Weller WTCPT tip not hot enough

[Eeyore]

Arfa Daily wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message

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 30mA I read somewhere IIRC. I had a fantastic picture of one once. It
shorted out a *crystal*.


Been some interesting stuff recently in Elektor mag on the subject, and how
the old AF117's used to fail in SO mixers used in early tranny radios. Seems
that was due to whiskers growing inside the metal can of the transistor,
which was tin plated, and shorting to the transistor itself. Many engineers
just used to snip the screen lead on the transistor, but I found that if you
quickly jabbed a screwdriver across between the screen and collector leads,
the short magically disappeared. I guess it was blasting off the microscopic
whisker by vapourising it.

Now how did you devise that technique ?

Graham

 

[nobody >]

Eeyore wrote:

Arfa Daily wrote:

I don't have info particularly collated anywhere, but if you want to contact
me off group with an address that's monitored for input, I'll send you a
copy of the article, which contains references to where I got info, and who
from. I don't think that there is any particular need to remove the surface
of RoHS compliant components' leads. I seem to recall reading somewhere that
most component leads are now tin plated, as in coated in neat tin, rather
than being 'tinned' with any kind of solder, as they were in the past. A
coating of pure tin should not cause any problems when used with a
conventional SnPb solder.

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
30mA I read somewhere IIRC. I had a fantastic picture of one once. It shorted
out a *crystal*.

Graham

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.

 

[Eeyore]

"nobody >" wrote:

Eeyore wrote:
Arfa Daily wrote:

I don't have info particularly collated anywhere, but if you want to contact
me off group with an address that's monitored for input, I'll send you a
copy of the article, which contains references to where I got info, and who
from. I don't think that there is any particular need to remove the surface
of RoHS compliant components' leads. I seem to recall reading somewhere that
most component leads are now tin plated, as in coated in neat tin, rather
than being 'tinned' with any kind of solder, as they were in the past. A
coating of pure tin should not cause any problems when used with a
conventional SnPb solder.

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
30mA I read somewhere IIRC. I had a fantastic picture of one once. It shorted
out a *crystal*.

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

 

[Jim Adney]

On Thu, 28 Aug 2008 11:03:18 +0100 "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

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.

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.

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.

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
700 F tip may not be sufficient, but it would be more helpful if they
had specific temp recommendations.

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.

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.

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 ...

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 jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Eeyore]

Arfa Daily wrote:

"Eeyore" wrote
Arfa Daily wrote:

Been some interesting stuff recently in Elektor mag on the subject, and
how the old AF117's used to fail in SO mixers used in early tranny radios.
Seems that was due to whiskers growing inside the metal can of the
transistor,
which was tin plated, and shorting to the transistor itself. Many
engineers just used to snip the screen lead on the transistor, but I found
that if
you quickly jabbed a screwdriver across between the screen and collector
leads, the short magically disappeared. I guess it was blasting off the
microscopic whisker by vapourising it.

Now how did you devise that technique ?

Christ knows Graham ! I was about 18 at the time and probably about the only
one in the workshop who was reasonably comfortable with the new fangled
transistors ...

Thinking about it, the leads went E-B-Scr-space-C. It was probably one of
those fortuitous 'mistakes' where I was measuring the collector voltage, and
the meter probe slipped ...

Unlike me designing power amps where a similar slip tends to result in a lot of
magic smoke being let out.

Graham

 

[Eeyore]

N Cook wrote:

Some of the bad joints i've seen in the last few years, you just do not come
across with leaded solder. And we're talking about kit only a year or two
old. eg totally unstressed (in temperature terms but subjected to vibration)
1/3 watt resistors (so no heatsinking at production) that you can pull out
of the "solder" joint by finger force.

Vibration is the killer with lead-free. Never mind the tin whiskers.

But did you also know about tin pest ? I have no idea how much the temperature
is affected by the copper (and silver for the rich) in lead-free but the Japs
also use bismuth IIRC.

" At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin
transforms from the (silvery, ductile) allotrope of ?-modification white tin to
brittle, ?-modification grey tin. Eventually it decomposes into powder, hence
the name tin pest.

The decomposition will catalyze itself, which is why the reaction seems to speed
up once it starts; the mere presence of tin pest leads to more tin pest. Tin
objects at low temperatures will simply disintegrate. "
http://en.wikipedia.org/wiki/Tin_pest

Graham

 

[Eeyore]

N_Cook wrote:

Eeyore wrote
N Cook wrote:

Some of the bad joints i've seen in the last few years, you just do not
come across with leaded solder. And we're talking about kit only a year or
two old. eg totally unstressed (in temperature terms but subjected to
vibration) 1/3 watt resistors (so no heatsinking at production) that you can
pull
out of the "solder" joint by finger force.

Vibration is the killer with lead-free. Never mind the tin whiskers.

