Chip Resistor Electrode Solder Wettability and Plating Process
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Solution Overview
Problem
Conventional methods for making chip resistors face challenges in forming a reliable solder fillet during surface-mounting due to insufficient solder wettability of materials like Ni—Cu-based alloys, and the process is inefficient with time-consuming steps like metal bonding and machining.
Innovation Solution
A chip resistor design featuring electrodes made of high-solder-wettability materials like Cu, with insulating films and conductor layers formed on a resistor element bar or frame, allowing for efficient plating and division into chip resistors, ensuring proper solder fillet formation during reflow soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alloys (Ni-Cu, Cu-Mn, Ni-Cr) are used for the resistor element, then the material properties are suitable for resistance function, but the solder wettability is insufficient making it difficult to form proper solder fillet
Solution Approach 1:
The patent introduces a solder layer as an intermediary substance between the conventional alloy resistor element and the cream solder. This solder layer has high solder wettability and acts as a mediator that enables proper solder fillet formation on the resistor element surfaces, resolving the wettability issue of the base alloy materials.
Solution Approach 2:
The patent creates a composite structure where a solder layer is formed on the resistor element surface. This composite material approach combines the resistance properties of conventional alloys with the solder wettability of solder materials, achieving both electrical function and reliable soldering.
2Ease of manufacture
If the conventional method of bonding metal plates and machining is used, then the chip resistor can be manufactured, but the process is troublesome and time-consuming reducing manufacturing efficiency
Solution Approach 1:
The patent forms the solder layer on the resistor element before the final cutting and separation into individual chips. This preliminary action allows the solder layer to be formed on the entire surface area at once, and subsequent cutting automatically creates the electrode structures with solder layers, eliminating the need for separate bonding and machining steps.
Solution Approach 2:
The patent extracts and eliminates the troublesome intermediate steps of bonding metal plates and machining from the manufacturing process. By forming the solder layer directly on the resistor element and using cutting to create the final chip structure, the patent removes unnecessary process steps while maintaining product quality.
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 ensures reliable solder fillet formation, enhances bonding strength, and improves manufacturing efficiency by using high-solder-wettability electrodes and efficient plating techniques, allowing for easy determination of proper mounting and effective heat dissipation.
Implementation Method 1
a solder layer 92 is formed on the lower surface of the metal plate 91'
Data Source
AI summary
A chip resistor includes a metal resistor element made in the form of a chip that includes an upper surface, a lower surface, two end surfaces, and two side surfaces. Two electrodes are formed on the resistor element to be spaced from each other in a longitudinal direction of the resistor element. Each of the electrodes is formed directly on the resistor element and extends continuously from the lower surface onto the upper surface via a corresponding one of the two end surfaces.