Basic soldering - and parts. Resistors, how much variance?

Thread Starter

Bartmanekul

Joined Oct 13, 2019
3
I'm starting a little project, which involves soldering LEDs.

Simple enough, and I've soldered before in a job. However then it was incredibly easy, this seems to be really difficult.The solder just would not melt.

I thought it was the iron first of all, even though brand new. So got another, this rated to 450C, the solder 250C. Still very difficult to solder, even letting it heat for a while.

Did I just have super ones at work?

Not sure if links are allowed, but I'd be grateful if someone could link something which actually works. Currently I'm using this: Edit - looks like links are not allowed :( It's a draper
61478 40W

(Please let me know if those sorts of links are not allowed).

My second question is for resistors. I've worked out I need one around 32ohm, but I can't find anywhere to buy these, only packs which turns out 20 is the nearest.

So, will 20 lead to burn out, and is there anywhere I can buy the 32's from?

Advice and links to kit on amazon UK that works would be appreciated.
 

jpanhalt

Joined Jan 18, 2008
7,871
Welcome to AAC.

Links are limited for posters with less than 10 posts to control spammers. Here's what I think you might have: https://www.drapertools.com/product/61478/Soldering-Station-(40W)

That soldering iron is perfectly good. Be sure your temperature is set right (above the melting point) and properly tinned (thin layer of molten solder on it). The tinning helps conduct the heat. For ordinary soldering with 63/37 leaded solder, I keep mine a little below 750°F (ca. 399°C) on the setting, i.e., between 745° and 750°. It's analogue.
 

Thread Starter

Bartmanekul

Joined Oct 13, 2019
3
That's whats confusing me, the solder won't even tin over it. It only melts after about 5 seconds constant contact, and just beads off the tip. It's brand new, not used.
 

atferrari

Joined Jan 6, 2004
3,446
Buying 20 resistors of a certain value (the most common for your case, of 33 ohms) is not dramatic. If you insist in doing some electronics in the future, just buy them. Do not waste time trying to save cents.
 

jpanhalt

Joined Jan 18, 2008
7,871
5 seconds is way too long for the solder to melt directly on the tip. Check the temperature and tinning again.
 

DickCappels

Joined Aug 21, 2008
5,877
Bartmankel wrote: "That's whats confusing me, the solder won't even tin over it. It only melts after about 5 seconds constant contact, and just beads off the tip. It's brand new, not used."

It sounds to me like you have an oxidized or otherwise contaminated soldering tip. Wipe your tip, scrub your tip, but don't sandpaper your tip. Just get it clean so that the metal makes good contact with your solder. After that you can use extra flux (non-acid only!) to help keep the tip clean and to eliminate or minimize the need to wipe.
 

Thread Starter

Bartmanekul

Joined Oct 13, 2019
3
Thanks for all the responses so far. In answer:

Buying 20 resistors of a certain value (the most common for your case, of 33 ohms) is not dramatic. If you insist in doing some electronics in the future, just buy them. Do not waste time trying to save cents.
I wasn't, I genuinely can't find a decent place to buy separate values in the UK. The usual places - amazon, Maplins etc don't see to do them, only packs. It's why I'm asking if anyone knows a good place to buy online from (for UK delivery).

Bartmankel wrote: "That's whats confusing me, the solder won't even tin over it. It only melts after about 5 seconds constant contact, and just beads off the tip. It's brand new, not used."

It sounds to me like you have an oxidized or otherwise contaminated soldering tip. Wipe your tip, scrub your tip, but don't sandpaper your tip. Just get it clean so that the metal makes good contact with your solder. After that you can use extra flux (non-acid only!) to help keep the tip clean and to eliminate or minimize the need to wipe.
I've wiped it and scrubbed it - though I don't have any brass wool, which might help.

What kind of solder are you using?

Bob
I'm using Tabiger, Sn-0.3Ag-0.7Cu
 

jpanhalt

Joined Jan 18, 2008
7,871
If the tip of your soldering iron does not have a shiny, "wet" look with the solder, the problem is that it is not properly tinned. That is the user's (your) responsibility.
 

be80be

Joined Jul 5, 2008
1,928
I'm using Tabiger, Sn-0.3Ag-0.7Cu
I one time got a roll of lead free from radio shack maybe 10 years ago it had no rosin core.
I had got maybe 2 rolls before it that said the same thing but this roll I still have it
The dang stuff solid core with no rosin in it at all.

It solders fine if you use rosin paste with it but without flux it just melt and roll off the iron.
 

RIKRIK

Joined Oct 11, 2019
24
It might be the lead free stuff, I still always used lead tin solder, as I find it much easier to work with, also lead free needs a higher melting temperature .

The value can have some leeway in a circuit design, if it not to critical going for the next resistor above or below it should work fine

blowing up is more down to the wattage of the resistor, 1/6W,1/4W,1/2W to 1W and above. Most resistors for low voltage electronics only need to be 1/4W. You will see this value with the ohms on the listing.

eBay's always good,
 

MisterBill2

Joined Jan 23, 2018
3,861
Bartmankel wrote: "That's whats confusing me, the solder won't even tin over it. It only melts after about 5 seconds constant contact, and just beads off the tip. It's brand new, not used."