But did you also know about tin pest ? I have no idea how much the
temperature is affected by the copper (and silver for the rich) in lead-free
but the
Japs also use bismuth IIRC.

" At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure
tin transforms from the (silvery, ductile) allotrope of beta-modification
white
tin to brittle, alpha-modification grey tin. Eventually it decomposes into
powder,
hence the name tin pest.

These phase changes are called allotropes.

The decomposition will catalyze itself, which is why the reaction seems to
speed up once it starts; the mere presence of tin pest leads to more tin
pest.
Tin objects at low temperatures will simply disintegrate. "
http://en.wikipedia.org/wiki/Tin_pest


In the situation where you can just pull a component from a board, not
desoledered, it is sometimes possible to see a grey powdery surface to the
component, suggestive of tin-pest.

No surprise. A guitar amp kept in the garage will see those temps.

And for using tin tinned new RoHS components destined for both old boards
and Pb-Sn solder or new boards and silver solder, burr the tin off with a
"diamond" cintride burr on a Dremmel, before tinning with the intended
solder. A solid layer of tin is asking for trouble - turn to dust tin-pest.

And whiskers.

The military etc are doing an enhanced version of what you describe.

Graham

 

[Eeyore]

N Cook wrote:

I'm not sure the critical temp is 13 deg C, has someone confused 13 deg F
and 13 deg C?. 13 degree C is quite a normal unheated room temperature.

No, it IS 13.2C.

http://ap.pennnet.com/articles/article_display.cfm?article_id=279192

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

Graham

 

[Eeyore]

N Cook wrote:

I'm not sure the critical temp is 13 deg C, has someone confused 13 deg F
and 13 deg C?. 13 degree C is quite a normal unheated room temperature.

Also see .....
http://findarticles.com/p/articles/mi_qa5348/is_200106/ai_n21473892

Which covers the popular manufacturing formula including 0.5% Cu.

Graham

 

[Eeyore]

N Cook wrote:

Its a time-temp-effect thing, must be less than 13.2 C to make any
appearance

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

Graham

 

[Michael A. Terrell]

Arfa Daily wrote:

Oh I had to work on them too ! Our company was responsible for background
music machines that were rented out ro shops etc. They used a sort of
cassette tape that was endless (!) in that it wound off the centre and back
on to the outside. Bit like an 8 track mechanism, but only had four tracks,
as I recall. Anyways, they had a bloody great amplifier built into them,
based on 2N3055s. Being an early design, there was no protection or bias
stabilization, and you only had to bring a 20k / volt meter near to some
points to get them to run away, releasing their magic smoke ... Happy days.
It's back when engineers learnt the business properly d:~}

That sounds a lot like the Viking/Telex decks that used a
Fidelipac/NAB Broadcast cartridge. They sold the bare decks, with or
without the heads and sensors, and the customer built their own
electronics. I think I still have the Sam's on the bare deck, somewhere.

http://en.wikipedia.org/wiki/Fidelipac

<http://images.google.com/images?hl=en&rls=com.microsoft:en-us:IE-SearchBox&rlz=1I7GGLD&resnum=0&q=Fidelipac&um=1&ie=UTF-8&sa=N&tab=wi>

The 3M background music system used a bigger cartridge, with a pair of
stacked, 7" Reels. It was four track as weel. it played to one end,
revesed direction to play track two. When that ran out, it reveresd
again, and selectd the third track... When it finished the fourh track,
it started over. It ran at a very low speed and had something like eight
hours of music.


--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

 

[Eeyore]

N Cook wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in message
N Cook wrote:

I'm not sure the critical temp is 13 deg C, has someone confused 13 deg F
and 13 deg C?. 13 degree C is quite a normal unheated room temperature.

Also see .....
http://findarticles.com/p/articles/mi_qa5348/is_200106/ai_n21473892

Which covers the popular manufacturing formula including 0.5% Cu.

Here is a pic I took of what was probably tin pest.
Ignore the top pic as just a control showing normal silvery appearance of
pins after desoldering.

http://home.graffiti.net/diverse:graffiti.net/solder.jpg
The black cap, the top pin could be pulled out and the bottom one needed
desoldering.

I see. I misunderstood that the first time you posted that pic.

It is just about possible to see the all grey dusty covering to
the top pin. So that 100 percent tin layer eventually turns to the grey form
, expanding in the process. So like a weed growing through concrete it
forces the solder apart as well as in itself being non-condusctive.

Quite possible, that seems to be the process.

Graham

 

[Eeyore]

N_Cook wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in message
N_Cook wrote:

And for using tin tinned new RoHS components destined for both old
boards and Pb-Sn solder or new boards and silver solder, burr the tin off
with
a "diamond" cintride burr on a Dremmel, before tinning with the intended
solder. A solid layer of tin is asking for trouble - turn to dust
tin-pest.

And whiskers.

The military etc are doing an enhanced version of what you describe.

