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UBLOX Tim-4A reflow problem

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#46111

UBLOX Tim-4A reflow problem | 8 December, 2006

I have just started production run using this component. After reflow I see that there is an undercut of solder between the pcb and the lead instead of a fillet. This means that some of the leads are sitting above the solder with no wetting to the component. It is as if the component is being pushed up by the paste when it goes to liquid. Other joints almost look like a BGA sitting on top of a ball. Initially we thought it was due to the pcb bowing in the oven and had some fixtures made to fix that . It didn't. Using 1:1 stencil without the recommended 0.2mm overprint. Have tried both 0.005" and 0.007" with various print gaps etc. PbFree Indium 5.1 and good old SnPb 63/37 show the same result. Profile is near copybook for the paste and has been OK'd by UBLOX. PCB Finish is ENIG. Don't know about the component terminations as yet. Double sided second pass. Rest of the comps are good. Components come in vac bags , taped, and are kept in a dry cabinet. I have tried different batches - all the same. Anyone had a similar problem? Bueller - anyone?

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aj

#46157

UBLOX Tim-4A reflow problem | 11 December, 2006

Hi,

We use UBLOX-LEA-LA.

Is this the same component as you are using?

We followed the recommended stencil design with a 6thou stencil and we have had no issues. We have run approx: 3k units so far.

We had some minor issues at the start but this was down to the profile.

aj...

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aj

#46160

UBLOX Tim-4A reflow problem | 11 December, 2006

Hi,

I checked out your component.They are differnet dimensions. You say you are not using the recommended overprint ? if this is the case, I would imagine that is your problem. If you want to contact me off line to discuss further plesae feel free.

aj...

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#46165

UBLOX Tim-4A reflow problem | 11 December, 2006

Hi AJ, Thanks for the reply. I'm beginning to think that we have some issues with different expansion rates of the two pcbs. When you say you had some profile issues... Did you stay within the recommended UBLOX reflow time of 20 - 40 seconds and did you use a soak or straight ramp etc. Cheers, Darby.

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aj

#46187

UBLOX Tim-4A reflow problem | 15 December, 2006

Straight ramp .

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#46214

UBLOX Tim-4A reflow problem | 17 December, 2006

Thanks AJ, It is looking like a CTE issue.

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aj

#46224

UBLOX Tim-4A reflow problem | 18 December, 2006

Darby,

You mentioned that you have not incorporated the recommended overprint ? is this so.

aj...

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#46246

UBLOX Tim-4A reflow problem | 18 December, 2006

AJ, No overprint. We have components in very close proximity that precluded that. Also we have differing areas of thermal relief for the pads from a large backplane, from none at all to open blocks to individual pad relief. After a few more experiments we are almost certain that the pcb/component are warping both up and down creating a gap between some areas. With different pads reflowing at different times combined with the warpage - I think herein lies the problem. There is evidence that the castellation of the component has initially wetted but then the solder splits between the pad and underneath the component. 4 boards to a panel with 180 degrees rotated origins. I think we ultimately will need a re-design.

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