PCB file introduction
PCB is a common circuit product in our life. In the electronic design industry, the final file of embedded product are also PCB documents.
A PCB project generally contains four files: xxx.SchDoc (PCB schematic diagram), xxx.PcbDoc (PCB package diagram), xxx.SchLib (PCB schematic library), and xxx.PcbLib (PCB package library).
The general process is as follows: first draw [PCB schematic library SchLib], then draw [PCB packaging library PcbLib], and associate schematic library components with packaging library.
Then draw the [PCB schematic diagram SchDoc], update it to the [PCB package diagram PcbDoc], Design ->update PCB Document, and finally layout copper.
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Introduction to Gerber files
Why use Gerber? Gerber, also known as photo file, is a standard file format. Gerber consists of two important parts,Gerber photo file,which is used to describe the contents of one layer (a bit similar to film),and NC Drill hole file.
PCB factories can directly produce the final PCB through Gerber. At present, the commonly used format is RS-274X, and most of the board factories also support the latest Gerber X2 format (with more stacking information and attributes of boards). Many engineers like to send PCB design documents directly to the board factory. In fact, this “lazy” approach is risky. Because the board factory ultimately needs to convert the PCB file to Gerber for production, there are many potential problems in the process from PCB to Gerber.
Due to the problem of EDA tool version, the PCB file opened by the board factory may have changed.
Due to lack of communication, some parameters on the PCB that do not need to be displayed are also left on the finished product.
In a word, the process of converting PCB to Gerber is not necessarily the same as copy, and designers should be responsible for this process. Therefore, most experienced engineers will convert PCB into Gerber by hand, and then check whether Gerber has problems through software such as CAM350, and then send it to the board factory for processing. In addition, whether you use Altium, Allegro or Expedition, as long as you convert to Gerber, the board factory can correctly identify. Another point is that it is difficult to reverse generate PCB from Gerber. For the sake of safety, enterprises are not willing to send the design source file directly to the board factory.
PCB gerber file normally include outline, CNC(plated & non-plated), silkscreen layer, solder mask layer, copper layer, solder paste layer as below:
How to identify correct Gerber files
The layout file consist of D-code and coordinates file. If there is no D-code, the trace will have no width, and the pad will have only outline; If there are no coordinates, there will be no graphics outline and board size; Ordinarily, the coordinate file will reflect the layout file, while the D-code file sometimes exists separately. At this time, we need to recognize these D-codes separately. If the software cannot recognize them, our engineers have to manually enter the D-code and send to customer to confirm whether the GERBER file is correct or not.
About CNC file, normally, including DDR file and drill file, in DDR file, there are hole size,count and plated or not just like below
About drill file,normally, its format is usually shown by “TXT” format,It is mainly used to provide the coordinate file required by the NC drill in production for the drill, indicating the drill to drill at the marked position of the program, and completing the process of PCB drilling, So, it start with M48,meanwhile,define drill file format(3:3 or 4:3),Units and Zero Suppression information, let us take a sample below,one sample P/N:20002131C below,
Origin of PCB file suffix
- The PCB file suffix of protel and the new version of altiumDesigner is "pcb" or "pcbdoc",Many PCB design files use this suffix
- The suffix of ZUKEN's Cadstar, CR5000 and other pcb files is generally "pcb"
- The PCB file suffix of Allegro and Eagle's PCB software under Cadence is "brd"
- PCB text format of PADS, protel, P-cad "asc" software
- The pcb output format of cam350 is "cam"
- The ODB++file format produced by pcb design file is "tgz"
Specific steps for opening PCB file
Common gerber file to pcb file
Method 1: 1. Directly export Gerber files to DXF format: Note: you need to select a lower version of DXF format. 2. Create a blank PCB and then import it:
Method 2: 1. Create a Gerber file 2. Perform the quick import action, import the Gerber file of each layer, as well as the NC Drill file. In addition, if you want to obtain the accurate network name, the IPC-D-356 file must also be imported together. 3. After all files are imported, then:
- Confirm that the layer information of each layer is correct
- And define NC tools. Of course, if this information already exists under the original NC tools, there is no need to redefine it.
- Extract the net list: Then you can see the following information under Camtastic: If IPC-D-356 is included in this Gerber, then: Rename Nets is enabled, and will accurately name the network in Gerber.
- The last step is to execute the command of exporting to PCB included in the software
- That is, the final PCB file can be obtained
Convert Gerber files to PCBs. The common one is Cam350. Now it can be realized by using altium designer to reverse Gerber files to PCBs.
Create a new CAM file.
Open Altium designer14.2 software, File — New — Cam document.
- Import the Gerber file. In the newly created CAM file, File – Import – Gerber, import Gerber file. Select the Gerber file to open, click Open, and select OK in the pop-up window.
- Import NC Drill and netlist files.
In the newly created CAM file, File — Import — drill, import the NC drill file.
Tool — Netlist — extract, extract the network of the imported Gerber file (treat the connected tracks as the same network, and the network name is randomly generated). If you do not import the network table, you cannot generate PCB files.
File — Export — Export to PCB to export CAM files to PCB. If the network table is not generated in the previous step, PCB export cannot be realized.
PCB file transfer to GERBER
Pcb file generation gerber file requires two steps: 1. generation of GERBER 2. generation of NC drilling file Run Altium Designer file, select Menu – File – Open the required PcbDoc file1. Select Menu – File – Enter Gerber file
About CNC file, The summary is to set the English or metric units (inch English milimeters metric system) and precision. The format is 4:4 or 4:3. Generally, the metric system is 4:4
DXF file transfer to GERBERUsing software cam350, it will be easy to transfer DXF file to Gerber, file- import -choosing DXF(Note,if ODB++ file from genesis2000 software, it can be recognized as well)
File — Export — Export to PCB to export CAM files to PCB. If the network table is not generated in the previous step, PCB export cannot be realized.
- So far, DXF file have been transfer to gerber file just like below
Finally, the file conversion between different software may hide certain hidden dangers, such as the recognition of special shaped pads, which need to be compared or confirmed with the original file. At the same time, it is necessary to realize that all software is not universal and has its use limitations.
Ancient Chinese proverb: Caution makes a ship of ten thousand years old!
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