Soldering Iron sizing

[Mornlock]

Greetings members,
I'm going to be replacing some capacitors for an LCD monitor (following this thread https://www.badcaps.net/forum/showthread.php?t=8844), and I wanted to see what suggestions there are for soldering irons.

I have two pen type soldering irons. One is rated at 15W, and the other is 35W. I've been using the 35W over the years, but it's been years since electronic classes, and I can't remember at what point to use the lower wattage one.

The pcb doesn't have any (sensitive?) ICs on them. The solder joints are good size, and the traces don't look flimsy.

Anyways, looking for suggestions or confirmation that the 35W iron will be ok.

[gilly1984]

Re: Soldering Iron sizing

I use a 30w cheapo iron for everything, not failed me yet.

Although i am a newbie to all this.

[mariushm]

Re: Soldering Iron sizing

I don't like those pens, they take ages to heat up and they don't maintain heat, once you put the tip on solder it immediately cools.

I've also had one of those large solder guns that look like this:



These are cheap (I see some as low as $13-20 on Amazon) and heat up quite fast and they're much better than those pen style solder irons.

But honestly, they're not really very suitable for electronics. The tip shape is not really adequate for working with the small solder pads and the tip may be too hot in some cases.

Ideally, you want to use a solder station which allows you to adjust the temperature of the tip. Such stations heat up the tip at a certain temperature and as soon as you put the tip on solder (therefore sucking up the heat on the tip), the station can send extra power to the tip and maintain the temperature where needed.

Lead based solder usually goes liquid at 180-190c while lead free solder mealts at 217c, but the copper pads and metal leads suck enough heat that usually such stations are kept at 300-350c ... pen style irons aren't capable of such performance.

Good solder stations are from about 50$ and up... there are cheaper solder stations but those don't really control temperature, they rather control the wattage, so those won't really have the benefits of the normal solder station (recovery of heat in the tip when it's put on copper pads for example)

For example this one would not be good:

http://www.amazon.com/Soldering-Stat...solder+station

The knob basically just changes between positions on a transformer inside, sort of like a variac...

A good solder station would be something like this:

https://www.amazon.com/dp/B000I30QBW...68BNVVZGYKPX0&

This is actually a clone of the classic Hakko 936, which is now replaced by Hakko 888 which is very good but much more expensive:

https://www.amazon.com/dp/B004M3U0VU...0TQTFGQ16H96G&

Anyways, for fixing just a single monitor, I guess if you're careful enough to wait until the tip is properly heated you should solder stuff properly. With such low cheap tools, it's possible to have bad solder joints if you don't solder at right temperature.

[momaka]

Re: Soldering Iron sizing

I've used several cheap 30-35W irons. For normal joints on PSUs and other single or dual layer boards, they will work fine. You just have to let the iron heat up for about 10 minutes to make sure it's nice and hot. Once that is done, also make sure to tin the tip. If the joint you're heating doesn't want to melt, add more solder. The flux in the solder will allow the solder on the tip to adhere to the solder on the joint, thus allowing it to melt much quicker.

My primary iron is a 35W Radio Shack "cool grip" (or something like that). I've had it for 10 years now and it still works very well. In fact, I actually was also able to do a motherboard recap with it... with the help of a heat gun of course.

I do also have the Circuit Specialists' version of the Hakko 936 clone. It's a very nice station for the price.

Having used both cheap "hobby" irons and very expensive professional irons, I can say there is indeed a great difference (being that the professional irons make soldering seem like a joke). However, for something as basic as a power supply, I doubt you will have any problems even with those cheap irons. Well okay, the 15W will likely be too weak for anything, but the 35W should work fine.

[Mornlock]

Re: Soldering Iron sizing

Thanks everyone.
I was able to recap the PS in the LCD monitor and the monitor is working again. It did take awhile to un-solder the caps. Just had to be patient for the old solder to melt.

[999999999]

Re: Soldering Iron sizing

A 35W iron is plenty for recapping a monitor PSU, you just need to make sure it has an appropriate shape tip in it (not fine conical if it can be avoided) that is reasonably clean and tinned. The main issue with the direct AC powered pencil irons (when not working with especially heat sensitive components) is the slow recovery time, it'll take a few seconds to heat up again for the next joint.

If I had to, for a single monitor repair I'd just get a $10 Radio Shack 30W iron that comes with enough solder to do the job. I wouldn't "like" using it, but it would get the job done. I can't recommend it for someone who envisions further soldering tasks but large pitch components on single sided PCBs are much easier to solder than some things are.

[Alohamora]

Re: Soldering Iron sizing

Everyone laughs at RadioShack soldering irons, but I have a 15W RS iron that works perfectly for soldering tiny surface mount parts (not that I do much SMD). Judging by appearances, the 15W iron is better made than the ordinary RS 25w iron. I inherited two 25W Weller irons from my father, I put a conical tip on one and a chisel tip on the other and used those 2 for many years. But, the Wellers are not getting as much use since I got a 25W xytronic iron. I don't remember where I got it, but it's really quite good for average through hole soldering.

Maybe I should stop being so cheap and get a real soldering station, but I don't really do enough soldering to justify the cost. If the xytronic ever dies, I suppose I'll reconsider.

[999999999]

Re: Soldering Iron sizing

My primary gripe with RS irons is most if not all use the same nickle plated copper screw-on style tip, which doesn't wet well, doesn't hold up as well as an iron tip, and the flux eats away a concave surface once the nickle has cracked. When I used one I always took a file or sandpaper and flattened down the tip before use because I didn't feel it was worth the $2 for a new tip.

There are cheap irons with better tips. For example a few years back I found a sale on one of these kits and while the wand is cheap junk, it actually solders ok due to the iron plug in the tip. Then the cord which was the flimsiest AC power cord I have ever seen, fell apart and I put a spare cord on. http://www.mpja.com/prodinfo.asp?number=16431+TL

[momaka]

Re: Soldering Iron sizing

My primary gripe with RS irons is most if not all use the same nickle plated copper screw-on style tip, which doesn't wet well, doesn't hold up as well as an iron tip, and the flux eats away a concave surface once the nickle has cracked. When I used one I always took a file or sandpaper and flattened down the tip before use because I didn't feel it was worth the $2 for a new tip.

Yeah, that's true. Mine has become quite concave as well. That's not necessarily a bad thing though. In fact, it makes through-hole soldering and desoldering easier because the concave part fits right onto the solder joint and makes a very good contact with it, thus transferring the heat from the tip very quickly to the joint. I also never clean it anymore either - just refill the concave part with flux-less solder and that's all . Not to mention that when I do that, I can very easily remove small SMD components that fit in the concave part of the tip. .

[japlytic]

Re: Soldering Iron sizing

I bought a 48W soldering station (Jaycar TS-1564) which is compatible with Weller-style tips and the soldering pencil can be easily be replaced (if it fails).
It has a temperature range of 150-450C and is compatible with lead-free solder - not a bad unit at $99.
A soldering station with regulated heat can help prevent flux from burning up too quickly and therefore is less likely to cause a dry joint, especially with lead free solder.