It sounds to me like you have an oxidized or otherwise contaminated soldering tip. Wipe your tip, scrub your tip, but don't sandpaper your tip. Just get it clean so that the metal makes good contact with your solder. After that you can use extra flux (non-acid only!) to help keep the tip clean and to eliminate or minimize the need to wipe.
If the TS has an iron with one of those long-life iron plated tips it can be a real challenge to tin the tip so that solder will melt with a good heat transfer. And they might have some of that lead-free junk solder that does have a higher melting point. That is why I choose to use a cheaper iron with a copper tip, and a light dimmer to control the temperature. It does work but it does need to be filed and re-tinned more frequently.

For resistors, yes, 33 ohms is a standard value, if they buy 10% resistors most will not be within 5% because those are sold as 5% tolerance resistors.And if they can get the 20 ohm resistors, then use 2 in series and 40 ohms will be close enough.
 

TeeKay6

Joined Apr 20, 2019
381
If the TS has an iron with one of those long-life iron plated tips it can be a real challenge to tin the tip so that solder will melt with a good heat transfer. And they might have some of that lead-free junk solder that does have a higher melting point. That is why I choose to use a cheaper iron with a copper tip, and a light dimmer to control the temperature. It does work but it does need to be filed and re-tinned more frequently.

For resistors, yes, 33 ohms is a standard value, if they buy 10% resistors most will not be within 5% because those are sold as 5% tolerance resistors.And if they can get the 20 ohm resistors, then use 2 in series and 40 ohms will be close enough.
@Bartmanekul
If the tip is iron with a copper or nickel plating, be careful not to damage the plating as solder will not adhere to a bare iron tip. The link for the soldering iron emphasizes that it's for 230VAC use; I assume that you are powering it from a 230VAC source?
 

SLK001

Joined Nov 29, 2011
1,494
I'm using Tabiger, Sn-0.3Ag-0.7Cu
This doesn't make sense. Perhaps you can tell us again what solder you are using. With what looks to be 70% silver, it's no doubt that you are having trouble melting your solder.

Find yourself some .63-.37 Tin-Lead solder and your problems will go away.
 

MisterBill2

Joined Jan 23, 2018
3,861
This doesn't make sense. Perhaps you can tell us again what solder you are using. With what looks to be 70% silver, it's no doubt that you are having trouble melting your solder.

Find yourself some .63-.37 Tin-Lead solder and your problems will go away.
Actually it ,makes a lot of sense that the lead free solder takes a lot more heat to melt and is really quite inferior. The poorer quality of the soldered connections results in more electronic waste in landfills. This is the unintended consequence of uninformed people passing laws based on misguided emotions. Yes, tin-lead solder with good solder flux will work much better. But that solder alloy may not be available in all areas, thanks to those fools!
 

SLK001

Joined Nov 29, 2011
1,494
Actually it ,makes a lot of sense that the lead free solder takes a lot more heat to melt and is really quite inferior. The poorer quality of the soldered connections results in more electronic waste in landfills. This is the unintended consequence of uninformed people passing laws based on misguided emotions. Yes, tin-lead solder with good solder flux will work much better. But that solder alloy may not be available in all areas, thanks to those fools!
I was referring to his "Tabiger, Sn-0.3Ag-0.7Cu" statement. He lists three elements but only two percentages (or proportions) - and those two percentages add up to the 100% (1.0) "whole". THAT'S what doesn't make sense. And +1 on the idiots banning leaded solder.
 

DickCappels

Joined Aug 21, 2008
5,877

upload_2019-10-14_17-29-33.png
From Amazon.com: "Tabiger Solder Wire, 0.8mm Lead Free Solder Wire with Rosin2 Sn97 Cu0.7 Ag0.3, Tin Wire Solder for Electrical Soldering"

I strongly suspect that these numbers are percentages, making the solder 97% tin, 0.7% copper, and 0.3% silver. Apparently it did not help that "Sn97" was missed when the quote was copied.


As far as I know lead solder is not banned everywhere, and especially for personal use.

Decided about 15 years ago I would rather use lead-free solder. After trying it I un-decided to use it. I just avoid licking my circuits and all is well.
 

kubeek

Joined Sep 20, 2005
5,599
I was referring to his "Tabiger, Sn-0.3Ag-0.7Cu" statement. He lists three elements but only two percentages (or proportions) - and those two percentages add up to the 100% (1.0) "whole". THAT'S what doesn't make sense. And +1 on the idiots banning leaded solder.
That means 0.3% silver and 0.7% copper, rest is tin. It is a standard cheap lead-free alloy, solidus 217°C liquidus 228°C which is a lot higher than eutectic lead solder which melts at 183°C.
 
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MisterBill2

Joined Jan 23, 2018
3,861
That means 0.3% silver and 0.7% copper, rest is tin. It is a standard cheap lead-free alloy, solidus 217°C liquidus 228°C which is a lot higher than eutectic lead solder which melts at 183°C.
But the worst part is that the cheap stuff does not wet the materials to be joined nearly as well. So even with flux, it is hard to make a good connection. And perhaps the much higher temperature promotes much faster oxidation of the surfaces to be joined. One of those nasty unintended consequences of making changes without understanding the facts.
 

SLK001

Joined Nov 29, 2011
1,494
I strongly suspect that these numbers are percentages, making the solder 97% tin, 0.7% copper, and 0.3% silver. Apparently it did not help that "Sn97" was missed when the quote was copied.
Even this is incomplete. 97% + 0.7% + 0.3% does not equal 100%. What makes up the other 2%? Apparently it is the flux, but alloys aren't specified in this manner, since the flux isn't part of the alloy.
 
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