What Files are Needed for PCB Assembly ?

We have been seriously committed to offering continuous solution services for printed circuit boards. This covers design, assembly, and manufacturing. Immediately the PCB design is set, there are some files you must export to ensure PCB assembly. When handling turnkey assembly manufacturing and inquiry, you will require BOM (bill of materials), centroid data, and PCB designs, which could be in either ODB++ or Gerber format.

Asides from the files above, it is also helpful to add additional files like assembly drawings or fabrication drawings, as well as any unique instructions for the project. We also offer preliminary quotes in line with early Gerber files; that’s if the design is not fully complete. In this article, we will be considering how to generate files for PCB assembly as well as how to export them. Also, we will talk about those important things that are useful in PCB assembly. Please continue reading to understand better.


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How to Generate the Files for PCB Assembly

PCB assembly works with some files in order to offer an important idea regarding the courtyard information, orientation, positions, of all the layers of the component. All these include assembly drawings, BOM, centroid, Gerber/ODB++, etc.

You can handle the generation of these files for the assembly and manufacturing of the board using documentation and design tools. Whatever procedure is useful in generating the files for PCB assembly depends on the type of design software you have used.

With full assembly documentation, you can be sure of having the basic insight into the inspection techniques and procedures necessary to deliver the final product. This is why it is important to gain some knowledge about the files and the procedures necessary for their generation. In this section, we will be discussing these files and how to generate them.

What Files are Needed for PCB Assembly?

Just like we have already mentioned in the introduction, the most important of all the files necessary for PCB assembly includes assembly drawings, Gerber/ODB++, BOM, and centroid file.

As a design engineer of PCBs, if you fail to communicate the vital information to the contract manufacturer via these files, you may end up coming across several errors. Some of these errors include component quantities mismatch, absence of polarity marking and pin 1, missing footprints, orientation indicators, and more.

These files are significant due to these reasons.

  • These files offer good communication between customers and vendors. This ensures an effectiveboard population.
  • If these PCB assembly files are absent, it may cause orientation and position-related errors of components. This may cause high costs during repair
  • There are some data you cannot obtain from silkscreen, but you will be able to get from the files
  • Absence of vital information such as through-hole components position or polarity markings when soldering manually may lead to discrepancies.

The following answers the question “what files are needed for PCB assembly?”


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Gerber or ODB++ Files

You can say that Gerber files are files that contain vital information regarding the printed circuit board layers for production. They are usually compressed into a .rar/.zip file. In addition to the Gerber files, make sure to add the board outline and drill files.

The drill file has within it the size and location of the drill holes. You may find multiple files for drilling, if you need back drilling and buried and/or blind vias for the process.

When your printed circuit board requires special processes, such as castellation, carbon ink, PSA tape bonding, cut-outs, edge plating, FPC stiffener(s), EMI shielding film, then there becomes a need to provide the necessary mechanical layer(s). Always ensure that you include the layer files. This makes sure that you don’t miss any of the requirements.

Also, you can replace the Gerber files with the ODB++file. You create both files in a specific archive, and this includes the fabrication of all the files together.


BOM has to do with a list of the parts, which will be together in the circuit board. The format of the BOM can be in the form of any Excel chart. You may have to give more information for partial turnkey and full turnkey service in contrast to what is necessary for kitted/consigned service.

Furthermore, BOM for Partial Turnkey and Full Turnkey service includes the following.

  • Reference Designator (this is necessary)
  • Item# (that’s if necessary)
  • Description (that’s if necessary)
  • Notes (that’s if necessary)
  • Package (that’s if necessary)
  • Part Number of the Manufacturer (this is necessary)
  • Quantity for each board (this is necessary)
  • Manufacturer (this is necessary; note that there are manufacturers that have same or similar part numbers)

For those positions left unassembled, or make sure you add “Do Not Include” (DNI) to the BOM. With this move, you are making the assembly’s inspection much easier in different stages. To reduce any possibility of having an error, you can highlight the rows, say in blue color.

The making of the assembly program and components sourcing has to do with the BOM. Then you must be very careful and accurate when transferring the data to the excel file.


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Centroid File

This is also the XY Coordinate or Pick-and-Place file. The centroid file has information regarding SMDs – surface mounting devices. These include where you can find each of the components on the circuit board, like rotation, value/package, X/Y position, reference designator, and layer.

There are design softwares, which generates this file automatically, while some cannot, however you may have to do a file modification as well as create a centroid file.

Assembly Drawings

Similar to the drawing of PCB fabrication, that of the assembly is also auto-generated. This is gotten from the CAD tools of the PCB design.

The assembly drawing’s purpose is to offer the operator of the assembly machine with more than enough information in checking that the rotation of the assembly rotation, as well as the polarity of all the assembled components is accurate and correct. Also, it helps the operator check that all the components are in the right position, just the same way the designer specifies it, most especially when there is an absence of silkscreen printing on the circuit boards.

