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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 18th Jun 2019, 8:21 pm   #1
duncanlowe
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Default Poor solderability of old components, solutions?

I bought a batch of opto-isolators for a project a while back but when I came to use them they won't take solder. I haven't put the leads under a microscope but they do look a bit dull to the naked eye. My guess is they haven't been stored well. They are old stock because the component has been obsolete for a while.

I managed to find a newer equivalent and build up my parts, but I'd like not to waste these parts I have and maybe use them on a next batch of parts.

I tried just using a flux pen and then tinning but no joy. So I was wondering which of these, or maybe any other suggestions, is likely to have best and or easiest results (I use four per board):

Fibreglass pencil?
Rubbing on very fine emery paper?
More active flux?
Anything else?

They are surface mount but will be hand soldered, so I need to keep the surface fairly flat prior to actually soldering to the board.
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Old 18th Jun 2019, 8:28 pm   #2
OscarFoxtrot
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Default Re: Poor solderability of old components, solutions?

Are you using leaded solder or lead-free?
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Old 18th Jun 2019, 8:36 pm   #3
MotorBikeLes
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Default Re: Poor solderability of old components, solutions?

A plan I adopted decades ago when soldering "new old stock" was to scrape every leg ON FOUR sides with the BACK of a small size "snap a piece off" craft knife.
Not sure why I adopted that method, but it DOES work.
Old metal oxide resistors that have got hot (scope deflection outputs) always got the "four scrapes treatment" with good results.
Les.
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Old 18th Jun 2019, 8:45 pm   #4
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Default Re: Poor solderability of old components, solutions?

Exactly! Scrape the leads clean and use proper solder, not this new rubbish!

I do it with ALL components regardless of whether they're new or old. I just use the side cutters gently closed on the leads and pull them through several times at different positions. I've always done it this way.
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Old 18th Jun 2019, 8:54 pm   #5
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Default Re: Poor solderability of old components, solutions?

I rub the ends of the leads with fine glasspaper then tin. Surface mount would be difficult though.
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Old 18th Jun 2019, 8:58 pm   #6
duncanlowe
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Default Re: Poor solderability of old components, solutions?

Leaded solder. Don't have anything else in the house! I reckon with SM I could do the bottom side OK, but not the top or sides.
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Old 18th Jun 2019, 9:09 pm   #7
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Default Re: Poor solderability of old components, solutions?

Some emery paper leaves an oily residue, first rule with soldering is everything as to be clean, i do like other scrape the wire clean.

I cannot find the report now but a housing estate was troubled with failed copper water pipe joints, the copper pipe and joints were top quality, the investigators found the problem of a plumber using a type of emery paper that left an oily residue that ruined the internal soldered joint in the couplings.
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Old 18th Jun 2019, 9:15 pm   #8
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Default Re: Poor solderability of old components, solutions?

Hi search
Beau Tech SH66 Component Lead Cleaner.
This as a tweezer thing with a stainless steel braid I have been using them for years , you squeeze it onto the wire and gently pull the component through. Great for dried on sticky bandoleer glue if you use it with a drop of lighter fuel. However searching now I cant find a UK stockest. RS used to do them.

As for fibre glass pens I hate them with a passion after a work colleague trimmed the end with a stanley knife and left the "cuttings" on the bench where I got them embedded in my cloths and skin. Horrid things completly banned!
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Old 18th Jun 2019, 9:43 pm   #9
duncanlowe
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Default Re: Poor solderability of old components, solutions?

Quote:
Originally Posted by G4_Pete View Post

As for fibre glass pens I hate them with a passion after a work colleague trimmed the end with a stanley knife and left the "cuttings" on the bench where I got them embedded in my cloths and skin. Horrid things completly banned!
Pete
Yes I'm nervous of the fibreglass. I do have one somewhere and remember pain. Car headlinings often have glass fibres in and I hate working on those with a passion...
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Old 18th Jun 2019, 9:52 pm   #10
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Default Re: Poor solderability of old components, solutions?

I use fibreglass pencils for this sort of thing. The slim little one I have (think it came from farnell or cpc) seems to break off in tiny powdered bits that doesn't stick in you. My old boss's glass Thistle Stick was another matter, maybe they've changed the formulation.

