Wiring substrate and its manufacturing method
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Solution Overview
Problem
Existing wiring substrates for semiconductor mounting face issues with peeling of the insulating solder resist layer from the electrode pad, caused by etchant penetration, thermal loads, and external stresses during manufacturing and long-term use.
Innovation Solution
A wiring substrate design that includes an etching barrier layer between the metal pad and the insulating layer, surrounding the lower end of the opening section and extending outward, to enhance adhesion and prevent peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface etching of the electrode pad is performed to form an undercut part, then the pad structure is enhanced for mounting, but the etchant penetrates between the electrode pad and solder resist layer causing peeling
Solution Approach 1:
An etching barrier layer is introduced as an intermediary between the electrode pad and the solder resist layer. This barrier layer prevents the etchant from penetrating into the interface between the pad and solder resist, thereby avoiding peeling while still allowing the undercut structure to be formed for enhanced pad strength and mounting capability.
2Device complexity
If the solder resist layer is formed directly on the electrode pad, then the manufacturing process is simple, but the solder resist layer peels from the pad due to thermal loads and external stresses
Solution Approach 1:
The etching barrier layer serves as a mediator between the electrode pad and the solder resist layer, providing a stable interface that resists thermal loads and external stresses. This intermediate layer prevents direct contact between the solder resist and the undercut portions of the pad, eliminating the peeling issue while maintaining manufacturing feasibility.
3Area of stationary object
If the opening section in the solder resist layer is made larger to expose more pad surface, then the mounting area is increased, but the undercut part becomes deeper allowing more etchant penetration
Solution Approach 1:
The etching barrier layer acts as a protective intermediary that lines the undercut portion and extends to the pad surface. Even when the opening section is enlarged to increase the mounting area, the barrier layer prevents etchant from penetrating deep into the undercut, thereby allowing larger opening sections without compromising adhesion.
Data Source
AI summary
A wiring substrate having, on a surface, a mounting pad for mounting a semiconductor device comprises a metal pad, an insulating layer, and a metal layer. A pad area of the mounting pad is defined by an opening section formed in the insulating layer. The wiring substrate further comprises an etching barrier layer provided between an upper surface of the metal pad and the insulating layer. The etching barrier layer is provided to surround a lower end of the opening section and extends outward from the lower end of the opening section to the outer periphery.