Weller WTCPT tip not hot enough

Before you guys all continue to pile on, you might want to actually read the link that Arfa posted. They are quite emphatic about avoiding the proceedure you're all supporting. Read it. It's informative.

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

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If you actually mean specific heat, yes.

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

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The board labeling certainly helps with the lead vs. lead free problem, but the link you posted also states that the different lead free alloys should not be mixed. The do seem to imply that mixing lead in with the lead free is worse, but I can't tell whether the problem there is an engineering problem or a legal one.

We should all remember that the big boys also had soldering problems before the lead free mandate. AFAIK, those problems were mainly due to trying to run the boards over the wave soldering machines too fast. I doubt that present day production quotas are any less compelling.

I'm glad to see that you do understand the difference between heat and temperature, and the causes and effects of heat flow, but we won't settle this argument until someone can post the actual melting point of 63/37 and the solidus/liquidus of some of the lead free solders. ISTR that the good old eutectic stuff melted at something like 370 F, but I wouldn't bet on it. I'm pretty sure that it's somewhere below

Cooper appears to recommend tools that start at the same temp, but have greater thermal mass and better thermal conductivity to the work. They also have some additional recommendations which I have not tried.

Weller sells a preheat "table" which heats your board from the bottom while you solder on top (or vice versa.) This would clearly help produce joints that have been heated to an even temperature, and Weller makes the point that it reduces stress in the finished joint. They also sell a special iron which floods the work with an inert gas while you solder.

Both of these seem pretty burdensome and extreme to me.

I don't find an actual tip temperature in the Weller link, but they do say to use the lowest temperature possible. Since I find that I have no trouble (really!) soldering with a 700 F tip, and everyone in our lab uses the same irons with the same alloys, I see no reason why anything hotter would be justified.

It is also quite true that I do not work under a quota requirement, nor am I paid by the joint, so I don't mind if the joint takes 3 seconds instead of 2. OTOH, I'm not really much aware of any change in my soldering habits or technique since I used my first WTCP iron in about 1977.

My earlier irons, starting with an American Beauty in about 1955, required much different skills, and I was young and foolish then, so when I go back and look at some of that work I often have to "tidy" it up a bit.

I think they would do just as well if they ran more slowly at lower temps, but they probably find that is even more expensive than the higher temps.

We won't really know the answer until we know the actual liquidus temps of the Rohs solders. A check here gives us some facts to consider:

I note that most of these range from 420 to 450 F, with 2 eutectic alloys that melt at 430 and 440. 700 F seems like plenty of overhead for working at those ranges, at least to me.

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

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right

and

compromising

soldering

the

non-existence,

though

and

You had it easy - when I started soldering it was a matter of heating , on the gas stove, a shaped block of copper on a steel shaft with wooden handle.

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

The military etc are still worried because of potential tin whiskers with closely spaced device leads.

There are known examples of such inter-lead shorts and they can support up to

Graham

That was the stuff. Couldn't remember the name.

Oh yes I remember well.

Yup. The Antex C15 was my first 'serious' iron for working on miniature components like TO-18 transistors. I recall BC109s were 6s/6d from Henry's Radio back then and building my first pre-amps from the Mullard Audio and Radio applications book.

Possibly just purer ?

Graham

My experience says otherwise. I'll have to time how long it takes to solder say a

Plus note my post about those cold joints that plagued an amp design that just 'went away' with 800F tips.

Graham

"Jim Adney" wrote in message news: snipped-for-privacy@4ax.com...

All points noted, and for the most part, agreed with. I think what I am saying, and probably Graham too, if I understand him correctly, is that for most modern service work, a small tip is needed, which is less than ideal for transferring heat from the iron's element to the actual joint, which should be being made by the joint itself being heated, and the solder 'fed in', as is the case with leaded solder. The result of that less than ideal sized tip is that inevitably, as a large joint leaches heat from it, the temperature drops, perhaps 50 or more degrees. With leaded solder, this is of little consequence, as the drop in temperature is still well above the point where the solder is able to be worked, to create a guaranteed good joint. However, that said, try it on a big enough joint, and that won't be the case. With lead-free, the drop in tip temperature is of greater significance, as it readily causes poor workability of the solder, a 50 or more degree drop taking you a lot nearer to the point where the solder works 'pasty' rather than fluidly.

So in this case, a tip that starts off at 800 deg and then drops towards 700 'under load' appears to represent a tool better suited to the job 'on average', bearing in mind that as service engineers, we are seeing many types of equipment that need, in theory at least, a similar variety of different soldering equipment. So what we are using is a working compromise, that has to be able to cope with leaded as well as lead-free solder, and everything from IC pins to BNC connectors or worse.

