PCB Tech - How to operate PCB copy board when making board

PCB copying for board making is two different concepts from PCB copying for steel net making. Both of them use different types of printed circuit board copying and software. Before, I briefly introduced how to copy the board when making PCB steel mesh. Today, I will introduce how to copy the board when making SMT board.

1. Precision of PCB copy board

For PCB copy board accuracy depends on two links: One is the accuracy of software, one is the original image accuracy, for precision of software using 32-bit floating-point representation can say there is no precision limitation, so the precision mainly depends on the original scanning image, for example, if with pictures of 1 million pixels making can wash 5 inch photos, but if you want to wash it into 20 inches of photographs that simply can't see clearly, The reason is the same, so for the high precision of the circuit board, to copy a very high accuracy of the PCB map, in the scan should choose a higher DPI.

DPI means how many dots per inch. So the distance between 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 = 2.5mil, which means that the accuracy is 2.5mil.

This is a scientific basis, so some people say that the accuracy can reach below 1mil, that is a premise. In fact, PCB copying accuracy mainly depends on the original scanning accuracy.

To sum up, DPI should be set according to the accuracy required by the actual board when scanning the board. If the accuracy required by the phone board line spacing is below 1mil, then the SCANNING DPI should be set above 1000DPI. Scanners on the market can meet this condition.

The higher the DPI, the clearer the picture, the higher the accuracy, but the disadvantage is that the picture is too large, the hardware requirements are high, so it needs to be set according to the specific situation. For the general accuracy of the board is generally used 400DPI is very good, mobile phone board can be set at more than 1000DPI.

2. Type of PCB copy board

At present, some people suggest that they can copy this or that board, which sounds rather uncertain. In fact, as long as PCB board copying software can directly open and save protel PCB files, all placed element attributes fully support PROTEL format, including the same placement function, you can copy out any type of board.

3. Selection of PCB copying software

The quality of PCB board copying software mainly depends on whether the function is complete. All the work can be done in PCB board copying software, so that the efficiency is high, including the placement of components support PROTEL99SE. At present, the component library of 99SE is very rich and can be accessed on the Internet. This is also critical. The era of making components by hand is over, because many components, like BGP components, contain hundreds of elements, and it is too expensive to build components by hand.

In order to make the circuit stable and reliable, there should be large copper skin and power supply or ground connection when designing the circuit, so as to reduce the noise and interference of the circuit. So it involves the problem of network copper laying, for the complex circuit board, there are a lot of copper laying is connected and a lot of copper laying is to be isolated, so if the problem is not solved, the copper laying can not be achieved, so here must define the network to lay copper (" the same network connected, different network isolation "), Simply fill all of them with copper and that will lead to enroute. This is also a key problem to measure PCB copying software.

4, wear plate

For multi-layer PCB board, the middle layer can not be scanned directly, to copy multi-layer PCB board must grind out the multi-layer, so copy multi-layer PCB board must scrap a board.

The current method is to use a good grinder and manual yarn paper grinding, using the latter method is a method of cost, sandpaper is the ordinary sandpaper that can be bought everywhere on the market, remember to rough sandpaper, fine sandpaper is difficult to grind.

The method is very simple, the board according to the good level of force with sandpaper grinding, if there is a large copper skin can be directly pulled off with pliers, or with flat file a few times to grind off the difficult grinding, and then use sandpaper grinding again.

In fact, there is no technical content of the grinding plate, purely empirical things, grinding a multi-layer PCB board will understand.