Partial Gel Curing to Stop Capillary Rise in Pressure Sensors
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Solution Overview
Problem
Semiconductor pressure sensor devices face mechanical and environmental damage due to capillary action during packaging, which exposes bond wires and dies to the ambient atmosphere, and increasing the gel material to prevent this can increase costs and affect sensor functionality.
Innovation Solution
A method involving partial curing of the pressure-sensitive gel material before capillary action completes, using overhead and underneath curing devices to balance surface tension and cohesive forces, preventing exposure of sensitive components while maintaining cost and size efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gel material is dispensed and allowed to cure completely before separation, then the bond wires and dies are protected from exposure to ambient atmosphere, but the production time increases due to waiting for complete curing
Solution Approach 1:
The gel material is dispensed and allowed to partially cure while the sensor devices are still mounted on the shared substrate, before the complete curing process is finished. This preliminary action of partial curing while maintaining the array configuration reduces the total production time while still providing protection against capillary action during the critical separation process.
2Reliability
If more gel material is dispensed to prevent capillary action, then the bond wires and dies are better protected, but the cost and size of the device increase
Solution Approach 1:
Instead of dispensing excessive amounts of gel material to ensure complete protection, the invention uses a controlled partial curing process that achieves sufficient protection with the standard amount of gel material. The partial curing state is maintained just long enough to prevent capillary action during separation, then complete curing is finished, avoiding both material waste and device size increase.
3Productivity
If the gel material is kept in a delayed state before curing, then it can be dispensed onto multiple sensor devices, but capillary action exposes the bond wires and dies to ambient atmosphere
Solution Approach 1:
The gel material is dispensed onto multiple sensor devices in the array configuration, and a preliminary partial curing process is initiated before the dispensing operation is completely finished. This allows the production system to maintain high throughput by continuing to dispense gel onto subsequent devices while the previously dispensed gel begins to cure, preventing capillary action exposure during the entire process.
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
Prevents exposure of bond wires and dies to the ambient atmosphere, ensuring reliable operation and accurate pressure sensing without significant increases in cost or size, while allowing for precise control of gel material distribution.
Implementation Method 1
capillary action shapes the upper surface 122 of the gel material 114. The capillary action occurs because the adhesion of the gel material 114 to the inner walls of the molding compound 102 is stronger than the cohesive forces between the molecules of the gel material 114.
Implementation Method 2
using overhead and underneath curing devices to balance surface tension and cohesive forces
Data Source
AI summary
A method for applying a pressure-sensitive gel material during assembly of an array of pre-singulated packaged semiconductor devices. In the method, pressure-sensitive gel material is dispensed onto a first semiconductor device of the array, where the first semiconductor device is disposed within a first cavity. A first curing process is performed to partially cure the pressure-sensitive gel material in the first cavity. Pressure-sensitive gel material is then dispensed onto another semiconductor device of the array, where the other semiconductor device is disposed within another cavity. The first curing process is initiated before the dispensing of the pressure-sensitive gel material inside of the other cavity is completed and initially cures pressure-sensitive gel material for fewer than all of the pre-singulated packaged semiconductor devices of the array.