Semiconductor Package Electrode Layout for Solder Alignment Control
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Solution Overview
Problem
Semiconductor packages with SON or QFN structures face issues of positional misalignment and orientation errors due to stress differences with printed circuit boards, leading to unreliable solder joints and potential electrical defects, especially in devices requiring high measurement accuracy.
Innovation Solution
The semiconductor device incorporates position/orientation control electrodes and lands arranged symmetrically to create balanced surface tension vectors during soldering, ensuring accurate mounting and reliable solder joints by offsetting centers and using symmetrical layouts to cancel out forces, thus maintaining the semiconductor package's position and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume of solder is increased to release stress and improve joint reliability, then the reliability of solder joints is improved, but the semiconductor package may move significantly causing shift in position and orientation
Solution Approach 1:
The electrodes are divided into two functional groups: signal electrodes for electrical connection and position/orientation control electrodes for mechanical alignment. This segmentation allows the solder volume to be optimized for stress relief without compromising positioning accuracy, as the position control electrodes with smaller solder volumes prevent excessive package movement.
Solution Approach 2:
Different electrodes are assigned different local qualities: signal electrodes use larger solder volumes for reliable stress-resistant joints, while position/orientation control electrodes use smaller solder volumes to minimize movement. This local differentiation resolves the contradiction between joint reliability and positioning precision.
2Manufacturing precision
If self-alignment is used to correct positional misalignment, then position-misalignment between electrodes and lands is eliminated, but errors in mount position and orientation remain
Solution Approach 1:
The position/orientation control electrodes are intentionally designed with asymmetric offset positions relative to their corresponding lands. This asymmetric arrangement creates unbalanced surface tension vectors during soldering that actively counteract stress-induced package deformation, thereby maintaining both alignment and mount position/orientation accuracy.
3Reliability
If stress relief is prioritized by increasing solder volume, then joint reliability is improved, but position and orientation control becomes insufficient
Solution Approach 1:
The electrode system is segmented into signal electrodes optimized for stress relief with larger solder volumes and position/orientation control electrodes optimized for precision with smaller solder volumes. This segmentation enables simultaneous achievement of high joint reliability and precise position/orientation control.
Solution Approach 2:
Different local qualities are applied to different electrode regions: signal electrodes have larger solder volumes for stress distribution, while position control electrodes have smaller volumes for precision. This local quality differentiation allows both reliability and precision requirements to be met simultaneously.
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 ensures precise mounting and enhances the reliability of solder joints, minimizing misalignment and orientation errors, thereby improving the accuracy of sensors like acceleration or angular velocity sensors in electronic devices.
Implementation Method 1
A phenomenon is known in which the position-misalignment of the electrodes of the semiconductor package with the lands on the printed circuit board may be corrected by the surface tension of solder melted upon joint of the electrodes to the lands to move the semiconductor package toward the locations of the lands.
Implementation Method 2
Each of the position/orientation control electrodes is arranged in a planar view thereof to overlap a respective one of the position/orientation control lands and has a center thereof offset from a center of the one of the position/orientation control lands which is joined to the position/orientation control electrode through the solder.
Data Source
AI summary
A semiconductor device includes a semiconductor package equipped with a plurality of electrodes and a mount member which is equipped with a plurality of lands and on which the semiconductor package is mounted. The semiconductor package has the electrodes joined to the lands through solders. One of the electrodes is designed as a position/orientation control electrode for the semiconductor package. One of the lands is designed as a position/orientation control land for the semiconductor package. The position/orientation control land is arranged inside the position/orientation control electrode in a planar view thereof and includes a plurality of first extensions which extend in different radial directions about the center of the semiconductor package. The position/orientation control electrode includes a plurality of second extensions which extend along the first extensions. Each of the first extension has an outer portion which is located outside an outer line of a facing one of the second extensions. The outer portions are arranged to be symmetrical with respect to the center of the semiconductor package.