QFN Package Support Structure for Longer PCB Solder Life
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Solution Overview
Problem
The connection life and reliability of solder in quad flat no led packages (QFN packages) used in high-performance small components for in-vehicle applications are compromised due to the downsizing of electrode terminals, leading to reduced heat cycle life.
Innovation Solution
An electronic control device with a printed circuit board and semiconductor package, featuring a semiconductor chip, molding resin, first and second metal terminals, and a resist formed on a third land to support the semiconductor package, ensuring the thickness of the solder connection is maintained, thereby preventing inclination and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electrode terminal is downsized to reduce package size, then the package size is reduced, but the heat cycle life of the solder connection portion is shortened
Solution Approach 1:
The invention divides the terminal structure into two functional parts: first metal terminals for electrical connection and second metal terminals (dummy terminals) for mechanical support. This segmentation allows the electrical terminals to be minimized while separate support terminals maintain solder connection integrity during heat cycles.
Solution Approach 2:
The second metal terminals act as intermediary elements that do not carry electrical current but provide mechanical support to the semiconductor package. These dummy terminals serve as mediators between the package body and the substrate, absorbing thermal stress and preventing solder joint failure.
2Device complexity
If the semiconductor package is mounted without additional support structures, then the device complexity is reduced, but the solder thickness at corner portions is insufficient leading to reduced connection reliability
Solution Approach 1:
The invention merges the electrical connection function and mechanical support function into a single integrated terminal structure. The first and second metal terminals are both part of the semiconductor chip package, eliminating the need for separate support structures on the substrate side.
Solution Approach 2:
The second metal terminals are pre-positioned at the corner portions of the semiconductor package before mounting. This preliminary arrangement ensures that adequate solder thickness is maintained at critical stress points during the soldering process, preventing future connection failures.
3Ease of manufacture
If the semiconductor package is inclined during soldering, then the manufacturing process is simpler, but the solder thickness cannot be secured and connection reliability is reduced
Solution Approach 1:
The second metal terminals at the corner portions act as counterweights or support points that prevent the semiconductor package from tilting during the soldering process. These dummy terminals provide mechanical stability, ensuring the package remains level and uniform solder thickness is achieved across all connection points.
Data Source
AI summary
An object of the present invention is to provide an electronic control device capable of improving the connection life and reliability of solder connecting a printed circuit board and a QFN type semiconductor package. For this purpose, a printed circuit board 106 includes a first land 109 connected to a first metal terminal 104 via a solder 107, a second land 110 connected to a second metal terminal 105 via a solder 108, a third land 112 disposed on the outer peripheral side of a semiconductor package 101 with respect to the first land 109, and a resist 113 formed on the third land 112 so as to be in contact with the lower surface of a molding resin 103.