Semiconductor Package Solder Pad Asymmetry for Thermal Stress Reduction
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Solution Overview
Problem
Semiconductor devices with ceramic substrates face thermal stress issues due to differences in thermal expansion coefficients, leading to potential cracks in solder connections and reduced mounting accuracy when soldered onto wiring substrates, necessitating improved connection reliability and mountability.
Innovation Solution
A semiconductor package design featuring a flat plate-shaped base member with electrode solder pads at the center and auxiliary solder pads on either side, where the auxiliary solder pads have a greater length perpendicular to the electrode pads, enhancing self-alignment and reducing thermal stress, thereby improving connection reliability and mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of each of the solder pads disposed at an outer side is reduced, then the self-alignment force is reduced, but the mounting accuracy at the time of soldering of the package to the wiring substrate decreases
Solution Approach 1:
The patent applies asymmetry by making the auxiliary solder pads longer in the second direction (perpendicular to the first direction) compared to the electrode solder pads. This asymmetric design enhances the self-alignment force during mounting while maintaining reduced pad size, thereby resolving the contradiction between connection reliability and mounting accuracy.
Solution Approach 2:
The patent applies local quality by differentiating the dimensions of auxiliary solder pads from electrode solder pads. Specifically, the auxiliary solder pads have a greater length in the second direction, creating localized structural variation that optimizes self-alignment force in critical areas without increasing the overall pad size, thus maintaining both reliability and precision.
2Reliability
If auxiliary solder pads are disposed on a substrate in a region at an outer side of a pair of electrode solder pads, then good connection reliability can be attained, but the package stability on a wiring substrate may be compromised
Solution Approach 1:
The patent positions auxiliary solder pads asymmetrically at both sides of the electrode solder pads in the first direction, with each auxiliary pad extending longer in the second direction. This asymmetric arrangement distributes thermal stress more effectively while maintaining package stability on the wiring substrate, resolving the contradiction between connection reliability and package stability.
Solution Approach 2:
The patent segments the solder pad structure into two functional types: electrode solder pads for electrical connection and auxiliary solder pads for mechanical support and stress distribution. This segmentation allows each type to be optimized independently, with auxiliary pads positioned to enhance both connection reliability and package stability without interference.
3Reliability
If a ceramic substrate is soldered onto a wiring substrate, then electrical connection is established, but thermal stress due to difference in thermal expansion coefficient may cause cracks in the solder connection portions
Solution Approach 1:
The patent segments the solder connection system into electrode solder pads for electrical function and auxiliary solder pads for mechanical function. The auxiliary pads are strategically positioned and dimensioned to distribute thermal stress away from the electrical connection points, reducing crack formation while maintaining electrical connection reliability.
Solution Approach 2:
The patent applies local quality by giving auxiliary solder pads a longer dimension in the second direction, creating localized stress distribution zones. These zones are positioned at the sides of the electrode pads, providing local reinforcement that mitigates thermal stress concentration and prevents solder joint cracking during thermal cycling.
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 design effectively reduces crack generation in solder connections and enhances mounting accuracy, maintaining reliable electrical connections and improving the overall reliability and mountability of semiconductor devices.
Implementation Method 1
In the case where the size of each of the solder pads disposed at an outer side is reduced, self-alignment force is reduced, which may lead to decrease in mounting accuracy
Data Source
AI summary
A package for a semiconductor device includes: a plate-shaped base member having a substantially rectangular shape in a plan view; a first and second electrode solder pads configured to be electrically connected to a semiconductor element when the semiconductor element is mounted on an upper surface of the base member, the electrode solder pads being disposed at a lower surface side of the base member to face each other in a first direction; and first and second auxiliary solder pads disposed on a lower surface of the base member, the auxiliary solder pads being disposed at both sides of the electrode solder pads such that the first and second electrode solder pads are disposed between the first and second auxiliary solder pads in a plan view.