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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wave solder of TQFPs

#3516

Wave solder of TQFPs | 19 July, 2000

Does anyone have any experience wave soldering TQFPs. Our R&D is wanting us to do this but we (production) are hesitant. I've found some recommended pad designs and solder theiving designs in a Philips app note "SMD Mounting Methods". The theory looks ok but whats it like in practice. The device is a TQFP32 0.8mm pitch.

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Boca

#3517

Re: Wave solder of TQFPs | 19 July, 2000

Kinda along the lines 'if it comes we will build it'.

Perhaps you can assemble it, I've not done it, but a question to ask a bit earlier is - should we. Check the specifications for the component, published by component vendor. Most of them really do not want the rate of temperature change wave generates, nor immersion in 500F solder.

Let us know what you find,

Boca

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DNC

#3518

Re: Wave solder of TQFPs | 19 July, 2000

Craig,

I'd be really hesitant in pursuing this method for a TQFP. Remember, most SMD's are rated for a maximum rising slope of around 4C/Sec. Immersing a fragile TQFP in a hot wave of molten solder will probably exceed this ramp up rate. Besides this, you can have other problems like bridging and popcorning amongst other short term and possibly long-term latent problems. I would pursue other avenues like using selective solder fixtures, temporary masking or even post wave hand soldering this device.

Anyway, good luck. Let us know how it turns out.

P.S. Sounds like your R&D needs a good DFM session.

Regrads,

Deon Nungaray SMT Mfg. Process Engineer GMI USA

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#3519

Re: Wave solder of TQFPs | 19 July, 2000

Craig: Waving TSOP should be your last choice. You should resist will high levels of red faced, neck vein bulging seriousness.

After you loose: * Philips pads are a good starting point. * Recognize you'll probably have to lay-out the pads on the board a couple of times to get it correct. * This will give you a chance to develop skills in skimming dross and other fine points of wave soldering. * Reliability of the TSOP package should be tested (as others pointed-out earlier)

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Bob Willis

#3520

Re: Wave solder of TQFPs | 20 July, 2000

All the points raised so far are correct. Only use QFPs if rearly pushed as the yield on your process will suffer.

I have wave soldered parts down to 0.020" in nitrogen with OK results but the pads and drainage pads need to be worked on.

Another reason why you have problems is again gassing on the wave below the board. bubbles can come out from under the package as it exits the wave, in this case there is no solder contact to pull the shorts off the back of the last legs.

Just run some QFPs on a glass plate through the wave and watch what happens.

Bob

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Joe H.

#3521

Re: Wave solder of TQFPs | 21 July, 2000

Craig,

Since you didn't share any detail regarding the component side of the board or what other components reside on the bottom side, I'm prepared to take a stab in the dark.

Have you considered doing a double sided reflow on this board?

Also, I agree with Deon in that your "R&D" folks need a serious DFM schooling.

Good Luck,

Joe

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reflow oven profiler