Furthermore, the drawing must show the position of pin 1 in all the ICs clearly. This also includes each component’s reference designator.

There are other types of polarity markings. These include the negative marking for the diodes (cathode) and the anode terminal marking, which is positive, for the tantalum capacitors.

Pick and place file

This file helps in describing the place of the component and gives the information regarding component reference, orientation, Y coordinate, X coordinate, and angle. The most recommended is the pick and place file having a CSV format. Also xlsx and xls are fine too.


The schematics file is optional. To achieve the best assembly effect possible, you ay decide to send the PCBA’s schematics to the company assembling your PCB.

3D Drawing

This is optional. With 3D drawing, you will be able to check the direction and position of the components on the PCBAs. You can create 3D drawings for the PCB assembly in the layout software. All you need to do is to tap on that small rectangle in your Altium designer, and from the options available, you can choose from any of the available 3D options.

Testing file of the PCBA

The testing file of the PCBA is also optional. This file is useful in testing end products. It has testing methods and programs in it.


It is necessary to add other notes. This will help in teaching the Printed circuit board assembly provider on ways to assemble the board. With reference to the board’s complexity, you may have to include some more things. Before you create the assembly drawing, consider these:

You must include all critical components, such as heat sinks or connectors, which require some specialized information regarding mounting, in the notes for assembly.

You must show other hardware, which you will add to the board, like ejectors, handles, or stiffener bars, with some instructions added in your drawing notes.

Furthermore, you must explore all the important areas related to PCB assembly properly or shown in detail, enlarging and pulling it away from the remainder of the board image. You must include the label and assembly stickers’ location in the drawing as well.

Important Things Useful in PCB Assembly

In order to create PCBAs, SMT stencils, PCBs, as well as electronic components are very important.

SMT Stencil

This is also PCB stencil. These are referred to as frameless stainless or laser-cutting framed stencils, which are very useful for SMT assembly. The solder paste passes through the SMT stencils’ openings to paste onto the pads of the PCB.

Most time, the manufacturing of the SMT stencils takes place during PCB manufacturing. The number of stencils you need depends on the number of SMT lines that will function for the printed circuit board assembly.

Electronic Components

On PCBs, you will find many electronic components. These components are either through-hole or surface mounted onto the circuit boards. Furthermore, the packaging numbers of the component include 0603, 0402, 0201, 01005, etc.

PCB companies don’t involve themselves in manufacturing; however, they source electronic components necessary for the assembly of printed circuit boards. In most cases, these companies source all usual components via bulk pricing. However, recently, ICs as well as some components have been in limited supply out there. By doing so, you will prepare them much better in advance even before you go ahead with the PCB assembly.

Printed Circuit Board

The manufacturing of printed circuit boards is usually done with respect to the Gerber files. The fabrication is done in the laminated layers, which includes glass fiber, copper foils, solder mask, adhesives, silkscreen, etc.

The design of a PCB is done using the layout software of the PCB, making use of a breadboard for testing circuits, and to help generate the Gerber files.

In the software of your PCB layout, you will be able to see both your PCB’s 2D & 3D images. After checking to confirm that the design is fine, you can then go ahead to give it to a PCB manufacturer to help in the manufacturing and assembling of your PCBs.


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Integrated Circuits

With integrated circuits, you can interconnect inductors, capacitors, resistors, transistors, as well as other components and necessary wiring in circuits on either one or more small dielectric substrate or semiconductor wafers.

Furthermore, the components are then packed in a case, therefore becoming a micro-structure having the necessary circuit functions. Integrated circuits represent the trend of high reliability, intelligence, and miniaturization in the electronics industry. These integrated circuits are usually the necessary and required components for projects of PCB assembly.


What Things Do PCB Assembly Manufacturers Do When It Comes to PCBA Projects?

Professional PCBA manufacturer has to check the Gerber and BOM files from the side of the customer. Before the production of the batch, PCBA manufacturers must inspect the first article. This ensures that the PCB assembly is good.

Furthermore, there is a need for the manufacturer to create the FAI report. This is for the review and acceptance of the customer for the PCBA production to go on. Once the customer has approved it, the production of the batch begins.


By now, you should have the answer to the question: what files are needed for PCB assembly? We have also given other vital information regarding PCB assembly. Note that PCB assembly is useful and important in all electrical and electronic devices for commercial and domestic uses. With our guidelines on PCB assembly, you will be ready for what PCB assembly is all about. Gerber files, BOM, centroid file, etc are the required files the company needs for PCB assembly. However, if there are other questions troubling your mind regarding PCB assembly problems, you can contact us. Also, we are here to help and we will surely provide answers to all your queries.


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