label: PCB process,PCB design,PCB Gerber output
PCB Gerber PCB process is a very important aspect of the transfer process in line among any errors that appear in this session, are likely to follow the process serious problems, so each step must be strictly inside.
(A) check the user's files
Users brought documents, we must first carry out a routine inspection:
1, check the file is intact;
2 Check whether the document with a toxic, poisonous, you must first antivirus;
3, if the Gerber files, or check whether the code table containing D codes.
(B) Check the PCB design meets craftsmanship factory
1, Check the customer files of various pitch PCB design meets the factory process: the spacing of the `line` pad and the pad and the pad spacing between the lines between between. All of the above should be greater than the minimum spacing distance between the factory production process can be achieved.
2, Check the wire width, the requirements should be greater than the width of the wire factory production process can achieve a minimum linewidth.
3, Check the size of vias in order to ensure a minimum aperture of the factory production process.
4, The size of its internal aperture inspection pad to ensure that the edge of the pad after drilling a certain width.
(C) To determine the process requirements
Determine the various process parameters based on user requirements.
Process requirements:
1, The sequence of the different requirements of the process to determine the PCB Gerber negatives (commonly known as the film) are mirroring. Principles film mirror: membrane surface (ie plastic surface) stickers membrane surface to reduce errors. Determinants film mirror: processes. If the screen printing process or dry process, then the membrane surface of the film substrate attached to the copper surface prevail. If you are using Diazo film exposure, since the mirrored copy diazo film, so its mirrored surface membrane should not stick to the film substrate copper surface. If the PCB Gerber negatives as a unit, rather than the imposition PCB Gerber on the film, you need to pay more a mirror.
2, To determine the parameters of the solder resist expansion.
Determine principles:
① large pad beside the wire is not exposed.
② not cover small pad.
Since the error operation of the circuit in Fig solder may vary. If the solder is too small, the results of deviation may be masked so that the edge of the pad. Thus requiring solder should be bigger. However, if too much solder expand, due to the deviation of the wire may be exposed to the side.
Seen from the above requirements, the solder resist expansion determinants:
① position deviation solder process, the solder resist pattern deviation value.
Since the deviation caused by a variety of processes are not the same, so the corresponding values for various solder process is also expanding different. Large deviation value should be chosen to be expanded solder bigger.
② board conductor density, a small spacing between the pads and the leads, solder smaller gain value should be selected; plate sub wire density, expanded value Optional solder was bigger.
3, According to the board if there is a printed plugs (commonly known as Goldfinger) to determine whether to add the process line.
4, According to the requirements of the plating process to determine whether to add the conductive plating of the border.
5, According to the hot air leveling (commonly known as HAL) process requirements to determine whether to add the conductive process line.
6, To determine whether to add the pad according to the center hole drilling processes.
7, To determine whether to add the process of positioning holes according to the order process.
8, To determine whether to add shape moldings according to the board appearance.
9, When the user requests the board width precision accuracy is very high, according to factory production levels to determine whether the line width correction to adjust the side effects of erosion.
(D) CAD files to Gerber file
CAM process in order to conduct unified management of all CAD files should be converted to a PCB Gerber Gerber machine and fairly standard format D code table.
During the conversion process, you should pay attention to the process parameters as required, because some requirements are to be completed in the transformation.
Now a common variety of CAD software in addition to Smart Work and Tango software, can be converted to Gerber, these two software tools can also be converted to Protel format, sub-Gerber.
(Five) CAM treatment
Process according to various predetermined process.
Of particular note: the user whether the file where the spacing is too small, you must make the appropriate treatment.
(Six) PCB Gerber output
After processing by the CAM files, you can PCB Gerber output.
Imposition job performed in the CAM can also be carried out at the output.
Gerber good PCB CAM systems have certain features, some process must be handled on a PCB Gerber machine, such as line width than the positive.
(Seven) darkroom processing
PCB Gerber negatives, subject to developing and fixing treatment follow-up process to get ready to use. When darkroom processing, to strictly control the following aspects: Development time: the impact of production Diban optical density (commonly known as black level) and contrast. Short time, optical density and contrast are not; too long, fog increased.
Fixing time: Fixing time is not enough, the lack of transparency in the production of negatives background.
Do not wash time: lack of time, such as washing, produce negatives easy to turn yellow.
Special Note: Do not scratch the film emulsion.
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