How to do DFM check of PCB fabrication and assembly?

Many PCB desingers have no profound understanding of PCB fabrication and assembly processes, so their designs will probably have some unclear or even defectives. When a PCB manfacutring and assembly supplier gets the design files, the first step is not to produce. At the very beginning, the DFM (Design for manufacturability) check is crucial for a good delivery to customer.

How to do DFM checks?

The standard design files probably include BOM (Bill of Materials), Gerber, drawings, pick & place file, ICT points etc. As a PCB fabrication and assembly manufacturer, we have to start following check procedures.

(1) Last update time and version of production files

This is very important, because many designs were changed for several times. There will be misunderstanding between customer and supplier. If production files are not 100% confirmed, it possibly stands for that a batch of PCBA boards will be reworked. We don't want to lose quality and the professional impression at customer side.

(2) Designators and polarity

Designators and their polarity are not indicated in design. So we have to find out these kind of item and confirm with customer during DFM stage.

(3) Complete component descriptions of part number, manufacturer, designator in BOM

Some part numbers of components are not included in BOM. For example, there are several part numbers can match keyword in BOM and actually there are minor function difference between these complete part numbers. So it is vital to confirm with customer about the unclear part numbers.

(4) PCB fabrication info

Engineering requests of PCB fabrication including laminate, layers, copper weight, thickness, surface finish, impedance control, special via should be confirmed before production.

(5) ICT & Function test

It is highly recommended that PCB assembly manufacturer gets in-circuit test and function test procedures from customer. This would be last quality control before delivery, although some customers have no test plan or test plan is not ready.

(6) Other special requirements

At same time, we have to communicate with customer about special requirements such as conformal coating, electrical test or not-populated components etc.

DFM of PCB fabrication and assembly is crucial for quality assurance, which is worthy of much more attentions.