How to Solder Videos: Why Is Soldering Difficult Sometimes?

by CuriousInventor.com

162K27178

Intro: How to Solder Videos: Why Is Soldering Difficult Sometimes?

This is another "How to Solder" instructable, but it also attempts to get at why soldering doesn't go easily sometimes. On the following pages, there are also numerous pictures showing good technique, good and bad joints, and some tools of the trade that you may not find in your local RadioShack. If you've ever wondered what wattage iron to get, the 3rd step has a video showing how some irons of different wattages fair on a couple soldering tasks.



Here is my list of the top reasons soldering doesn't work well (looking forward to your opinions on this):

1. Soldering tip has oxidized (turned black) and solder won't stick to it. This happens when the tip is left bare while on--a naked tip will quickly oxidize at hot temperatures. The best advice for preventing this is to glob solder on the tip every time you set the iron down. Weller (high-end iron manufacturer) actually recommends holding solder against a new tip the first time you turn it on so that the solder will melt and cover the tip the very instant the it gets hot enough. One of the best guides out there that emphasizes tip care: Weller's HowTo

2. Bad technique: applying solder to the iron, letting it sit there for a while, and then trying to carry it over to the joint. If you let the solder sit on the iron, the flux quickly boils off (the fumes are from flux, not the lead). And without flux, soldering becomes almost impossible. Flux removes oxidation from metals, and it's crucial because solder won't stick to oxidized metals, and metals oxidize very quickly at soldering temperatures.

3. Not enough heat: A 15 Watt iron is fine for small chips, but any larger connectors or wire bigger than 16 gauge will cause problems. 25W-30W is probably fine for most hobby applications. Is there any risk to getting a 100W iron? Wattage is separate from temperature, right? ... depends on the iron. Watch the video on the next page.

4. Dirty or oxidized parts: Bare copper oxidizes relatively quickly (this is why most components are tin / lead coated), so older parts or bare copper that has been exposed for only a week or two can require a light sanding (pink erasers are great) or stronger flux.

Shameless plug: This instructable is an except from a larger guide with many more pictures found here: www.CuriousInventor.com/HowToSolder. There is also a desoldering guide, a review of the cold heat iron, and advice for choosing solder / flux types. And, of course, a store to buy stuff :)

Thanks for any corrections / feedback.

STEP 1: Good Technique

You want to hold the iron tip to get as much contact between the tip, component, and board as possible. Add a small amount of solder in between the tip and component to act as a heat bridge--this may not be necessary if enough solder is already on the tip when you tinned it.

Finally, add solder to the opposite side of the joint. Solder will run towards the heat, so this helps to spread out solder, and also ensures that the components were indeed hot enough for solder to melt and adhere to them.

STEP 2: How Much Wattage Do I Really Need?

One question I never got a satisfying answer from RadioShack was "How much wattage do I need?" What's the right temperature to solder at? How does wattage relate to temperature? What is the recommend soldering temperature?



Answer: Wattage is how much heat can continuously be supplied by the iron. This is, in principle, independent of the tip temperature. On expensive irons, the heat (wattage supplied to the tip) is throttled to maintain a certain tip temperature. The wattage is really a maximum heat output. However, cheaper irons contain a simple heater that is always generating the rated heat, so tip temperature can vary widely. A 15W may only reach 550 degrees F, whereas a 40 Watt can get over 800 degrees.

In general, manufacturers recommend soldering temperatures to be between 650 and 750 degrees F for lead-based solder, and maybe up to 800 degrees for lead-free solder. But why is this if solder melts below 400 degrees? The larger the temperature, the quicker heat will transfer to your parts, so higher temperatures speed up soldering. You could solder at 450 degrees, but this would require some patience. On the other hand, soldering at 1000 degrees would lead to a number of other problems. Parts would be more likely to burn out, the board could be damaged, flux would boil off too fast, soldering tips would burn out quicker, the joints would become more brittle, and the lead would be more likely to atomize and float around in the fumes. All these factors are why many recommend soldering at the lowest temperature possible, but you have to balance the above concerns with the speed that you can solder.

STEP 3: Good and Bad Joint Pictures

The most important thing to look for is good adhesion or "clinging" between the solder in the surfaces it's attached to. Lead-free solder can appear dull and still be perfectly fine, but typical lead-based solder should be shiny in appearance.

STEP 4: Tools You Won't Find in Radioshack

A SOIC surface mount chip remover, dry tip cleaner, solder pot for tinning lots of wires, knife blade soldering tip, alcohol saving pump bottle, and a video of a vacuum desoldering tool (30 sec):


78 Comments

TimothyC38 8 years ago

Are there videos on this? Because they're not showing up. Just big blank spaces the right size for a video.

bitsandbots 9 years ago

Well done! Great pictures!! I hope you won't mind if I share your link!

