PCBA Assembly Order

#1. Incorrect Gerber File Format for Stencil Paste

Fix: The gerber format MUST be RS274X (opposed to RS274D). The RS274X

format is the most current industry standard and includes aperture information in the gerber itself instead of requiring a separate aperture file.. (Google for “RS274X format”) All current version CAD programs can generate the -X format although some may default to the older format for the sake of backwards compatibility.


#2. Missing a gerber file for stencil paste for one or both sides

Fix: We need a paste layer in order to generate a paste stencil. (if you have 2-sided SMT, then there will be 2 paste layers) This is not the same gerber as the solder mask. A normal paste layer/gerber will contain ONLY SMT PAD features. A paste gerber will seldom include: un-tented vias, holes for axial or radial leads, or mounting holes with annular rings. Also, a paste gerber does NOT need a board outline, dimensioning marks, labels, or company logo/info boxes.

Note: The solder paste layer may have to be generated separately from the FAB layers and named as a cream or stencil gerber using your CAD system.


#3. Bill of Materials (BOM) data is not in a format we can use accurately or quickly.

Fix: We need an “Assembly BOM” (not just a ‘Purchasing BOM’) in CSV format. XLS can lose data (cell over-flow ####) and a simple text format is hard to parse due to non-standard field usage or separators. A PDF document is never suggested because it cannot be converted.


#4. The PCB Assembly BOM is missing important details of each part.

Fix: Since a BOM is used for purchasing parts, then think of an expanded BOM for pcb assembly manufacturing. We do more than just order parts for you. For electronic assembly processing, the “Assembly BOM” needs to include reference designators, value, package/decal, description, and part number. Part parametric information for the part is needed regardless of the actual part number. A part number could change by the manufacturer, or cross references could be different.


#5. Parts just arrive without any kind of packing list documentation.

Fix: Ideally, you’ve used our free labels to make the incoming inventory error free. Our receiving personnel needs a PACKING LIST OR INVOICE with every shipment for comparison with your BOM. Also, please include a reference to our in-house job

number on the box (i.e. B1001).