To some extent, the points raised are moot in that there are now much better tools on the market for coping with the modern situation, without having to compromise. Someone mentioned Metcal stations for instance. Any station with a tight control loop, is much better than a TCP for general service work these days. I run an Antex temperature adjustable station, which I keep idling at about 680 degrees. I turn it up to 750 when using lead-free, as I find from a purely personal point of view, that this temperature suits both me, and the Ersin 306 alloy that I use. I still keep my TCP running, with a

As far as the manufacturers having trouble with the stuff goes, I don't think that it is to do with deadlines per se. I can remember when PCBs were first around, and the technology advanced very quickly, driven mainly by the big Jap consumer market manufacturers, to the point where bad joints on their equipment were virtually unheard of, and that has remained the situation for many years now. Given that wave and reflow soldering were fully mature and largely trouble free and reliable technologies, one would have expected that the degree of understanding that they must have of the processes involved, would have allowed them to slip seamlessly into similarly reliable manufacturing with lead-free. This doesn't appear to have been the case, and equipment is still coming out of factories with less than satisfactory joints, which tells me that the problem is with the technology itself, not how the manufacturers are incorporating it into their overall manufacturing time budget. When push comes to shove, it is a replacement technology that arguably wasn't required in the first place. The original technology involved in soldering was the right one, as has been shown over many years, and the replacement uses materials deemed to be ecologically better, but which don't actually readily do the job that they are needed to. The lead-free solder is being 'made to fit' on the back of the "green" ticket if you will, and sod the consequences ...

Arfa

And what you mean is 'heat capacity' which is NOT the same thing ! Although it's value depends on specific heat too.

" Heat capacity (symbol: Cp) ? as distinct from specific heat capacity ? is the measure of the heat energy required to increase the temperature of an object by a certain temperature interval. "

Graham

On its way. Check your incoming. Let me know if any probs.

Arfa

Sent again using the first 'reserve' address. Let me know ...

Arfa

I also use one of those, and if anything, my tips last longer. Andy Cuffe

snipped-for-privacy@gmail.com

with

got

All received, not had a chance to read it yet

The same thing happened with early-manufactured 72 'pin' SIMMs that had tin contacts (typically the cheap generic RAM sitcks). 30 'pin' tin contact SIMMs were 'coarse pitch' enough that the problem occurred rarely.

I also saw the same issue on some UK-manufactured electric traffic counters (those boxes with the hoses laid across the pavement). They left the thru-leads so long that the tin coating on on the leads protruding out of the hole would grow whiskers. We had no schematics and the chips were all marked only with proprietary numbers, all we could do to fix them locally was to check discrete components on guesstimate as to what their function was, and do an extremely close scrutiny on the boards. We found those whiskers on quite a few of them, so it became a shop standard to trim all the leads on the boards and scrub them before giving up and RMAing the units. That cured probably 70% of the problems.

Pathetic.

Bloody alleged 'greens' and gullible politicians.. Combine the two and you have a disaster.

Graham

I agree with this, except that in the case where I encounter a large joint, I always find that I can heat the joint using the side of the tip, thus greatly increasing the thermal conductivity.

Since I've never made any temp measurements across a soldered joint, I really don't know how much temp drop one might find. It appears that we have 250 F of headroom available with a 700 iron, which seems like it should be plenty, but I have no data to support that. Weller's suggestion to preheat the bottom side of the board while soldering from the top (or vice versa) would seem to support your claim that the

One of my co-workers uses a Metcal for surface mount work and swears by it. Since it heats and senses right at the tip, it's bound to be better as you say.

I tend to work (repair) a lot of items that are quite old, so I've seen a number of failed joints on old boards. They tend to crack around large joints where not enough heat got into that joint to allow the solder to wick in far enough to make a sound mechanical connection. I can only speculate that the cause was insufficient pre-heat time in the wave soldering machine, due to running the line too fast.

Now, I have a confession to make. When I started my current job 9 years ago, they told me they were switching to lead free solder. I tried some of it at that time and it seemed fine. In the course of this conversation I realized that I had no idea exactly what version of lead-free we were using, so today I went into our shop and looked at one of the spools, since I usually just pull off a few feet to take back to my office where my bench is. What I found was spools of 60/40 tin/lead. I don't know how long that's been in use here, or if they ever bought any more of the Rohs solder.

So at this point I have to admit that it's possible that I've been mistaken for the past 9 years and I may have almost no Rohs soldering experience. I apologize for my statements to the contrary. It now seems clear why my "experience" with Rohs solder seemed to be so positive. I'll try to find some actual Rohs to try.

I DO know that my previous workplace HAS made the switch to Rohs. I still have friends there and it is a manufacturing environment. One of those friends is one of their electrical engineers, so I'll make a point of asking him how that changeover went and whether it has given them any continuing problems.

Maybe I'll find that they went to 800 F tips, or maybe not.

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

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No, it IS 13.2C.

No idea how much the alloying helps. But it will do a bit.

Graham

Also see .....

Which covers the popular manufacturing formula including 0.5% Cu.

Graham

How cold does the electronics in your car get in winter ?

Graham