Semiconductor Package Lead Frame Rigidity Warping
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Solution Overview
Problem
Semiconductor packages with ball grid array (BGA) connections are prone to warping during solder reflow, leading to poor soldered connections or open circuits due to the susceptibility of the carrier substrate.
Innovation Solution
A semiconductor device with external leads formed integrally from a single sheet of electrically conductive material, where the die support and external leads provide additional rigidity, and the die support can act as a heat sink, reducing the likelihood of substrate warping during solder reflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If BGA connections are used to increase connector density, then the minimum obtainable size of the packaged device is reduced, but the carrier substrate becomes susceptible to warping during solder reflow
Solution Approach 1:
The patent combines the carrier substrate with a rigid support structure (lead frame) to create a hybrid assembly. The lead frame provides mechanical rigidity and dimensional stability during solder reflow, preventing substrate warping while maintaining the compact BGA form factor. This merging allows the device to achieve small size without sacrificing reliability.
Solution Approach 2:
The invention uses a composite structure combining the flexible organic carrier substrate with the rigid inorganic lead frame. This composite construction leverages the electrical connectivity and fine-pitch capabilities of the substrate while the lead frame provides thermal and mechanical stability during the soldering process, resolving the warping issue.
2Ease of operation
If wire bond lead connections are used, then external electrical connection is provided, but the leads are relatively large and increase the minimum obtainable size of the packaged device
Solution Approach 1:
The patent transitions from peripheral lead connections (wire bonds around the edges) to a planar array configuration. The external connectors are arranged in a grid pattern on the surface of the carrier substrate, utilizing two-dimensional space efficiently. This dimensional change allows for high connector density without increasing the device footprint, enabling compact packaging while maintaining ease of external electrical connection.
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 solution reduces the probability of carrier substrate warping and provides additional rigidity to the package, ensuring stable connections and reducing the risk of open circuits during solder reflow.
Implementation Method 1
the die support can act as a heat sink, reducing the likelihood of substrate warping during solder reflow
Data Source
AI summary
A semiconductor device has a die support and external leads formed integrally from a single sheet of electrically conductive material. A die mounting substrate is mounted on the die support, with bonding pads coupled to respective external connection pads on an external connector side of the substrate. A die is attached to the die mounting substrate with die connection pads. Bond wires selectively electrically couple the die connection pads to the external leads and the bonding pads and electrically conductive external protrusions are mounted to the external connection pads. An encapsulant covers the die and bond wires. The external protrusions are located at a central region of a surface mounting side of the package and the external leads project outwardly from locations near the die support towards peripheral edges of the package.