How Do You "TIN" a soldering iron?

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On Mon, 29 Nov 2010 12:37:39 -0800 (PST), DerbyDad03

The devices in the circuit board are mechanically held in place by virtue of passing through the board - and the solder just stiffens the wire to make it harder to pull apart, then glues the twisted wires so they cannot easily move in relation to each other. Two wires laid together and soldered can be separated relatively easily in comparison - and a wire just laid on a circuit board and soldered WILL fail.
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On Nov 29, 5:16pm, snipped-for-privacy@snyder.on.ca wrote:

re: "The devices in the circuit board are mechanically held in place by virtue of passing through the board"
Not on any boards I've built or repaired. The wire or component leads are loose in the holes and will pull right out unless solder is applied to the tinned pad on the lead side.
Ever encounter a cold solder joint on a circuit board? A nice neat mound of solder that looks good on visual inspection but a component lead that will pull right out through the board because there is nothing holding it in place.
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On Mon, 29 Nov 2010 15:15:56 -0800 (PST), DerbyDad03

They are held "in place" except for one direction. Might be more accurate to say they are "located" by the holes.
Surface mount is a different story - and they DO tend to fail on occaision.

Yes I have - but if it was not in the hole the cold solder joint would just be a spot of copper - and a component rattling around somewhere. Also, PROPER installation involves spreading the leads slighly when they come through the hole so the component stays in place when you either turn the board over to solder it, or move the board to the wave soldering machine.
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On Mon, 29 Nov 2010 19:45:54 -0800, Smitty Two

Mechanically placed components virtually all have (or at least had) that little kink that held the part in place. All the custom boards I had made also did. (we are talking in the computer industry) And all the automotive computers I've worked on/repaired (up until the '90s)
And a very large number of SMTs are glued to the board (solder paste in some cases) which does not do much for the final strength, but keeps the part in place until it is soldered
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On Mon, 29 Nov 2010 23:58:11 -0800, Smitty Two

A lot of the stuff I worked on was custom - and not high volume - and the little "hook" was standard, virtually across the board. Dealt with some pretty high end contract assemblers. Waterloo Region is NOT the low-tech part of the country. A lot of the work these guys did was aerospace or high end industrial electronics.
Ever hear of Dalsa, ComDev,Christie Digital, RIM, Agile Systems, Accellerated Systems, SRE Controls, Navitas, Virtek, Raytheon, NCR, ATS, just for starters.
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wrote:

Correct.
Nope, unless you consider "solder paste" to be "glue". The normal SMT process uses no glue, rather does a pass through the oven for each side. Glue is sometimes used but not generally.
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DerbyDad03 wrote:

Your technique may need revision.
I was taught to push the lead through the hole, bend it over to provide mechanical connection, solder, then clip the dog leg.
You are evidently skipping the "bend over" step. Your technique makes removing the component MUCH easier - until the component simply falls out on its own.
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On Mon, 29 Nov 2010 17:16:23 -0500, snipped-for-privacy@snyder.on.ca wrote:

Wrong.
Were that the case, SMT would never work.
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On Mon, 29 Nov 2010 22:42:41 -0600, " snipped-for-privacy@att.bizzzzzzzzzzzz"

When the joint area approaches or excedes the area of the device itself, and the mass of the solder involved in the joint is a significant fraction of the mass of the device, and there is no "wire" involved, you are pretty safe. That pretty well describes SMT.
Lay a wire on a PC trace and solder it on and see how much abuse it takes (generally before pulling the trace off the board - but occaisionally pulling the wire off the trace)
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On Tue, 30 Nov 2010 01:37:37 -0500, snipped-for-privacy@snyder.on.ca wrote:

You're talking through your ass. Think BGAs.

It is perfectly normal to surface solder wires onto SMT boards. Mechanical connections are *not* required, nor desirable, before soldering. As has been stated by others here, the only reason to have a mechanical connection before soldering is if the connection won't make it until it's soldered.
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On Mon, 29 Nov 2010 19:48:46 -0800, Smitty Two

I've spent as many years in the computer repair business as I have fixing cars.
Instead of just dissagreeing with everyone why don't you give us some real information - like what you work on that things are done differently. I'm sure there are many reasons for doing things differently in diferent industries and situations.
Educate us.
My experience has been MOSTLY automotive and computer, with some communications and audio and avionics thrown in for good measure. I've done component level repair on automotive electronics and computers, as well as pre and early solid state radio and audio equipment.
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wrote:

I've actually done more "discrete component" assembly than LSI stuff - and a fair amount of the old "point to point" as well. Printed circuits were still pretty crude when I got started. Did a fair bit of vacuum tube stuff too.
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Smitty Two wrote:

Oh. Didn't know that. I suppose the cheap, disposable tips are merely plated (maybe even just painted in bright colors) - the ones I use are solid copper.

Agreed solder IS a mechanical connection; a piss-poor mechanical connection at that. Lay two wires side by side and solder them together. Then pull them apart. Next tie the two wires together in a knot, solder them, and pull them apart. If you can.
There's a HUGE difference between a soldered mechanical connection and the mechanical connection of a solder joint.
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HeyBub wrote:

The cheapy screw-in tips I get at radio hack are copper base. Dunno what the plating is on top, though.
As for tinning them, after I degrease them (when new), I put a very thin dab of flux on the tip and wrap it with flux-core solder, then I plug in the iron.
This gets it tinned before it has a chance to oxidize, and seems to work well for me.
Jon
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Jon Danniken wrote:

Ooo! Good idea.
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I prefer to use a "Western Union" style splice if possible. It's mechanically sound.
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On 11/29/2010 4:13 PM, HeyBub wrote:

A properly soldered joint doesn't not need a mechanical connection, like twisting the wires together, in order to make a permanent electrical connection. Matter of fact, NASA prohibits any such joint. They prohibit it because if repairs are needed it is too difficult to take apart.
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On Tue, 30 Nov 2010 00:10:25 -0500, Tony Miklos

You are using a double negative so appear to be disagreeing with tourself - but regardless, nasa notwitstanding (if it is true) acceptable standards for aircraft repair ( I believe it is AC 43.13) specifies joints must be mechanically secure before soldering, but also (quite severely) limits where soldering is acceptable in aircraft wiring. Solder wicking back a stranded wire hardens the wire and makes a stress point where that hardening stops - a failure waiting to happen when exposed to vibration.
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On 11/30/2010 1:00 AM, snipped-for-privacy@snyder.on.ca wrote:

Ah, a typo. Read it as a single negative and you will understand what I mean. Another reason solder joints shouldn't be mechanically secure before soldering is because that practice can hide poor solder joints. It may be a cold solder joint but it doesn't show up easy as if it would without a separate mechanical connection.
As far as solder wicking up wire, yes I agree the wicking and vibration is a very bad combo. As far as NASA, I believe that was mostly applied to components on circuit boards.
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On 11/30/2010 12:10 AM, Tony Miklos wrote:

Oops! That should read "doesn't need" not "doesn't not need".
like

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