably copper or brass threads. The cushion is provided at one surface or at both opposite surfaces of a heating press with a full surface cover provided as a coating or a foil. A friction coefficient of the full surface cover is 0.01-0.5. The full surface cover is firmly connected with the press cushion through a glue in a full surface glue layer, where the glue or the glue layer is high temperature resistant.