Catching DFM problems during PCB design

DFM From the narrow meaning is: to make the design more suitable for production requirements, it requires us to design with fully consider in the case of production, so that the design can be produced out.

From the broad sense: that is designed to meet the majority of the production requirements, enabling design stuff of more choice and lower costs. That is Design for money!

The purpose of designing a part for manufacturing is to improve the product along three dimensions: quality, delivery and cost. Utilizing sound DFM practices will ensure quality, reduce delivery lead-times and provide a reduction in the product cost by carefully selecting the best component for your application.

In this day of global competition where cost, quality and speed to market are the key to a successful product, too often we witness very simple mistakes that are costly for our customer that could have been easily corrected during the design stage. Many errors are systemic across different customers and industries. Some of the most common errors:

1. Missing or given misunderstood important manufacturing information.
2. The package of selection of components are not matched with the footprint designed.
3. Via holes & board pad proximity too close.
4. Incorrect gap between components so assembly conflict emerged.
5. PCB specifications not adequately detailed (e.g. board material, thickness, surface finished etc).
6. Pitch of PADS (or PTH holes) mismatch with pitch of components' pin.
7. PTH holes incorrectly sized for TH parts.
8. Connectors, switchers or other similar components designed in Opposite direction.
9. Selection of components that cannot withstand process temperatures (reflow process).
10. The design requires unnecessary "extra" manual assembly effort.
11. Selection of components that cannot be assembled by machine (e.g.: reversed mount LED used as a normal mount LED ).
12. Holes & board edge/ slots/ rout/ V-groove pads proximity too close
13. Holes on SMD PAD.
14. missing or incorrect polarity marking on silk-screen layer.

There are many other cases not listed, some cases are often neglected by new designers. Catching DFM problems early during PCB design saves time because fixes become more difficult to make at later stages. Also in this process, designers become more "manufacturing aware" as they work.

Almost every PCB designer has had problems when a product has gone to manufacturing. They are often associated with PCB manufacturing processes or yields, or with PCB assembly, and result in scrap or a lot of rework. When they occurs, modifications become necessary and the product is re-spun at the design level until a satisfactory match with the intended manufacturing process is achieved. So modifications and trial production become necessary for new product introduction.