Ceramic Circuit Board Waviness Control for Thick Lead Terminals
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Solution Overview
Problem
Ceramic circuit boards face challenges in maintaining high thermal cycle test (TCT) characteristics and preventing curvature when used with thick lead frames or terminals, especially at elevated operation temperatures, leading to poor mounting and reduced durability.
Innovation Solution
A ceramic circuit board design with controlled waviness profiles and specific thickness ratios of ceramic substrates and metal plates, combined with active metal joining layers, to enhance thermal conductivity and reduce waviness, allowing for thicker lead terminals without curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a thick lead frame is used to increase ampacity, then current carrying capacity is improved, but the ceramic circuit board curves and mounting quality deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by forming a waviness profile on the ceramic substrate surface before joining the lead frame. This pre-formed waviness counteracts the curvature that would otherwise occur during lead frame attachment, allowing thick lead frames to be used for increased ampacity without causing mounting problems.
Solution Approach 2:
The patent changes the surface geometry parameter of the ceramic substrate by introducing a controlled waviness profile with specific amplitude and wavelength parameters. This parameter change allows the substrate to accommodate thick lead frames while maintaining flatness for proper mounting, resolving the contradiction between ampacity and curvature.
2Reliability
If the ceramic circuit board is subjected to high temperature thermal cycle testing, then operational reliability is improved, but stress on the board increases and TCT characteristics deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming the waviness profile to counteract thermal expansion stresses before they occur during high-temperature operation. This allows the ceramic circuit board to withstand thermal cycle testing at 175°C and above without developing excessive stress that would deteriorate TCT characteristics.
3Weight of moving object
If the ceramic substrate is made thinner to reduce weight, then weight is reduced, but manufacturing precision and durability decrease
Solution Approach 1:
The patent applies local quality by creating a non-uniform surface structure with localized waviness features on the ceramic substrate. This allows the substrate to be made thinner for reduced weight while the localized waviness profile maintains the necessary surface precision for proper lead frame joining and electrical performance.
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 improves TCT characteristics and mountability, ensuring reliable operation at elevated temperatures up to 175°C with reduced waviness and improved heat dissipation, even with thick lead terminals.
Implementation Method 1
a front metal plate 3 and a rear metal plate 4 joined to the ceramic substrate 2
Implementation Method 2
enhance thermal conductivity and reduce waviness, allowing for thicker lead terminals without curvature
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A ceramic circuit board comprises: a ceramic substrate with a 1.0 mm thickness or less including a first surface and a second surface, the first surface including a first area and a second area; a first metal plate joined to the first area; and a second metal plate joined to the second surface. The second area has a first waviness profile along a first side of the first surface, the first waviness profile having one extreme value or less. The second area has a second waviness profile along a second side of the first surface, the second waviness profile has not less than two nor more than three extreme values.