Polymeric Buffer for Wafer Edge Stress and Light Transmission
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Solution Overview
Problem
Conventional wafer-level packaging technologies face issues such as stress-induced damage to thinner wafer portions during molding, obstruction of light transmission and visual inspection, poor heat dissipation, and chipping during dicing, which can lead to shadows and additional inspection requirements.
Innovation Solution
The use of a polymeric member disposed in grooves along scribe lines before molding, acting as a buffer to protect against stress, allowing light transmission, enhancing heat dissipation, and reducing chipping, while also being flexible and softer than the substrate to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molding material is compressed against a thinned wafer, then wafer-level packaging is completed, but stress damages thinner portions of the wafer
Solution Approach 1:
A cushioning layer is formed on the back surface of the wafer before the molding process. This layer acts as a buffer to absorb compression stresses during molding, preventing damage to thinner portions of the wafer while still allowing the molding material to be compressed against the wafer to complete wafer-level packaging.
Solution Approach 2:
The cushioning layer serves as an intermediary between the molding material and the wafer back surface. It mediates the stress transmission, distributing the compression force evenly and preventing direct stress concentration on vulnerable thinner portions of the wafer during the molding process.
2Illumination intensity
If conventional molding material is used, then packaging is achieved, but light transmission is blocked
Solution Approach 1:
The patent changes the optical parameter of the molding material by selecting materials with specific light transmission properties. The molding material is chosen to transmit light at wavelengths matching the laser marking operation, enabling alignment marks to be utilized during laser marking while still providing packaging integrity.
Solution Approach 2:
The patent employs composite material selection where the molding material combines packaging functionality with optical transparency. The material is selected from epoxy resin, polyimide, or polyester that specifically transmits light in the wavelength range of 400-1100nm, creating a composite functional material that satisfies both packaging and light transmission requirements.
3Temperature
If conventional molding material is used, then packaging is achieved, but heat dissipation is poor
Solution Approach 1:
The patent changes the thermal parameter of the molding material by selecting materials with superior heat dissipation properties. The molding material is specifically selected to have a thermal conductivity of 0.3-1.5 W/m·K, which significantly improves heat dissipation capability while maintaining packaging integrity and structural stability.
4Productivity
If wafer is diced through, then individual units are separated, but chipping occurs
Solution Approach 1:
The cushioning layer is formed on the back surface of the wafer before the dicing process. During dicing, this layer absorbs mechanical stresses and prevents chipping at the edges and corners of individual wafer units, ensuring high-quality edge finish while maintaining efficient mass production capability.
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
The polymeric member effectively reduces edge cracking, enables clear light transmission for alignment and inspection, and improves heat dissipation, thereby protecting critical areas and simplifying the inspection process during wafer dicing.
Implementation Method 1
allowing light transmission
Implementation Method 2
improves heat dissipation
Data Source
AI summary
A semiconductor device includes a substrate comprising a front surface, side surfaces, a back surface, and a recessed edge between the side surfaces and either the front surface or the back surface, the front surface comprising an active region, the active region comprising at least one contact pad, a polymeric member disposed and contacted with the recessed edge of the substrate, a mold disposed over the front surface of the substrate and the polymeric member, and an interface between the mold and the polymeric member.