PCB Tech - PCB circuit board light painting (CAM) operation process

The operation flow of PCB circuit board light painting (CAM) is as follows:

(1) PCB inspection user's file

The files brought by the user must first be routinely checked:

1, check whether the disk file is intact;

2, check whether the file contains a virus, if there is a virus, you must first kill the virus;

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

(2) Whether the PCB inspection design meets the technological level of the PCB factory

1, check whether the various spacings designed in the customer files conform to the factory process: the spacing between the line and the spacing between the line and the pad. The spacing between the pad and the pad. 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, it is required that the width of the wire should be greater than the minimum that can be achieved by the factory's production process

Line width.

3, check the size of the via hole to ensure the smallest diameter of the factory's production process.

4, check the size of the PCB pad and its internal aperture to ensure that the edge of the pad after drilling has a certain width.

(3) Determine process requirements

Various PCB process parameters are determined according to user requirements.

Process requirements:

1, the different requirements of the subsequent process, determine whether the light painting film (commonly known as film) is a mirror image. The principle of negative film mirroring: the drug film surface (that is, the latex surface) is applied to the drug film surface to reduce the error. The determinant of the mirror image: craftsmanship. If it is a screen printing process or a dry film process, the copper surface of the substrate on the film side of the film shall prevail. If the diazo film is used for exposure, since the diazo film is a mirror image when copied, its mirror image should be the film surface of the negative film without the copper surface of the substrate. If the light-painting is a unit film instead of imposition on the light-painting film, you need to add another mirror image.

2, determine the parameters of solder mask enlargement.

Principle of determination:

1. The wire next to the pad should not be exposed.

2. Small can not cover the pad.

Due to the error during operation, the solder mask may have deviations on the circuit. If the solder mask is too small, the result of the deviation may mask the edge of the pad. Therefore, the solder mask should be larger. But if the solder mask is enlarged too much, the wires next to it may be exposed due to the influence of deviation.

From the above requirements, it can be seen that the determinants of solder mask expansion are:

1. The deviation value of the solder mask process position of the PCB factory, and the deviation value of the solder mask pattern.

Due to the different deviations caused by various processes, the solder mask enlargement value corresponding to various processes is also

different. The enlargement value of the solder mask with large deviation should be selected larger.

2. The board has a large wire density, and the distance between the pad and the wire is small, and the solder mask expansion value should be selected smaller;

The density of sub-wire is small, and the solder mask enlargement value can be selected larger.

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

4, according to the electroplating process requirements, determine whether to add a conductive frame for electroplating.

5, according to the hot air leveling (commonly known as tin spraying) process requirements to determine whether to add conductive process line.

6, determine whether to add the center hole of the pad according to the drilling process.

7, determine whether to add process positioning holes according to the subsequent process.

8, according to the board shape to determine whether to add the outline angle.

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 factory's production level to adjust the influence of side erosion.

(4) Convert CAD files to Gerber files

In order to perform unified management in the CAM process, all CAD files should be converted to the standard format Gerber of the light plotter and the equivalent D code table.

During the conversion process, attention should be paid to the required process parameters, because some requirements are to be completed during the conversion.

All kinds of common CAD software, except Smart Work and Tango software, can be converted to Gerber. The above two softwares can also be converted to Protel format through tool software, and then to Gerber.

(5) CAM processing

Various process treatments are carried out according to the set PCB manufacturing process.

Special attention is needed: whether there are any places in the user file that are too small, and corresponding treatment must be made

(6) Light painting output

The files processed by CAM can be outputted by light drawing.

The imposition work can be done in CAM or during output.

A good light drawing system has a certain CAM function, and some process processing must be carried out on the light drawing machine, such as line width correction.

(7) Darkroom treatment

light-painted negatives need to be developed and fixed before they can be used in subsequent processes. When dealing with the darkroom, the following links must be strictly controlled:

Development time: Affect the optical density (commonly known as blackness) and contrast of the production master. If the time is short, the optical density and contrast are not enough; if the time is too long, the fog will increase.

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

Non-washing time: If the washing time is not enough, the production base plate is easy to turn yellow.

Special attention: Do not scratch the film of the negative film.