How to guarantee PCB copy board quality

In order to ensure the quality of PCB copy board function and performance, various tests should be done after PCB copy board. Otherwise, the quality of PCB copied board can not be guaranteed, only after various tests can be guaranteed.

First, electrical test

In the production process of electronic products, the cost loss caused by defects has different degrees in each stage, and the earlier the discovery, the lower the cost of remediation. Electrical testing for PCB operators, for early detection of circuit defects of the board. Test conditions and methods mainly include test data sources and formats, test conditions, such as voltage, current, insulation and connectivity, equipment manufacturing methods and selection points, test chapter, repair specifications.

In the manufacturing process of PCB, the three stages that must be tested are the inner layer after etching, the outer line after etching, and the finished product.

Two, the method and equipment of electric measurement

Electrical testing methods include: special type, general type, flying needle type, non-contact electron beam, conductive cloth, capacitance and brush test, among which the most commonly used equipment are three kinds of special testing machine, general testing machine and flying needle test machine. To better understand the functions of each device, the following compares the features of the three main devices.

1. Dedicated testing

The reason why the special type of test is special type is mainly because the fixture used is only suitable for one material number, different material number of the board can not be tested, and can not be recycled.

2. General test

The basic principle of general test is that the layout of PCB circuit is designed according to the grid, and the hole position is made of a G10 substrate as a Mask. Only at the hole position can the probe be electrically measured through the Mask. Therefore, the fabrication of fixture is simple and fast, and the probe can be reused. The number of general test points is usually more than 10,000 points, and the test density in or is called on-grid test, which belongs to off-grid test, and its fixture must be specially designed. Generally, the test density of general test can reach QFP.

3. Flying needle test

The principle of flying needle testing is simple. Only two probes are required to move x, y, and z to test the two ends of each line one by one. Therefore, there is no need to make additional expensive fixtures. However, since it is an endpoint test, the measurement speed is extremely slow.

Three, technical comparison

At present, flying needle test is the most suitable electrical testing equipment for small production and sample, but if it is used in medium and large production, the testing cost will be greatly increased due to the slow measurement speed and the high cost of equipment. However, no matter what level of board is used for general use and special type, as long as the output reaches a certain number, the testing cost can reach the standard of scale economy. It accounts for only two to four percent of the selling price. But as the speed of change in electronic products accelerates, the life cycle of products with a single circuit design version becomes shorter. E-Beam, CEM, or plasma discharge technologies, which are currently being actively improved, are good and feasible solutions for electrical performance testing if they can be improved in test efficiency.

The basic problem and inspection method of air conditioning circuit board

How much do you know about air conditioning circuit board failure? Since air conditioning maintenance is generally some complex, it also requires a certain amount of technology and experience. If it is a friend with strong hands-on ability, it is recommended to look at the relevant maintenance knowledge. Today, Xiaobian mainly introduces several methods of fault maintenance of air conditioning circuit board, hoping to help you understand.

Air conditioning circuit board fault maintenance:

1, air conditioning circuit board reset circuit repair method:

Reset voltage is the voltage delayed rise, which can be observed by the DC voltage file of the multimeter. If the observation is not clear, it can also be detected by oscilloscope. When detecting with the oscilloscope, a baseline can be jitter and then become high, which is the startup process of reset voltage. If no baseline jitter is seen, the reset circuit is faulty.

2, air conditioning circuit board crystal vibration circuit maintenance method:

Power on and start, normally use a multimeter to measure the two-pin voltage of quartz crystal oscillator is +2.2V or so. If the value is less than 1.5V, the circuit stops vibration. It can also be removed by removing the quartz crystal oscillator tube and discriminating with the ohm gear of the multimeter. The outstanding quartz crystal oscillator tube should be open circuit with the multimeter. If a short circuit is found, the crystal is damaged. On the open circuit fault (broken line or crack), with a multimeter is unable to distinguish, then can be viewed by alternative method.

3, air conditioning circuit board power circuit maintenance method:

Air conditioning circuit board power circuit characteristics are generally intact fuse and a boot on the fuse. On the former fault, use the multimeter to communicate whether the primary and secondary transformer has 220V and 10-13V voltage, if so, and then use the multimeter DC gear 7812 and 7805 whether there is +9-12V and +5V voltage, so as to distinguish the fault location. The latter, there is a short circuit circuit, the use of multimeter ohm stop resistance value detection, in order to identify the short-circuit position of the circuit. Can also choose the segmentation method to see, such as through the disconnect transformer primary winding, energizing test machine, if also burning fuse, burning fuse because there is a short circuit in the varistor or porcelain capacitor, otherwise, because there is a short circuit in the transformer or rectifier tube.

Air conditioning circuit board replacement

1. Prepare the same control circuit board used by the original air conditioner;

2, the plug line on the original circuit board, the joint of this kind of mark, remember the original position, and then remove it;

3, then according to the mark and position, the plug line on the circuit board, the joint inserted in the corresponding position on the new board can be!

4, of course, if it is convenient to remove a line from the old board, install a line to the new board, and then fixed that is also very good!

5, if it is a different board that the replacement is a little trouble, according to the new and old board corresponding control function to refit!