4 inspection methods for medical PCB open and short circuits

Four inspection methods for open and short circuits of medical PCB:

1. Open the medical PCB file, light up the short-circuited network, and see where the lines are closest and easiest to connect together, especially the short-circuit problem inside the IC.
2. Before manual soldering, check the medical PCB board, and use a multimeter to check whether there is a short circuit problem in the key parts. During the soldering process, do not throw the soldering iron at will to avoid solder throwing onto the solder legs of the chip, and all soldered medical PCB chips need to be tested again with a multimeter to ensure that there is no short circuit problem between the power supply and the ground.
3. When soldering surface-mount capacitors of small-size medical circuit boards, pay attention to the power filter capacitors (103 or 104), as too many of them can easily cause a short circuit between the power supply and the ground.
4. If the short circuit problem is found, you can take a PCB board with a short circuit problem for blind wire, so as to gradually eliminate each part of the template.

PCB test point setting specification

The layout of the PCB test points is as important as the layout of the traces and other components. With the precision design of electronic products getting higher and higher, and the size of products becoming more and more lightweight, when designing PCB circuit boards, in addition to the circuit layout giving engineers a headache, the reasonable setting of PCB test points is also a very brain-burning thing. For circuit board proofing factories, the reasonable layout of PCB test points can not only improve manufacturing efficiency but also reduce the cost of PCB fixtures.

Although the treatment surface can be customized on both sides, it is best to put the points to be tested on one side as the focus of the test;

Implement the priority of measurement points (I..Test points/II..Foot parts/III..Through-hole holes);

The moment between the measured point and the pre-drilled hole is better than 2.54mm;

The measured point should be at least 2.54mm away from the nearby components.

The measured points should be evenly distributed on the PCB circuit board, and it is not recommended to over-arrange the local test;

The diameter of the measuring point shall not be less than 0.7mm;

In addition to the test points, the board also needs to be designed with positioning holes, and there are at most two positioning holes on each PCS circuit board, and the holes cannot be stained with tin;

How does the PCB look at the number of test points

Before learning how to calculate the number of PCB test points, let’s have a general understanding of what is a PCB test point. For circuit board manufacturers, the factors in estimating the PCB price also include the number of test points, and some manufacturers standard at 30,000 test points per square meter, more than the number of additional on the base price. The charging standard for the number of test points of each company is inconsistent, so how do circuit board manufacturers quickly calculate the number of PCB test points?

1. Calculated according to NET points: each NET is a PCB trace, and each endpoint needs to be pinned, and there are as many NET points as there are.
2. There are as many test points as there are probes on the test rack according to the data. Normal is: the number of pads on the top surface + the number of pads on the bottom surface + the number of drilled holes * 2, if the number of vias is too much, it is necessary to consider whether some can be removed without affecting the function operation when designing PCB data, otherwise the number of vias is too much, and the cost will increase.
3. Use the PCB drawing software, open the file and close all the circuit layers, pad layers, text and other layers (except the hole layer), and select all the displayed holes to get the final number of PCB test points. In order to judge whether the components on the PCB circuit board meet the specifications and solderability, it is necessary to make an accurate judgment by testing the PCB points. The number of PCB test points mainly depends on whether you are testing PCB or PCBA. If it is a PCB, a NET, is a PCB trace, the end point has to go down the needle If it is a PCBA test fixture, the number of points is a NET (PCB trace) a needle, how many NET means how many test points.

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