Insulating Substrate Warpage Control for Semiconductor Heat Dissipation
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Solution Overview
Problem
Existing semiconductor devices with insulating substrates face challenges in achieving stable warpage and close contact with cooling members, leading to inefficient heat radiation and reduced productivity due to issues with heat radiation grease distribution and curing shrinkage of direct-potting type seal resins.
Innovation Solution
A semiconductor device design where the insulating substrate is warped into a convex shape by controlling the thickness and linear expansion coefficient of the resin relative to the substrate, ensuring a stable close contact with the cooling member, and using a direct-potting type seal resin with a higher thermal expansion coefficient to manage warpage and prevent air bubble formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct-potting type seal resin is used to improve productivity and reliability, then manufacturing efficiency is improved, but curing shrinkage causes larger deformation and warpage of the insulating substrate
Solution Approach 1:
The insulating substrate is preliminarily warped into a convex shape before the resin filling step. This preliminary warpage compensates for the deformation caused by resin curing shrinkage, ensuring that the substrate maintains proper contact with the cooling member after resin solidification.
Solution Approach 2:
The linear expansion coefficient of the resin is controlled to be equal to or greater than that of the insulating substrate (α2≥α1), and the resin thickness is controlled to be equal to or greater than the substrate thickness (t2≥t1). These parameter changes allow the resin to generate sufficient expansion force during curing to maintain substrate warpage and prevent reverse deformation.
2Temperature
If heat radiation grease is used to transmit heat from the insulating substrate to the cooling member, then heat radiation is improved, but air bubbles trapped in the grease reduce heat radiation efficiency
Solution Approach 1:
The insulating substrate is preliminarily warped into a convex shape before resin filling to ensure that the central portion contacts the cooling member first. This prevents air bubbles from being trapped in the heat radiation grease, ensuring stable and efficient heat radiation throughout the device's operation.
3Temperature
If the insulating substrate is warped into a convex shape to ensure close contact with the cooling member, then heat transmission is improved, but wire bonding workability deteriorates
Solution Approach 1:
The substrate is preliminarily warped into a convex shape, but wire bonding is performed before the resin filling step when the substrate is still relatively flat and easier to work with. After wire bonding, the resin is filled and cured, which finalizes the convex warpage shape for optimal heat contact.
4Strength
If screws are used to secure the cooling member to the insulating substrate, then mechanical connection is improved, but reverse warpage and air trapping may occur
Solution Approach 1:
The linear expansion coefficient of the resin is controlled to be equal to or greater than that of the insulating substrate (α2≥α1). This parameter change ensures that the resin's expansion during curing generates sufficient force to counteract the reverse warpage caused by screw tightening, preventing air bubbles from being trapped between the substrate and cooling member.
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
This approach enhances heat radiation efficiency, improves manufacturing yield, and maintains high reliability by stabilizing the warpage of the insulating substrate and preventing air bubbles, thereby improving the overall performance and productivity of semiconductor devices.
Implementation Method 1
assuming that the thickness of the insulating substrate is denoted by t1, the thickness of the resin is denoted by t2, the linear expansion coefficient of the insulating substrate is denoted by α1, and the linear expansion coefficient of the resin is denoted by α2, the relationship therebetween satisfies t2≧t1 and α2≧α1
Implementation Method 2
In order to transmit heat from a bottom surface of the insulating substrate to the cooling member
Data Source
AI summary
It is possible to provide a semiconductor device which can be obtained at a high reliability by warping an insulating substrate stably into a convex shape while ensuring a close contact between a cooling member and the insulating substrate. The semiconductor device includes an insulating substrate, a semiconductor element disposed on a first surface of the insulating substrate, a case connected to the insulating substrate, and a resin filled inside the case. Assuming that the thickness of the insulating substrate is denoted by t1, the thickness of the resin is denoted by t2, the linear expansion coefficient of the insulating substrate is denoted by α1, and the linear expansion coefficient of the resin is denoted by α2, the relationship therebetween satisfies t2≧t1 and α2≧α1, and a second surface of the insulating substrate opposite to the first surface thereof is warped into a convex shape.