Common Problems with Gerber Files and How to Avoid Them!
The reasons we want to address these common problems is to help reduce the number of errors, mistakes and time delays when manufacturing your PCB. All of these reflect in higher costs in the long run which no one needs!
Obsolete File Format:
There are basically two types of file formats: 274D (requires aperture list) and 274X (apertures are embedded into the files). 274X is preferred since the apertures are embedded into the file data. The advantage is that it does not require any manual input from a CAM operator. 274D requires the creation of an aperture wheel that is manually added by a CAM operator. This opens the door for errors of adding and interpreting of the apertures. It can also be a very time consuming process as well.
ODB++ is another file format that works very well also.
Confusing File Labels:
The naming of each Gerber file should reflect the board layer and be easily interpreted. We have jobs that come in that the layers are labeled: .GBL, .GBS, and so on. It can be very confusing. It would be best to provide a text label in the Gerber data that will clearly indicate the files and they layer they represent. In most cases we can work through them and figure it out but mistakes can happen and it takes additional time.
Fabrication Drawing Files:
Often when Gerber files are sent, there are no “Fabrication Drawings” sent with them. What is in a Fab Drawing? It will show the overall dimensions of the board as well as any cut outs or special routing. It can also contain any notes related to the fabrication of the boards. Things like file names, material type, thickness, finish, etc. Any information that would help us know exactly what you are looking for in the fabrication of your board is helpful. This aids in eliminating mistakes and will help if we have to work with an outside vendor on some part of your fabrication.
Drill files often do not have the proper drill format included in the file leaving us to guess by trial and error as to what the proper drill format is. The header should include information that clearing indicates the format. As an example: 2.4, Absolute, Trailing, which is the recommended drill file format.
Registration of Layers:
If at all possible having the files registered to a common data point is recommended. Some files come in with the layers at a different datum alignment (like a target) so then manual alignment of the layers is necessary. We can do this but again we like to avoid errors and things that take additional time.
Often plane layers or layers with shield areas come in filled with 1 mil or 2 mil vectors. This causes the file to be quite large in size and requires us to try and contourize the data. When you panelize this type of data the files often become too large for our plotter to digest. It is better for areas to be filled using “raster” or “contour” data.
Some design software uses composite layers to create one layer. For example a plane layer with embedded traces will use three layers just to create one layer. First you have the plane layer, then the clearance layer, then the trace layer. Some layers are positive images while others are negative images. This should all be combined then output as a single Gerber layer.
Some design software creates surface mount pads with vectorized data, meaning the pad is composed of many small vectors arranged in such a manner s to create a surface mount pad. We then have to go and substitute all these pads out to create one flash pad. This not only reduces the amount of data, also helps in the editing of such files. Better to use flash pads if you can.
If you have any questions about the format of your files just give us a call. We will be glad to help. 650-367-8444