|Ask the Experts|
October 9, 2020
Question About PPM Defect Rate for Reversed Packages
Which process/equipment has the higher ppm defect rate for reversed packages: SMT pick-and-place or component taping-and-reeling? I have seen some PCBs with reversed packages.
The component supplier's tape-and-reel system uses a camera to confirm package orientation before tape-and-reel. The pick-and-place system doesn't have optical pre-placement verification that I know of.
|Expert Panel Responses|
Very seldom you'll find a reversed package from a component supplier. On the other hand, reversed packages from SMT placement equipment are a little more frequent. This is not because the pick and place equipment does not have optical verification like it seems to be your case but because all SMT components are dependent on the information entered in their part descriptors or product libraries.
Many times a change done to one part descriptor could affect one or all components that share the same characteristics on the same assembly. The same change could also affect more than one assembly, in some cases dozens.
Senior Manufacturing Engineer
We'll have to assume that we are ruling out "systematic" errors, e.g. an entire reel of parts loaded opposite of what is expected or a program error that causes a specific reference designator to be rotated; in other words, what we are talking about is uncommon, sporadic occurrences. If so, then I would suggest that the SMT equipment is highly unlikely to place a part in the wrong orientation.
It knows what the orientation is when it picks the part, and what the rotation needs to be on the CCA. If the parts are in fact all correct in the reel, then the part would need to slip/rotate relative to the pick head between the pick point and the camera. Not impossible, just very unlikely.
Some things to do:
This is not likely come from the taping and reeling service supplier.
Also the pick and place equipment is going to execute what we are programming it to do. What I have seen in the past:
Engineering and Operations Management
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