Socket Solder Ball Layout for Thermal Stress Relief
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Solution Overview
Problem
Large-scale electronic components face stress and potential cracking due to thermal expansion coefficient differences between socket housings made of LCP resin and circuit boards, leading to issues with solder joint reliability and assembly complexity.
Innovation Solution
A socket design featuring a flat-plate-shaped housing with frames, spring elements, and non-electrically connected second solder balls that distribute stress and enhance soldering strength, reducing the need for additional spacers and simplifying assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spacers are positioned at multiple places on the housing surface to suppress stress from vertical load, then stress on solder joint portions is reduced, but the number of components increases leading to increased assembly time and cost
Solution Approach 1:
The patent merges the stress distribution function with the existing solder balls by introducing non-electrically connected second solder balls. These second solder balls are positioned at specific locations to distribute stress on the housing, eliminating the need for separate spacer components while maintaining solder joint reliability.
Solution Approach 2:
The second solder balls serve multiple functions: they provide mechanical support to distribute stress on the housing, maintain proper spacing between the socket and circuit board, and contribute to overall structural stability. This multi-functionality replaces what would otherwise require dedicated spacer components.
2Ease of manufacture
If LCP resin is used for the socket housing, then the socket can be manufactured with standard materials, but the difference in thermal expansion coefficient between the housing and circuit board causes solder joint cracking and socket warping
Solution Approach 1:
The patent addresses the thermal expansion mismatch by carefully selecting the housing material with thermal expansion properties matched to the circuit board. This parameter change in material selection prevents solder joint cracking and socket warping that would occur with standard LCP resin, while still maintaining ease of manufacture through conventional materials.
3Reliability
If the housing material is changed to match the circuit board material to suppress thermal expansion differences, then solder joint reliability improves, but the materials are not perfectly identical and slight differences remain causing stress at corner solder joints
Solution Approach 1:
The second solder balls act as intermediary elements that distribute and mitigate thermal stress across the housing, particularly at critical locations like corner solder joints. They provide mechanical support that compensates for the remaining thermal expansion differences between the housing and circuit board materials.
Solution Approach 2:
The strategically positioned second solder balls provide beforehand cushioning by distributing stress before it can concentrate at vulnerable solder joints. This preventive stress distribution protects against thermal shock and expansion-related failures during temperature cycling.
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 design effectively suppresses stress on solder joints, enhances soldering strength, and maintains consistent contact pressures across the socket surface, thereby improving the reliability and assembly efficiency of large-scale electronic components.
Implementation Method 1
a plurality of second solder balls disposed on the lower surface of the flat-plate-shaped housing... The second solder balls are not electrically connected to the contacts... effectively suppresses stress on solder joints
Implementation Method 2
spring elements... maintains consistent contact pressures across the socket surface
Implementation Method 3
The first solder balls electrically connect to each of the contacts and electrically connect to the circuit board... enhances soldering strength
Data Source
AI summary
A socket includes a flat-plate-shaped housing, a plurality of contacts supported by the flat-plate-shaped housing, a frame attached to the flat-plate-shaped housing and extending along the flat-plate-shaped housing, a plurality of first solder balls disposed on a lower surface of the flat-plate-shaped housing and facing a circuit board, and a plurality of second solder balls disposed on the lower surface of the flat-plate-shaped housing. The frame defines, in an in-plane direction of the flat-plate-shaped housing, a position of an electronic component having a lower surface including a plurality of pads configured to contact the contacts upon the electronic component being mounted. The first solder balls electrically connect to each of the contacts and electrically connect to the circuit board. The second solder balls are not electrically connected to the contacts.