Localized Laser Heating for MEMS Die Release
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Solution Overview
Problem
The existing methods for separating MEMS devices from a handle substrate, such as using thermal or UV release adhesives, are time-consuming and can cause damage due to uneven heating and thermal expansion, leading to bottlenecks in high-volume production.
Innovation Solution
A method involving a die picker with a localized heat source, such as a laser, is used to quickly heat the thermal release adhesive on each MEMS device, allowing for rapid release without damaging adjacent devices, and a vacuum is applied to securely lift the devices from the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot air is used to heat the adhesive to release temperature, then the MEMS device can be released from the handle substrate, but the process takes 15-20 seconds per die creating a bottleneck in high volume production
Solution Approach 1:
The patent applies localized heating directly at the interface between the MEMS device and the handle substrate through the handle substrate itself. This concentrates thermal energy precisely where needed (at the adhesive layer) rather than heating a large volume of air, dramatically reducing the time to reach release temperature from 15-20 seconds to a fraction of that time.
Solution Approach 2:
The patent replaces the mechanical convection-based hot air heating system with a thermal conduction-based heating system. Instead of using hot air circulation (mechanical convection), the heat is conducted directly through the handle substrate to the adhesive interface, eliminating the need for air heating and circulation infrastructure.
2Productivity
If UV release adhesive tape is used, then the drying process takes about 30 minutes in an oven which is a rate limiting step
Solution Approach 1:
The patent extracts and eliminates the drying step entirely by using a thermal release adhesive system that does not require pre-drying. The adhesive is designed to release upon heating without needing prior moisture removal, completely removing the 30-minute oven drying step that limits production throughput.
3Productivity
If thermal release adhesive is used with localized heating, then rapid release can be achieved, but uneven heating and thermal expansion may cause damage to adjacent devices
Solution Approach 1:
The patent segments the heating process by applying heat locally at each individual MEMS device location rather than heating the entire wafer or large areas simultaneously. This localized approach ensures that thermal energy is concentrated only where needed (at the adhesive interface of the target device) and does not propagate to adjacent devices, preventing thermal damage while achieving rapid release.
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 required to release each MEMS device to about 1 second, eliminates the need for oven drying, and minimizes damage, enabling higher throughput and yield in MEMS device production while maintaining precise control over heating rates and temperatures.
Implementation Method 1
individually bonded to it via a thermal release adhesive that reduces its adhesion to the MEMS device when heated above a threshold temperature
Implementation Method 2
applying a heat source to at least part of one surface of each of the MEMS devices to heat the MEMS device above the threshold temperature
Implementation Method 3
By applying localized heat to a part of the MEMS device to heat the whole device by conduction
Implementation Method 4
The single MEMS device can then be lifted away with a vacuum actuated 'die picker'
Data Source
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AI summary
A method of removing MEMS devices (2) from a handle substrate (1), where the MEMS devices are individually bonded to it via a thermal release adhesive (3) that reduces its adhesion when heated above a threshold temperature. The method heats the MEMS devices (2) individually with a heat source (10) to conductively heat the thermal release adhesive (11) above the threshold temperature. With the adhesive (11) directly in contact with the back side (5) of the MEMS device (2) no longer bonding it to the glass handle (1), the devices (2) can be individually removed by a die picker (6). This method quickly heats the adhesive to release each die in about 1 second. This is comparable to UV release adhesive and does not require a prior 30 minute drying bake. Furthermore, heating the die by conduction, will in turn conductively heat the adhesive s that only that adhesive which is closely localized to the die is released. The adhesive that bonds the adjacent dies to the glass handle remains unaffected.