What Should You Include in a PCB Pre-order Checklist?
PCB design and fabrication of electronic circuits has become complex. However, this aspect is often avoided. Instead, there is more focus on other interesting aspects of the PCB. The truth is, unless the PCB is designed properly, your circuit is going to face issues. Many times, the design issues occur due to lack of clarity regarding PCB design components. Hence, the next time, when you approach a PCB assembly and fabrication service provider for a PCB quotation, you should send them a PCB pre-order checklist. This post discusses the essential components of a pre-order checklist.
Information to be Included in a Pre-Order Checklist
Most PCB assembly and fabrication services will ask you to send a pre-order checklist. The concept of the pre-order checklist for a PCB assembly will remain the same everywhere. You need to include the following in it:
- Dimensions: This is the most important aspect of any PCB design project. The dimensions along X and Y should be added. During the assembly, a CNC router is used to cut the PCB panel. The router utilizes the dimension layer to cut the panels. Hence, it is very important to mention the shape of the printed circuit board. Most PCB assembly services will allow you to cut any shape. During the assembly and fabrication, the PCB fabricators mostly concentrate on the following aspects. Hence, it is very important to include the mention in your file:
- Hole diameter
- Finished hole sizes: This is >=10 mils greater than lead
- Silkscreen legend text weight: This value is always kept >=10 mils
- Components: This value is always measured as >=0.2″ from edge of PCB
- Pads: This is generally set >= 15mils greater than finished hole sizes
- Traces: The traces lie at >=20 mils from the board edge
- Through-hole Tolerances: This information should include thru-hole drill tolerance, soldermask tolerance, legend, and route tolerance.
- Trace width: This should be sufficient for the current carrying. Also, care should be taken to include sufficient clearance for high voltage traces
- Component Labels: Many times, part values are not mentioned while sending the pre-order checklist. This creates confusions during the prototype building. Thus, each component should be accompanied with an appropriate value.
- Other Details: In addition to the above-mentioned, you need to add the following points:
- Layer stack up
- Material of construction
- Surface finish
- Copper thickness/weight – Inner layer and outer layer
- Soldermask and color
- Soldermask type
- Silkscreen legend and color
- Drill file
Generally, the pre-order checklist and a PCB design is sent together. Most PCB assembly and fabrication services ask for Gerber RS-274X format files in DDB/PCB (Protel) and .BRD Eagle formats. If the files are converted to RS – 274 X format, the following should be included:
- Positive Gerber Layers: Top and Bottom ( inner layers should be included for multilayer PCBs)
- NC Excellon Drill file
- Aperture/Dcode file ( if not RS274X)
- Drill Tool List ( if it is not listed in NC drill file)
All the above-mentioned information will help you receive an instant pcb quote online. If you wish to approach a PCB manufacturer for turnkey PCB services, then you need to send BOM and a PCB design file. At times, manufacturers may provide their own template, or you need to make one of your own because it helps them speed up the quote process.