Production Process and Failure Analysis of Chip Resistor

Structure of Chip Resistor

The chip resistor comprises four parts: the substrate, the resistive film layer, the electrode, and the protective medium, and the electrode part is divided into the inner electrode (silver-palladium), transition layer (nickel), external electrodes (mainly tin-strontium).

The substrate of the chip resistor is a high-purity alumina ceramic material, which has exceptionally high mechanical strength and insulation strength, excellent thermal conductivity, and high-temperature resistance; the resistive film layer is mainly ruthenium oxide-based glass glaze paste after high temperatures. Firing makes it; the inner layer electrode is generally silk screen or dipped, and the re-sintered silver layer, the transition layer, and the outer electrode are genotypic of electroplated nickel and tin. The protective layer is an unusually-temperature sintered glass glaze.

Production process and process of chip resistors

Back Electrode Printing→ Firing→Surface Electrode Printing→ Firing→ Resistor Printing→ Firing→Primary Glass Printing→ Firing→Laser Trimming→Secondary Glass Printing→ Mark Printing→ Firing→Primary Cutting→End Sealing→ Firing→Secondary Cutting → Electroplating Electrodes → Test Sorting → Taping and Packaging

Problems in the Application of Chip Resistors

SMD resistors are generally produced by automation on a large scale, and the product consistency is good. The most common problems in incoming materials are not many, and the following problems often occur during use:

1Electrode falls off: If this happens after welding, the reason should be analyzed from two aspects: first, the electrode adhesion strength of the resistor itself is not good, and second, the electrode is burnt due to high temperature during welding, especially during manual welding. situation. This situation is verified by the soldering heat resistance test (260℃*10S, checked under a microscope).

2Substrate fracture: This situation is mainly caused by the resistance being damaged by external mechanical stress. Of course, thermal stress may also cause substrate fracture, but it is rare in practice.

3 Variation of resistance value: Generally, the resistance value becomes more prominent and fails. This situation is mainly caused by long-term overload. Circuits used in chip resistors often have relatively high component density and poor heat dissipation conditions. Working under such harsh conditions for a long time, a power reduction design should be carried out when selecting resistors to prolong the life of chip resistors.

4 Oxidation of the external electrode: This situation will affect the welding effect of the chip resistor and easily cause false welding. Whether the outer electrode is oxidized can be judged from two aspects. One is to observe under a microscope, and the external electrode can be seen to be black; the other is to conduct a solderability test (235°C*3s) to keep the tin on the outer electrode (requires the terminal to be solder coverage area greater than 90%)

Resistor Failure Case Study 1

Case 1: Guangdong XXX Electronics Co., Ltd. A V9636 main panel resistance fracture case

Time: July 10, 2020

Recently in the quality control report of the production line, R407/2.2Ω resistors break on the main panel of A V9636 were found with a defect rate of 0.5% (sometimes as high as 4%). The root cause of the badness here is:

1. The V-groove between the panels of the AV9636 main panel is relatively shallow, and it isn’t easy to separate the boards. The manufacturer used too much force during the board-splitting process, breaking the resistor body

2. For the defective products brought by the engineering personnel, the relevant personnel of Gaohua confirmed that some of the semi-finished PCB boards had not been tested

Our company’s solution to the above problems is as follows:

1) Relevant personnel must inform the PCB manufacturer to change the V-groove, and IQC is responsible for confirming the effect of the change.

2) Please ask the developer to change the PCB board (AV9636-0), R408 to 2.2Ω, and R407 to a copper skin for a direct short circuit.

3) For the semi-finished PCB boards in stock (AV9636-0), after communicating with the outsourced manufacturer, we agree to return the boards that arrived before July 10, 2020, to the factory without affecting the average production of our factory Retest.

4) The outsourced manufacturer will make the corresponding sub-board tooling for the produced PCB board during production, and the outsourced manufacturer will design the tooling;

5) Personnel testing must be arranged when our production line uses the boards that arrived before July 10, 2020.

Resistor Failure Case Study 2

Case 2: Zhejiang XXX Electronic Technology Co., Ltd. VD017K game has no function case

Time: July 5, 2018

the product line produced VD017 K, and about 70% of the games on the machine had no function (sometimes no function). After analysis and testing, it was found that the decoding board R17 (6.8 kΩ /1/16W) deteriorated, resulting in low voltage. This board is a new patch, batch numbers: 2629 and 2630. Now do the following:

1. For further analysis and verification, please use another manufacturer’s 6.8kΩ / 1/16W (material number: 0090002) chip resistor 300PCS.

2. Replace R17 directly when reproducing, measure the resistance value after completion, and ask QE to verify.

3. The supply department should notify the external manufacturer to assist in the investigation of the resistor supplier, suspend the use of resistors from this manufacturer, and at the same time invite the manufacturer to come to take samples and analyze them.

4. Please ask the Type Experiment Center to test and verify all the specifications of the manufacturer’s resistors and take samples of the wrong resistors for analysis.

5. Please ask the relevant department to check the inventory of the resistors of this manufacturer and check whether there are resistors of the exact specification from other manufacturers simultaneously. If not, please immediately ask the supply department to purchase a resistor of the precise specification from other manufacturers.

After re-examination, the main reason for the failure of chip resistors is caused by poor test fixtures. There is a row of thimbles on the decoder board test frame (this row of thimbles is on the game signal output socket of the decoder board), and there is a skew phenomenon. Resistor failed.

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