Stacked Chip Upper Pad Recesses for Fine-Pitch Thermo-Compression
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Solution Overview
Problem
Current semiconductor packages face challenges in preventing short-circuits and non-wet issues during thermo-compression processes, especially when using fine-pitched solder balls and small-pitched upper pads, which can lead to contact defects and reduced yield.
Innovation Solution
The semiconductor package design includes upper pads with recesses and extension apertures on a first semiconductor chip, where the recess depth is less than the pad thickness, and the apertures extend horizontally, allowing connection terminals to be securely positioned and preventing excessive spreading during thermo-compression, thus avoiding short-circuits and non-wet issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fine-pitched solder balls and small-pitched upper pads are used, then the productivity and integration density are improved, but short-circuits and non-wet issues occur during thermo-compression processes
Solution Approach 1:
The patent applies local quality by creating recesses in specific regions of the upper pad structure. The recesses are strategically positioned to provide localized support where needed, allowing the pad structure to maintain both fine pitch dimensions and bonding reliability. This localized structural modification enables fine-pitched solder balls to be properly supported without causing short-circuits or non-wet issues during thermo-compression.
Solution Approach 2:
The recesses are formed in advance during the chip fabrication process, before the thermo-compression bonding occurs. This preliminary structural preparation ensures that when fine-pitched solder balls are later compressed onto the upper pads, the recesses are already in place to prevent excessive spreading and maintain proper bonding geometry, thereby preventing short-circuits and non-wet issues.
2Ease of manufacture
If upper pads without recesses are used, then the manufacturing process is simpler, but connection terminals spread excessively during thermo-compression causing short-circuits
Solution Approach 1:
Instead of making all pads complex, the patent applies recesses only to specific upper pad regions where terminal support is critical. This selective approach maintains relative manufacturing simplicity while providing the necessary structural control to prevent terminal spreading and ensure precise positioning during thermo-compression bonding.
Solution Approach 2:
The recesses are formed during the chip fabrication process before bonding, preparing the pad structure in advance to control terminal positioning. This preliminary action ensures that when thermo-compression occurs, the terminals are constrained within the recess boundaries, preventing excessive spreading and maintaining manufacturing precision without requiring complex real-time control during bonding.
3Reliability
If recess depth is equal to or greater than pad thickness, then connection terminal support is improved, but void formation occurs between solder balls and upper pads
Solution Approach 1:
The patent carefully controls the recess depth parameter, setting it to be less than the pad thickness. This parameter optimization ensures that the recess provides sufficient support for connection terminals while leaving enough pad material above the recess to maintain uniform contact during bonding. This prevents void formation between solder balls and upper pads while still providing the necessary terminal support reliability.
Data Source
AI summary
A semiconductor package including a substrate; a first semiconductor chip on the substrate; a second semiconductor chip on the first semiconductor chip; and at least one connection terminal between the first semiconductor chip and the second semiconductor chip, wherein the first semiconductor chip includes a first semiconductor chip body; and at least one upper pad on a top surface of the first semiconductor chip body and in contact with the at least one connection terminal, the at least one upper pad includes a recess that is downwardly recessed from a top surface thereof, and a depth of the recess is less than a thickness of the at least one upper pad.