Multi-chip Package Assembly Using Selectively Weakened Adhesive Layers
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Solution Overview
Problem
The increasing miniaturization and decreasing cost of individual chips in multi-chip packages lead to higher assembly costs due to the need for one-at-a-time bonding, which is inefficient and time-consuming.
Innovation Solution
A method involving the use of support wafers with selectively weakened adhesive layers to bond multiple chips simultaneously, allowing for the transfer and debonding of chips from one wafer to another, ultimately bonding them to a target substrate in a cost-effective and time-efficient manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one-at-a-time bonding is used, then assembly cost is reduced when chip cost is high, but productivity decreases and assembly time increases
Solution Approach 1:
The adhesive layer is segmented into regions of different adhesive strengths, allowing selective debonding of specific chips from the first support wafer while retaining others. This enables batch transfer of multiple chips to the target substrate in a single operation, dramatically improving productivity while maintaining cost-effectiveness.
Solution Approach 2:
Different regions of the adhesive layer are given different adhesive strengths through selective application or curing. Some regions have strong adhesive strength to retain chips that need to stay on the first support wafer, while other regions have weak adhesive strength to allow easy debonding and transfer of specific chips. This local differentiation enables efficient batch processing.
2Productivity
If multiple chips are bonded simultaneously, then productivity increases, but adhesive control complexity increases
Solution Approach 1:
The adhesive strength parameter is varied across different regions of the adhesive layer. By changing the adhesive strength parameter locally through selective application methods or differential curing conditions, the system achieves complex transfer patterns without requiring complex adhesive layer structures. This allows simultaneous bonding of multiple chips with different retention requirements.
Solution Approach 2:
The first support wafer acts as an intermediary carrier that temporarily holds multiple chips during the transfer process. The adhesive layer on this intermediary wafer is designed with varying strengths to enable selective release. This intermediary approach simplifies the overall process by decoupling the bonding and transfer operations.
3Manufacturing precision
If selective debonding is implemented, then chip transfer precision improves, but process complexity increases
Solution Approach 1:
The adhesive weakening process applies local quality by targeting specific regions of the adhesive layer for degradation. Through selective application of weakening agents or localized energy input (such as UV exposure or chemical treatment), only the adhesive regions corresponding to chips intended for transfer are weakened, while other regions maintain full adhesive strength. This ensures precise chip transfer to the correct locations on the target substrate.
Solution Approach 2:
The adhesive weakening is performed as a preliminary action before the actual chip transfer. By pre-weakening the adhesive in specific regions, the system prepares the chips for controlled release at the optimal moment. This preliminary weakening ensures that when transfer is needed, the chips can be easily and accurately placed on the target substrate without requiring excessive force or complex manipulation.
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 approach significantly reduces the time and effort required for bonding multiple chips, lowering the overall assembly cost and improving the efficiency of multi-chip package production.
Implementation Method 1
An adhesive layer is formed directly on the glass wafer substrate. A plurality of chips are bonded to the glass wafer substrate by the ultraviolet-sensitive adhesive layer.
Data Source
AI summary
Methods of bonding chips to a substrate and transfer wafers used for such bonding include bonding chips to a first support wafer by a first adhesive layer. The chips are bonded to a second support wafer by a second adhesive layer. Regions of the first adhesive layer are selectively weakened to decrease an adhesive strength in weakened regions. The weakened regions correspond to a subset of chips. The second support wafer is separated from the first wafer, such that the subset of chips in the weakened regions debond from the first support wafer. The subset of chips are bonded to a target substrate.