Power Module Primer Layer Prevents Epoxy Delamination
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Solution Overview
Problem
Epoxy resin encapsulants used in power modules face delamination issues due to differing coefficients of linear expansion with semiconductor chips, leading to reliability concerns, especially at high temperatures.
Innovation Solution
A power module design that uses a primer layer composed of a silicone-modified polyimide resin composition, including radically crosslinking and epoxy curable silicone-modified polyimide resins, to bond the encapsulating body to the base member, enhancing high-temperature durability and preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy resin encapsulant is used to protect semiconductor chips, then protection and encapsulation are achieved, but delamination occurs due to different coefficients of linear expansion at high temperatures
Solution Approach 1:
A primer layer comprising a cured product of silicone-modified polyimide resin composition is introduced between the epoxy resin encapsulant and the base member. This intermediary layer has a coefficient of linear expansion that bridges the gap between the epoxy resin and base member, reducing thermal stress and preventing delamination at high temperatures while maintaining bonding reliability.
Solution Approach 2:
The primer layer uses a composite material formulation combining silicone-modified polyimide resin with specific additives (radical initiator, solvent, antioxidant, and hydrophobic fumed silica). This composite structure provides both thermal stability and adhesion properties, enabling the encapsulant to withstand high temperature operations without delamination.
2Reliability
If epoxy resin is used for encapsulation, then encapsulation protection is provided, but peeling occurs due to high hardness and poor moisture proofing
Solution Approach 1:
The primer layer acts as a mediator that improves moisture resistance at the bonding interface between the encapsulant and base member. The silicone-modified polyimide resin composition provides both adhesion promotion and moisture barrier properties, preventing peeling that would otherwise occur due to epoxy resin's poor moisture proofing and high hardness.
Solution Approach 2:
The primer layer changes the surface properties and chemical composition at the bonding interface. By applying the silicone-modified polyimide resin composition containing hydrophobic fumed silica and antioxidant, the interface gains improved moisture resistance and bonding strength, preventing peeling under humid conditions.
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 effectively prevents delamination between the semiconductor device and epoxy resin encapsulant, allowing the power module to operate reliably at temperatures of 175°C or above, as demonstrated by moisture reflow and heat resistance tests.
Implementation Method 1
a primer layer comprising a cured product of a silicone-modified polyimide resin composition... (A1) 100 parts by weight of a radically crosslinking silicone-modified polyimide resin... (Bc) 0.1 to 10 parts by weight of a heat decomposable radical initiator
Data Source
AI summary
According to the present invention, a power module that has a base to which a power semiconductor device is bonded and a sealing body for sealing said base and in which the base and the sealing body are bonded with a primer layer interposed therebetween, said primer layer being formed of a cured product of a silicone-modified polyimide resin composition containing, for example, components (A) to (E) below, has high reliability because delamination of an epoxy sealing resin under high temperature conditions is suppressed.(A) Silicone-modified polyimide resin represented by formula (1)Ee-Ff-Gg (1)E is represented by formula (2), F is represented by formula (3), G is a divalent group derived from diamine, f+e+g=100 mol %, the molar ratio f/(e+g) is 0.9-1.1, and e is 1-90 when the sum of e and g is 100.RA is a divalent hydrocarbon group, R1 and R2 are alkyl groups, R3 and R4 are monovalent aliphatic hydrocarbon groups, R5 and R6 are aryl groups or the like, m is an integer of 0-20, n is an integer of 1-20, o is an integer of 0-20, and m+n+o is an integer of 1-30.-Im-X-Im- (3)Im is a cyclic group including a cyclic imide structure, and X is a single bond or the like.(Bc) Heat-decomposable radical initiator(C) Solvent(D) Antioxidant(E) Fumed silica.