Gerber files are a collection of document formats used by circuit board industry software to describe circuit board (circuit layer, solder mask layer, character layer, etc.) images and drilling and milling data. It is the standard format for image conversion in the circuit board industry.
No matter how powerful your design software is, you must eventually create a Gerber format light painting file in order to light paint film.
Early light plotters were composed of a precise servo system and an X-Y table controlled by it for loading high-contrast film. A very bright light source passes directly through the shutter, through the aperture, and is focused on the film. The control system commands Gerber into appropriate table movement, wheel rotation, and shutter opening and closing.
When the shutter is opened, the light beam passes through the aperture and exposes the image of the aperture on the film. When the shutter is opened and the desk moves simultaneously, lines or stripes are imaged onto the film. Using the correct commands to control the movement of the desk, the selection of aperture and the operation of the shutter, the light plotter can generate any desired image on the film.
Gerber Scientific (now Gerber Systems) began to control the photoplotter industry by producing precision machines. The word Gerber is no longer worthy of its name in the light painting industry.
Gerber file
Gerber's classification
There are two existing versions of Gerber:
Extended Gerber is RS-274X, which is widely used;
The standard Gerber is RS-274D, which is an old version and is gradually being abandoned and replaced by RS-274X.
RS-274X
RS-274X (also known as extended Gerber format, or X-Gerber format) is a two-dimensional vector image description format and is also the standard format for image description in the circuit board industry. RS-274X is a readable ASCII format that contains a series of control codes and coordinate information. The elements that make up the image are lines and flash that draw outlines at specific positions. Positive and negative graphic objects can be combined.
The RS-274X file contains a complete description of the image of each layer of the circuit board and has all the elements needed for circuit board graphics imaging without the need for file extensions. Aperture can define positive objects and negative objects. Copper does not need to be designated as a "fill block" or "fill line" as in RS-274-D.
RS-274X is a complete, powerful and clear standard description of each layer of the circuit board, which can be automatically imported and processed. This allows it to be used for fast and secure data conversion as well as trusted and automated workflows.
Aperture files in the RS-274X format are integrated in gerber files, so aperture files (that is, containing D codes) are not required.
RS-274-D
The old RS-274-D (also known as the standard Gerber format) is a data format derived from the EIA's RS-274-D standard code and used to control CNC machine tools in many fields. The Gerber RS-274-D is used to control a vector light plotter, which is a two-dimensional CNC machine tool. Gerber RS-274-D is an ASCII format that contains control codes and X, Y coordinates.
Gerber RS-274-D was developed in the 1960s and 1970s to control vector light plotters. This machine has now been replaced by a laser plotter. Gerber RS-274-D itself cannot describe image information. It does not contain coordinate organization and Aperture information. Aperture is the shape description of an object, similar to the font of a PDF file. The operator of the light plotter manually sets the coordinate organization and Aperture, describing it in a text file, which is called an Aperture file or, for historical reasons, a wheel file. Aperture files are mainly used for operators to read and write, and there is no standard. Each EDA software and even each designer has its own different aperture file design and name conversion habits. PCB manufacturing personnel must understand it themselves and input it into the CAM system manually.
RS-274-D only supports simple image operations. Because of its extreme limitations, people have to create some complex graphics, such as stroking, which is filled blocks or filled lines.
RS-274-D is a numerical control standard rather than an image description standard. An RS-274-D file is useless without a matching Aperture file. But there is no unified standard for Aperture files.
Problems with exporting GERBER files from CAD
There are RS-274X files produced by some CAD software that are difficult to process. Some files contain grammatical or semantic errors. Some of the archival data is too inaccurate, resulting in huge rounding errors in very precise circuit board factories.
1. Gerber export accuracy (grid calculation) is usually at least 10 times higher than the accuracy of CAD systems.
2. Some CAD systems still use fill blocks to fill instead of using shape fill, or use filled SMD instead of using flexible Aperture definitions. Padding blocks will not invalidate the archive, but it will make processing longer and more difficult. For this reason, padding blocks should be discarded.
Source of the Gerber Archives
1. Customer supply files
Gerber file sent directly by customer A;
BGerber files transferred based on *. PCB format files.
2. Based on the PCB sampling points provided by the customer, the obtained Gerber file in metric 3.2 format.
The original PCB files can be converted to Gerber format using the following software:
1. Pads 2000 (*.job) D code (*.rep) Gerber (*.pho)
2. PowerPCB (*.job/*.pcb) D code (*.rep) Gerber (*.pho)
3. Protel (*.PCB) D code (*.APT) Gerber (*.GTL/ *GTP/ *GTO)
4. AutoCAD (*.dwg) Gerber (*.dxf)
5. Orcad (*.max) D code (*.APP)
6. Gerber (*.TOP/ *.SST/ *.SPT/ *.SMT)
Protel（*PCB）
1. D code (*.APT/ *.APR (99se))
2. Gerber file ("T" in the extended format name below means the top layer, and "B" means the bottom layer)
A. Line layer *. GTL *. GBL
B. Silk screen layer (character) *. GTO *. GBO
C. SMD layer *. GTP *. GBP
D. Green oil layer (solder mask) *. GTS *. GBS
E. Border layer *.GKO or *.GM1
Power PCB (*.job/ *.pcb)
1. D code (*.REP)
2. Gerber file ("01" in the extended format name below represents the top layer, "02" represents the bottom layer of a double-sided board, "04" represents the bottom layer of a 4-layer board, and "06" represents the bottom layer of a 6-layer board)
A. Line layer art01.pho art04.pho
B. Silk screen layer (character) sst0126.pho sst0429.pho
C. SMD layer smd0123.pho smd0422.pho
D. Green oil layer (solder mask) smo0121.pho smo0428.pho
OrCAD(*.max)
1. D code (*.APP)
2. Gerber file
A. Line layer *. TOP (toplayer) *. BOT (bottomlayer)
B. Silk screen layer (character) *. SST (silkscreentop) *. SSB (silkscreenbottom)
C. SMT layer*. SPT (solderpastetop)*. SPB (solderpastebottom)
D. Green oil layer (solder mask)*. SMT (solermasdtop) *. SMB (solermasdtop)
Circuit board
The most beautiful thing about Gerber data is its simplicity. Gerber only has four basic commands plus corresponding data. The circuit board library had to be defined simply and compactly because the first machines were powered by punched paper tape. This requires compressing as much information as possible into as few bytes as possible to explain many problems. At the time, we did not expect that storage space would use hundreds of megabytes instead of hundreds of bits. The group came to measure today.