Wiring Substrate Pad Design for Flat Bonding Surface
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Solution Overview
Problem
Conventional methods for forming projection pads on built-up wiring substrates using wet-etching result in inconsistent depths and non-flat surfaces, leading to unreliable connections with semiconductor chips due to the dome-like shape of the pads.
Innovation Solution
A wiring substrate design featuring a pad forming part with a recessed area and a weir part, where the pad body has a flat surface at its end, increasing the contact area and improving connection reliability by forming a flat surface for bonding with semiconductor chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet-etching method is used to form recess parts in the support body, then the projection pads can be formed, but the depths of the recess parts become inconsistent due to uneven etching amount
Solution Approach 1:
The patent introduces a mold as an intermediary tool to form the recess parts. Instead of directly etching the support body, the mold with its cavity is pressed into the support body to create recess parts. This intermediary approach ensures consistent depth and shape of recess parts, solving the precision problem while maintaining ease of manufacture.
2Ease of manufacture
If the projection pad has a dome-like shape, then it can be formed by conventional methods, but the center part cannot be flat resulting in small contact area with projection electrode
Solution Approach 1:
The patent applies local quality by creating a flat surface specifically at the center of the projection pad where contact with the projection electrode is needed. The mold is designed with a flat bottom surface that contacts the support body, ensuring the center of the projection pad is flat while the edges can still have a dome-like shape. This localized flat area maximizes the contact area with the projection electrode.
3Device complexity
If wet-etching is used to form recess parts, then the process is simple, but the etching amount is uneven leading to inconsistent bonding strength
Solution Approach 1:
The mold serves as an intermediary that transfers the precise cavity geometry to the recess parts. The mold is designed with a flat bottom surface, and when pressed into the support body, it creates recess parts with consistent depth and flat bottom surfaces. This ensures uniform projection pad formation and consistent bonding strength, improving reliability while maintaining process simplicity.
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 enhances connection reliability between the pad and the semiconductor chip by increasing the contact area and preventing inconsistencies in pad height, thus improving bonding strength and reducing the likelihood of inconsistent bonding strengths.
Implementation Method 1
The end part of the pad body includes a flat surface... the area in which the projection pad contacts a corresponding projection electrode of the semiconductor chip is small
Implementation Method 2
an eave part formed on the weir part... enhance cohesiveness with the insulating layer
Data Source
AI summary
A wiring substrate includes an insulating layer that is an outermost layer of the wiring substrate and includes an external exposed surface, a pad forming part formed on a side of the external exposed surface, and a pad that projects from the external exposed surface. The pad forming part includes a recess part recessed from the external exposed surface, and a weir part that projects from the external exposed surface and encompasses the recess part from a plan view. The pad includes a pad body formed within the recess part and the weir part, and an eave part formed on the weir part. The pad body includes an end part that projects to the weir part. The eave part projects in a horizontal direction from the end part of the pad body. The end part of the pad body includes a flat surface.