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1. Basic requirements for PCB engineering

The quality of PCB engineering production is a reflection of the designer's skill level and the technical capabilities of the printed board manufacturer. Due to the integration of PCB engineering with computer-aided design and auxiliary manufacturing, precision and accuracy must be extremely high. Any mistakes in the production process can lead to errors in the final onboard electronic products, and in serious cases, the entire batch of printed boards may need to be scrapped. This can delay the manufacturer's contract delivery time and result in economic losses.

When processing PCB design files, it is important to double check the following:

- Ensure that the receiving document meets the designer's rules and can meet the PCB manufacturing process requirements.

- Check if there is a positioning mark.

- Verify if the line layout is reasonable and if there are any conflicts between components in 2D and 3D space.

- Confirm that the printed board size matches the processing drawing.

- Check if any graphics added to the PCB graphics, such as icons and markers, will cause a signal short circuit.

- Check if there is a process line on the PCB and if the solder mask meets the requirements of the production process. Also, make sure that the solder mask size is appropriate and that the character mark is pressed on the device pad to avoid affecting the quality of the electrical equipment.

PCB Engineering

2. Generation of light mapping data

2.1 Panel

PCB design is completed when the PCB shape is too small to meet the production process requirements or when a product consists of several PCBs. In such cases, it is necessary to combine small boards into one large area that meets the production requirements. This helps in the production of electrical equipment. The former method is similar to a stamp plate. It can meet the PCB production process conditions and facilitate the installation of electrical components. It is very convenient to separate when in use. The latter method is to assemble several sets of PCB boards of one product, which is convenient for production. It is easy to identify a product using this method.

2.2 Generation of Light Drawing Data

The basis for PCB production is the film bottom plate. The accuracy of the base map must be the same as that required for the printed board, and compensation for variations in the production process should be considered. The base map can be provided by the customer or the manufacturer. The two parties should cooperate and negotiate closely so that they can meet the requirements of the user and adapt to the production conditions.

If the user provides the base map, the manufacturer shall inspect and approve the base map, and the user may evaluate and approve the original or the first printed board product. The production methods for base maps include hand drawing, texture, and CAD drawing. With the development of computer technology, the CAD technology of printed boards has been greatly improved, and the production level of printed boards has been continuously increased to multiple layers. The fine wires, small apertures, and high-density directions have been rapidly improved. The original film-making process was unable to meet the design needs of the printed board, so light painting technology appeared.

Using the photoplotter, the PCB design data file of the CAD design can be directly sent to the computer system of the photoplotter, and the photoplotter can be used to directly draw the image on the film by using the light. Then, after development and fixing, a film bottom plate is obtained. Printed board film base made by photo-painting technology, fast speed, high precision, and good quality, and avoids human error that may occur when manually mapping or drawing a base map, greatly improving work efficiency and shortening the printed board production cycle.

The standard data format used by photoplotters is the Gerber-RS274 format, which is also the standard data format for the printed board design and production industry. The naming of the Gerber format is quoted from the pioneer of the design and production of photoplotters - Gerber Corporation of the United States.

The generation of light drawing data is to convert the design data generated by the CAD software into light drawing data (mostly Gerber data), and then modify and edit it through the CAM system to complete the photo-painting pre-processing (imposition, mirroring, etc.) to achieve Printed board production process requirements.

The processed data is sent to a photoplotter and converted into raster data by a rasterizer (Raster) image data processor of the photoplotter. The raster data is sent to the laser photoplotter through a high-speed fast compression reduction algorithm to complete the photoplotting.

2.3 Photographic data format.

The format used for light drawing data is based on the Gerber data format of the vector photoplotter. This data format has been expanded to be compatible with other formats such as HPGL HP plotter format, Autocad DXF, TIFF, and other dedicated and generic graphics data formats. Some CAD and CAM developers have also extended the Gerber data.

The Gerber data format is officially known as the Gerber RS-274 format. Each symbol on the vector ray plotter corresponds to a D code (D-CODE) in the Gerber data. This allows the photoplotter to control and select the code disc through the D code to draw the corresponding graphic. The shape and size of the symbols corresponding to the D code are listed in a D code table. This D-code table has become a bridge from CAD design to photoplotter using this data for light painting. The user must provide the corresponding D code table while providing Gerber light mapping data. This enables the photoplotter to determine which symbol disc should be used for exposure based on the D code table to draw the correct pattern.

A D code table should generally include the D code, the shape and size of the code wheel corresponding to each D code, and the exposure mode of the code wheel. For instance, Protel, the most commonly used electronic CAD software in China, has a D code table with an extension.APT. This is an ASCII file that can be edited using any non-text editing software.

Each line in the D code table defines a D code that consists of six parameters:

1. The D code serial number, which consists of the letter 'D' plus one digit.

2. A shape description of the symbol represented by the D code. For example, CIRCULAR indicates that the shape of the symbol is a circle, and SQUARE indicates that the shape of the symbol is a square.

3. The dimensions of the symbol pattern in the X direction.

4. The dimensions of the symbol pattern in the Y direction.

5. The size of the center hole of the symbol graphic.

6. Explanation of how the symbol disk is used. For instance, LINE indicates that the symbol is used for scribe lines, FLASH indicates pad exposure, and MULTI indicates that it can be used for both scribe lines and exposure pads.

In the Gerber RS-274 format, the D code is also used for exposure control of the photoplotter, in addition to defining the symbol disc. Some other commands are also used for the control and operation of the photoplotter. There may be some minor differences in the Gerber data format generated by different CAD software, but the overall framework remains unchanged for the Gerber RS-274 format.

Why Choose China PCBA Supplier KSPCBA as Your PCB Engineering Manufacturer?

– Experienced and skilled team

– State-of-the-art equipment

– Strict quality control

– Excellent customer service

– Competitive price