Socket Housing Material Match for Thermal Expansion
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Solution Overview
Problem
The difference in thermal expansion coefficients between liquid crystal polymer (LCP) resin sockets and circuit boards can cause soldering issues, such as cracking or warping, and existing connectors with gaps allow solder to flow inadequately during soldering, leading to insufficient electrical connections.
Innovation Solution
A socket with a housing made of the same material as the circuit board, featuring passageways with conductive inner walls and conductive pads, where contacts are press-fitted and soldered to prevent solder flow into the passageways, ensuring reliable electrical connections and thermal expansion matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LCP resin is used for the socket housing, then the housing can be manufactured with good processability, but the difference in thermal expansion coefficient causes soldering portion cracking or socket warping
Solution Approach 1:
The patent changes the material parameter of the housing from LCP resin to the same material as the circuit board (e.g., FR-4). This parameter change in thermal expansion coefficient matches the circuit board, preventing warping and cracking during thermal cycles, while still maintaining manufacturability through standard PCB fabrication processes.
Solution Approach 2:
The patent employs a composite structure where the housing is made of the same material as the circuit board, creating material homogeneity. This eliminates the thermal expansion mismatch between dissimilar materials (LCP resin and circuit board), resolving the reliability issue while preserving manufacturing capabilities.
2Ease of operation
If press-fit holes are used without proper sealing, then contacts can be easily inserted, but solder flows into the passageways causing insufficient soldering to the circuit board
Solution Approach 1:
The patent introduces a solder resist layer as an intermediary substance coating the inner wall of the passageway. This layer acts as a barrier that prevents solder from flowing into the passageway during the soldering process, while still allowing the contact to be press-fitted through the hole. The solder resist mediates between the need for easy insertion and the need for precise soldering.
Solution Approach 2:
The patent extracts the harmful function of the passageway (allowing solder flow) by coating it with solder resist. The passageway retains its structural function for contact insertion but loses the harmful property of allowing solder infiltration, thus separating the useful function from the harmful function.
3Adaptability or versatility
If the housing material differs from the circuit board material, then manufacturing flexibility is improved, but thermal expansion mismatch causes warping and cracking
Solution Approach 1:
The patent applies homogeneity by making the housing material the same as the circuit board material. This creates uniform thermal expansion characteristics throughout the assembled structure, eliminating differential thermal stress that causes warping and cracking. The homogeneity principle sacrifices material selection flexibility for structural stability.
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 prevents solder flow into passageways, ensuring reliable soldering and electrical continuity while matching thermal expansion with the circuit board, reducing the risk of warping and improving connection quality.
Implementation Method 1
Each passageway extends through the housing and has an inner wall surface plated with a conductive material
Implementation Method 2
Multiple solder balls corresponding to the contacts are disposed on a second surface of the housing
Implementation Method 3
The LCP resin, however, has a coefficient of thermal expansion different from that of the circuit board
Data Source
AI summary
A socket comprises a housing made of an insulating board and a plurality of contacts arranged on a first surface of the housing. The housing has a plurality of passageways. Each passageway extends through the housing and has an inner wall surface plated with a conductive material. The housing also has a conductive pad formed on a second surface of the housing so as to correspond to one of the passageways. The conductive pad is electrically continuous with the conductive material of the inner wall surface of the passageway and extends from the passageway. The housing also has a solder ball attached to the conductive pad. Each of the contacts corresponds to one of the plurality of passageways and is electrically connected to both the conductive material of the inner wall surface of the passageway and a contact pad of an electronic component.