Stacked Welding Pad Structure for Stronger Solder Ball Bonding
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Solution Overview
Problem
The existing package structures with planar welding pads have poor bonding strength due to inadequate contact area with solder balls, leading to unreliable connections and increased occupied space on the substrate, which hinders miniaturization and performance enhancement.
Innovation Solution
A package structure featuring stacked welding pads with protruded peripheral surfaces on the top layer, allowing for three-dimensional wrapping by solder balls, thereby increasing contact area and bonding strength while reducing the substrate's occupied space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If planar welding pads are used, then the manufacturing process is simple, but the bonding strength with solder balls is poor
Solution Approach 1:
The patent transitions from planar (2D) welding pads to three-dimensional stacked welding pads with protruded peripheral surfaces. This dimensional change allows the top layer welding pad to extend beyond the bottom layer, creating multiple contact surfaces for the solder ball to wrap around, thereby significantly increasing the bonding strength while maintaining manufacturing feasibility through sequential plating processes.
2Area of moving object
If planar welding pads are used, then the structure is simple, but the contact area with solder balls is insufficient
Solution Approach 1:
By stacking welding pads in multiple layers with the top layer protruding beyond the bottom layer, the patent creates a three-dimensional structure that provides multiple contact surfaces (top surface, side surfaces, and bottom surface of the protrusion). This dimensional transformation dramatically increases the total contact area between the welding pad and solder ball compared to conventional planar designs.
3Strength
If larger welding pads are used to improve bonding, then the bonding strength increases, but the occupied space on substrate increases
Solution Approach 1:
The stacked welding pad structure utilizes the vertical dimension (z-axis) to increase bonding area rather than expanding horizontally. The top layer welding pad protrudes upward and outward, providing extensive contact surfaces for the solder ball while the entire structure occupies a compact footprint on the substrate, thus achieving high bonding strength without increasing the occupied space.
Solution Approach 2:
The welding pad structure employs a nested configuration where the top layer welding pad is partially positioned over the bottom layer welding pad. This nesting arrangement allows the protruded portions of the top layer to provide additional bonding surface area while the nested structure maintains a compact overall footprint, reducing the occupied space on the substrate compared to a purely planar expansion.
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 enhances the reliability and strength of solder connections, supports miniaturization, and improves heat dissipation and electrical performance by optimizing the contact area and alignment margins.
Implementation Method 1
at least one solder ball, where the at least one solder ball is welded to the substrate and the chip
Data Source
AI summary
A package structure includes: a substrate, where a plurality of welding pads are disposed on a surface of the substrate, each of the plurality of welding pads includes a bottom layer welding pad and a top layer welding pad which are stacked onto one another, and at least two of peripheral surfaces of the top layer welding pad are protruded relative to peripheral surfaces of the bottom layer welding pad; a chip located on the substrate and spaced apart from the substrate; and a plurality of solder balls, where the plurality of solder balls are welded to the substrate and the chip, and the plurality of solder balls wrap the top layer welding pads.