Weller WTCPT tip not hot enough

I still use 700s because of the problem of 800s burning out quicker when left idling all day, but I might try 800s again, if only for the improvement on the dreaded lead-free. I only said about the RoHS regs because there will be a lot of people reading the thread, who perhaps wouldn't understand the implications of the legislation. A while back, there was a lot of confusion and misconceptions about what it meant to the service industry, not helped by a couple of trade bulletins on the subject which were put out by at least one major Jap manufacturer, and one soldering equipment manufacturer, and which gave entirely the wrong impression. It was this which prompted me to write the article.

Arfa

No, it's not part of the magnetic circuit. The magnestat works just fine without the sleeve. The only problem is that without the sleeve, when the tip becomes non-magnetic at the Curie temp it falls out of the iron.

Now THAT's a useful tip! Thanks.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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The tips are made of copper, but copper is slightly soluble in tin-lead solder, so the copper is plated with iron, which is much less soluble. To keep the iron from rusting, they do some sort of plating over the iron. Finally the very tip of the tip is tinned with solder. I suspect that one difference between a Rohs tip and a non-Rohs tip would be what solder alloy the tip was tinned with.

It's also possible that they use a slightly different alloy in the Curie point sensor to change the temp. set point, but I doubt it.

Maybe the thermal contact between the old tip and the new one got so bad that there could be 150 deg difference in the temp between them. Seems unlikely, but I suppose it's possible since the tip is exposed but the sensor is not.

I'm glad you found a simple solution. In 30 years of working with these WTCP irons, I've never seen a problem like yours.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I have to disagree. 700 F is already way above the melting point of the solder. If you need more heat you might want to use a larger tip, with greater thermal mass, but higher temps are much more likely to damage the board.

Good soldering technique will not give cold solder joints, regardless of the tip temp. High tip temp is probably a poor way to overcome poor technique. Using a higher temp iron will certainly pump more heat into the joint in a given time, but it also results in more temp difference across the joint, so you may be more likely to get what looks like a good joint on the heated side, but with little penetration.

We've been using Rohs solder for quite a few years now, and I don't have a bit of trouble with it using a 700 F tip.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I would absolutely dispute that statement

??

I would suggest Jim, that it does rather depend on what exactly you are soldering. If you are making consistently good lead-free joints with a 700 deg Weller tip in all circumstances, then you are doing a lot better than most of the major manufacturers. Since they started using the stuff, the service industry has seen a huge leap in bad joints - and not always in 'traditional' places where you might expect to find them.

Whilst you are correct in that a 700 deg tip melts lead-free solder, it does not do so anything like as well as it does with leaded solder. Although lead-free solder does not have as nice a melt / flow characteristic as leaded in the first place, this undesirable quality is made much worse by not having enough temperature on it - particularly when soldering a component with a high thermal inertia, such as a connector or power semiconductor. The fact that lead-free solder is much worse at wetting most of the metals commonly used in electronic circuit construction, further exacerbates the problem, and dictates that more aggressive fluxes are used in the hateful stuff. Unless these are given the opportunity to do their work, by allowing them to reach the temperatures they need to at the soldering surface, then the likely result will be a bad joint - and one that's invisible to the naked eye, and may not give trouble for some time, at that. Many bad joints in lead-free that I come across in daily work, show no signs of external distress at all (except that *all* lead-free joints look distressed), and do not respond to tapping, freezing or heating. The only conclusion has to be that whilst the solder has stuck ok to the copper pad, it hasn't to the component leg inside the joint. Probably, a classic example of the 'cold' joint that engineers your side of the pond, are fond of calling them.

Use of a bigger tip to improve its own thermal inertia, is not an option these days for general electronic service work. A finely pointed conical or small screwdriver tip, is the order of the day. Component pin densities, and component placement densities, are such that only a small tip and fine gauge solder are appropriate in most cases, and it's just not a practical proposition to keep changing tips, depending on what exactly is on your bench at the time.

When Weller came up with the 700 deg tip, it was with a traditional tin lead solder alloy in mind. It is the tip that has always been supplied with these irons from new. Lead-free melts at a temperature of 30 to 50 deg F higher than leaded, so based on Weller's determination of 700 deg being appropriate for leaded solder, you would have to extrapolate this thinking to come up with a tip temperature of perhaps 750 deg, which is what I have both my variable temperature controlled station, and vacuum desoldering stations set to, for lead-free work.

So I'm with Graham on this one (who is, like me, experienced in daily soldering over many many years) in that for lots of lead-free work with a Weller Magnastat iron, the best combination is a small tip, but with a lot of heat behind it in the form of it being an 800 deg rated one. I don't dispute that you can make good joints in lead-free with a 700 deg tip, as I do it myself, but it does require very considerable care and experience to 'do it right'. There are now more appropriate soldering tools on the market for lead-free work, than the good old TCP irons.

