How to ensure the quality of PCB copy board
2024-01-17
In order to ensure the quality of the function and performance of the PCB copy board, various tests need to be done after the PCB copy board. Otherwise, there is no way to guarantee the quality of the PCB after copying, and it can only be guaranteed after various tests.
First, Electrical test
In the production process of electronic products, the cost of defects varies from stage to stage, and the earlier it is detected, the lower the cost of remediation. For PCB manufacturer, electrical testing is aimed at finding board with defective wiring at an early stage. The test conditions and test methods mainly include the source and format of the test data, the test conditions, such as voltage, current, insulation and connectivity, equipment manufacturing methods and points, test seals, and repair specifications.
In the manufacturing process of PCB, the three stages that must be tested are after the inner layer is etched, after the outer circuit is etched, and the finished product.
Second, the method and equipment of electrical measurement
The methods of electrical testing are: special type, universal type, flying probe type, non-contact electron beam, conductive cloth, capacitive type and brush test, among which there are three most commonly used equipment, namely special testing machine, general testing machine and flying probe testing machine. In order to better understand the functions of each device, the characteristics of each of the three main devices are compared below.
1. Special test
The reason why the test of the special type is a special type is mainly because the fixture used is only suitable for one part number, and the board with different part numbers cannot be tested and cannot be recycled.
2. General-purpose test
The basic principle of the general-purpose test is that the layout of the PCB circuit is designed according to the grid, and the hole position is made of a G10 substrate as the Mask, and only the probe can pass through the Mask for electrical testing at the position of the hole, so the production of the fixture is simple and fast, and the probe can be reused. The number of general-purpose test points is usually more than 10,000 points, and the test density in or is called on-grid test, which belongs to the off-grid test, and its fixture must be specially designed, and the test density of the general-purpose test can reach QFP.
3. Flying probe test
The principle of flying probe testing is very simple, only two probes need to be moved by x, y, and z to test the two endpoints of each line one by one, so there is no need to make expensive fixtures. However, since it is an endpoint test, the speed test is extremely slow.
Third, Technology comparison
The flying probe test is currently the most suitable electrical test equipment for small mass production and samples, but if it is to be used in medium and large production, the test cost will be greatly increased due to the slow measurement speed and expensive equipment, and the general-purpose and special type no matter what level of board is used, as long as the output reaches a certain number, the test cost can reach the standard of economies of scale, and only accounts for about 2~4% of the selling price. However, as the pace of change in electronic products accelerates, the product life cycle of a single circuit design version becomes shorter. E-Beam, CEM or plasma discharge technology, which is still being actively improved, will be a good and feasible solution for electrical testing if the test efficiency can be improved.
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