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QFP Solder PROBLEM

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MM

#36172

QFP Solder PROBLEM | 18 August, 2005

We recently had some boards returned that have me stumped. Word was QFP pins were coming out of the solder in the field. Upon inspection it was true!! If you press gently on the pins they SLIDE out of the joint. The joints look good, shiny ect but it is like clay???? To make matters worse it is only in one location on every board the upper right side of each QFP. Never seen this in 20 yrs!!

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#36295

QFP Solder PROBLEM | 24 August, 2005

Sounds to me like you have one of two problems. First would be the pasting of the board. Possiblilty exists that the machine/operator didn't wash the stencil thouroughly, causing a permanent partial blockage in that one corner.

Second thing could be the perhaps the component itself? Are these components with this problem from the same batch? A thought to consider. Possible that the part has the problem.

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bobpan

#36299

QFP Solder PROBLEM | 24 August, 2005

Sounds like a part problem with me too. I would suspect that something could be up with the leads. What do the joints look like under a microscope??? What do the part leads look like under the scope???

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DannyJ

#36305

QFP Solder PROBLEM | 25 August, 2005

Hi MM,

Off the cuff, is it possible that the QFP leads were not coated? I'm by no means an expert in QFP manufacturing, but I do believe that there is a coating which enables solderability that is added to the leads somewhere in the process. I have seen this a couple of times, and in our instances, it is due to this. But, it is usually caught by inspectors who realize that our toe/heel fillet is not adequate...

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PWH

#36306

QFP Solder PROBLEM | 25 August, 2005

Agree with Dan - we have had non-plated IC's that are a bit corroded come in and seen similar problems. Could it be that the tinning/plating process missed a corner somehow???

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#36307

QFP Solder PROBLEM | 25 August, 2005

Could it be cold solder? Are there parts nearby that might be soaking up lots of heat, or maybe lots of internal grounding near that corner? Once I saw something similar except it was on two different assemblies. Each time it was on the side of the QFP towards the inside of the board. But the QFP was different angles on each board. So on one board the bad side was say side 1 and on the other it was side 2. But in each case it was the side towards the middle. IIRC a profile change fixed it up. It could be that the QFP is marginally solderable and therefore sensitive to the profile.

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#36318

QFP Solder PROBLEM | 25 August, 2005

I would attack the simplest possibility first. Make SURE you have enough solder paste going on the pads. If you don't, not only will you not have enough solder to make a good fillet, but you might not have enough flux available to allow what little solder you have to wet the lead...especially if it's solderability is questionable.

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Just a Viewer

#36371

QFP Solder PROBLEM | 29 August, 2005

Hi,

Wanna to know if you have extra boad (Solder Sample) and extra parts to waste ??? If so, place the parts in all different angle on your solder sample boards... see what going to happens ???

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Kris

#36378

QFP Solder PROBLEM | 29 August, 2005

what is the plating on the component ? Lead free ?

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MM

#36404

QFP Solder PROBLEM | 30 August, 2005

All of your response were similar to our investigation. Paste was sufficient, pcb's and parts came from several different lots run in at least 2 seperate ovens. Joints look good but the solder is soft?

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#36447

QFP Solder PROBLEM | 1 September, 2005

The parts could still be the problem regardless if they came from different lots. If you look under a high mag microscope you should be able to see to some extent if once the lead is gone does it look like the lead plating is gone from the lead and is still in the joint. Look real close at the possible heatsinking around that particular lead. Also, if you can track the times the boards were built, if the static pressure in the facility changes, it may cause a problem on heatsinked leads that normally look good. i.e. UPS swings open a dock door and the venting on your oven goes up big time reducing reflow temp for 15 min or so. This can be a big deal.

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