PCB Die Attach Pad Adhesion Strips to Prevent Mold Delamination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mold compound poorly adheres to die attach pad material in electronic packages, leading to delamination and potential electrical connection failures due to differences in thermal expansion coefficients between materials.
Innovation Solution
Incorporating one or more adhesion strips outside the die attach pad on a printed circuit board, which facilitates the adhesion of a mold compound over the die attach pad, thereby preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mold compound is applied over die attach pad, then die attach pad provides electrical connection, but mold compound delaminates from die attach pad due to poor adhesion
Solution Approach 1:
An adhesion strip made of die attach pad material is introduced as an intermediary layer between the mold compound and the original die attach pad. This mediator provides a surface that the mold compound can adhere to, while the adhesion strip itself bonds to the original die attach pad, thus resolving the adhesion incompatibility between mold compound and die attach pad materials
Solution Approach 2:
The solution uses a composite structure consisting of the original die attach pad, the adhesion strip (made of same material as die attach pad), and the mold compound. This composite approach combines materials with compatible adhesion properties to achieve both electrical connection and mechanical bonding
2Adaptability or versatility
If different materials are used for die attach pad and mold compound, then functional requirements are met, but delamination occurs due to different coefficients of thermal expansion
Solution Approach 1:
The adhesion strip is placed locally at the interface between mold compound and die attach pad, specifically where adhesion is needed. This localized application allows different materials to be used in different regions: the die attach pad material where electrical connection is needed, and the adhesion strip material where bonding to mold compound is critical
Solution Approach 2:
The adhesion strip acts as a mediator that accommodates the thermal expansion mismatch between different materials. By being made of the same material as the die attach pad, it provides a thermal expansion buffer that reduces stress concentration at the mold compound interface during temperature cycling
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 adhesion strips effectively prevent delamination of the mold compound from the die attach pad, ensuring reliable electrical connections and maintaining the integrity of the electronic package under varying thermal conditions.
Implementation Method 1
one or more adhesion strips outside the die attach pad to facilitate adhesion of a mold compound over the die attach pad
Implementation Method 2
different materials have different coefficients of thermal expansion (CTE), which can result in the mold compound delaminating from the PCB for certain components that experience large differences in CTE
Data Source
AI summary
A printed circuit board for use in an electronics package has a die attach pad and one or more adhesion strips outside the die attach pad. The adhesion strip(s) facilitate adhesion of a mold compound over the die attach pad and die and inhibits (e.g., prevents) delamination of the mold compound from the die attach pad.