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Soldering long lead thru hole parts

Mike F


Soldering long lead thru hole parts | 9 December, 1999

Does anyone have a suggestion for soldering boards with 1 inch long leads sticking out the bottom? Our vendor is using a drag solder machine, but I'm not happy with the preheat and controls on it. We assemble boards with numerous LED's( 200 to 700 per board)that are used in custom displays, then take them to a local assembly house to be soldered and lead cut. We leave the leads long because it gives an easy way to check polarity after the parts are loaded, among other reasons. We will soon add on to our building, and want to bring that work back in house, but I'm looking for a better way to do the soldering.

Thanks, Mike

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Re: Soldering long lead thru hole parts | 9 December, 1999

Mike, It sounds like you have a serious problem, I don't know much about drag soldering or what your specific soldering problem is with your present supplier. I do know that with a conventional solder machine these leads won't even make it through! I would hope that you could spec a different LED that has another way to ID the polarity such as a flat edge or something. If you must leave them long you may want to try to bend them flush to the board if it won't cause any shorts. You may also be able to contact a prep equipment supplier and have a die set made that will cut the leads at two different lengths and will prevent the operator from putting them in backwards into the machine.

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Re: Soldering long lead thru hole parts | 9 December, 1999

Mike, Russ is right, no 'normal' wave machine will solder PCB's with 1" long lead length. I have seen waves modified to clear up to 5/8" leads, but the deeper the wave the uglier things get. They get uglier in that a lot more dross is produced, control and repeatability of the wave shape suffer, and the list goes on...

If the long lead length is required, stick with the drag solder, profile it and control it. Even if it's not a pretty system, it may have the repeatability needed.

If you can, reconsider the requirement. 1-Check polarity other ways, many LED's have a flat on the component body, or look in the lense to see the internal construction. 2-Use a cut and clinch machine, ensure polarity is correct at assembly, check it electrically in test.

Hope it helps, Boca

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Jeff Sanchez


Re: Soldering long lead thru hole parts | 9 December, 1999

Mike, A drag solder system is not so bad. If it's not discoloring the silk screen , damaging your parts or blistering your boards than it looks like a safe bet. I am not sure what other components you have on the boards besides the LED's? But the LED's are pretty rugged. It appears as though you're trying to keep the cost down by not giving the shop that's soldering your boards the whole job? Or you may just be keeping people busy? Either way the long leads are for the benefit of your people being able to place them without much error. If you have a shop that is willing to only solder with out doing the placement and the boards are in good health than keep them. You're getting the best of both worlds! Is there another shop down the street that you can get to take your boards if they have shorter leads? Will they take a job if it's just soldering? Will you tell them it's just a short relationship until you build your new lines? If your only concern is the fact that your contractor is using a drag solder system than let your proof be in the pudding. Are you getting good boards on time and are they using good standards? You want one inch leads and these guys seem to deliver. You make a valid point. But I think it comes down to cost and compromise.

Just trying to see from both angles..........Jeff Sanchez

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Mike F


More info | 10 December, 1999

Some of our boards have over 700 LED's, so looking for the long leads is the most accurate way to check polarity. Also, not all LED's have a flat side and tinted domes can make it difficult to see the internal structure. Auto insertion didn't work, for several reasons. HP recommends their LED's see solder for a max of 4 seconds. The current soldering vendor has a drag system that dips the board into a pan of flux, which applies a lot of flux, top and bottom, which in turn has led to a variety of problems they have done nothing to resolve. Turnaround time is also part of the drive to bring this work back in house. I know I can't do this with a regular wave solder machine. Has anyone ever used a Kirsten Jet wave? Would it work?

Thanks, Mike F.

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Brian W.


Re: Soldering long lead thru hole parts | 10 December, 1999

It sounds like the process is very labor intensive, and all the verification is done after the parts are soldered. Assuming you are hand placing the components:

1 - Contact Systems semi-automatic placement machine. It show polarity when placing, so operators would know how to place the part, then cuts and clinches the leads. Then wave solder.

2 - Depending on how many differrent color LEDs, make some fixtures that only allow certain LEDs to be placed, with markings to show polarity. Have different operators place different color LEDs. Then cut and clinch the leads and wave solder. I have done this one before and had it work very successfully. It fool-proofs the system as much as possible.

In either case, put audits into place to make sure that placements are correct prior to soldering. It is much cheaper to find and correct prior to soldering than after the parts are soldered.

Brian W.

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Re: More info | 10 December, 1999

Hi Mike consider buying your LEDs from a value added distributor or sending the to a service house for trimming. It's no trick to cut so that one lead is longer than the other although you may have to pay a tooling charge. These people are equipped to prep these parts much more efficiently and quickly than you can (read that cheaper). The prepped part still has a visual indication of polarity, the short leads allow the LED to be inserted by automation, they are able to be fluxed and soldered by conventional equipment, it could be a no-clean process, and the assemblies might not need mass trimming after soldering. The amount you save by not wasting all that flux and solder on the long leads and not having to clean up the mess could pay for the prep work and more. Wouldn't the amount of solder on these trimmings make them toxic waste? John Thorup

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varen blake


Re: Soldering long lead thru hole parts | 11 December, 1999

pls. send me more info on a no-clean process i would like to know more about this.

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