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Missing SMT Chip Components

Bing Feng

#9636

Missing SMT Chip Components | 13 September, 1999

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?

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#9637

Re: Missing SMT Chip Components | 13 September, 1999

| 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? | | | Where are these parts located, maybe near the edge of the PCB ? There should be enough space to the edge of a PCB where no components should be mounted for transportation and clamping purpose in the placer. Did you find the missing parts somewhere or is it actually that they are not mounted by your placer? Try to run in step-by-step-mode to see if they are beeing mounted, if so let the PCB run through and watch for mechanical parts on the way out which probably remove them.

Good luck Wolfgang

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#9638

Re: Missing SMT Chip Components | 13 September, 1999

| 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

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KEVIN SIMPSON

#9639

Re: Missing SMT Chip Components | 14 September, 1999

| | 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 | Hi, I do agree with dave, but it is probably a very simple problem. If your program told the (what type machine) to put the part down,I would bet a good bit it did do just that.If it did not get to that point,well the machine has a minor problem ,I refer to as lack of P.M. I've seen these occur on various types of equipment. Can you tell if the part ever hit the paste? Let me know what type of equipment it is ,and I'll tell you a solution,or get you on the right track anyway. thanks, K.S

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Charles Stringer

#9640

Re: Missing SMT Chip Components | 15 September, 1999

| | | 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 | | | Hi, | I do agree with dave, but it is probably a very simple | problem. If your program told the (what type machine) | to put the part down,I would bet a good bit it did do | just that.If it did not get to that point,well the | machine has a minor problem ,I refer to as lack of | P.M. | I've seen these occur on various types of equipment. | Can you tell if the part ever hit the paste? Let me | know what type of equipment it is ,and I'll tell | you a solution,or get you on the right track anyway. | thanks, | K.S | We had a really obscure problem about 3 years ago where our chip capacitor manufacturer had plating solution left in the terminations. The result was that the components (0805 & 1206)behaved like jumping beans when they got into the reflow oven. At first it looked like a misplacement problem and after a full set of PM on the placement machines and a lot of measel charts before and after reflow, we tracked it down to something happening in the oven. We went through our stock with the manufacturer using a simple lab hot plate and a few components from each reel. Those that failed were really obvious (wear safety glasses!) I know this is far from mainstream but you never know

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Bach Huss

#9641

Re: Missing SMT Chip Components | 15 September, 1999

| | 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? | | | | | | | Where are these parts located, maybe near the edge of the PCB ? | There should be enough space to the edge of a PCB where no components should be mounted for transportation and clamping purpose in the placer. | Did you find the missing parts somewhere or is it actually that they are not mounted by your placer? | Try to run in step-by-step-mode to see if they are beeing mounted, if so let the PCB run through and watch for mechanical parts on the way out which probably remove them. | | Good luck Wolfgang |

I have experience in missing part at certain location of the board. If this is your case, maybe you want to analyze your placement sequence where a tall/high component has been placed first beside the smaller component which is always missing. Whenever the smaller/lower component is placed, here there are possibilities that the component will hit the taller component and go elsewhere.

Rgds Bach Huss

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