I dont envy you with SMD mind you. Save your sanity and bin them!
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Old 18th Jun 2019, 10:15 pm   #11
60 oldjohn
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Default Re: Poor solderability of old components, solutions?

If the above methods do not work, are you sure they are not aluminium contacts? I have some small trimmer capacitors, on one lead I have to use Aluminium Solder, on the other Tin Lead works ok strange but true.




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Old 18th Jun 2019, 10:59 pm   #12
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Default Re: Poor solderability of old components, solutions?

I wonder if your components have been "electroless" tinned: we found that this type of plating was virtually unsolderable after several years.

My "discovery" re. cleaning leads etc is to use a specific type of kitchen scourer "Stainless Steel Scourer" (sold by Morrisons etc): they look like very perfect lathe-turnings and are quire soft to the touch, but excellent for removing dirty plating. They do not shed anything either (as opposed to wire wool or emery).

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Old 18th Jun 2019, 11:37 pm   #13
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Default Re: Poor solderability of old components, solutions?

I've always been a convert to using flux on anything I solder. Dip the legs in and I find solder takes well/
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Old 18th Jun 2019, 11:46 pm   #14
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Default Re: Poor solderability of old components, solutions?

the fibre glass pencils can be filled with a brass insert thats available on ebay .I seem to recall they were included if you had a gunson colour tune kit to clean the gunson spark plug
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Old 19th Jun 2019, 3:03 am   #15
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Default Re: Poor solderability of old components, solutions?

When I find a stubborn area that wont take the solder I use "wet and dry" paper to clean it up, obviously using it dry. I think the problem is the metal becoming heavily oxidized over time thus resisting the solder.
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Old 19th Jun 2019, 9:54 am   #16
Peter.N.
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Default Re: Poor solderability of old components, solutions?

I retired 15 years ago and have a workshop full of NOS items which I occasionally use and have the same problem, scraping the legs with a sharp blade usually works as already mentioned, failing that, acid based flux should do it but it will need cleaning off afterwards.

Peter
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Old 19th Jun 2019, 10:13 am   #17
Radio Wrangler
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Default Re: Poor solderability of old components, solutions?

A cheap and easily available etchant for cleaning up metal is car alloy wheel cleaner. It's basically an acid and detergent mixture. It's job is to remove iron dust build-up from the debris from brake discs and pads, try some on a tarnished penny! the effect is quite rapid. Be sure to wash the stuff off before soldering. I use 'Wonder wheels' for all sorts of cleaning jobs, and for removing tarnish before assembling old tarnished PCBs

There is also 'Oust' kettle descaler which is citric acid. This etches and cleans even quicker... I use a lot for decoking shower mixer valves as well.

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Old 19th Jun 2019, 1:04 pm   #18
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Default Re: Poor solderability of old components, solutions?

I've got some "Iskra" ceramic- and cracked-carbon resistors acquired at a bargain price some time in the 1980s (before Yugoslavia imploded). These have the difficulty-of-soldering issue - I use one of the little fibreglass brushes on these as a matter of course. Works every time!

The worst things for soldering, I find, are brass battery-tags which have ever suffered any kind of corrosion due to leaking electrolyte. Such tags go coppery-red when cleaned up, but the 'copper' is porous because the Zinc has been dissolved out of it, and it then won't reliably take solder.
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Old 19th Jun 2019, 2:10 pm   #19
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Default Re: Poor solderability of old components, solutions?

I use a fibre pencil thing and it works a treat and so far I haven't suffered the 'sticks and itches' that some seem to suffer from.
Just slightly off-topic: Any idea what material is used for the flat tins that contain kippers, sardines in oil etc? A while ago I decided to cut one up to use as screening for a homebrew project and then discovered it would not take solder no matter how much I cleaned or fluxed it.
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Old 19th Jun 2019, 2:19 pm   #20
G6Tanuki
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Default Re: Poor solderability of old components, solutions?

A lot of the fish-cans these days are aluminium.

Check with a magnet to see if it's plated-steel or something else. [I can confirm that 'Branston' baked-bean cans are solderable, plated steel, having today used a slice of one to make-up a grounding strap for the outer-braid of some thick coax]
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