PCB Light Painting Operation Process

writer: G July 02, 2019

(1) Check the user's file

The files that the user brought are first checked routinely:

1. Check if the documents are in good condition;

2. Check if the file is poisonous, and if it is toxic, it must first be disinfected;

3. If it is a Gerber file, check if there is a D code table or a D code.

(2) Check whether the PCB design meets the factory's technological level

1. Check that the various spacings of the PCB design in the customer file conform to the factory process: the spacing between the lines, the spacing between the lines and the pads, and the spacing between the pads and the pads. The above various spacings should be greater than the minimum spacing that can be achieved by the factory's production process.

2. Check the width of the wire, and the width of the wire should be greater than the minimum that can be achieved by the factory.

Line width.

3. Check the size of the via hole to ensure the minimum aperture of the factory production process.

4. Check the pad size and its internal aperture to ensure a certain width of the pad edge after drilling.

(3) Determining process requirements

Various process parameters are determined according to user requirements.

Process requirements:

1. Different requirements of the post-order process to determine whether the PCB photo-shadow film (commonly known as film) is mirrored. The principle of mirror image: the film surface (ie, the rubber surface) is applied to the film surface to reduce the error. The determinant of the film image: the process. In the case of a screen printing process or a dry film process, the surface of the substrate film is attached to the copper surface of the substrate. If it is exposed with a diazo film, since the diazo film is mirrored when it is copied, its mirror image should be such that the film surface of the film is not attached to the copper surface of the substrate. If the PCB is painted as a unit negative, rather than on a PCB-printed negative, an additional mirror is required.

2. Determine the parameters for the expansion of the solder mask.

Determine the principle:

1) large can not expose the wire next to the pad.

2) small can not cover the pad.

The solder mask may deviate from the line due to errors in operation. If the solder mask is too small, the result of the bias may cause the pad edges to be masked. Therefore, it is required that the solder mask should be larger. However, if the solder resist is expanded too much, the side conductor may be exposed due to the influence of the deviation.

It can be seen from the above requirements that the decisive factors for the expansion of solder resist are:

1. The deviation value of the solder resist process position and the deviation value of the solder resist pattern.

Since the deviation caused by various processes is different, the resistance increase value corresponding to various processes is also different. The value of the solder joint with a large deviation should be chosen to be larger.

2. The board has a high density of wires, the spacing between the pads and the wires is small, and the expansion of the solder resist should be selected to be smaller; the density of the wires of the board is small, and the expansion value of the solder resist can be selected to be larger.

3. According to whether there is a printed plug (commonly known as gold finger) on the board to determine whether to add a process line.

4. Determine whether to add a conductive bezel for electroplating according to the plating process requirements.

5. Determine whether or not to add a conductive process line according to the requirements of the hot air leveling (commonly known as spray tin) process.

6. Determine if the center hole of the pad is to be added according to the drilling process.

7. Determine whether to add a process positioning hole according to the subsequent process.

8. Determine whether to add a shape angle according to the shape of the board.

9. When the user's high-precision board requires high line width accuracy, it is necessary to determine whether to perform line width correction according to the production level of the factory to adjust the influence of side erosion.

(4) Conversion of CAD files into Gerber files

In order to carry out unified management in the CAM process, all CAD files should be converted to the standard format of the PCB photoplotter Gerber and the equivalent D code table.

During the conversion process, the required process parameters should be noted, as some of the requirements are to be completed during the conversion.

Now all kinds of general CAD software, except Smart Work and Tango software, can be converted to Gerber. The above two softwares can also be converted to Protel format by tool software, and then transferred to Gerber.

(5) CAM processing

Various processes are performed according to the specified process.

Special attention should be paid to whether there is any space in the user file that is too small and must be handled accordingly.

(6) PCB light drawing output

After the CAM processed file, the PCB light output can be output.

The work of imposition can be done in CAM or at the time of output.

A good PCB light mapping system has a certain CAM function, and some process processing must be performed on a PCB photoplotter, such as a line width correction.

(7) Darkroom treatment

The PCB-photographed film needs to be developed, and the fixing process can be used for subsequent processes. When dealing with darkrooms, the following links must be strictly controlled:

Development time: affects the optical density (commonly known as blackness) and contrast of the production master. The time is short, the optical density and contrast are not enough; the time is too long and the fog is aggravated.

Fixing time: If the fixing time is not enough, the background color of the production base is not transparent enough.

Do not wash time: If the washing time is not enough, the production plate is easy to turn yellow.


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