The positive film is the usual method of routing on the top layer and the ground layer. The copper wire is used for the wire and the copper is filled with the Polygon Pour. The PCB negative is just the opposite. The default copper is applied. The line is the dividing line. After the negative film is formed, the whole layer has been coated with copper.
The thing to do is to divide the copper and set the copper after the division. network of. In the previous version of PROTEL, Split was used to split. Now the version of Altium Designer Summer 09 is directly divided by Line and shortcut key PL. The dividing line should not be too thin, using 30mil. To split the copper, just draw a closed polygon frame with LINE and set the network with copper in the double-click box.
Both positive and negative films can be used for the inner layer, and the positive film can also be realized by routing and copper plating. The advantage of PCB negatives is that the default bulk copper fill, the addition of vias, changing the copper size and so on do not need to re-rebuild, thus eliminating the time for PROTEL re-copper calculation. When the middle layer is used for the power layer and the GND layer, most of the layers are copper-clad, so the advantage of using the PCB negative is obvious.
The PCB negative film has no dead copper option. If there is dead copper, the check will report the unconnected error. You can use Polygon Pour Cutout to remove the dead copper one by one. Add all the thick copper on the original copper foil board before you have a choice. For retention or removal, this is a subtractive method. Conversely, the location of the line that needs to be retained on the copper foil is revealed after the pattern transfer process for selective thickening of the copper-plated tin, which is the positive process.
The PCB negative design heat pad is easier for these heat sinks. To put it simply, the positive film refers to the process of producing the circuit board. The transparent place of the film is blank, and the opaque place is the line. The negative film of the PCB is the place where the line is drawn without copper skin, but not the picture.
Contents
1 How to judge the PCB negative film from the process, the positive film
2 The disadvantages of PCB negatives are mainly in three aspects.
3 PCB negative film, positive film process comparison
4 How do you see from the GERBER data of the multi-layer board that the line is a positive film or a negative PCB?
5 Cadence positive film and PCB negative interpretation
How to judge the PCB negative film from the process, positive film
The PCB negative is because the required line or copper surface is transparent after the negative film is produced, and the unnecessary part is black. After the line process exposure, the transparent part is chemically hardened due to the light of the dry film resist, and the subsequent development process will wash away the dry film without hardening, so that only the dry film is washed away during the etching process. Part of the black foil/backsheet black part, while leaving the transparent film part of the dry film that has not been washed away -> lower process
The positive film of the circuit board: the pattern process, the liquid used is alkaline etching.
If the positive film is viewed from the negative film, the required line or copper surface is black, and the part is transparent. After the exposure of the line process, the transparent portion is chemically hardened by the dry film resist, and the subsequent development process will wash away the dry film without hardening. Followed by the tin-plated lead process, the tin-lead is plated on the copper surface washed by the previous process/developing dry film, the film removal action (removing the dry film hardened by the light), and in the next process etching, The alkaline potion bites off the transparent part of the copper foil/backsheet that is not protected by tin-lead. The rest is the line we want (the black part of the film) --> the next process
PCB negatives are mainly in three aspects
1. The PCB negative film needs to be masked and etched, and the size of the hole ring is required;
2. PCB negative film dry film adhesion is limited, the line width <4mil easy to aponeurosis;3. The residual copper is large, the plating cost will increase
PCB negative film, positive film process comparison
Positive film process: (double panel) cutting - drilling - PTH (primary plating / thickening copper) - wiring - two copper (graphic plating) - SES line (rewinding - etching - tinning)
Negative film process: (double panel) cutting - drilling - PTH (primary plating / thickening copper) - wiring (without two copper pattern plating) - DES line (etching - peeling)That is to say, the PCB negative film does not take the picture, and the process is relatively simple.
How do you see from the GERBER data of the multi-layer board that the line is positive or negative?
Imported with cam 350, simply say, if you can see that the trace is a positive, if you see a black, the middle of the hole is the PCB negative.
Positive films and PCB negatives refer only to two different display effects of one layer. Whether the layer is a positive or a negative PCB, the PCB is the same. Only in the process of cadence processing, the amount of data, DRC detection, software processing is different.
It is also two ways of expressing a thing. The positive film is to see what is what, see the wiring is the wiring, the real existence.
The PCB negative is what you see is not what you see, you see the copper that needs to be etched away.
The advantage of the positive film is that if the moving component or via needs to be re-plated, there is a more comprehensive DRC check.
The advantage of PCB negatives is that the moving components or vias do not need to be re-plated, automatically updating the copper, and there is no comprehensive DRC check.
The PCB file generated by the positive film is large, and the PCB file generated by the PCB negative film is small.