Product design for manufacturing (DFM) considerations

Product design for manufacturing considerations can culminate into an exhausting list of items depending on the electronics product and product requirements.

Taking measures to consider as many aspects of a product's design requirements as early as possible during the product development phase can help companies save time and money.

Contract manufacturers with experience in product design can be an OEM's best source for helping to put together a checklist of product design considerations.

Below are some items broken out by activity, or process, companies should consider.

Design, component selection

Verify components are available in production quantities
Minimize number, and number of, different components
Confirm no end-of-life (EOL) components designed in
Minimize sole-source devices, components
Multiple, alternative manufacturers specified for all components
Second sources checked for mechanical and electrical fit
Component tolerance issues identified and evaluated
Component temperature ranges considered
BGA vs fine-pitch QFP considerations
Trim pots eliminated where possible
Design for environment: for recycle, re-use, repair

General board layout considerations

Visible orientation marks on silkscreen layer for all polarized components
Polarized components in proper directions
Layer numbers visible on PCB or break-offs
Names on artwork

Board assembly manufacturing processes

Workmanship requirements established (e.g., IPC, military, aerospace)
Number of processes identified and minimized
Hand soldering minimized
Hand insertion and assembly minimized

Through-hole components

Non-plated tooling holes for through-hole automation
Drill sizes: lead diameter + X for auto-inserted through-hole (may suggest size of ‘finished hole' instead so design house can determine which size drill to use to allow for plate up)
Dual in-line package (DIP), axial and radial inserted components (note some exceptions on non-plated, single-sided boards)
Customary for DIP socket drill holes to be 0.040"
Orientation of auto-insert components at 0°, 90°, 180°, and 270°
DIP components oriented same way on volume boards
Axial components oriented same way on volume boards
Transistor lead layouts spaced properly, in-line, pad-to-pad
No stand-up axial components
Minimum annular rings on through-hole pads

SMT land patterns

Fine-pitch land patterns at 60% pad width/pitch
Land patterns match to actual physical components
Use of land patterns fall in with DFM optimization
No natural bridges on fine-pitch SMT
Non-solder mask defined pads for BGAs

Wave-soldered bottom side SMT components

Confirm lower-yielding process required
Bottom-side SMT wave land patterns optimized
Component orientation optimized for waved SMT components
4-sided SMT and fine-pitch SMT not soldered
Minimum component-to-component spacing equal to height of tallest of two components
Other wave solder shadowing considerations to prevent ‘skips' (solder surface tension does not break when waving, therefore solder cannot properly wet the interface to form a solder joint)
No SMT components on bottom within clinch head footprint on mixed-technology PCBs