Solder Columns Reinforce Thin Dies During Transfer Molding
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Solution Overview
Problem
Conventional semiconductor die packages face mechanical stress issues during transfer molding, leading to cracking and increased costs due to the inability of thin dies to withstand the stresses generated by the molding process, especially in smaller form factor packages.
Innovation Solution
The implementation of solder columns applied to a substrate to provide structural support to the leadframe-based semiconductor packages, which are then surface mounted and encapsulated, allowing the solder columns to counteract the forces exerted by the molding compound during the encapsulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If wafer backgrind is used to thin die to reduce form factor, then package size is reduced, but die strength decreases making them unable to withstand molding stresses
Solution Approach 1:
Solder columns are introduced as intermediary support structures between the substrate and the thin semiconductor die. These solder columns act as mechanical mediators that bear the molding stress, preventing it from being transmitted directly to the fragile thin die. The solder columns are positioned to contact the bottom surface of the die, providing localized reinforcement exactly where needed during the encapsulation process.
Solution Approach 2:
The solder columns are pre-positioned and pre-heated to a molten state before the die is mounted and before the molding process begins. This preliminary preparation ensures that the support structure is in place and ready to immediately counteract molding stresses when the encapsulation process starts, preventing stress concentration on the thin die during the critical molding phase.
2Volume of moving object
If thin die are used to achieve smaller form factor packages, then portability is improved, but reliability during molding process deteriorates due to cracking
Solution Approach 1:
Solder columns serve as intermediary support structures that decouple the molding stress from the thin die. By positioning the solder columns to contact the bottom surface of the die, they create a mechanical buffer zone that protects the die from direct stress transmission during encapsulation, thereby maintaining reliability despite the use of thin die for small form factor applications.
Solution Approach 2:
The solder columns are prepared in advance and positioned beneath the die before the molding process. When molten, they provide a cushioning effect that absorbs and distributes the molding forces, preventing stress concentration that would otherwise cause cracking in thin die. This beforehand preparation ensures protection is already in place before the harmful molding stresses are applied.
3Reliability
If transfer molding process is used for encapsulation, then package protection is improved, but mechanical stress on thin die increases causing cracking
Solution Approach 1:
The solder columns function as intermediary stress-distributing elements between the molding compound and the thin die. During transfer molding, the solder columns contact the die bottom surface and provide a compliant interface that distributes the molding pressure over a larger area, reducing peak stress concentrations that would cause cracking while still allowing complete encapsulation protection.
Solution Approach 2:
The solder columns undergo a parameter change from solid to molten state during the molding process. When molten, they provide fluid-like compliance that allows them to conform to and support the die under molding pressure. After cooling, they solidify into rigid support structures. This phase change enables them to adapt their mechanical properties to different stages of the molding process, protecting the die during high-stress encapsulation.
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 solder columns significantly reduce mechanical stresses within the semiconductor package, preventing cracking and ensuring the integrity of the package during the encapsulation process, thereby reducing the number of defective packages and associated costs.
Implementation Method 1
the solder columns provide structural support to the leadframe-based package mounted to the substrate on top of the solder columns... the solder columns provide structural support to counteract the forces exerted on the leadframe-based semiconductor package by the molding compound during the encapsulation process
Data Source
AI summary
An integrated circuit, and a semiconductor die package formed therefrom, are disclosed including solder columns for adding structural support to the package during the fabrication process.