PCB CAM Basics: Introduction and Classification of CAM Software for PCB Manufacturing

1. The Concept of PCB CAM

Everyone is familiar with the concept of CAD, but when using a photo plotter, the concept of CAM is essential. Because each factory has different process flows and technical levels, to achieve the user’s final requirements, necessary adjustments must be made in the manufacturing process to meet the user’s requirements for precision and other aspects. Therefore, CAM is an indispensable process in the photo plotter production center. All the process requirements mentioned earlier must be prepared before photo plotting. For example, mirroring, solder mask expansion, process lines, process frames, line width adjustment, center holes, and outline lines must all be completed in the CAM process.

2. Processes Performed by PCB CAM

1. Pad size correction and D-code merging.
2. Line width correction and D-code merging.
3. Minimum spacing check: between pads, between pads and lines, and between lines.
4. Hole diameter check and merging.
5. Minimum line width check.
6. Determination of solder mask expansion parameters.
7. Mirroring.
8. Adding various process lines and process frames.
9. Line width correction for side etching compensation.
10. Formation of center holes.
11. Adding outline corner lines.
12. Adding positioning holes.
13. Panelization, rotation, and mirroring.
14. Panel splitting.
15. Graphic overlay processing, corner cutting, and line cutting processing.
16. Adding user trademarks.

3. Organization of CAM Processes

Because there are many types of CAD software popular on the market, as many as dozens, the management of CAD processes must first start from the organizational level. Good organization will achieve twice the result with half the effort. Since the Gerber data format has become the standard in the photo plotting industry, Gerber data should be the processing object in the entire photo plotting process. If CAD data is used as the object, the following problems will arise.

1. There are too many types of CAD software. If all process requirements must be completed in CAD software, every operator must master the operation of every type of CAD software. This requires a long training period before an operator can become a skilled worker and meet actual production requirements. This is uneconomical from both time and economic perspectives.

2. Because there are many process requirements, some requirements cannot be realized by certain CAD software. Because CAD software is used for design and does not consider the special requirements in process processing, it cannot meet all requirements. CAM software is specifically used for process processing and is best at doing this work.

3. CAM software has powerful functions, but all operations are performed on Gerber files and cannot operate on CAD files.

4. If CAD is used for process processing, every operator is required to be equipped with all CAD software, and each CAD software has different process requirements. This will cause unnecessary confusion in management.

In summary, the PCB CAM organization should have the following structure, especially for large and medium-sized enterprises:

a. All process processing should uniformly use Gerber data as the processing object.
b. Every operator must master the skills of converting CAD data into Gerber data.
c. Every operator must master the operation methods of one or several CAM software.
d. Formulate unified process specifications for Gerber data files.
e. CAM processes can be relatively concentrated and handled by a few operators for easy management.

A reasonable organizational structure will greatly improve management efficiency and production efficiency, effectively reduce the error rate, and thus achieve the effect of improving product quality.

4. CAM Software

The following are several common CAM software types.

1. PC Gerber, Ver 5.62

PC Gerber became popular in China relatively early and has been widely used, especially in the north. Because its functions are limited and cannot meet increasingly diverse requirements, it has been gradually eliminated in recent years.

Its functions are as follows:

1. Can operate 32 files at the same time.
2. Each file can be operated independently, opened, and closed.
3. Can accept various Gerber data formats, basic formats: relative coordinates, absolute coordinates, metric, imperial, leading zero suppression, trailing zero suppression.
4. Can merge multiple Gerber files into the same file.
5. Can perform various editing operations: add, delete, modify.
6. Can operate on the following objects: Flash, Trace, Arc, Circle, Vertex, Poly, Text.
7. Can perform window operations and group operations.
8. Can modify D codes.
9. D codes have 9 forms: Round, Square, Rect, Target, Thermal, Donut, Octagon, Oblong, Custom.
10. Can perform data measurement.
11. Can perform unit conversion.
12. Can perform rotation, mirroring, copying, and other panelization and panel splitting operations.
13. Can perform contour filling.
14. Can accept 1000 D codes.

Its disadvantages are:

1. Can only accept its own format D code table.
2. Slow operation speed.
3. Weak editing functions.

2. View 2001, Ver 3.04

This software has powerful functions and fast response speed and is popular in the south. In addition to the functions of PC Gerber, it also has the following characteristics:

1. Powerful editing functions:
a. Can lock a certain element.
b. Can independently close Pad or Trace.
c. Can cut Trace.
d. Pads can choose separate colors to distinguish them from lines.

2. Zooming in and out during display is simple and fast. Click the left mouse button to zoom in and the right mouse button to zoom out.

3. Can accept extended Gerber format containing D codes.

4. Can operate on up to 100 files at the same time.

5. Can accept D code tables generated by the following multiple CAD files: Lavenir, Mentor, Optrotech, PADS, Cadence, Interactive, P-CAD, Protel, Zuken, OrCAD, CadStar, Eagle, Tango, EE-Designer.

6. Can convert drill files in TXT format into Gerber files.

7. Can generate drill files in TXT format from Gerber.

8. Can read HPGL format files and convert them into Gerber files.

9. Can decompose extended Gerber into basic Gerber and D code tables.

10. D codes have 15 forms.

11. Can accept 9990 D codes.

12. Can convert DMPL files into Gerber files.

3. ECAM

It has powerful functions, but because of its high price, it is rarely used.

4. GCCAM

Among the CAM software currently popular in China, it has the most powerful functions. Its outstanding feature is the concept of negative D codes, breaking through traditional limitations.

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