Printed Wiring Board Cavity Recesses for Thermal Adhesion
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Solution Overview
Problem
Existing methods for forming electrical connections in printed wiring boards, such as vias and through-holes, face challenges in effectively removing resinous residues and ensuring robust adhesion between conductors and insulating layers, particularly with materials like polyphenylene ether resin and polyphenylene oxide resin, leading to potential cracking and peeling under temperature variations.
Innovation Solution
A method involving plasma treatment followed by ultrasonication is used to form recesses in the inner wall surfaces of cavities, enhancing adhesion by creating first and second recesses that increase the contact area between the conductor and insulating layer, thereby improving thermal reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If chemical treatment or plasma treatment is used to remove smear in the cavity, then the resinous residue is removed, but the adhesion between conductor and insulating layer is insufficient leading to cracking and peeling under temperature variations
Solution Approach 1:
The cavity inner wall surface is subjected to plasma treatment and ultrasonication before conductor formation to create recesses in advance. This preliminary surface preparation removes smear and creates an uneven surface structure that enhances subsequent conductor adhesion, preventing cracking and peeling under temperature variations.
Solution Approach 2:
Ultrasonication is applied to the cavity inner wall surface to mechanically remove smear and create recesses through vibrational energy. The ultrasonic waves generate cavitation and mechanical stress that effectively clean the surface and form an uneven structure, improving conductor adhesion without chemical treatments.
2Object-generated harmful factors
If the inner wall surface of the cavity is smooth after smear removal, then the surface is clean, but the contact area between conductor and insulating layer is reduced leading to poor adhesion
Solution Approach 1:
The cavity inner wall surface is subjected to plasma treatment and ultrasonication before conductor formation to create recesses in advance. This preliminary surface preparation removes smear and creates an uneven surface structure that enhances subsequent conductor adhesion, preventing cracking and peeling under temperature variations.
Solution Approach 2:
The ultrasonication process creates curved and uneven surface features (recesses) on the cavity inner wall instead of a smooth surface. These curved surface structures increase the effective contact area between the conductor and insulating layer, improving adhesion through mechanical interlocking.
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 method effectively removes resinous residues and enhances adhesion, preventing cracking and peeling of conductors, ensuring high thermal reliability and maintaining radio-frequency signal transmission characteristics.
Implementation Method 1
a smear produced in the insulating layer in the cavity forming step is removed by plasma treatment
Implementation Method 2
a second recess is formed in an inner wall surface of a first recess in an inner wall surface of the cavity by ultrasonication after the plasma treatment step in such a manner that the particles contained in the insulating layer and exposed to view at the inner wall surface of the cavity come off the insulating layer
Data Source
AI summary
A printed wiring board includes an insulating layer and a conductor part. The insulating layer includes a cavity perpendicular to a first surface of the insulating layer. The conductor part includes a connection conductor fitted in at least part of the cavity. The cavity includes a first recess provided in an inner wall surface of the cavity. The connection conductor is partially fitted in the first recess. The first recess includes a second recess provided in an inner wall surface of the first recess. The connection conductor is partially fitted in the second recess.