A variable temperature soldering iron that's always set to 350? - Page 1
Forum section: electronics / beginners

author: pussyfoot
author_rank: Newbie
timestamp: March 25, 2013, 09:27:54 pm
content: I watched the videos about soldering and it's strongly suggested to get a good variable temperature soldering iron. However, the temps in the examples seem to always be around 350 degrees Celsius. What's the point then?

author: mariush
author_rank: Super Contributor
timestamp: March 25, 2013, 10:01:09 pm
content: The tip temperature drops a bit as soon as you touch the leads or copper surface of the material that's soldered. So the temperature of your tip needs to take in consideration how fast the surface "sucks" the heat from the tip cooling it down.When you solder some things, you only need a bit above the solder temperature (example soldering a capacitor lead on a tiny through hole pad where 250c may be fine), on other things you may need a much higher temperature, for example when soldering a thick wire on a banana plug or something like that, where you might need 450c.So why not use 450c all the time? That can be too much for tiny traces, burning them or ungluing them from the board, and the tip also oxidizes much faster as temperature increases... you would have to constantly shock it and clean it from oxides were you to use it at that setting.350c is just a good compromise value, which assures you pretty much can solder anything in a reasonable amount of time and that's what matters for tutorials.

author: digsys
author_rank: Unknown
timestamp: March 25, 2013, 10:59:49 pm
content: Most people will likely use their Soldering Irons at a particular temperature most the time. It may be a bit too "high" or "low" forsome jobs, but once you get the hang of it, you automatically work out changing the time you spend on a joint. For SMALL tempchanges, it's quicker than fiddling with the adj pot / buttons. BUT -When you start going from tiny S/Mount to large caps, connectors etc, and changing tips / solder type etc, THAT'S when you'llappreciate having larger temp control. ie Try going from Silver solder on a large connector to S/M paste on a 0805 - it'll become clear :-)

author: mrflibble
author_rank: Super Contributor
timestamp: March 26, 2013, 04:32:07 am
content: Quote from: mariush on March 25, 2013, 10:01:09 pmPretty much this... Good compromise value. And for those super big components or random other things with large heat capacity you crank up the temperature to say 425 C.And just for the fun of it I just checked, last time I used it my iron was set to 375 C for a regular not-too-small-not-too-big soldering job. So there's an anecdotal data point for you.

author: cyr
author_rank: Frequent Contributor
timestamp: March 26, 2013, 06:38:49 am
content: It depends a lot on how good regulation the iron has as well, I usually stay at 340C or so for everything from tiny SMD parts to large battery connectors. Have the right tip for good contact is key though, and of course having the right temperature for the type of solder and flux.I think the most important reason to get a "proper" variable temperature soldering station isn't so much the variable part, but that it's actually temperature controlled and stays more or less at the value you have selected. What you absolutely don't want is one of those unregulated irons you just plug into the wall. It might go up to 500C if untouched for a while, and drop to 200C when you try to do large joints.

author: robrenz
author_rank: Super Contributor
timestamp: March 26, 2013, 06:32:37 pm
content: The boosting of temperature to try to compensate for higher thermal demand solder joints is common for general quality soldering equipment. But it realy does not work forrepetitivehigh thermal demand soldering because the iron can not actualy maintain the temperature. Its heat input and rate of thermal recovery is insufficient. This is where high performance high thermal recovery soldering stations realy work great. They have the ability to pour a lot ofcontrolledpeak wattage (130W or more) into the low mass tips to better maintain the set temperature. Because of this you can solder at much lower temperature settings with these units.I intentionaly did not mention any brands, I am just trying to extol the virtues of high thermal recovery soldering systems. I am also well aware that many cannot afford $400 plus soldering stations but that is no reason to not be aware of thier benefits.Low temp exampleHere

author: pussyfoot
author_rank: Newbie
timestamp: March 27, 2013, 06:34:46 pm
content: How would one go about measuring the temperature of of a soldering iron tip? I got a Weller SP40L as a gift. The specs say it can go to 900 F, which sounds too much. I'd like to do some tests and possibly introduce aoff the shelf dimmerto see if it makes a difference.

