Possible defects in SMT Assembly: Defect Opportunities

ASM Siplace Siemens X4 SMT Assembly Machine

1. Component opportunities (OC)

All parts that need to be assembled on board (incl. PCB)

Every part counts for one defect opportunity

Defect example: damaged parts

Component defects:

Base material damage
Bent lead
Birdcaged wire
Blisters, mealing, peeling
Board warped or bowed
Cable made wrong
Circuitry damaged
Connector damaged
Gold not removed
Improper stress relief
Incorrect terminal flange
Insulation or wire damage
Lead bend problem
Lead coplanarity out of spec
Lead forming wrong
Lead / cable length wrong
Leads bent under
Leads not tinned
Marking incorrect
Part damaged
Part lead stressed
Plating or other finish problem
Sleeving problem
Solderability problem
Spliced where not permitted
Unprepped part
Wire damage

2. Placement opportunity (OP)

All parts that need to be placed on board, based on bill of materials (excl. PCB)

Every part counts for one defect opportunity

Defect examples: misaligned parts, missing parts

Placement defects:

Wire not tinned where required
Cable connected wrong
Parts / loose / missing / wrong
Crimping wrong
Improper mounting
Lead / cable routing wrong
Min. electrical clearance violated
Part height wrong
Part misaligned
Part extra
Part mounted wrong
Tilted part
Wire connected wrong
Wire routing wrong

3. Termination opportunity (OT)

Any hole, pad or land or other surface to which a component is electrically terminated

Every termination counts for one defect opportunity (example: QFP48 48 leads 48 termination opportunities)

Termination defects:

Blow holes
Cold solder joint
Disturbed solder joint
Fractured solder joint
Insufficient solder
Lead protrusion wrong
Part coating meniscus in joint
Solder bridge
Solder wetting unacceptable
Unsoldered connection

4. Assembly opportunity (OA)

An overall defect opportunity that is not captured within component, placement or termination opportunity defect classes

Defect examples: conformal coating, cleaning

Assembly defects:

Assembly not clean
Conformal coating absent
Conformal coating peeling
Conform. coat. present unwanted
Solder balls / splash