Screen Printed Adhesive for Thin Die Stacking
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Solution Overview
Problem
Current methods for stacking thin semiconductor dies, particularly those less than 50 μm thick, are costly and inefficient, with limitations in die attach processes such as DAF tape separation and laser cutting, which are not adaptable to small die sizes and are economically restrictive.
Innovation Solution
A method using a screen printing technique to form a B-stageable adhesive layer on the substrate of a MEMS device, allowing direct contact and adhesion with a thin ASIC die, eliminating the need for DAF tape and enabling cost-effective stacking of thin dies on MEMS sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If DAF tape is used for thin die attach, then die attach is enabled, but tape separation and manipulation become difficult and costly
Solution Approach 1:
The patent removes the DAF tape from the process entirely, extracting the problematic intermediate carrier that caused separation and manipulation difficulties. The adhesive is applied directly to the substrate, eliminating the need for tape handling and separation operations.
Solution Approach 2:
The adhesive is pre-applied to the substrate before die attachment, preparing the bonding surface in advance. This preliminary action eliminates the need for subsequent tape application and separation steps, streamlining the overall process.
2Adaptability or versatility
If DAF laser cutting is used for tape separation, then any die size can be processed, but costs increase and throughput decreases
Solution Approach 1:
By removing the DAF tape from the process, the patent eliminates the need for laser cutting operations entirely. The adhesive is applied directly to the substrate without requiring tape separation, thereby increasing throughput while maintaining adaptability to different die sizes through the screen printing process.
3Ease of manufacture
If DAF tape expansion at low temperatures is used, then tape rupture occurs along kerf lines, but the process is not isotropic and breakages are inconsistent
Solution Approach 1:
The patent removes the DAF tape and its associated expansion process entirely. By applying adhesive directly to the substrate using screen printing, the method achieves consistent, isotropic bonding without the unpredictable tape rupture issues that plagued previous approaches.
4Length of moving object
If grinding process is used to reduce die thickness, then thin dies can be achieved, but die attach becomes more challenging
Solution Approach 1:
The patent replaces mechanical tape-based attachment systems with a chemical bonding approach using screen-printed adhesive. This substitution enables reliable attachment of ultra-thin dies (20-50 μm) that cannot be handled by mechanical tape methods, while maintaining manufacturing simplicity.
5Adaptability or versatility
If tape cut-and-place process is used, then large dies can be processed, but additional hardware and reduced tape sizes limit application
Solution Approach 1:
The patent removes the tape-based system and its associated hardware requirements entirely. The screen printing process applied directly to the substrate eliminates the need for specialized tape handling equipment, reducing device complexity while maintaining versatility across different die sizes.
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 provides a reliable and cost-effective method for stacking thin ASIC dies on MEMS sensors, reducing package dimensions and eliminating the need for DAF tape separation, while maintaining electrical integrity and allowing for mass production.
Implementation Method 1
forming, using a screen printing technique, an adhesive layer on the first dies at the first surface coupling regions
Implementation Method 2
utilizing a thermal curing process for strong bonding
Data Source
AI summary
A method of stacking a plurality of first dies to a respective plurality of second dies, each one of the first dies having a surface including a surface coupling region which is substantially flat, each one of the second dies having a respective surface including a respective surface coupling region which is substantially flat, the method comprising the steps of: forming, by means of a screen printing technique, an adhesive layer on the first dies at the respective surface coupling regions; and arranging the surface coupling region of each second die in direct physical contact with a respective adhesive layer of a respective first die among said plurality of first dies.