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  • PCB flying probe test operation skills

    This article will share techniques such as alignment, fixing, and warping board testing in flying probe test operations for reference only.

    1. Counterpoint

    The first thing to talk about is the choice of counterpoints. Generally, only two diagonal holes should be picked as counterpoints. ?) Ignore the IC. The advantage of this is that there are fewer alignment points, and less time is spent on alignment. Generally speaking, etching always has undercuts, so it is not very accurate to select pads for alignment points. If there are a lot of open circuits, you do n’t need to stop immediately, and stop when the open circuit test is completed and start the short circuit test, because you can already view the open circuit errors at this time, you can add targeted positioning according to the reported error location point.

    Let’s talk about manual alignment again. Strictly speaking, the holes are not in the center of the pads, so when positioning, should the dots be placed in the center of the pads as much as possible, or try to coincide with the real holes? Generally if there are many points to be tested For the hole, choose the latter. If it is mostly IC, especially when the IC is prone to false open circuit, you need to place the alignment hole in the middle of the pad.

    Second, fixed frame

    The fixed frame is the fixed test bracket. The framed data is represented by two boxes. The outer frame is the frame. For such a board, the size given by the machine can be used directly. For the data without frame, It is represented by a box. We can use the show board command (which will be used when looking at the direction of the board) to see which pad is tested on the closest edge. Compare it to the real board to see its distance from the edge How much is used to compensate.

    3. Crossing

    For the patch board, the selected single can be tested. We can use this function to realize the test of the patch board where the distance between the pad and the board edge is too small to test. The method is to block the pads that cannot be held by the tray. The single test is crossed out, and after the test, the tray is placed on the fixed plate of the tested single, and the board that was not tested last time is selected, so that the whole board can be tested by 2 tests. Therefore, we should flexibly use the functions provided by the equipment to fulfill some special needs.

    Fourth, warpage

    The size in one direction is too large, especially when the size in the other direction is relatively small, the board will naturally warp (caused by gravity) when placed on the test machine, and our flying probe machine has a little structure Small problem, the size in the X direction is larger, but only one pallet is placed, and in the Y direction with a smaller size, three pallets can be placed. Therefore, the machine chooses the long direction of the board to be measured When it is set to the X direction of the machine, it is best to manually arrange it, rotate the board 90 degrees, and place its long direction in the Y direction, which can solve the problem of board warpage in the test to a certain extent. (This adjustment must be handled in DPS).