| Hi, | | Recently encountered missing components problem at the SMT process. | Among 13 chip components from the same part number mounted on the board, only 4 ( located in a same row and next to each other) were missing after post reflow. Checked the pick & place program steps and found that these 4 locations are somewhere in the middle of the 13 steps but not together. Could not understand how this could happen and where it can happen. | | Anyone have this problem before ? If yes, what is the possible root cause? | | | Bing: Yes, there's there's two main reasons why you're missing components.
1 You never put them on the board 2 You put them on the board, but they got off some time
The problem in figuring-out something more specific is you're not real detailed in describing the problem. For instance:
1 How wide-spread is the problem? 1 board / every board 2 What is the frequency? once in a while / all the blankin' time 3 Timing 1? New or old problem? 4 Timing 2? Start of a run / through-out run / any time it wants to 5 Product breadth? one product / evry product 6 When do you notice the missing part? after placement / after reflow 7 etc etc
So your request for a "root cuase" is kind of off the wall.
A few reasons for missing parts are:
* Part sticks to paste on the nozzle from previous placement * Part doesn't release from nozzle because the part has sticky stuff on it * Part is stuck to the carrier tape and never picked by the nozzle * Part fell from the board during handling because there was no paste on the pads * Blowers in the oven deposited the part on the floor before reflow
Good luck
Dave F
reply »