PCB Design Guidelines-Required files for PCB manufacturing and the assembly (populate the components)

Various PCB design files and other forms of documentation are required for Hopetimepcb to fabricate a printed circuit board and populate the components onto that board . There are two file formats we can translate and acceptfor manufacturing: ODB++ and Gerber version RS-274X.
In the OBD++ format, all data required for PCB fabrication and assembly are included within the .TGZ compressed archive. Should you choose to use this format, you only need to provide the .TGZ archive, along with a Bill of Materials (BOM) for assembly.
If you choose to use the Gerber file format, please ensure that you are using the RS-274X version. This format specifies a set of files, where each individual file represents one type of design drawing, such as top copper, bottom solder mask, or top silkscreen. Please ensure that you provide a Gerber file for each design element in your PCB layout, as well as any other relevant documentation for fabrication and assembly. When using the Gerber format, additional files are required for board assembly, a centroid file for pick and place, as well as a Bill of Materials with part numbers.

1.Gerber Files – RS-274X Format
RS-274X, also known as Extended Gerber or X-Gerber, is one of three distinct formats for Gerber files and is the current industry standard. RS-274X format is an open ASCII vector format used by standard PCB design industry software for processing 2D binary images. All Gerber Files are also Computer Numerical Control (CNC) files, and so it is possible to drive a PCB fabricator using Gerbers since fabricators are CNC machines. Gerber files describe various board images, such as copper layers, solder mask, silkscreen, and paste mask. This data includes traces, vias, pads, component footprints, and planes, as well as drilling and milling data.
RS-274X is the “middle child” of the three Gerber file formats. The oldest format for Gerber files is RS-274D, or Standard Gerber, which has now been generally deprecated in favour of the Extended Gerber format. The data in RS-274X is much more comprehensive than RS-274D since the RS-274D format keeps many of its critical information separate from the main data file. The RS-274X format offers several benefits over the nowobsolete RS-274D, including high-level commands and controls, allowing for more precise machine plotting. 
Gerber X2, the third and latest Gerber format, was released in February of 2014. It is fully backwardscompatible with the RS-274X format but includes some extra metadata to avoid ambiguity. Gerber X2 has not yet seen widespread industry adoption, and so RS-274X remains the standard at present.
PCB layouts are created using a computer-aided design (CAD) system and saved in the RS-274X format, where the Gerber set contains the complete description for each layer of the PCB. Typically, the CAD system outputs one Gerber file for each relevant layer. These Gerber files can be loaded into a computer-aided manufacturing (CAM) system to provide data for each step of the PCB production process. 
In keeping with industry standards, we at hopetimepcb accept the RS-274X Gerber format. This allows our clients to use the CAD design tool of their choice, provided that they can output their finished design files in Gerber format. The Gerber RS-274X format includes separate files for the different copper layers, silkscreen layers, solder mask layers, and milling/drilling locations included in a given design. Along with your Gerber files, you should send a PCB Manufacturing Drawing and a PCB Assembly Drawing , as well as a Bill of Materialsfor your order. A brief description for each of these file types is given in Table 1 below:


2.ODB++
ODB++ is a printed circuit board (PCB) manufacturing database, with different data stored in a hierarchy of files and file folders. For convenient transmission of data, some common operating system commands can be used to create a single compressed file, while preserving the hierarchy information. That compressed file containing the printed circuit board (PCB) design information can be sent directly to a PCB Fabrication and Assembly company, such as hopetimepcb. ODB++ stands for Open Data Base, with the ‘++’ suffix added in 1997 when component descriptions were enabled . ODB++ was developed and disseminated by Valor Computerized Systems, but was later acquired by Mentor Graphics in 2010.The vast majority of electronic devices include a PCB, which acts to house the electronic components that power the device, and also to connect these components in a specific manner. Computer-aided design (CAD) software is often used to create the layouts for these PCBs, and that layout information must then be transferred to a photolithographic computer-aided manufacturing (CAM) system. These CAD and CAM systems are generally produced by different companies, and therefore must use an intermediary file format, such as ODB++, for successful data exchange. ODB++ has two versions: the original (owned by Mentor), as well as an XML version called ODB++(X), which was donated to the IPC organization by Valor Computerized Systems.
We at hopetimepcb can work with ODB++ files of revision 7.0 or lower; there are no restrictions on the design tool used for PCB layout, as long as the design can be translated to ODB++ format files. That being said, we hopetimepcb can NOT accept ODB++(X) files. If you find some trouble in outputting your ODB++ files, please forward your .CAM or .PCB files to us to attempt the conversion on your behalf.

