Curved Through-Hole Conductor for Printed Wiring Board Thermal Stress
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Solution Overview
Problem
Conventional printed wiring boards face issues with thermal stress and short-circuiting due to differences in thermal expansion coefficients between insulation layers and through-hole conductors, leading to warping and cracking, especially when exposed to heat cycles.
Innovation Solution
A method for manufacturing a printed wiring board involving a core substrate with a metal layer and insulation layers, where a first penetrating hole is formed in an arc shape and filled with resin, and a second penetrating hole is created with specific opening portions aligned using a laser, allowing for a through-hole conductor that connects conductors on opposite surfaces, reducing thermal stress by distributing it through the resin-filled first penetrating hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If through-hole conductors are formed in straight shape with resin filling, then manufacturing is simplified, but thermal stress causes warping and cracking due to thermal expansion coefficient differences
Solution Approach 1:
The penetrating hole is formed with a curved configuration instead of a straight shape. The hole curves from the first opening toward the second opening, allowing the through-hole conductor to follow a curved path. This curvature enables the conductor to accommodate thermal expansion and contraction stresses, preventing warping and cracking while maintaining manufacturing feasibility through laser drilling or electro-discharge machining.
2Area of stationary object
If signal and power-source conductors are placed close together, then space utilization is improved, but noise interference increases
Solution Approach 1:
The curved configuration of the penetrating hole creates localized spatial separation between signal and power-source conductors in critical regions. By curving the hole path, the design optimizes the distance between conductors at specific locations where noise interference would be most problematic, while maintaining compact overall board layout. This local optimization reduces electromagnetic interference without sacrificing space utilization.
3Device complexity
If through-hole conductors are formed with standard configuration, then manufacturing process is simple, but short-circuiting occurs due to thermal warping
Solution Approach 1:
The curved penetrating hole configuration prevents thermal warping that leads to short-circuiting. The curvature allows the through-hole conductor to flex and accommodate dimensional changes in the insulation layers during thermal cycles, maintaining proper spacing from other conductors. This can be implemented using laser drilling or electro-discharge machining, which can create curved holes without significantly increasing manufacturing complexity.
4Reliability
If resin is filled in penetrating hole, then thermal stress is reduced, but manufacturing precision is required for alignment
Solution Approach 1:
The curved penetrating hole is formed by sequential drilling or electro-discharge machining from first and second opening portions. The curvature provides a gradual transition that is more tolerant to alignment variations compared to a straight hole requiring perfect alignment through the entire thickness. Resin filling is then performed to complete the through-hole conductor, with the curved path already established to provide thermal stress resistance.
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 minimizes thermal stress and warping, reduces the likelihood of short-circuiting, and enhances the reliability of through-hole conductors by maintaining a greater distance between signal and power-source conductors, thereby reducing noise interference and improving heat dissipation.
Implementation Method 1
forming a second penetrating hole having a first opening portion aligned with the first penetrating hole on a first-surface side of the core substrate and a second opening portion aligned with the first penetrating hole on a second-surface side of the core substrate
Data Source
AI summary
A method for manufacturing a printed wiring board includes preparing a core substrate having a metal layer having a first penetrating hole and insulation layers formed on the metal layer such that the metal layer is interposed between the insulation layers, forming in the core substrate a second penetrating hole having a first opening portion aligned with the first penetrating hole on a first-surface side of the core substrate and a second opening portion aligned with the first penetrating hole on a second-surface side of the core substrate, forming a first conductor on a first surface of the core substrate, forming a second conductor on a second surface of the core substrate on the opposite side of the first surface of the core substrate, and filling a conductive material in the second penetrating hole such that a through-hole conductor connecting the first conductor and the second conductor is formed.