Files needed for PCB Assembly

GUIDELINES TO A SUCESSFULL 
PCB ASSEMBLY PROJECT

1. Submit necessary 
data files

By following the file requirements from the start means the manufacturing process will proceed without delay. 

2. Meet our 
PCB Requirements

For your PCBs to be assembled smootly and quickly we require some conditions to be met. Such as Fuducials, Components and size of PCBs. 

3. PCBs assembled 
without delay

A successful PCB assembly project completed smoothly.

Step 1. 
Submit all the necessary files

Chromatec Manufacturing require various files before the PCB assembly can start. 
  • Gerber files
  • Bill of Materials (BOM) 
  • Centroid file (XY)

Gerber Files (Working or Panelized)

The Gerber files are required to manufacture the Solder Paste Stencil for our Solder Paste Machine. 

Solder paste stencilling is the process of using a stencil to quickly apply solder paste to all of the pads on your bare board. This stencil contains various holes, which represents all of the SMD footprint pads on your board layout. 

If you already have a solder paste stencil - please contact us and we will discuss if it is compatible. 

NOTE: If possible, panelized gerbers are preferable. Please let us know if you do not have panelized gerbers, and we will generate the panelization using working Gerber files)

The Gerber files must contain:
  • Outline Layer
  • Copper Layers
  • Soldermask Layers
  • Solder Paste Layer - Stencil Data
  • Drill Data
  • Silkscreen layer

Of course we will also review your files before assembly starts to make sure all the information is complete and accurate for assembly. 

Bill of Materials (BOM)

The Bill of Material (BOM) is a list of all the required parts to assemble the printed circuit boards. It details what parts are needed, and the where are the parts are placed when assembled. 

If possible, please ensure when the BOMs are exported from your schematic design program - each item is on a separate line. 

See an example of a BOM file here.

We accept the BOM in .xls, or .csv. 

Note: For turnkey assembly orders, we require additional items in the bill of material such as a distributor, distributor’s part number, manufacturer’s name, manufacturer’s part number, etc.
Column Description Example
Reference Designator Part Reference on PCB R23
Manufacturer (If applicable) Texas Instruments
Manufacturer Part Number (If applicable) TP1234
Package Type 0805
Fitted YES

Centroid File
(XY Data)

Together with the Bill of Material (BOM) the XY data allows the components to be placed on the PCB. The XY data includes the location of the component along with the designators that allows the Pick and Place machine to correctly place the parts. 

We accept the XY Data in .xls, or .csv. 

See an example of a Centroid file file here.

Please ensure Fiducials are included in the Centroid File. See Step 2 for more information on fiducial markers. This is an important step. 

NOTE: All dimensions shall be in millimetres for X-Y locations and degrees for rotation. 

Column Description Example
Reference Designator Part Reference on PCB R23
X Location X-Location of Part from Origin (mills) 120
Y Location Y-Location of Part from Origin (mills) 270
Rotation Angle of the Component 180

Step 2. 
Meet our requirements

1. All boards have fiducial markings

Fiducials are reference points on the PCB which help to recognise the position components in relation to the board. 

NOTE: Generally, it is advisable to have 3 fuducial marks. However, we can work with PCBs already fabricated without fiducials.
2. PCBs are Panelized 

The purpose of panelization is to secure PCB boards during manufacturing, and assembly processes, whilst 
optimising output of PCBs assembled. 

We generally require panelized PCBs - especially if SMT components are too close to the edge of the PCB. 


3. Parts are clearly identified (usually by silkscreen layer)

The silkscreen is a very useful tool in identifying components on the board. 

Please ensure the silkscreen includes key markings, such as polarity, or send a detailed file with any special requirements highlighted. 


4. Providing enough components

Even in small prototype builds - it still may be cheaper purchasing a reel of components than smaller strips. You must include overage when purchasing components such as resistors and capacitors - we suggest around 50 above quantity required.
  • Ensure components are on a reel or continuous strip - rather than small individual strips for each PCB.
  • Trays are suitable - please ensure they are packaged securely. 
  • Always send a packing slip listing all items and quantities if possible, in the kit provided.

Note: Please get in touch if you need any help or advice purchasing components.

Interested in our services? We’re here to help!

If you require a quote please email the Gerber files, Bill of Materials (BOM) and centroid file to pcb-assembly@chromatec.com. 
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