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missing component after placement



missing component after placement | 26 January, 2000

Hello! all

Will anybody give me advice for missing componets for 0402, 0603 R or C chips? I am not gonna tell you which machine I use, but from my experience, every p&p machine has possibility for missing component after placing 400 or more components in one board with very high speed (0.2 or less / chip) My questions is that what is the main cause for missing component? Board support, wrong component data, vision error, vacuum error, poor printing, and what else? Thanks in advance

Dennis Lee

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Re: missing component after placement | 26 January, 2000

Dennis: I cast my vote for: poor maintenance.


Dave F

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Re: missing component after placement | 27 January, 2000

Dennis, The solder paste is responsible for holding the component in place pre-reflow. Several things to look at:

Is the paste accurately printed on the pad? If not, there may not be enough of the component in contact with the paste to provide adiquate adheasion. Did the component hit the pad? If the paste has been disturbed/displaced by the component, look at the tooling. Is it providing sufficiant support to prevent excessive vibration? Is the machine purging the component from the nozzle when it retracts? Is there solder paste on the nozzle? Is the solder paste drying out and loosing adheasion? If the solder paste has not been disturbed, is the program placement/component data correct? Is the machine properly calibrated? The paste will tell you if the component ever got to the placement area and therefore can eliminate some possibilities. Hope this helps

My $.02


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Re: missing component after placement | 27 January, 2000

Dennis, Not sure why your so secrative about what machine but I guess it doesn't matter. When you start placing 0402 & 0603 packages the difference between height and width and length gets lost in tolerance. This allows the machine to pass parts that have not been picked up correctly and try to place them. The result is missing components. As far as paste being a problem I wouldn't focus to much on that. This is going to be a machine problem. It could be vision, board supports, or lack of maintenance. Most likely it happens because the vision tolerance has not been tightened enough to compensate for old feeders.

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Re: missing component after placement | 27 January, 2000

Thanks! It is right that solder paste is somewhat responsible for misssing components in our case. I took a look at the board after placement and I found that component hit the paste, but no where on the board. I guesss dry solder paste (operater prints a lot of boards and stock in a magazine and use them another line, room temperature is a bit high) is the reason. some vibration took component out of the board I guess.


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