Printed Wiring Board Magnetic Material Adhesion
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Solution Overview
Problem
Existing printed wiring boards with through-hole conductors penetrating magnetic material portions face issues with adhesion and peeling due to thermal expansion coefficient differences and inadequate bonding between the magnetic materials and conductors, especially during heat cycles.
Innovation Solution
The printed wiring board incorporates magnetic material portions with magnetic particles and resin, where gaps are formed between the particles and the resin, and a first chemical copper plating film is deposited in these gaps to enhance adhesion, with the conductors formed by a combination of chemical and electrolytic copper plating films on the side walls of the through holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-hole conductors are formed on magnetic material portions, then connectivity between conductor layers is achieved, but adhesion and peeling issues occur due to thermal expansion coefficient differences
Solution Approach 1:
A resin layer is introduced as an intermediary material between the magnetic material portion and the through-hole conductor. This resin layer has a thermal expansion coefficient that matches both the magnetic material and the conductor, serving as a buffer that absorbs thermal stress during heat cycles and prevents peeling while maintaining reliable electrical connectivity.
2Adaptability or versatility
If magnetic material portions are formed in openings, then inductor components can be accommodated, but inadequate bonding between magnetic materials and conductors occurs
Solution Approach 1:
The resin layer acts as a bonding intermediary between the magnetic material portion and the through-hole conductor. It provides adequate bonding strength by chemically or physically adhering to both materials, ensuring strong bonding while allowing the magnetic material portions to accommodate inductor components effectively.
3Ease of manufacture
If conventional plating is used on magnetic material, then conductor formation is achieved, but peeling occurs during heat cycles
Solution Approach 1:
The resin layer is positioned between the magnetic material portion and the through-hole conductor to serve as a thermal buffer. During heat cycles, it absorbs differential thermal expansion stresses, preventing peeling at the interface while allowing conventional plating processes to form conductors easily on the magnetic material surface.
Solution Approach 2:
The thermal expansion coefficient parameter of the resin layer is specifically selected to match both the magnetic material and the conductor materials. This parameter matching creates a gradual transition zone that reduces thermal stress concentration, thereby improving thermal stability during heat cycles.
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 significantly increases the adhesive force between the through-hole conductors and the magnetic material portions, preventing peeling and ensuring reliable connectivity over time, even under thermal stress.
Implementation Method 1
a first chemical copper plating film is deposited in these gaps
Data Source
AI summary
A printed wiring board includes an insulating substrate having openings, a first conductor layer formed on a first surface of the insulating substrate, a second conductor layer formed on a second surface of the insulating substrate, magnetic material portions formed in the openings of the insulating substrate and having through holes extending from the first surface to second surface of the insulating substrate, and through-hole conductors formed on side walls of the through holes such that the through-hole conductors connect the first conductor layer and second conductor layer. The magnetic material portions include magnetic particles and resin such that the magnetic particles include particles forming the side walls and that gaps are formed between the particles and the resin, and each of the through-hole conductors includes a chemical copper plating film such that the chemical copper plating film is deposited in the gaps formed between the particles and the resin.