author: nanofrog
author_rank: Super Contributor
timestamp: March 27, 2013, 07:05:22 pm
content: Quote from: pussyfoot on March 27, 2013, 06:34:46 pmSoldering Iron Temperature Tester (Hakko FG-101 clone:http://www.ebay.com/itm/DIGITAL-THERMOMETER-SOLDERING-IRON-TESTER-Hakko-FG-100-/261159249673?pt=LH_DefaultDomain_0&hash=item3cce4de709)BTW, good quality temp regulated irons typically top out at ~850F, so that 900F figure isn't horribly high IMHO.

author: SeanB
author_rank: Super Contributor
timestamp: March 27, 2013, 07:10:27 pm
content: Cheap DVM with temperature measurement with a cheap type K thermocouple in the package. Tin the bit and touch the probe. Otherwise you can get a soldering iron tip temperature checker pretty cheap on eBay.

author: nanofrog
author_rank: Super Contributor
timestamp: March 27, 2013, 07:21:33 pm
content: Quote from: SeanB on March 27, 2013, 07:10:27 pmI've never been confident on a reading this way (had the K probe clamped in a hemostat, and it wouldn't stay as still as I'd have liked when trying to touch it with the iron).Maybe not enough weight to the clamp?Figured the Y configuration of the thermocouple used on the Hakko FG-101 & clones make it much more mechanically stable.

author: SeanB
author_rank: Super Contributor
timestamp: March 27, 2013, 08:01:07 pm
content: Cardboard with probe on it, place tip on cardboard touching tip and add a drop of solder to improve heat transfer.

author: nanofrog
author_rank: Super Contributor
timestamp: March 27, 2013, 08:04:07 pm
content: Quote from: SeanB on March 27, 2013, 08:01:07 pmI'll give it a try, thanks.

author: pussyfoot
author_rank: Newbie
timestamp: March 30, 2013, 12:01:05 am
content: I checked the specifications out for standard incandescent bulb electrical dimmers and the minimum power needed is usually around 40 watts. Lutron said their dimmers that have a neutral (white) connection can go down to 5 watts, but those dimmers cost as much as a variable temp soldering iron.Building my own dimmer circuit should be pretty straight forward. I can use a Quadrac (Diac-triac combo in a single package), a potentiometer and a 0.1 uF cap to make the whole circuit under $5. Here's the data sheet:http://www.littelfuse.com/data/en/Data_Sheets/E3Quadrac.pdfThe test circuit in there shows the schematic. There's no RF filtering, but I don't know how important that will be for a soldering iron. Is there any reason why this circuit won't work well for low power conditions? I.e., 20W-40W?It seems wild that a soldering iron that can heat up to 900 degrees F only needs 333 milliamps. P=V*I, so I guess that's right...right?

author: SeanB
author_rank: Super Contributor
timestamp: March 30, 2013, 09:37:03 am
content: I have one, it does work, though it is always set at max if I use it.

author: Things
author_rank: Regular Contributor
timestamp: March 31, 2013, 10:48:51 am
content: Heh I dunno, I kinda have mixed feelings about the whole temp controlled soldering iron thing. I've never used a temp controlled iron, so I can't really comment on if they're better, but I have been using a $12 25W fixed temp iron from Jaycar for over 8 years now and apart from the occasional overly thick, 10AWG+ (Or minus I suppose), it has done everything for me.I've soldered banana terminals, 12AWG wire, 0605, 0603, TQFP, MSOP, pretty much everything a plain ol electronics hobbyist would ever need, and never had an issue. Would a temp controlled iron be nice? Sure, and if your day job is assembly, then it might be worthwhile, BUT, you can make do without.

author: cwalex
author_rank: Frequent Contributor
timestamp: March 31, 2013, 11:30:42 am
content: Quote from: Things on March 31, 2013, 10:48:51 amLike Dave Jones discovered. Once you have used a JBC iron for a while, you will never want to use another iron again. It is a shame we can't buy them for the same sort of pricing the yanks get

author: Things
author_rank: Regular Contributor
timestamp: March 31, 2013, 11:42:24 am
content: Yeah, I'd imagine, that is a pretty sexy iron.I suppose one major upside to the temp controlled irons is they can compensate for various heat loading much faster than cheap irons. Since pretty much all the cheap non controllable irons use bi-metallic strips to control the temp, they have some pretty bad hysteresis.