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PC How to check and confirm the open circuit position of defective soft FPC

Author:Luwis zeng Date:5/26/2018 10:06:12 AM
 When we have problems with FPC (flexible circuit board) open/closed circuit, the easiest way is to check the problem of the breakage of the wireless circuit under the microscope, because FPC is usually a single-layer board, so it's a terrific three-layer board. Most of the lines can be seen through optical instruments. However, working bears have encountered many cases. Under the microscope, the problem of line breakage cannot be detected. However, the place where the golden finger is measured directly by a three-meter meter It can be measured as an open circuit, or it can be a good or bad situation when contacted.

Actually, there is no need to be fussy about the result because the FPC is called “soft board” because it is flexible and can be bent. This is also the advantage and disadvantage of the FPC. The disadvantage is that it can be bent because it may cause copper foil. The copper trace is broken.

Although the copper foil is soft, repeated repeated bending or reciprocating movements or impacts are still very likely to cause the fracture. If the naked eye can see the fracture is easy to solve, because only observe the location of the fracture, In general, the cause of the fracture can be known, and further measures can be taken.

It is more difficult to measure the open/closed circuit from the very end of the golden finger, but there is no way to find the position where the copper foil breaks. If the position cannot be found, it is difficult to confirm what caused the breakage.

Working bears usually use the segment elimination method to analyze the problem of breakage of the soft flat cable when the naked eye or the microscope is difficult to detect.

1. First, use the microscope to observe the problem of the line, first find the location of suspicious fracture marks.

2. If the microscope can't find any suspiciously broken locations, you can also divide the circuit into small segments.

3. At the ends of the line where the line may be broken, or in the segmented position, carefully cut the cover film of the soft plate with a blade, preferably with a new utility knife or a carving knife. The blade was placed on the outer protective film to move left and right to scrape the cover film and expose it to the underlying copper foil line. In this way, you can use three meters to measure the line. Then, the location where the fracture may occur is gradually eliminated in order, and finally, the exact fracture location of the copper foil line can be found.

4. If you are concerned that this method may break the copper foil, you can also try to cut the place next to the copper foil where there is no copper foil, and try to tear open the cover film to achieve the same purpose. .

(This method requires great care and dexterity. The working bear believes that capable engineers should all be able to do it.)

5. Once you have found the exact location of the copper foil break, if you still cannot see the break, try bending the soft board in this position under a microscope so that you can highlight and amplify the opening of the broken copper foil.

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