PCB Technical - What design files are included in PCBA assembly?

The basic documents that a general circuit board assembly (PCBA) factory should have when transferring:

1. Gerber file or PCB CAD file

Gerber file or PCB CAD file

Gerber file is the most basic PCB circuit board manufacturing file. After the PCB factory receives the Gerber file and imports the CAM software, it can provide production data for each PCB process. Gerber data can also provide image data for specific equipment, Such as automated optical inspection equipment (AOI), can also be used to define the basis of PCB steel plate aperture (aperture).

2. Fabrication drawing (manufacturing specifications)

Fab drawing (manufacturing specifications)

This specification generally requires the PCB manufacturer to complete a circuit board, so the above usually contains the following information. The circuit board assembly factory usually uses this specification as the basis for inspection during incoming inspection:

.The color of the insulating printing ink. It is generally green, but there are also black and red.

▪ Screen printing ink color. It is generally white, but also yellow. Other colors are rare.

▪ Surface Finished of the printed circuit board, such as ENIG, HASL, OSP...etc. Some ENIGs also specify the thickness of the gold layer and the nickel layer, and some even specify the thickness of the copper foil.

▪ The substrate grade of the circuit board. The current circuit boards are divided into lead-free and lead-free processes. The temperature resistance requirements of the lead-free process are relatively high. When necessary, it is best to specify the Tg value (lead-free 150C or more) and Td value (lead-free 325C) of the FR4 substrate. Above), Z-axis expansion coefficient (300ppm/degree or less).

▪ The electrical characteristics of copper foil. Especially high-frequency products.

▪ V-cut and additional processing or drilling information.

▪ The style and size of the jigsaw puzzle. (Jigsaw/Connected boards will be discussed in the next project)

3. Panel drawing (Jigsaw/Connected board specifications)

Panel drawing (Jigsaw/Connected board specifications)

The above Gerber document only defines the data of a single-chip PCB. However, in order to improve the utilization rate of the circuit board and the efficiency of the manufacturer, the actual output of the circuit board is designed by the board/connected board. The shape of the board is, The style and size will affect the design of the following tools, and different jigsaw methods will even make the original tools unusable:

▪ Steel (Stencil)

▪ Vacuum block

▪ Parts Visual Inspection template (Visual Inspection template)

▪ MDA (Manufacturing Defect Analyzer) or ICT (In-Circuit Tester) test fixture

▪ FVT (Function Verification Tester, function test fixture)

When transferring between different production lines and different factories, remember to use the original jigsaw style. If the original file does not define the jigsaw style, you can request it from the original circuit board manufacturer and then standardize it.

4. Placement Component X-Y table (XY coordinates of SMT parts)

Placement Component X-Y table (XY coordinates of SMT parts)

The SMT printing machine determines the position of the part to be placed on the circuit board according to the X, Y coordinate axes defined by the user. Of course, there are other parameters (Z axis, rotation...) to form the SMT printing machine. Piece program, the circuit board designer can generate a part's X, Y coordinate table through PCB CAD, and it can greatly reduce the time for SMT engineers to write the program.

If there is no way to generate X, Y coordinate tables from PCB CAD, you can still use the traditional method to slowly measure out one part by one part with the projector, or open the Gerber file and measure it on the computer. However, no matter which method is used to measure the result, it is actually necessary to fine-tune the SMT machine to match the actual coordinates.

5. Readable plots file (readable circuit board layer)

Readible plots file (readable circuit board layer)

Ordinary people may not be able to directly understand Gerber's files. Generally, we will output each layer of the PCB into a readable PDF document, including solder paste layer, silk screen layer, mask layer and various circuit layers.

6. PCB Assembly drawing (circuit board assembly specification)

Generally speaking, today's circuit board assembly is based on the BOM (parts list), but occasionally there are some extra jumpers or there is no way to use the BOM and part position indicators to standardize, so usually it is still needed. PCB Assembly drawing (circuit board assembly specifications) defines how the PCB factory can assemble the entire circuit board except for SMT or plug-ins. For example, for the circuit board to indicate the part number after assembly, additional dispensing... and other actions.

7. Schematic drawing (circuit diagram)

Schematic is generally used as a reference for electronic engineers or repair technicians to repair circuit boards. Sometimes circuit diagrams are used to design test fixtures.