There are some interesting notes here about why the 'standard' tips burn out quickly, when used with lead-free

Arfa

temp

It is easy , on checking different tips rather than soldering, to not replace the cover. Whether it is a magnetic effect or a positioning effect, I don't kniow, but it can affect the switching action.

Another tip ;-) Fit a TO220 transistor insulator/ washer above and below each of the 3 screw-heads that hold the end plate to the plastic handle - stops excess heat cracking the plastic at the screws.

I must be doing something right , my one is at least 22 years of daily use with the same heater, switch, cord etc, I've only changed bits. I only switch on prior to use , not left on all the time. Gives a time to reflect - is the kit powered up? , have I confused left and right on turning the board over? etc.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

As would I. The temperature has to be at least high enough to bring the solder to its "liquidus" state. (Which is one of the reasons eutectic solder is preferable.)

This is bilge.

On Tue, 26 Aug 2008 10:56:32 +0100, "Arfa Daily" wrote: [snip...snip...]

Interesting phrase there: "Clean the tip on a watery swamp." That one required a quick mental recalibration...

On that issue, though, what are your thoughts on the use of brass turnings as a tip cleaner vice a dunk in the swamp? I switched over to the bowl of brass a while ago and now prefer it to the damp sponge.

--
Rich Webb     Norfolk, VA

The tips are copper, with an iron-alloy slug for temperature control, and iron/silver plated. To re-tin after the silver is gone, use silver solder (90% Ag kind of silver solder... jewelry craft suppliers will sell by the ounce). It takes at least a hot propane torch, MAPP or air/acetylene is better, to get to temperature for this kind of operation.

I don't let that happen and re-tin and wipe the tip regularly. I probably 'waste' as much solder as I use !

Plus Farnell IIRC sells some aggressive (iron) oxide remover that can help restore a 'damaged' tip. It comes in a little circular tin.

Fair comment.

Graham

Thanks, Arfa for the dissertation on RoHs solder. I'm lucky enough to have had no dealings with the nasty stuff as most (as in 95%+) of the repairs in newer stuff I work on is boardswap or exchange. I know I'll eventually have to mess with it and miss the old leaded stuff I've been doing since 1959...

I'll have to look up what Pace is doing for RoHs soldering and desoldering tips.

At least I know my own home WTCPT unit will cope with RoHs solder in a fashion.

I have some, and jolly good it is too, although I wonder just how much that's eating away at the tip, as well ...

Arfa

"Arfa Daily" wrote in news:Nx1tk.379066$ snipped-for-privacy@newsfe23.ams:

IIRC,that has some powdered solder mixed in with the flux. It cleans AND tins.

(of course,AFAIK,it's not lead-free....)

--
Jim Yanik
jyanik
at
kua.net

I certainly agree that we have to work above the liquidus. You're also quite right about the advantage of working with a eutectic.

700 F is still quite a bit above the liquidus.

Before you get in too deep arguing for higher temps. you might want to check out the reference that Arfa so kindly provided.

It's clear that you disagree, but is it possible that you don't understand the problem?

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Yes, that was quite confusing for a few moments.

I've never used one of those, but I've wondered how they would be. I'd be concerned that they would wear thru the tip plating quickly and lead to early death of the tips. Have you noticed any of that?

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I just did the most fundamental test on the sleeve. It's not ferromagnetic at all. Therefore I don't see how it can have any effect on the magnetic field at all. What kind of effect do you think you've seen.

Sounds reasonable, except that I've never seen heat damage to the screw anchor points in the plastic. I've certainly seen damage due to careless starting of the screws without regard to not starting in the original thread.

I'm surprised that those washers tolerate that heat. I'd expect it to be a lot hotter there than the application they were designed for.

Mine's 31 years old. Not used all that often, but left on once I'm on a job. I like these because you CAN leave them on without much harm.

My original heater burned out last year. Other than fixing the base station outlet wiring when it was new, that was the only repair it's needed. I think I'm on my second tip. I retin them by stirring them around in that brown greasy soldering flux.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Not sure what you're basing this on, since I doubt that any major manufacturer is using irons in production. I would expect any real production to be wave soldered for the last 20 years. I'm sure, however, that wave soldering, with which I have no experience, has its own set of problems.

My own experience doesn't support your claims. I wish I could tell you exactly what alloy we have at work, but it melts and flows perfectly well. That could certainly be due to the flux, but I've noticed no adverse effects from the flux. You also seem to be confusing the concepts of heat and temperature, and the distinction between the two is important.