3. Drill / Route File
Drill Files define the size and coordinates of any holes to be drilled in a PCB design. These files can be used to control a drilling machine, which creates holes for Vertical Interconnect Access (VIA), mounting, and THT component placement.
On a standard 2-sided PCB, drill files are needed for the CNC machine to make accurate through-vias. For more complex multi-layer boards, many of the holes will be micro-vias, which pass through only a few layers rather than the entire board. These types of holes are also known as blind and buried vias. We will need a separate drill file, with a distinct name, for each layer pair that will be included in your design.
For Example: Let us assume that you have a 4-layer board with most vias extending all the way from top to bottom, and some buried vias extending from layer 1 to layer 2. In this case, you should have two drill files, with one of them named “Drill_1-4” and another named “Drill_1-2”.
Route Files are a type of file that define the electrically-conductive copper traces, known colloquially as “routing”, on a PCB design. These files are used to control a fabrication machine in order to lay copper traces on a PCB board.
Regarding the submission of drill and route files to hopetimepcb: if you use the ODB++ format, drill files and route files will both be included in the .TGZ compression file. If you choose to use the Gerber RS-274X format,then separate drill files and route files will need to be provided in RS-274X format.

4.Netlist File
Netlist files contain the connectivity information for an electronic circuit. A netlist file is a collection of several related lists, one list for each group of electrically-connected pins. This file is generated from the circuit’s schematic design, and it is used in PCB layout to determine which component pads should be connected by copper traces on the finished PCB
We at Hopetimepcb request a netlist file for the electrical testing of your bare PCBs; we ensure an exact match between the actual connectivity on your PCB and that of your netlist file for every board that leaves our facility. The ODB++ format contains your netlist file by default, and so there will be no need to provide one separately . If you use the Gerber RS-274X format, then you will need a separate netlist file in IPC356 format.

5.Centroid File / Pick and Place File
We require a centroid data file –also known as a Pick and Place file– in order to accurately assemble a PCB. The main purpose of a centroid data is to hold information on the position and orientation of all surface mount technology (SMT) devices on a circuit board design. Centroid files contain data regarding reference designators,XY locations, rotations, component packages, and placement on either the top or bottom side of the board.
• Reference Designator – Short alphanumeric code assigned to each part in the layout (R12, C17)
• Component Value/Package – Component part numbers, part values, and package size
• Layer – Either the top or the bottom side
• XY Location – Cartesian coordinates, beginning at the origin• Rotation – Described part orientation in degrees (0, 45, 90, etc.)

6.Assembly Bill of Materials (BOM)
Bill of Materials is a list of all the parts that are needed for the PCB Assembly and matches those parts to the Reference Designators in the PCB layout. We require this list in a Microsoft Excel format. If multiple instances of the same part are used on one board,then they are all listed on one line of the BOM with their corresponding reference designators and total quantity. The following information comprises the BOM; incomplete BOMs may be acceptable, however, it is always best to include all of the following information in your BOM to minimize the risk of purchasing errors.
• Item # - Unique item number for each component (1, 2, 3)
• Ref Des – Matches BOM item to PCB layout location
• Quantity – Quantity of this component that will be needed for each board
• Manufacturer – The name of this component’s manufacturer
• Manufacturer Part # - The part number assigned to a component by its manufacturer
• Description – Brief component description
• Package – Packaging size (ex. 0805) or type (ex. BGA, QFN)
• Type – SMT or THT
• Your Instructions – Any special requirements that you have for this part
We provide a sample Bill of Materials on our website that may be used as a basis for your Bill of Materials.

7.Drawings
Design drawings are not strictly required for all PCB fabrication and assembly projects, but they can help to make your intentions clearer to our production team, particularly regarding special requirements. We recommend you include design drawings for projects with a high number of layers or components.

7.1 PCB Manufacturing Drawing
PCB manufacturing drawings only contain that information which is needed for the fabrication of the PCB. This could be information such as the project name, board dimensions, board thickness, tolerances, material, copper weight, number of copper layers, or surface finish. These may be a list of notes beside the board’s artwork or listed in a separate file. Other special information may also be included in the manufacturing drawing, such as controlled impedance requirements, via-in-pad tenting, gold-plated edge connectors, and so on.

7.2 PCB Assembly Drawing
PCB assembly drawings contain that information that is needed for assembly of the various components onto a PCB. Basic component information, such as position and orientation, are provided on this drawing, along with special requirements, such as height limit. Three-dimensional renderings could also be included to clarify special requirement areas but are not necessary for typical boards.

8.Standard Manufacturing Specifications
The following list outlines the parameters we require to manufacture your design. Please provide this information when requesting a quote as well, in order to price your project properly.
• Project Name – PCB name and Version #
• Dimensions [inches] – Board length and width
• Number of layers – 2, 4, 6, 8, 10, 12, 14, 16 layers
• Total thickness [inches] – Board thickness for one board with all layers included
• Surface Finish – Example: HASL, ENIG, Immersion Tin, Immersion Silver
• Solder mask – Indicates the desired solder mask colour for your PCB, and to which sides of the board that solder mask will be applied. 

Advanced parameters which may also be specified include
• Profiling – Indicate any panelization requirements for your project
• Impedance Control – Do you require a specific impedance for RF transmission lines
• Material (substrate) – Example: FR4 or IT-180A
• Silkscreen (Legend)– Indicates the desired silkscreen colour for your PCB, and to which sides of the board that silkscreen will be applied
• Testing – Electrical testing is standard with all our orders and cannot be excluded to ensure quality.
• Printed board handling and storage guidelines – Special information regarding safe handling if required

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