Wiring Substrate Metal Post Concave Surface Underfill Adhesion
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Solution Overview
Problem
The existing wiring substrates face issues with thermal shrinkage of underfill resin leading to gaps between copper posts and resin, resulting in reduced adhesive force and insulation performance due to differing linear thermal expansion coefficients, which affects the reliability of electronic component devices.
Innovation Solution
A wiring substrate design featuring a metal post with a concave surface and a recessed seed layer, increasing contact area with underfill resin and preventing resin deviation through a protruding connection metal layer and eroded seed layer, enhancing adhesive force and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper post is used on the wiring substrate, then good electrical connection is achieved, but gaps are generated between the copper post and underfill resin due to thermal shrinkage
Solution Approach 1:
The metal plated layer is formed with a concave side surface instead of a flat surface. This curved geometry increases the contact area between the metal post and underfill resin, allowing the resin to better conform to the post surface during thermal shrinkage, thereby preventing gap formation and maintaining adhesive force
Solution Approach 2:
The connection metal layer is formed with a protrusion that extends beyond the metal post surface. This localized structural modification creates an overlapping region where the underfill resin can be mechanically interlocked, providing enhanced local adhesion and preventing resin deviation at the critical interface between metal post and resin
2Reliability
If underfill resin is filled between semiconductor chip and wiring substrate, then insulation and mechanical support are provided, but thermal shrinkage causes resin deviation and gap formation
Solution Approach 1:
The connection metal layer protrusion creates a localized mechanical interlock structure. The underfill resin fills the space between the protrusion and the metal post, forming an overlapping region that mechanically constrains the resin and prevents it from deviating during thermal shrinkage, thereby maintaining the insulation structure
Solution Approach 2:
The concave side surface of the metal plated layer provides a curved geometry that allows the underfill resin to conform better during thermal shrinkage. This curvature accommodates the resin's dimensional changes without causing deviation or gap formation, maintaining the integrity of the insulation structure
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 design significantly increases the adhesive force between the metal post and underfill resin, preventing gaps and ensuring reliable insulation performance even under thermal stress, thus improving the reliability of electronic component devices.
Implementation Method 1
forming, on the seed layer in the first opening and the second opening, a metal plated layer and a connection metal layer in corresponding order by an electrolytic plating
Implementation Method 2
etching side surfaces of the metal plated layer and the seed layer by a first wet etching, thereby forming a side surface of the metal plated layer as a concave surface recessed inward from a lower end of the connection metal layer
Data Source
AI summary
A wiring substrate include a pad, an insulation layer having an opening arranged on the pad, a metal post including a seed layer and a metal plated layer, the seed layer arranged on the pad and an upper surface of the insulation layer, the metal plated layer arranged on the seed layer, and a connection metal layer formed on the metal plated layer. A side surface of the metal plated layer has a concave surface recessed inward from a lower end of the connection metal layer. A side surface of the seed layer is recessed inward from a lower end of the metal plated layer.