Analysis of PCB electrical test technology

- Aug 28, 2018-

I. electrical test

PCB in the process of production, hard to avoid the short circuit, open circuit and leakage caused by external factors, such as electrical flaws, coupled with the continuous toward high density PCB, fine spacing and the evolution of multi-level, and failure to timely to bad plate screening out, and let it flow into the process, is bound to cause waste more cost, so in addition to the improvement of the process control, improve test technology is also can offer the PCB maker to reduce scrap rate and improve product yield solutions.

In the production process of electronic products, the cost loss caused by defects is different in each stage.The Rule of 10's "is often used to evaluate The cost of a PCB repair when defects are found at different stages of The manufacturing process.For example, if the break in the plate can be detected in real time after the making of the empty plate, it is usually only necessary to patch the line to improve the flaw, or at most lose one empty plate.However, if the plate is not detected to be broken, the plate will be shipped to the downstream assembler to complete the part installation, also through tin and IR remelting. However, the circuit is found to be broken at this time. Generally, the downstream assembler will ask the manufacturer to compensate the cost of parts, heavy industry, inspection, etc.If, more unfortunately, the defective boards are still not found by the assembler's test, and enter the finished products of the whole system, such as computers, mobile phones, automobile parts, etc., the loss discovered by the test will be a hundred, a thousand times, or even higher than the timely detection of the empty boards.Therefore, electrical test for PCB operators, is the early detection of circuit functional defects board.

Downstream vendors will usually require PCB manufacturers to conduct 100% electrical testing and will agree with PCB manufacturers on the specifications of the test conditions and test methods, so the parties will first clearly define the following:

1. Test data source and format

2. Test conditions, such as voltage, current, insulation and connectivity

3. Equipment manufacturing method and selection

4. Test chapter

5. Repair specifications

There are three stages of PCB manufacturing that must be tested:

1. After inner layer etching

2. After etching the outer circuit

3, the finished product

In each stage, there will be 2~3 times of 100% test, and select the defective board for heavy processing.Therefore, the test station is also the best data collection source to analyze the problem points in the process. According to the statistical results, the percentage of circuit breaking, short circuit and other insulation problems can be obtained. After the heavy industry is carried out, the data can be checked again.