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MQFP soldering issues - how can I improve?

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#64867

MQFP soldering issues - how can I improve? | 19 August, 2011

I got this MQFP-144 and the soldering looks always very flimsy.

I think I use a suitable leaded paste (water-soluble) and the stencil thickness is also OK. The IC on the image looks a bit shifted, that's not the problem. The problem is rather that the pins don't look well connected and the solder isn't really running up the pins.

Any out of the head advise for me?

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#64868

MQFP soldering issues - how can I improve? | 19 August, 2011

What do the heel fillets look like and what level of IPC-610 (class 1,2, or 3) are you working to? Do the joints on all 4 sides look bad or just the one side? Do other parts on the board look OK?

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#64873

MQFP soldering issues - how can I improve? | 20 August, 2011

I will try to get a pix for heels.

Normal IPC standard

Yes, all for sides are the same (ignore the little misalignment, usually that is fine).

I wonder if the IC is maybe too lite and 'swims' on the liquid tin and if it would help to put some weight on the IC?

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#64876

MQFP soldering issues - how can I improve? | 22 August, 2011

very often toes on the QFP packages are exposed to base material and during time they oxidize. That is why you can have problem with solder fillet. Most important is heel fillet.

Regarding your misalignment of IC if this is repeatable check your placement machine. If random check your oven: - fan’s speed, - conveyor and vibration level.

janz

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#64884

MQFP soldering issues - how can I improve? | 22 August, 2011

No, don't put weight on it. If the part is really "floating" on the solder and not wetting properly and the solderability looks good on all your other parts then I'd suspect a part problem. Get with the QFP supplier and make sure the Sn isn't too thin or some other problem with the plating.

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#64920

MQFP soldering issues - how can I improve? | 25 August, 2011

Solderability could be an issue. We usually buy the IC and stock it for up to 9 month. This time the ICs was from a broker and the datecode was not the latest.

This said, we use already a solder paste that contains watersoluble flux, which is supposed to be more agressive then normal RMA flux and therefore 'should' give better wetting.

How about running a trial and pre-flux the IC leads? We did that with other parts and the result was usually good.

PS: Just forget the misalignment. It's usually good and not an issue.

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#64930

MQFP soldering issues - how can I improve? | 27 August, 2011

It's tough to say from the picture, but it looks like the connection has not gotten hot enough to cause the solder to flow properly. What was the time above liquidous plus 20*C?

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