Chip Resistor Flat Surface Design Prevents Tombstone Mounting Failures
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Solution Overview
Problem
Conventional chip resistors experience mounting failures due to height differences caused by bulging end portions of the resistor, leading to potential tombstone phenomena when the upper face is used as a mounting surface.
Innovation Solution
The length of the resistor portion on the first upper-face electrodes is made longer than the portion between them, ensuring that end portions do not protrude upward and preventing inclination or slope on the second upper-face electrodes, thus maintaining a flat surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the resistor is formed between the first upper-face electrodes with end portions at the electrode end portions, then the resistor structure is simple and easy to manufacture, but the end portions bulge upward causing height differences and mounting failures
Solution Approach 1:
The resistor is divided into two distinct portions: a first portion formed between the first upper-face electrodes and a second portion formed on the first upper-face electrodes. This segmentation allows different regions of the resistor to serve different functions - the first portion provides the primary resistive path while the second portion acts as a buffer to prevent bulging at the electrode ends, thereby resolving the contradiction between manufacturing simplicity and surface flatness.
Solution Approach 2:
The invention extends the resistor structure in the planar dimension by adding the second portion that protrudes toward the second upper-face electrodes. This dimensional extension prevents the vertical bulging problem by distributing the resistor material more evenly across the upper face, maintaining flatness while preserving ease of manufacture through standard thick film deposition processes.
2Productivity
If the end portions of the resistor overlap with the second upper-face electrodes, then the resistor can be fully utilized, but the second upper-face electrodes protrude upward creating an inclination or slope
Solution Approach 1:
The resistor is designed with non-uniform distribution: the first portion has higher concentration between the electrodes for optimal resistance, while the second portion extends toward the second electrodes with reduced height to prevent protrusion. This local quality variation allows full utilization of the resistor material without creating the harmful inclination or slope on the upper face.
3Reliability
If the protective film covers the entire upper face including protruding end portions, then complete coverage is achieved, but the protruding portions cause tombstone phenomenon during mounting
Solution Approach 1:
The second portion of the resistor is designed in advance to counteract the bulging effect before it occurs. By extending this portion toward the second upper-face electrodes, the invention preemptively prevents the formation of protruding end portions that would otherwise cause the protective film to uplift and create tombstone phenomenon during mounting, thus ensuring both protective coverage and mounting reliability.
Data Source
AI summary
An object of the present disclosure is to provide a chip resistor that reduces a possibility of occurrence of a mounting failure. The chip resistor of the present disclosure includes: insulating substrate; a pair of first upper-face electrodes that is provided at both end portions of an upper face of insulating substrate; and resistor that is provided on the upper face of insulating substrate and is formed between the pair of first upper-face electrodes. The chip resistor also includes: a pair of second upper-face electrodes that is formed on upper faces of the pair of first upper-face electrodes and is connected to resistor; and protective film that is provided to cover exposed resistor and part of the pair of second upper-face electrodes.