Ceramic Wiring Substrate With Step Portion Heatsink Brazing
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Solution Overview
Problem
Existing ceramic packaging with metal heatsinks face limitations in mounting size and number of elements due to restricted through-hole openings and thermal shrinkage-induced cracking and peeling at the joining interface.
Innovation Solution
A ceramic substrate with a step portion on its inner wall and a flange on the heatsink, where a stress-relaxing ring is used between the step portion and the flange for brazing, allowing for increased mounting area and reduced stress transmission during thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the heatsink is inserted into a through hole with narrow opening width to ensure structural integrity, then the joining strength is improved, but the mounting area on the heatsink surface is reduced
Solution Approach 1:
The invention introduces a step portion that creates a multi-level structure within the through hole, transforming a single-dimension insertion problem into a multi-dimensional solution. The step portion provides both structural support for joining strength and creates additional space that preserves mounting area on the heatsink surface.
Solution Approach 2:
The through hole is segmented into multiple levels by the step portion, creating distinct functional zones: an upper region for mounting elements and a lower region for structural joining. This segmentation allows the narrow opening to serve dual purposes without compromising either joining strength or mounting area.
2Strength
If the heatsink is brazed directly to the ceramic substrate to ensure strong joining, then the joining strength is improved, but thermal shrinkage stress causes cracking and peeling
Solution Approach 1:
The step portion acts as an intermediary structure between the heatsink flange and the ceramic substrate. During brazing, it provides a gradual transition zone that reduces thermal shrinkage stress concentration, preventing cracking and peeling while maintaining strong joining strength.
Solution Approach 2:
The step portion is designed in advance to cushion and absorb thermal shrinkage stress that occurs during brazing. This pre-configured stress-absorbing structure prevents cracking and peeling before they can occur, ensuring reliability of the joined assembly.
3Manufacturing precision
If the through hole opening width is reduced to ensure precise positioning, then the positioning precision is improved, but the element size and mounting capacity are restricted
Solution Approach 1:
The step portion creates a multi-level structure that separates positioning function (at the narrow opening) from mounting function (at the expanded step region). This allows precise positioning through the narrow opening while providing sufficient mounting area at the step portion for large elements and multiple components.
Solution Approach 2:
The through hole is segmented into a positioning zone (narrow opening) and a mounting zone (expanded step region). This segmentation enables the narrow opening to provide precise positioning while the expanded step portion provides sufficient mounting capacity for multiple and larger elements.
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 configuration allows for larger element sizes, increased mounting capacity, reduced cracking, and enhanced thermal stress management, preventing peeling at the joining interface.
Implementation Method 1
brazing is performed between the step portion and the flange
Implementation Method 2
shrinkage stress occurring in the heatsink due to thermal shrinking after the brazing is transmitted to the adjacent ceramic layer
Data Source
AI summary
A wiring substrate includes: a substrate body made from ceramic, having a front surface and a rear surface, and having a through hole penetrating between the front surface and the rear surface; and a heatsink inserted into the through hole. A step portion protruding in a direction perpendicular to an axial direction of the through hole, is formed over an entire periphery on an inner wall surface of the through hole of the substrate body. A flange opposed to the step portion is provided so as to protrude, over an entire periphery on a side surface of the heatsink. A stress relaxing ring is arranged over an entire periphery between the step portion and a joining surface opposed to the step portion. A brazing material is provided between the ring, and the joining surface and the step portion.