Gerber format is a collection of document formats for describing images and drilling/milling data of circuit boards (circuit layers, solder mask layers, character layers, etc.) in the circuit board industry software. What is the use of Gerber files? Can we just draw the PCB circuit diagram?
Simply put, Gerber files are the process of peeling off PCB files layer by layer for the convenience of Computer Aided Manufacturing (CAM), while also ensuring the confidentiality of the drawn circuit.
Introduction to Design/Board Layers&Color in Protel DXP
(1) Signal Layers: Signal Layers
The ProtelDXP circuit board can have 32 signal layers, where Top is the top layer, Mid1-30 are the middle layers, and Bottom is the bottom layer. Traditionally, the top layer is also known as the component layer, and the bottom layer is also known as the solder layer.
The signal layer is used to place copper film traces that connect digital or analog signals.
(2) Masks: Masks
Top/Bottom Solder: solder mask layer. There are two layers of solder mask, which are used for screen printing of solder mask. The auxiliary solder mask prevents solder from flowing freely and avoids short circuits between various electrical objects. Solder surface refers to the solder mask layer, which is used to apply solder mask materials such as green oil to prevent areas that do not require soldering from being contaminated with solder. This layer will expose all the solder pads that need to be soldered, and the openings will be larger than the actual solder pads. This layer of information needs to be provided to the PCB factory.
Top/Bottom Paste: Solder paste layer. There are two layers of solder paste used to attach surface mount components (SMD) to circuit boards. Use a paste mask to pour semi melted solder paste onto the circuit board and then attach the SMD components to complete the soldering of the SMD components. Paste surface refers to the solder paste layer, which means it can be used to make a steel mesh for printing solder paste. This layer only needs to expose all the solder pads that need to be surface mounted and soldered, and the openings may be smaller than the actual solder pads. This layer of information does not need to be provided to the PCB factory.
(3) Silkscreen: Wire mesh layer
Top/Bottom Overlay: The screen layer has two layers, namely the topmost and bottommost layers of the printed circuit board. This is to facilitate the installation and maintenance of circuits, and to print the required logo patterns and text codes on the upper and lower layers of the printed board.
(4) Internal Plan: Inner plane
The inner plane is mainly used for power and ground wires. ProtelDXP can have 16 power and ground layers. The copper film of the power and ground layers is directly connected to the power and ground pins of the component. The inner plane can be divided into sub planes for network routing.
(5) Other: Other layers
Drill Guide: Determine the location of drill holes on the printed circuit board.
Keep Out Layer: This layer prohibits wiring.
Drill Drawing: Determine the shape of the drill hole.
Multi layer: Set multiple layers.
(6) Mechanical Layers: Mechanical Layers
The mechanical layer is used to place various indications and explanatory text, such as circuit board dimensions. The mechanical layer can be printed together with other layers.
(7) System Colors: System Colors
Connect "," DRC Error ", 2" Visible Grid "," Pad Holes ", and" Via Holes ". Some of these layers are used by the system itself, such as the Visible Grid layer, which is designed for designers to easily locate during drawing. Each layer can choose its own preferred color, usually red for the top layer, blue for the bottom layer, green or white for text and symbols, and yellow for solder pads and vias.
2. How to generate Gerber files using Protel DXP
1) The premise is that the PCB has already been drawn, enter the menu for exporting Gerber files: File Fabric Output Gerber Files
2) Unit and precision settings:
In the "General" section, select "Inches" as the "Unit" and choose a format of 2:5. This dimension has a relatively high accuracy, but of course, it is necessary to first negotiate with the board processing factory to determine the accuracy.
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Select the layer to export:
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In "Aperture", select "Embedded Aperture (RS274X)" (check the box).
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Finally, click "OK" to generate the required Gerber file.
3. The correspondence table between the extensions of each layer in the Gerber file generated by Protel2004 and the original layers of the PCB
The gerbers generated by Protel are all standardized.
(1) The first letter 'g' in an extension generally means' gerber '.
(2) The second digit of the extension represents the surface of the layer, b represents the bottom surface, t represents the top surface, g represents the middle circuit layer, and g p represents the power layer.
(3) The last digit of the extension represents the category of the layer. L is the circuit layer, o is the silk screen layer, s is the solder mask layer, p represents solder paste, m represents the outer frame, reference hole, mechanical hole, and others are generally not important,
Top (copper) Layer: GTL
Bottom (copper) Layer: GBL
Mid Layer 1, 2,..., 30: G1, .G2, … , .G30
Internal Plane Layers 1, 2,..., 16: GP1, .GP2, … , .GP16
Top Overlay: GTO
Bottom Overlay: GBO
Top Paste Mask: GTP
Bottom Paste Mask: GBP
Top Solder Mask: GTS
Bottom Solder Mask: GBS
Prohibit wiring layer Keep Out Layer: GKO
Mechanical Layer 1, 2,..., 16: GM1, .GM2, … , .GM16
Top Pad Master: GPT
Bottom Pad Master: GPB
Drill Drawing, Top Layer - Bottom Layer (Through Hole): GD1
Drill Drawing, other Drill (Layer) Pairs : .GD2, .GD3, …
Drill Guide, Top Layer - Bottom Layer (Through Hole):. GG1
Drill Guide, other Drill (Layer) Pairs : .GG2, .GG3, …
Mechanical layer: It defines the appearance of the entire PCB board. In fact, when we talk about the mechanical layer, we refer to the external structure of the entire PCB board.
Prohibited wiring layer: Define the boundary of copper with electrical characteristics when we lay it out. That is to say, after we first define the prohibited wiring layer, the wires with electrical characteristics we lay out in the future cannot exceed the boundary of the prohibited wiring layer.
Top overlay and bottom overlay: Define the silk screen characters for the top and bottom layers, which are the component numbers and some characters commonly seen on PCB boards.
Top paste and bottom paste: The top and bottom pad layers refer to the exposed copper platinum that we can see on the outside. For example, if we draw a wire on the top wiring layer, what we see on the PCB is just one wire, covered by the entire green oil. However, if we draw a square or a point on the top pad layer at the position of this wire, the square and point on the board will have no green oil, but copper platinum. The top and bottom solder layers are just opposite to the previous two layers, so it can be said that these two layers are meant to cover the green oil. Layer, multilayer. This layer is actually similar to the mechanical layer. Gu Ming'enyi, this layer refers to all layers of the PCB board
