Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


dsp shiffting

#33689

dsp shiffting | 13 April, 2005

Hi there, this is my first ever post . please forgive me if it does not come out right. I randomly have problem with DSP shiffting in either x-axis or y-axis. It is enough that production has to reject the fully populated board. I have checked the followings: transfer from fuji Qp to station before oven. I do not believe QP is capable of doing this but, I checked the QP nozzles, vaccum pads , vaccum hoses and vaccum generators any way. I also checked the oven chain for any viberation. Nothing yet. Any help would be greatly appreciated. Thank you.

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RDR

#33690

dsp shiffting | 13 April, 2005

Are you saying that the component is on pad before the oven and then off after reflow? Also please tell us what the package is QFP, BGA, ?

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#33691

dsp shiffting | 13 April, 2005

It is QFP 208 legs. I have sat by the machine for hours and did not see a problem before the oven. I walk away from it and get a call again.

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#33693

dsp shiffting | 13 April, 2005

Thats called technician syndrome (fine when your there and bad when you walk away). Is someone inspecting the board before reflow? If so make sure they don't touch it and run about 5 boards and see if it's consistent for placement.

What type of programming process you have in play? Fuji Cam, Fuji Flexa?

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#33710

dsp shiffting | 14 April, 2005

No, there is no operator sitting before the oven inspecting the boards. Like I said this problem is so random, sometime I do not hear from production for days. Then there are days more than once a day it happens. We are using Fuji Flexa platform.

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#33712

dsp shiffting | 14 April, 2005

Play around and setup the coplanarity in Fuji Flexa and see if this can help you at all. Other than that I wouldn't have a clue as to what it might be.

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RDR

#33714

dsp shiffting | 14 April, 2005

Have you checked the component height in the package data to ensure that it is the same? how about the PCB itself, could there be some warp or twist thay may cause the component to be dropped onto the board? any support problems? this is all I can think of,

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#33720

dsp shiffting | 14 April, 2005

we already are using cop. option. And it is setup to pretty tight tolarence of .1.

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#33721

dsp shiffting | 14 April, 2005

Programmer assured me that PD is the same as any other line we have at this facility. And I checked it myself also.

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#33724

dsp shiffting | 14 April, 2005

The board warp is a good place to look. Also: -Are you pre-rotating? -Are you using the largest nozzle possible? Most of the time this ends up being a component slip on the nozzle caused when the part is rotated if not doing pre-rotate, or slippage on the nozzle due to a slight drop in vacuum. Pre-rotate and a large nozzle will help reduce this.

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HOSS

#33739

dsp shiffting | 15 April, 2005

It's a longshot but.....I have seen low-standoff parts move caused by via's under the part erupting from within internal layers (outgassing). If this is a multilayer PCB and vias are not well plated or pourus, they can and will expand when heated.

We had TSOPs that were shifted at best and being flipped completely over on their backs at worst.

Try removing a part that has shifted and inspect any vias underneath for altitude.

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#33740

dsp shiffting | 15 April, 2005

Part is being pre rotated already and I also changed the nozzle size from 15mm to 17.5mm this morning. There is no board warpage at all and production is watching for it while an operator puts on a barcode label.

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#33741

dsp shiffting | 15 April, 2005

I did not think about it, but next time I get call back again for this problem. I would definatly look into it.

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