Molding Compound Opening Design for Package Warpage Compensation
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Solution Overview
Problem
In conventional package-on-package (POP) processes, warpage due to differing coefficients of thermal expansion between top and bottom packages can lead to cold joints and joint failures, particularly when the warpage of the top package does not match that of the bottom package.
Innovation Solution
The solution involves evaluating the warpage status of bonded packages and strategically designing the sizes of openings in the molding compound to accommodate solder, with inner openings being larger for negative warpage and smaller for positive warpage, to ensure proper alignment and reduce the likelihood of cold joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional POP process is used with standard uniform openings, then manufacturing simplicity is maintained, but cold joints and joint failures occur due to warpage mismatch
Solution Approach 1:
The patent applies local quality by varying the sizes of openings in the molding compound based on their location. Inner openings (closer to the center of the package) are made larger while outer openings are made smaller. This local differentiation compensates for warpage effects, ensuring adequate solder volume and proper joint formation in regions affected by positive or negative warpage, thereby improving joint reliability without requiring complex process changes.
2Manufacturing precision
If uniform opening sizes are used in molding compound, then manufacturing process is simple, but solder distribution is inadequate under warpage conditions
Solution Approach 1:
The patent implements parameter changes by modifying the geometric parameters of openings in the molding compound. Specifically, the size (diameter or width) of openings is changed based on their radial position from the package center. This parameter variation optimizes solder distribution by providing larger openings in regions where warpage reduces solder volume, while maintaining smaller openings in regions with adequate solder, thereby achieving precise solder placement without complex manufacturing processes.
3Reliability
If top and bottom packages have different warpage characteristics, then package integration is achieved, but cold joints increase due to warpage mismatch
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for warpage effects through non-uniform opening design before the bonding process. By making inner openings larger and outer openings smaller in the molding compound, the design anticipates and counteracts the negative effects of warpage mismatch between top and bottom packages. This preliminary adjustment ensures that solder joints are properly formed despite warpage differences, reducing cold joints and improving bonding reliability without requiring additional alignment operations.
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 effectively reduces the occurrence of cold joints by optimizing the solder distribution and alignment of package components, enhancing the reliability of the bonded package structure.
Implementation Method 1
a polymer region molded over the top surface of the first package component
Data Source
AI summary
A device includes a package component having conductive features on a top surface, and a polymer region molded over the top surface of the first package component. A plurality of openings extends from a top surface of the polymer region into the polymer region, wherein each of the conductive features is exposed through one of the plurality of openings. The plurality of openings includes a first opening having a first horizontal size, and a second opening having a second horizontal size different from the first horizontal size.