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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wave Soldering Upflow


MGL

#25367

Wave Soldering Upflow | 5 August, 2003

Through hole question - what methods can be used to obtain upflow on multi layer pwbs with huge ground planes. We are using a water soluble flux with a max temp of 220 topside. I am pushing the limits of the flux and hitting 250 topside in an attempt to obtain upflow. We have tried many of the known tricks - warming the pwb, fluxing topside etc. (Granted these are things not recommended but we are thinking outside the box. ) Equipment - New Vitronics Soltec wave - top and bottom preheat with spray fluxer. Any ideas appreciated - Thanks.

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CAL

#25370

Wave Soldering Upflow | 5 August, 2003

Hi matt- You describe the board but did not indicate the components being inserted (even there is a part being inserted).

Assuming your hole dimensions are ok... Are you cutting and clinching the parts? If so what is you clinch angle?

We to have multi layer boards with monsterous ground planes and emi shields....and solder just fine with our lil pallet system. We Foam the Flux and use no clean chemistry.

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Kris

#25373

Wave Soldering Upflow | 5 August, 2003

Hi,

Have you tried increasing the vibration at the main wave or using a chip wave?

try increasing the temperature of the solder by about 10 Deg C.

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CSIMFGENG

#25374

Wave Soldering Upflow | 5 August, 2003

Another variable is whether the ground pads have proper thermal reliefs. If the pad has solid ground plane around the perimeter, the heat being applied will quickly dissipate to the surrounding metal. A proper relief of the pad will prevent the heat from escaping.

As mentioned prior, hole sizing is important relative to the lead being inserted.

Correct preheat and contact time with the solder are all players here.

Good luck! I hope a little of this helps.

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D

#25375

Wave Soldering Upflow | 5 August, 2003

Try to mechanically force the solder up the holes if it is equipped with a Smartwave. The Smartwave tries to provide additional wave action like the Electrovert Omega wave. Try more time in the wave. How did the old wave machine perform on these boards? It might be a clue to solving it on the new machine.

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#25376

Wave Soldering Upflow | 5 August, 2003

Check the areas that are getting solder on the top side. If you have internal ground planes, and the ground plane pth's are not getting solder on top, and signal pth's are, it's a heat problem.

If the ground planes are in the middle of the board you may not be getting them warmed up. The top and bottom are hot, but the heat has not had enough time to conduct to the center of the board so when the solder gets to this cooler area it becomes solid in the middle of the board.

If this is what is happening you have a couple of choices. First is to slow down your conveyor so the board has more time for the heat to conduct to the center. You'll also have to lower your preheat temps some so you don't burn the top and bottom surfaces. The bad part of this is the increased time in the solder, which may or may not be a problem. A little more solder contact can help transfer more heat, but too much will start to damage the bottom of the board.

The second choice is to put the boards in an oven for a period of time just before running through the wave solder. The idea is to warm up the center ground planes 20 or 30 degrees above room temp so the preheaters can do the rest.

Good luck, Mike F

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D

#25377

Wave Soldering Upflow | 5 August, 2003

more heat heat, more time in wave

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#25378

Wave Soldering Upflow | 5 August, 2003

Hi,

One thing you might want to do has to deal with the venting over the top of your spray fluxer. Many times the exhaust comes from the side; instead of directly inline on top of the spray fluxer. This will draw the flux up the thru-hole joints more effectively and create (in many cases) a better top-side fillet. This has worked at companies such as Nortel and Solectron. Anytime you try and wavesolder an extremely heavy board with large heat sinks it is tough.

Good luck, Brad

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MGL

#25379

Wave Soldering Upflow | 6 August, 2003

Thanks to all who have responded. The boards we are waving are approximately 14X14. SMT bottomside, lots of Dips topside, M39014 caps, and a variety of resistors and diodes. Lead to hole ratio looks good. Board thickness is .090". Picture frame pallet is being utilized. Thanks again - Matt.

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Dean

#25401

Wave Soldering Upflow | 7 August, 2003

Is it possible the solder hole(s) is too large and the solder is falling back in the hole? I see this on right angle BNC type connectors.

Is this happening on all component types? All areas of the boards? Always the same pins (but other pins in the same area solder fine)?

More description please.

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Shawn

#25402

Wave Soldering Upflow | 7 August, 2003

We do allot of multi layer boards with heavy ground planes or heat sinks attached. We have a Trieber, use RMA flux, solder pot temp at 500F, foam fluxer, spray the top if need be, and would warm up the PWB to around 240F over the preheaters. We have both top and bottom side pre-heaters and dwell over the solder pot as long as possible, 2 to 5 seconds.

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MGL

#25408

Wave Soldering Upflow | 8 August, 2003

Problem areas are always ground connections. 20 pin dips have great flow on 18 of 20 pins, caps have poor upflow on the ground side only etc. That's my problem. 90% of the pwb looks great. Bottomside - awesome. Ground connections do not meet the 75% fill in all cases. Then we need to hand solder in order to pass inspection. Any info in regards to hand soldering for upflow is also greatly appreciated. Currently we warm the board then attempt to get upflow. Sometimes we can't. Any info appreciated. Thanks - Matt.

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N

#25411

Wave Soldering Upflow | 8 August, 2003

what, no top side preheat?

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MGL

#25412

Wave Soldering Upflow | 8 August, 2003

Top and bottom preheat - topside temp 250 plus at times attempting to get the upflow. Vitronics / Soltec machine using smart wave. Thanks - Matt

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Brian W.

#25435

Wave Soldering Upflow | 11 August, 2003

Assuming you are working to IPC standards, are you working to Class2 or Class 3? Class 2 has an exception to the 75% barrel fill (para 6.3.1, page 6-7). "As an exception to fill requirements of Table 6-2 on PTHs with thermal planes or conductor planes that act as heat sinks, a 50% vertical fill of sodler is permitted, but with solder extending 360� around the lead with 100% wetting from barrel walls to lead on the secondary side, and surrounding PTHs meet requirements of Table 6-2". If it's Class 3, you are SOL, it's a defect. We did some 24 layer, .125" thick boards by slowing the conveyor speed as much as possible, applying flux from the top side as well, and raising our solder pot temp to 500�F. This was done on a wave solder machine that is 15 years old, with no bells and whistles.

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