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SMT transformer misalignment

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#61692

SMT transformer misalignment | 26 April, 2010

Hi, friends Need your urgent help on bellow issue .......

we are facing issue of misalign of one bulky SMT transformer during the placement itself rejection @40% & after reflow rejection @5 % using SMT m/c QP242 , placing this component at end of all component this Xmer having 4 leads at one side & 8 leads at other side also pl. see atached snaps for same

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#61698

SMT transformer misalignment | 26 April, 2010

Sudhir, This part appears to have a lot of mass, thus it may be very heavy. What type of placement machine are you using? Is the PCB held in a fixed place on the table while the gantry moves in the X and Y? Or does the PCB move in the X and Y while the placement head stays stationary? My guess is that the part is moving after placement. Try placing this part last, and using whatever machine settings are available to slow the table down after placement to it's lowest level. You also might want to verify that the solderpaste has not exceeded it's workable life. If so, it will become much more thixotropic, and won't hold the part in place as well. (FYI...more thixotropic equals less "tacky")

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#61724

SMT transformer misalignment | 30 April, 2010

We are using QP fuzi m/c during the placement of comp. PCB is fixed & placement head is movable This component is placed at last but still we are getting the problem Comp. is placed with slowest setting also slowest comp. transfer speed of nozzle head solder paste is not expire, it is in shelf & also storage is as per std requirement but still we are facing the problem pl. suggest

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#61726

SMT transformer misalignment | 30 April, 2010

We do a similar part on a Fuji IP3. Set table speed to low. I do not know the QP, but if it's similar to the IP make sure the board clamp/unclamp is smooth. On our IP it got dirty and was jerking causing the board to jump a little which bounced our transformer around. We ended up using a step stencil to give us more paste on these pads to help hold them in place.

If you are sending perfectly aligned parts into the oven and get this out, check the oven chain for smooth movement. Any jerking or jumping will knock them around.

Jerry

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#61734

SMT transformer misalignment | 2 May, 2010

I do agree with Jerry: you should apply more paste on it, either with a step stencil, or doing overprint on it by, let's say 120% on Transformer's pad. Also, you need to check : a) there's smooth movement on transport process after the placement, not only inside the placement machine, but conveyors are aligned and there's not a variance on speed through conveyors.. a)there's is not air hitting the transformer during the reflow process, because this component is too heavy and I can be moved easily when liquidous.

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#61769

SMT transformer misalignment | 5 May, 2010

Make sure that both lead frames are contacting the PCB pads when the part is on the placement head. We had an SM xfrmer that we were handling with vacuum by a ferrite cap that was not glued on straight. The part would contact one set of pads and get dropped on the other set do to the feature we were picking it up by being crooked. That drop was enough to skew the placements on the majority of parts no matter how slow we set the machine placement and the parts that did get placed on pad were not seated in the paste very well causing them to skew in reflow. When the vendor was asked about coplaniarity they could not guarantee a number that was even remotely close enough to being good enough for smt so we ended up hand placing until they were gone and switching back to through hole parts. I would have tried a stepped stencil if the vendor’s coplaniarity spec was just a small amount off.

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aj

#61787

SMT transformer misalignment | 8 May, 2010

From looking at your images I would say it could be poor solderability on the terminations of the component itself.

Can you get your hands on a different date code and try them out?

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