PCB reverse engineering

- Jun 15, 2017-

1, Engineering reverse accuracy

For the accuracy of the board, depending on the two links, one is the accuracy of the software, one is the original image accuracy, for software accuracy, the use of 32-bit floating point representation can be said that there is no precision limit, so the most important Depending on the original image accuracy of the scan, for example, if the photo with 1 million pixels to shoot photos can be washed 5-inch photo, but if you want to wash it into 20-inch photos it simply can not see, the reason is The same, so for the high precision requirements of the circuit board, in order to copy out the very high precision PCB map, in the scan will choose a higher DPI.

The meaning of DPI is how many points per inch. That is to say, the distance between every two points on the scanned image is 1000 / DPI, mil.

If DPI is 400, then the distance between the two points on the image is 1000/400 = 2.5 mil, which means that the accuracy is 2.5 mil.

This is the most scientific basis, so some people say that the accuracy can reach 1mil the following, it is a premise. In fact, copy board accuracy depends mainly on the original scanning accuracy.

In summary, in the scan board set DPI will be based on the actual board required accuracy, if the phone board line spacing and other precision requirements below 1mil, then need to scan DPI should be set at 1000DPI or more The Scientists on the market today are able to meet this condition.

DPI higher, the picture is more clear, the higher the accuracy, but the disadvantage is too large, the hardware requirements are higher, so according to the specific circumstances of specific settings. For the general accuracy of the board is generally used 400DPI is very good, such as mobile phone board can be set above 1000DPI.

2, copy board type

At present, some of the proposed to copy the board, it sounds more suspended, in fact, as long as the copy board software can directly open and save the PROTEL PCB file, all the elements of the property fully support PROTEL format, including the same function, you can copy any Type of board.

3, copy board software selection

Copy board software is mainly depends on whether the function is complete, it is best to all the work can be done in the copy board software, so efficient, including the placement of components to support PROTEL99SE for the best, the current 99SE component library Very rich, can be downloaded to the Internet. This is also a very critical thing, by hand-made components of the era has passed, because many of the components like the BGP package has hundreds of elements, by hand to build components cost too much.

In order to stabilize the circuit is reliable, in the design of the circuit generally have a large piece of copper and power or ground connection, which can reduce the circuit noise and interference. So it is related to the problem of network copper, for the complexity of the circuit board, the copper is a lot of copper to connect there are a lot to be isolated, then if the solution is not good this problem, copper can not be achieved, so here must Define the network to shop copper ("the same network connected, different network isolation"), simply put all the stuffed with copper as it will appear on the end of the road. This is also a measure of copy board software a key issue.

4, grinding plate

For the multi-layer board, the middle layer is not directly scanned out, to copy the multilayer board must be more than a multi-layer grinding out, so copy the board must be scrapped a board.

The best way to use the current method is to use a good grinding machine and hand-polished paper, the latter method is the lowest cost of a method, sandpaper is available anywhere on the market to buy ordinary sandpaper, remember to coarse sandpaper, Fine sandpaper is difficult to wipe. The method is very simple, the board by a good level of hard with sandpaper grinding, if there is a large piece of copper can be used directly to pull the pliers can be pulled out, or with a few sets of rough put it difficult to wear off, and then switch to sandpaper and then grinding.

Grinding plate in fact no technical content, purely empirical things, grinding a multilayer board to understand.

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