PCB Die Attach Pad Adhesion Boundary Against Mold Delamination
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Solution Overview
Problem
Mold compound delamination from die attach pads on printed circuit boards due to poor adhesion and mismatched thermal expansion coefficients, leading to broken electrical connections.
Innovation Solution
Incorporation of adhesion strips outside the die attach pad to facilitate adhesion of mold compound and prevent delamination, using exposed metal or etched surfaces to enhance bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mold compound is applied over die attach pad, then electrical connection is established, but mold compound delaminates from die attach pad due to poor adhesion
Solution Approach 1:
An adhesion strip made of dielectric material is introduced as an intermediary layer between the mold compound and the die attach pad. This mediator provides a surface that bonds well with both materials, preventing delamination while maintaining electrical connectivity through the die attach pad.
Solution Approach 2:
The adhesion strip uses a composite structure combining dielectric material with specific surface properties. The dielectric material provides electrical insulation while its surface characteristics enable strong bonding with both the mold compound and the underlying die attach pad, creating a multi-functional composite solution.
2Reliability
If mold compound is applied over die attach pad, then circuit device is enclosed and protected, but mold compound delaminates due to mismatched thermal expansion coefficients
Solution Approach 1:
The adhesion strip acts as a thermal buffer between the mold compound and die attach pad. Its dielectric material properties provide thermal expansion compatibility, absorbing differential expansion stresses that would otherwise cause delamination during temperature cycling.
Solution Approach 2:
The adhesion strip modifies the thermal expansion parameter profile at the interface between mold compound and die attach pad. By introducing a material with intermediate thermal expansion characteristics, the abrupt mismatch between dissimilar materials is softened, reducing delamination risk under thermal stress.
3Reliability
If adhesion strip is added outside die attach pad, then adhesion is improved, but device complexity increases
Solution Approach 1:
The adhesion solution is segmented and applied only where needed - specifically at the periphery of the die attach pad where delamination is most likely to occur. This localized approach provides effective adhesion enhancement without adding complexity to the entire device structure.
Solution Approach 2:
The adhesion strip is positioned locally at the critical interface region between mold compound and die attach pad. This localized placement addresses the specific delamination problem at the periphery without requiring global structural modifications, thereby minimizing added complexity.
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 mold compound delamination, ensuring stable electrical connections and improved adhesion by matching thermal expansion coefficients.
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
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.