Fine-Pitch Joining Pad Geometry to Prevent Solder Bridging
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Solution Overview
Problem
As transistors and integrated circuit (IC) chips shrink in size, the increased proximity of electrical joints leads to a higher likelihood of short circuit connections, increasing production scrap and reducing manufacturing efficiency.
Innovation Solution
The implementation of non-coextensive shapes for solder bumps and electrode pads, with gaps and discontinuous laps, to prevent bridging and ensure electrical connectivity even at fine pitches, using a spacer to manage excess solder material during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the space between electrical joints is reduced to increase computing density, then the packaging can accommodate more connections, but the possibility of short circuit connections between contacts increases
Solution Approach 1:
The electrode pad is designed with an asymmetric shape that is non-coextensive with the solder bump, creating a specific geometric relationship where the pad extends beyond the bump in certain directions. This asymmetric configuration establishes controlled gap regions that prevent short circuits while maintaining electrical connectivity, directly resolving the contradiction between reduced spacing and short circuit prevention
Solution Approach 2:
The electrode pad is designed with non-uniform geometry, having different dimensions in different directions relative to the solder bump. This local variation in pad geometry creates specific gap regions in critical areas while maintaining contact in other areas, allowing the structure to simultaneously achieve fine pitch compatibility and short circuit prevention
2Ease of manufacture
If standard coextensive shapes are used for solder bumps and electrode pads, then alignment is simpler, but excess solder material can cause bridging and short circuits
Solution Approach 1:
The electrode pad is designed with an asymmetric shape that is non-coextensive with the solder bump, creating a specific geometric relationship where the pad extends beyond the bump in certain directions. This asymmetric configuration establishes controlled gap regions that prevent short circuits while maintaining electrical connectivity, directly resolving the contradiction between reduced spacing and short circuit prevention
Solution Approach 2:
The non-coextensive pad design converts the potential harm of excess solder material into a benefit by directing it into controlled gap regions. The geometry is specifically designed to channel excess solder away from critical areas where bridging could occur, transforming what would be a manufacturing defect into a feature that enhances reliability
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 allows for reliable electrical and structural connection at fine pitches, reducing the risk of short circuits and enhancing manufacturing efficiency by managing excess solder distribution.
Implementation Method 1
solder bumps positioned in the holes, respectively... connected to the solder bumps
Implementation Method 2
solder bumps positioned in the holes, respectively... electrode pads extending from the substrate and connected to the solder bumps
Data Source
AI summary
A semiconductor device includes two integrated circuit (IC) chips. The first IC chip includes substrate, a spacer connected to the substrate and including holes, wherein at least one of the holes has a first shape, and solder bumps positioned in the holes, respectively. The second IC chip includes a substrate, electrode pads extending from the substrate and connected to the solder bumps, respectively. At least one of the electrode pads that corresponds to the at least one of the solder bumps has a second shape, and the first shape and the second shape are non-coextensive such that there is at least one gap between the first shape and the second shape when projected on each other.