Semiconductor Pixel Bonding via Curable Polymer Underfill
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Solution Overview
Problem
Existing methods for bonding semiconductor pixel detectors to substrates, such as bump bonding, often result in mechanically weak and fragile connections due to the secondary addition of a dielectric underfill, which is difficult to achieve consistently, especially with complex pixel structures and high-energy radiation applications requiring thicker materials and larger pixel sizes.
Innovation Solution
A method where an intermediate mechanical bonding/dielectric layer is created first, using a curable flowable polymer that is selectively patterned to align with vias in the substrate, allowing for subsequent conductive connections to be made through these vias, thereby enhancing mechanical and dielectric consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bump bonding is used to create conductive connections first, then electrical connection is achieved, but mechanical strength is weak and fragile
Solution Approach 1:
The patent applies preliminary action by creating the mechanical bond with underfill material before creating the conductive connections. The underfill is applied to form a mechanical bond between the pixel detector and substrate, and only after this mechanical bond is established are the conductive connections made through vias. This reverses the conventional sequence and ensures mechanical strength is established first, preventing bond failures.
2Strength
If underfill is applied secondarily to improve mechanical bond, then some mechanical strength is added, but the process is difficult to achieve consistently
Solution Approach 1:
The underfill is applied as a preliminary step before conductive connections are made. By establishing the mechanical bond first with the underfill material, the process ensures consistent mechanical support is available during subsequent conductive connection formation. This preliminary mechanical bonding step makes the overall process more consistent and reliable, especially for complex pixel structures.
3Reliability
If conductive bonds are made small and at low temperature, then electrical connection is achieved, but mechanical weakness increases
Solution Approach 1:
The mechanical bond with underfill is established preliminarily before the small, low-temperature conductive bonds are made. This preliminary mechanical support allows the conductive bonds to be small and low-temperature (suitable for temperature-sensitive materials like cadmium telluride) without compromising overall mechanical strength, since the underfill already provides the mechanical framework.
4Reliability
If pixel size is increased for high energy radiation detection, then radiation detection capability is improved, but underfill flow consistency deteriorates
Solution Approach 1:
The underfill is applied preliminarily to establish mechanical bonding before conductive connections are made in larger pixel structures. This preliminary mechanical bond provides a stable foundation that compensates for the reduced flow consistency issues inherent in larger pixel geometries, ensuring reliable mechanical support across the entire pixel array.
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 improves mechanical strength and consistency of the bond, reducing the likelihood of conductive bond failures under mechanical stress and ensuring reliable electrical connections in high-energy radiation applications.
Implementation Method 1
an intermediate mechanical bonding/dielectric layer is created first, using a curable flowable polymer
Data Source
Figure 1a~1b
Figure 2a~2b
AI summary
A method of bonding a semiconductor structure to a substrate to effect both a mechanical bond and a selectively patterned conductive bond, comprising the steps of mechanically bonding a semiconductor structure to a substrate by means of a bonding layer; providing gaps in the bonding layer generally corresponding to a desired conductive bond pattern; providing vias though the substrate generally positioned at the gaps in the bonding layer; causing electrically conductive material to contact the semiconductor structure exposed through the vias. A device made in accordance with the method is also described.