Card Edge Connector Metallization for Low Contact Resistance
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Solution Overview
Problem
In-vehicle electronic modules face challenges in maintaining long-term electrical conduction reliability and cost-effectiveness under harsh environments, particularly in card edge connectors, due to issues like increased resistance from intermetallic compound growth, surface oxidation, and high manufacturing costs associated with noble metal plating.
Innovation Solution
The use of a card edge connector configuration with a Sn-based solder layer containing Ag and a Cu alloy core, combined with a multi-layer metallization structure featuring Ag, Pd, and Pt, where the outermost layer has a thickness of 1 μm or more and the underlying layer has a hardness of 100 Hv or more, to prevent intermetallic compound exposure and maintain low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If noble metal plating (Ni/Au) is used on connector terminals, then contact resistance is reduced and electrical conduction reliability is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies different plating materials to different regions of the connector terminal. The contact portion (outermost layer) is plated with noble metals (Ni/Au) to ensure low contact resistance and high reliability, while the underlying layer uses base metal (Cu) to reduce manufacturing cost. This local differentiation of material quality resolves the contradiction between reliability and cost.
Solution Approach 2:
The connector terminal employs a composite plating structure with multiple layers: a noble metal layer (Ni/Au) on the contact surface and a base metal layer (Cu) underneath. This composite material approach allows the terminal to exhibit both the low contact resistance of noble metals and the cost-effectiveness of base metals, simultaneously achieving reliability and ease of manufacture.
2Ease of manufacture
If the board connection terminal uses thin plating to reduce cost, then manufacturing cost decreases, but intermetallic compound growth increases contact resistance over time
Solution Approach 1:
The patent applies a sufficiently thick noble metal plating layer (Ni/Au) on the board connection terminal before assembly, creating a protective barrier that prevents Cu-Sn intermetallic compound growth during service. This preliminary protective action ensures long-term contact resistance stability while maintaining cost-effectiveness through optimized plating thickness.
Solution Approach 2:
The patent uses a cost-effective base metal (Cu) as the underlying layer of the board connection terminal, which is protected by the noble metal plating. The base metal serves as a sacrificial layer that prevents intermetallic compound exposure, providing long-term reliability at lower cost.
3Reliability
If card edge connector uses spring mechanism for contact pressure, then connection reliability is improved, but insertion force increases
Solution Approach 1:
The patent employs a spring mechanism in the card edge connector that provides dynamic contact pressure. The spring automatically adjusts to maintain optimal contact force between the board terminal and connector terminal, ensuring reliable electrical connection while minimizing insertion force through elastic deformation.
Solution Approach 2:
The patent optimizes the spring constant and pre-load force of the spring mechanism to achieve the desired balance between connection reliability and insertion force. By carefully selecting spring parameters, the connector maintains sufficient contact pressure for reliable connection while keeping insertion force within acceptable limits.
Data Source
AI summary
There is a problem that an oxide film or high resistance abrasion powder is formed at the contact interface due to micro sliding abrasion in a high temperature environment or temperature cycle to increase the contact resistance at the contact portion of a non-noble metal connection terminal. Provided is an in-vehicle electronic module, a connector, and a connection structure thereof, which have the same connection reliability as noble metals even when exposed to a harsh environment and can reduce cost of members.The in-vehicle electronic module includes a circuit board on which an electronic component is mounted, and a protection member accommodating the circuit board and protecting the circuit board from a surrounding environment and has a structure where a surface layer at an end portion of the circuit board is made of an 1 Ag-containing Sn-based solder having average thickness of 4 μm or more, and a surface material of a connection terminal of one card edge connector has a two layer structure of a soft noble metal layer of Ag, Pd, Pt, or the like/a reaction layer of a hard noble metal and Sn or an Ni layer.