Fire wire (i.e. wire on fire!) - Page 1
Forum section: electronics / beginners

author: PerranOak
author_rank: Frequent Contributor
timestamp: August 22, 2017, 03:09:22 pm
content: Often, when I am soldering onto a Vero board, the insulation on the connecting wire gets so hot that it melts back and recedes up the core!This means that a short is highly likely.Is there any connecting wire that can stand the heat?Cheers.

author: Zero999
author_rank: Super Contributor
timestamp: August 22, 2017, 03:19:01 pm
content: If the insulation is catching fire, then the soldering iron is too hot. You should invest in a temperature controlled iron.Silicone and PTFE insulation are strong enough to withstand the heat, but they're much more expensive than PVC.Whatever wire you use, tin it before you solder to the board, that way the insulation can be flush with the board, even if it receded during tinning.

author: Cliff Matthews
author_rank: Unknown
timestamp: August 22, 2017, 09:45:06 pm
content: For bridge wire between pads, pre-tin (as mentioned) but you could strip more wire than needed and use an aligator clip to draw away heat, then clip when done. If the iron's too old/powerful, use a variac if you have one. YMMV

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 22, 2017, 10:00:45 pm
content: Quote from: Cliff Matthews on August 22, 2017, 09:45:06 pmThe alligator clip might be a good tip. It's amazing how effective adding even a relatively small amount of mass can be as a heat sink.

author: PerranOak
author_rank: Frequent Contributor
timestamp: September 04, 2017, 10:26:21 am
content: Thanks all.I have a Hakko FX-888D set to 325 Centigrade - is this too hot? I get advice of anything between 300 and 350 so I went for the middle!Cheers for tips.

author: Zero999
author_rank: Super Contributor
timestamp: September 04, 2017, 10:38:51 am
content: Quote from: PerranOak on September 04, 2017, 10:26:21 amThat temperature should be fine, however if the wire is catching fire, then the actual temperature is much higher and the temperature control must have failed.Does the iron's element emit a deep red glow, when it's dark?

author: Ian.M
author_rank: Super Contributor
timestamp: September 04, 2017, 11:21:47 am
content: Sn60Pn40 solder melts at 188°C. The excess temperature of your soldering iron bit over that (or of the melting point of whatever solder alloy you are actually using) provides the temperature differential needed to get enough energy to melt the solder into the joint. A greater differential melts the solder faster.Thermoplastic insulation is often damaged at much lower temperatures than the solder melting point. e.g. for PVC it typically softens around 90°C, starts to decompose around 120°C and melts at around 140°C. Therefore *ANY* temperature hot enough to solder will damage the insulation, the extent of the damage depending on how long its above 120°C.It may seem counter-intuitive, but a soldering with a hotter bit often does less damage to the insulation when in the hands of a competent user. The solder melts faster, and the flux is more active so the dwell time on the joint can be drastically reduced, reducing the time the wire is above 120°C.For a point of reference, Weller TCP series irons, (which used to be the workhorse of manual production lines and the service industry for many years before affordable variable temperature soldering stations), come with a 700°F (~370°C) bit as standard. I wouldn't recommend going significantly hotter than that, and for small, low thermal mass joints, especially SMD parts, you can run a lot cooler without significantly increasing the dwell time required to make a good joint. However Veroboard has relatively wide and heavy copper tracks, and doesn't have any tin plating to aid wetting, so too low a bit temperature is counter-productive.It can be worth pre-fluxing your Veroboard with a rosin based liquid flux - pick one that dries hard as its best applied by wiping it along the tracks of the bare board and drying it before soldering the first component(after thoroughly cleaning the board with a green pan scourer and alcohol to remove all grease and oxides, and drying it without touching the tracks except with a clean lint free cloth or tissue), to reduce the time it takes to wet the track with solder and thus to make the joint. Cleaning and pre-fluxing the board has far less benefit if its 'factory fresh' bright copper and you peel the protective film off immediately before use, but on an older board that has even slightly oxidised, it makes a major difference to its solderability.Pre-tinning the wire also helps significantly as the extrusion process stretches out and aligns the plastic molecules and the first time the wire is heated above the insulation softening point, if unconstrained the insulation will shrink back as increasing temperature frees the molecules to contract back into their preferred more random alignment. Also if the wire is pre-tinned, the time to make the joint is significantly reduced. You'll need to start with an over-length wire so that after pre-tinning it, you can trim back the bare ends to compensate for the shrinkage.@Hero999: I think the O.P's topic title was sarcastic click-bait.

author: forrestc
author_rank: Unknown
timestamp: September 04, 2017, 11:32:23 am
content: One note to add to this discussion is that the quicker you can complete the joint the better. Sometimes something as simple as adjusting your iron temperature up a few degrees and/or changing the tip to some other tip which allows you solder more efficiently helps greatly. Pre-cleaning oxides off of the board also will help. If you can cut your soldering time in half, then you may be able to reduce the time the wire is hot enough to melt the insulation.My preferred method to avoid what you describe is actually to pre-tin the wire so that there is a good coat of solder on the wire. It also tends to "pre-shrink" the insulation. Then, insert the wire in the board, and then apply solder to the pad *first*. Once the pad is wetted, it should naturally flow to the pre-tinned wire. The solder on the wire will then melt and make a good joint. The last bit, where the wire has melted solder on it is a very short period.