Justin Lam 14 years ago

i have an 80W soldering iron with a chisel tip (Weller brand) that i bought for $20, but i find that it's too hot and the tip is too thick. Could i stick the tip in a lathe and grind it down so it's like a cone shaped tip, or would that ruin the tip? and when i was soldering connections on a plastic battery pack, the plastic started melting..... should i just get a cheaper soldering iron with less watts?

static 13 years ago

Too bad the link results in a 404 error message. I understand that being an instructor or a student at a tech university, a small business partner, and life in general forces one to manage their online time. Having said that IMO it isn't cool to direct responses to comments that include questions and reader of those  who also may benefit s from the answer away from  an instructable.

earlye 12 years ago

404 again. You ought to consider setting up some permalinks that redirect to the correct location when your site changes again.

CuriousInventor.com 12 years ago

We decided to take the forums offline. If you notice any other bad links to our guides I'd be grateful to know about them.

static 13 years ago

Great, thanks. Not knowing what you recommended a held off in pointing out some tips are plated and sanding or grinding them will ruin them. In the event your group ever revise your instructions that would be something to include. along with that "loose" tips can cause problems. My suggestions to =D where going to be to get an iron in the 40-45 watt range and get a new tip for the 80 watt iron, and make sure it was tight when installed to see if it will tin, if not use a light dimmer to make a simple control to reduce the heat, to see if will tin then. The simple control will turn that 80 what monster into a dual purpose iron, and will be usable for any iron purchased in the future. Nawadays the digital readout infrared thermometers. make calibrating the simple temp controls much easier.

Justin Lam 14 years ago

thanks a bunch! I'll just go out and buy those el cheapo soldering irons, one of them i found for $8 and it's from my favourite electronics part store, so i'm sure it's fine. thanks again!

CameronSS 16 years ago

Where can one get one of those desoldering pumps for relatively low cost? I checked eBay, and they have a huge selection of three.

Also, beautifully done Instructable. Should this be somehow added to the How to Solder Instructable?

CuriousInventor.com 16 years ago

Added it to the "How to Solder" group. Thanks for the compliment and suggestion.

That desoldering tool is great (and over $600), but for occasional stuff the RadioShack iron with a bulb works great. If you really want one, the cheapest place that I've seen equipment like this is Madell Tech--here's their page of desoldering irons. I actually prefer wick / braid since it's easier wipe up every last bit of solder with that. Shameless plug: you can get it here.

Tip: If you do get one of the vacuum desoldering tools, sometimes it's helpful to add more solder to the joint first because they're most effective when they can create a strong vacuum, and it's hard to create a strong vacuum over a mostly clear hole.

CameronSS 16 years ago

I'm still in awe of that pump, and still trying to figure out a cheap version. What if a vacuum pump were attached in place of the bulb, and a hopper set up to catch the solder? Is that basically what the fancy version does?

static 13 years ago

My guess is any vacuum source could be used, even a home vac., with a chamber behind the tip to catch the cooled solder and a screen between the chamber and vacuum line.  Post an intractable of what you try. My spring loaded solder sipper works for what I need for board repairs. My board component salvaging methods aren't elegant, so I don't need a pump for that.

CuriousInventor.com 16 years ago

The fancy irons do indeed have a hopper of sorts to catch the solder, but I'm not sure how it's integrated with the vacuum line, etc. One problem with those things is that you constantly have to use little cylindrical files to clean out the tips. It'd be neat try hacking up that radio shack thing, attaching a vacuum and screen and trying it out. I suspect the airflow will prevent it from getting how enough. But if you let it heat up for a while without air flow, and then only cut it on when the solder is molten it might work. A lot of people have made cheap hot air pencils out of that by attaching a fish tank pump tube to the bulb and blowing air through the tip. This did not work for me at all regardless of every permutation on tip shape and "stuffing" that I put in it. The air temp was never hot enough.

cowtipper97 15 years ago

I know exactly what you need. It's the radio shack desoldering pump model #64-2098. I own and there great, plus they only cost $9.98. I highly recommend this if you want a good low cost desoldering pump.

ReverendSapp 14 years ago

As a person who has had hit and miss luck with soldering, I am happy I stumbled upon this video. Your video helped me to realize all the mistakes I have made in the past, I still have a way to go I'm sure but this is an excellent start. Thanks!

jethrow815 14 years ago

Question, I have a new Weller 40W chisel tip, using Oatey 40tin 60lead rosin core.

Cant tin the tip if my life depended on it.
 the solder just rolls off the tip in little perfect balls onto the mat

any ideas?

thank you~

corsi 14 years ago

bravo well done. the videoo helped alot. it is easy to get lost when there is only text. good job i learned how to solder properly now.
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