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Barrel fill with Pb Free Wave Solder

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#57558

Barrel fill with Pb Free Wave Solder | 10 December, 2008

Are there any good solutions for getting good barrel fill on PTH boards using Pb Free solder and No Clean flux. All of our boards are having issues getting minimum required fill per IPC. It does not matter if the board is 062 or thicker, any pin connected to a ground plane just will not fill. Any suggestions?

JA

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#57565

Barrel fill with Pb Free Wave Solder | 10 December, 2008

Are you using no-clean solder, or just no clean flux?

If you're using a solder with WS flux in the core, and a no-clean flux; we'd suggest switching to a WS flux to help during the soldering.

If you are using a no-clean solder/flux combination, you might try pre-heating the board, or using a hot plate for these areas.

We've experienced the problem that you've noted; but, for us, the fix was to add no-clean flux separately. My solderers typically try not to add flux when soldering no-clean, and try to only use the flux contained in the solder core. For tough to solder joints, the answer has almost always been to use a separate flux on the joint.

You may also consider increasing the iron tip temperature, and ensuring that the solderer stays on the joint long enough. One thing I've found with solderers switching over to lead-free from leaded solder is that they're resistant to staying on the joint longer. To keep the tip temps as low as possible (to minimize damage to parts or boards), we've found that solder time is increased, due to the different performance of the lead-free solder.

cheers ..rob

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#57567

Barrel fill with Pb Free Wave Solder | 10 December, 2008

Oops...just noticed you were referring to wave soldering.

We'd still suggest a water-soluble flux, instead of the no-clean; especially at wave soldering.

Also, checking pre-heat temps, and dwell time on the pot.

Is the wave a chipper wave? If not, is this option available? I've experienced solder fill issues in the past with leaded solder, and the fix was to run the board with the chipper wave, as the turbulence helped to avoid any potential shadowing issues to the PTH's.

cheers ..rob

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#57569

Barrel fill with Pb Free Wave Solder | 10 December, 2008

on the front end in design, minimize the pth connections to ground planes. this takes alot of work by the pcb designer and the approval of the design engineer.

connect maximum of 4 ground planes to pth, minimum 1 plane. use spoked connections. evely distribute the connected planes vertically in the fab stack-up. increase hole diameter (as pitch allows) to 20 mils over pin diameter. increase hole diameter as pcb thickness increases.

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#57573

Barrel fill with Pb Free Wave Solder | 11 December, 2008

I have done a few studies on this issue here. As a result we have increased hole diameter on heavily ground planed pins to a min of .015" over the lead diameter as well as preheating the PCB when hand soldering. I have also had to order the upper pre heat option for our wave to help with this. The combo of these two items have helped immensely.

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#57578

Barrel fill with Pb Free Wave Solder | 11 December, 2008

some lead free solders do not flow well and need encouragment. what are you using solder/flux wise and machine/settings including dwell times cheers greg

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#57582

Barrel fill with Pb Free Wave Solder | 12 December, 2008

Greg,

You say �some lead free solders do not flow well� Are there lead free solders that flow as good as conventional leaded solders?

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#57583

Barrel fill with Pb Free Wave Solder | 12 December, 2008

Hi Patrick

Yes we have some that you cant tell the difference. BUT machine set up and angle are extremely important with Lead Free as is the dosing alloy. Cheers Greg

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#57584

Barrel fill with Pb Free Wave Solder | 12 December, 2008

Greg,

I totally agree with you that machine settings are very important in wave soldering and soldering in general. I disagree that lead free alloys can produce wetting like in the attached picture (leaded alloy). Lead free alloys have a much higher resistance to flow and much higher surface tension compared to leaded alloys. Therefore lead free alloys have higher wetting angles and all other associated problems related to poor wetting behavior.

Attachments:

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#57585

Barrel fill with Pb Free Wave Solder | 12 December, 2008

Hi Patrick We get this with the right settings in a small machine without Nitrogen Nice picture of yours as well Cheers Greg

Attachments:

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#57619

Barrel fill with Pb Free Wave Solder | 16 December, 2008

We ran into this problem before, on all of our models. We never quite found out the reason, we do know that if the PCB is passed through a reflow oven that is extremely dirty with evaporated solder paste flux, it will make it extremely difficult (or impossible) to solder through the wave. Oxygem PPM's being too high in reflow can also cause this issue.

The only solution we could find was to crank the flux up to about 2.5x the normal level. This gave us good hole fill on all pins.

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#57644

Barrel fill with Pb Free Wave Solder | 18 December, 2008

I think the BLT solder joints look very shiny for no-lead. We are getting very good top side solder with ours though. They look like this.

- Gold Enig plating - Alpha EF-6100 Flux - SAC305 - Preheat topside temperatures at 110 to 120C

Attachments:

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#57646

Barrel fill with Pb Free Wave Solder | 18 December, 2008

Hi Peter

Its looks on a par with mine so not bad at all but our alloy is considerably cheaper than SAC305 and significantly shinier We used our 10-75-30-R VOC free flux with topside of 100 - 105C Cheers Greg

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reflow oven profiler