author: PerranOak
author_rank: Frequent Contributor
timestamp: May 04, 2018, 01:25:46 pm
content: Quote from: forrestc on September 04, 2017, 11:32:23 amBeauty! I will try! Thank you.

author: Nerull
author_rank: Frequent Contributor
timestamp: May 04, 2018, 05:01:47 pm
content: Quote from: forrestc on September 04, 2017, 11:32:23 amI see a lot of new people do this. They're afraid of overheating things, so they go slow. They tap the iron trying to apply as little heat as possible and it ends up taking them ages to do a single solder joint - during which time they've done far more heat damage to everything around it than they would have if they just committed and done it in one go - plus the joints inevitably look terrible.I can't see your soldering technique, so I'm not sure if you're doing this or not, but don't be afraid of the iron's heat. Apply heat to the joint, get it done, and get out, all in one go and your wires and boards will be much happier.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: May 04, 2018, 05:28:54 pm
content: Quote from: PerranOak on August 22, 2017, 03:09:22 pmAll of the above, but if you are still seeing the problem, slide some heat shrink onto your wires before soldering, and then slide them back up as far as possible to the solder joint and then shrink. I do this as a norm for several reasons, one of which is that it looks very professional when I am done. I am a bit OCD about cutting all of my heat shrink tubing to the exact same length so they all look very uniform.Hope this helps...

author: Electro Detective
author_rank: Super Contributor
timestamp: May 05, 2018, 01:46:26 am
content: Yep, any narrow metal clipon put on 'tightly' gets the job done every time and wicks away heat where it should not beHeatshrink can work too, done it many timesbut be advised if the iron is too hot or kept on there too long, it can still burn small wire strands to oblivion underneath the heatshrink, and you won't know

author: amyk
author_rank: Super Contributor
timestamp: May 05, 2018, 03:51:04 am
content: Soldering too slowly will do that. For the average 20-24 gauge wire, you shouldn't need more than 500ms or so of contact with the iron and solder. The tip should be clean, tinnned, and hot enough that the solder melts instantly on contact with it.

author: ogden
author_rank: Super Contributor
timestamp: May 05, 2018, 05:59:20 am
content: Quote from: PerranOak on August 22, 2017, 03:09:22 pmUse wire with PTFE insulation and as already said - soldering iron with temperature control.

author: austfox
author_rank: Regular Contributor
timestamp: May 05, 2018, 10:26:20 am
content: Depending on the type of veroboard you are using, some of them take a while for the flux to do it's work and allow the solder to 'stick'. A light sand with steel wool or fine wet and dry sandpaper can often help.I've used Protostack veroboards with great success, much better than the generic phenolic veroboards.

author: PerranOak
author_rank: Frequent Contributor
timestamp: May 05, 2018, 01:06:03 pm
content: Ah right, cheers.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 21, 2018, 03:27:07 am
content: There are also a lot of different plastics used for the insulation of wires.Some wire insulation has such a low melting point that they are simply not possible to solder decently. My suspicion is that the insulation already melts around 100Celcius or so.The best way of pre - tinning wires is with a solder pot.First strip the wire, and put a bit of flux on it.Then dip it in a solder pot with liquid solder.All that liquid solder has a very high heat capacity, which will even pre-tin the thickest wires fast and easy.

author: JS
author_rank: Frequent Contributor
timestamp: May 21, 2018, 04:15:22 am
content: I use tweezer, the ones that close themselves, clip the tweezer on the wire (also for temperature sensitive components) and solder fast. The insulation might end up squeezed and retain that form (flatter where the tweezer was) but I like it much better than no insulation at all.The other option, not always possible, is to strip little wire, force the insulation back a bit more with some pliers, use the twezzer to retain that position and avoid over heating, solder, force the insulation back out. When the insulator is soft and melts easily this is the best way, but as I said, not always possible, depends a lot on the kind of wire used.JS

author: Zero999
author_rank: Super Contributor
timestamp: May 21, 2018, 10:03:27 am
content: Quote from: Hero999 on August 22, 2017, 03:19:01 pmAnother point about using PFTE or silicone insulation: another thing to bear in mind is it won't stop solder wicking up the conductor, which will make it brittle. To minimise wicking, the joint should be completed as quickly as possible.Tin the wire conductor before soldering it. Check that the solder has not wicked up the conductor by sliding back the insulation. If it has, strip the insulation off a little more.Stripboard can be pre-tinned, before soldering the cable to it. Apply the solder, if it's covered the hole, remove it using a de-soldering pump or braid.