One thing that DOES bother me about the lead free solders is that everyone suggests that it is important to do repairs with the same alloy as originally used. However there seem to be several lead free alloys, and it does not seem that one can tell the difference between them visually. So how does one know what to do when presented with a lead free board to repair?

I agree that you can't be expected to use a large blunt tip on a fine pitch high density board, but the link you provided below points out other ways to accomplish the same thing.

This assumes that the 700 F was chosen because it was perfect for tin/lead solder. There were probably other considerations, too, like heat content and the typical thermal mass of electrical connections when these irons first came out. Since many of those connections were still point-to-point they would have needed much more heat than present day junctions.

It's certainly clear that we're each entitled to our opinions.

That's an interesting link that I haven't seen before and I appreciate your pointing it out. I can't help mentioning that one thing it says is that one should be very careful to avoid the temptation to increase the soldering temperature when using lead free solder.

The first thing I actually noticed about this pdf was that it seemed to be extremely poorly written. As Cooper Tools is a US company, I thought it unusual that their English would be so poor. I'm even more surprised to see that this comes from Cooper Tools GMBH (Germany.)

In spite of the poor translation, I suspect that they have much more experience with the lead free problem than we do, and the meaning of their writing is still, in most cases, clear.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Don't know about different types of lead-free solder. But distinguishing lead free I've found is

1/ conical rather than domed solder joints 2/ putting a stainless steel sewing needle in some of the solder after melting and extracting needle while still molten, it is much more difficult to remove the cold solder from the needle than doing the same with leaded solder.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

"N Cook" wrote in message news:g92u87$1bf$ snipped-for-privacy@inews.gazeta.pl...

And many boards now actually state that they are lead free or "PbF" on the silk screening. As far as I have been able to tell, it's not so much about mixing different types of lead-free alloys, which may or may not contain small traces of other metals such as silver, but more a case of not mixing lead-free with leaded solder.

To Jim. All of my experience with this stuff is from a service rather than production point of view. You are of course right that manufacturers use wave or reflow soldering, and have done for many years. The point I was making about lead-free joints and Weller TCPs at 700 deg, versus manufacturers' joints, was perhaps not grammatically well-made. What I was basically saying was that the manufacturers, with all of their expertise and expensive production soldering equipment, still can't get to grips with the stuff themselves, and are still producing equipment littered with bad joints from day one. So, if you are making consistently good 'production' joints in lead free, using 700 degree hand soldering equipment designed way way before any eco-prat had ever come up with the concept of taking the lead out of solder, then you (your company) are doing, on average, better than the big boys.

As far as heat and temperature are concerned, I take your point that they are not the same thing, and I don't think that I am confusing the two. They are however, inextricably linked to one another by external influences. Energy, in the form of heat, is what has to be put into a body in order to raise its temperature. All solder has to have its temperature raised to the point where its liquid state becomes suitable for making a soldered joint, and then maintained at that temperature until the joint is completed. The temperature at which this condition occurs for lead-free solder, is higher than that of leaded solder. If you are just making small joints, then this is of no consequence, and a 700 degree tip is fine for the job. With a leaded joint - even a large one that causes the tip temperature to drop by a few degrees - that drop is again of little consequence, as there is plenty of temperature 'overhead' available from a 700 deg tip. However, with lead-free, 50 degrees of that overhead, have already gone, so if a joint is any bigger than 'small', the additional temperature drop at the tip, caused by the joint leaching heat from it, results in a less than adequate tip temperature being maintained, to correctly complete the joint. The result is a bad or 'cold' joint. A 700 degree tip simply cannot maintain enough heatflow into the solder, to keep it at a sufficient temperature to do a 'good job' on anything other than a small joint, and this is particularly the case where a 'typical' repair workshop tip of small dimensions is used.

I have a repair service for a particular board which uses lead-free, and I see many of them where the shop that's sending it back to me, have attempted some rework or component replacement, and it's quite obvious that they have been trying to use their normal leaded soldering equipment to do the job, with the inevitable consequences.

I can accept what Cooper say about not being tempted to increase the tip temperature, but I think that they are probably talking more about not going up far enough to get the same 'feel' with lead-free, as with leaded. Most commentators on the subject, including soldering equipment manufacturers, agree that a higher nominal tip temperature is required to work reliably with lead-free.

One of the main reasons that manufacturers are having so much trouble with the stuff, is that they have to run their soldering processes at a higher temperature. This then brings them close to the maximums that some of the components can tolerate for any length of time, so they have to compromise and run the process at a slightly reduced temperature. That is fine until you have to solder a connector or power semiconductor - particularly one that is mounted on a heatsink, and that is where many lead-free bad joints are occuring. Trust me, if manufacturers didn't *have* to run their processes at a higher temperature, with all of the implications of that, including a higher energy useage, to cope with lead-free, then they wouldn't ...

Arfa