Multilayer PCB With Low-Expansion Substrate To Reduce Thermal Stress
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Solution Overview
Problem
Existing multilayer printed wiring boards face challenges in thermal expansion mismatch between semiconductor elements and substrates, leading to thermal stress and potential cracking, especially when using high-temperature solder materials, and they often require complex reflow procedures that can reduce wiring reliability.
Innovation Solution
A multilayer printed wiring board design incorporating a low-thermal-expansion substrate with a core base material and through-hole conductors, where the low-thermal-expansion substrate is accommodated within the core base material's penetrating portion, filled with a filler, and connected via a via conductor, reducing thermal stress and simplifying the reflow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional substrate is used for mounting semiconductor elements, then the substrate can be easily manufactured, but thermal expansion mismatch causes thermal stress and potential cracking
Solution Approach 1:
The low-thermal-expansion substrate is nested within the core base material, forming a composite structure where the low-thermal-expansion substrate is positioned in a penetrating portion of the core base material. This nesting approach allows the beneficial low-thermal-expansion properties to be integrated into the overall substrate structure without completely replacing the conventional substrate architecture.
Solution Approach 2:
The invention creates a composite substrate structure combining core base material with a low-thermal-expansion substrate. This composite approach leverages the complementary properties of different materials: the core base material provides structural support while the low-thermal-expansion substrate minimizes thermal stress, thereby improving cracking resistance without excessive complexity.
2Strength
If high-temperature solder materials are used for mounting semiconductor elements, then stronger bonding is achieved, but thermal stress increases causing cracking
Solution Approach 1:
The invention changes the thermal expansion parameter of the substrate by incorporating low-thermal-expansion material. This parameter change allows the substrate to better match the thermal expansion characteristics of the semiconductor element and high-temperature solder, reducing thermal stress while maintaining the ability to use strong high-temperature solder bonds.
Solution Approach 2:
The invention directly addresses thermal expansion mismatch by using a low-thermal-expansion substrate that better matches the thermal expansion coefficients of the semiconductor element and solder materials. This reduces differential thermal expansion during temperature cycles, preventing cracking even when high-temperature solder is used for strong bonding.
3Reliability
If complex reflow procedures are used for mounting semiconductor elements, then reliable electrical connection is achieved, but the process time increases and wiring reliability may be reduced
Solution Approach 1:
The low-thermal-expansion substrate is installed beforehand to prevent thermal stress and cracking issues before the reflow process occurs. This preliminary measure addresses potential reliability problems in advance, allowing for simpler and faster reflow procedures without compromising connection reliability or wiring integrity.
4Reliability
If a low-thermal-expansion substrate is used to minimize thermal stress, then cracking resistance improves, but the substrate structure becomes more complex
Solution Approach 1:
The low-thermal-expansion substrate is nested within the core base material in a penetrating portion, creating an integrated composite structure. This nesting approach incorporates the low-thermal-expansion functionality without requiring a complete redesign of the substrate architecture, thereby limiting the increase in structural complexity.
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 design minimizes thermal stress-induced cracking, enhances connection reliability, and reduces the complexity of reflow procedures, thereby improving the overall reliability and productivity of the multilayer printed wiring boards.
Implementation Method 1
a low-thermal-expansion substrate accommodated inside the penetrating portion of the core base material and having a first surface for mounting a semiconductor element
Implementation Method 2
The wiring layer has a via conductor connecting the first through-hole conductor and the conductive layer
Implementation Method 3
a filler filled in a gap between the low-thermal-expansion substrate and an inner wall of the core base material
Data Source
AI summary
A multilayer printed wiring board includes a core base material having a penetrating portion, a low-thermal-expansion substrate accommodated inside the penetrating portion of the core base material and having a first surface for mounting a semiconductor element and a second surface on the opposite side of the first surface, a first through-hole conductor provided inside the low-thermal-expansion substrate and provided for electrical connection between the first surface and the second surface of the low-thermal-expansion substrate, a filler filled in a gap between the low-thermal-expansion substrate and an inner wall of the core base material, and a wiring layer formed on at least one of the first surface and the second surface of the low-thermal-expansion substrate and having a resin insulation layer and a conductive layer. The wiring layer has a via conductor connecting the first through-hole conductor and the conductive layer.