Do you know of a precise term, military or civil, for the process of
mechanical (or other method) removal of full tin tinning of component legs,
prior to use ?

I don't myself but there must be one since there's a market for it.

With that pic of tin-pested cap I should have said that the solder joints
otherwise looked normal, only this surface layer tinning of the pin had
transformed to grey.

I followed.

Graham

 

[Eeyore]

Arfa Daily wrote:

"Eeyore" wrote
Arfa Daily wrote:
"Eeyore" wrote
Arfa Daily wrote:

Thinking about it, the leads went E-B-Scr-space-C. It was probably one
of those fortuitous 'mistakes' where I was measuring the collector
voltage, and the meter probe slipped ...

Unlike me designing power amps where a similar slip tends to result in
a lot of magic smoke being let out.

Oh I had to work on them too ! Our company was responsible for background
music machines that were rented out ro shops etc. They used a sort of
cassette tape that was endless (!) in that it wound off the centre and
back on to the outside. Bit like an 8 track mechanism, but only had four
tracks, as I recall. Anyways, they had a bloody great amplifier built into
them,
based on 2N3055s. Being an early design, there was no protection or bias
stabilization, and you only had to bring a 20k / volt meter near to some
points to get them to run away, releasing their magic smoke ... Happy
days.
It's back when engineers learnt the business properly d:~}

An, the days of 50uA meter movements. I do still have a small one and even
found a leather BT case designed for it on the local market.


My good old AVO 8 Mk IV, which was originally issued to me as an apprentice
in about 1970, is still used every day. For 'resistance path' fault finding,
and semiconductor junction basic proving, it is still my instrument of
choice. There's something very comforting about seeing a needle swing over
to 'about the right place'.

And it's horrid seeing the movement protection fail !

I do of course have a raft of digital multimeters, both portable and bench,
and a full array of digital capacitance and ESR and so on meters for more
precise measurements where needed, but I find that a good quality analogue
meter still fits the bill for much general service work.

I only really use it where the mechanical averaging is useful, such as noise
measurements.

Otherwise it's my trusty Fluke 77. I think I've only ever seen one 'go wrong'
and it was repaired or replaced under warranty even though we didn't have the
invoice because they track the serial numbers themselves.

Graham

 

[Eeyore]

Arfa Daily wrote:

"Eeyore" wrote
N Cook wrote:
Eeyore wrote
N Cook wrote:

I'm not sure the critical temp is 13 deg C, has someone confused 13
deg F

and 13 deg C?. 13 degree C is quite a normal unheated room
temperature.

Also see .....
http://findarticles.com/p/articles/mi_qa5348/is_200106/ai_n21473892

Which covers the popular manufacturing formula including 0.5% Cu.

I see that in that article

Tin pest in Sn-0.5 wt.% Cu lead-free solder

Sliver solder does not supress tinpest, very much reduces its growth, but
not supressed like leaded solder.

I wonder just what we have waiting in store for us.

I had considered applying to the Comission for exemption for all goods
regularly subjected to vibration (such as used on location video and sound
recording) and which also might be subjected to freezing temps in use or
transit which could at least exempt pro A/V gear.

I guess that just about covers almost all electronic gear then ! Lets just
go for a complete ban on lead-free solder ! Power to the electronic
engineering industry !!!!!

Hmmmm. Video gear on location in freezing temperatures .... "So viewers,
after a 2 hour descent, we see the first signs of the Titanic coming into
view in remarkably sharp detail ... " Phhhttt !!! "Oh shit ..."

LOL !

The freezing often occurs overnight in the truck. Never mind road quality for
vibration getting it there.

Graham

 

[Eeyore]

N Cook wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote in message

I wonder just what we have waiting in store for us.

I had considered applying to the Comission for exemption for all goods
regularly subjected to vibration (such as used on location video and sound
recording) and which also might be subjected to freezing temps in use or
transit which could at least exempt pro A/V gear.

It seems one (at least one) loudspeaker manufacturer successfully got an
exemption on these grounds.

It seems that if you produce kit and some of it, as little as 5 percent, is
used in medical/military/aeronautical/space, even if only in R&D/analysis
laboratories attached to any of those industries, then you can get a
derogation for all production. On the grounds that it is unreasonable to
force a company to run 2 parallel production lines.

Is this a specific ruling you've come across ? Certainly interesting.

Graham

 

[Jim Adney]

On Sat, 30 Aug 2008 10:42:02 +0100 "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

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.

No problem Jim, and it's nice to know that there are still people out there
honest enough to admit to such a situation ! I would be interested to know
what your friend's findings have been.

Well, it seems that info was also bad. I called him just to find out
what their experience had been so far and found that so far they are
still exempt They have not made the switch.

Thanks for your understanding. I was very reluctant to admit my
mistake, but I felt that it was only fair to keep the discussion
honest.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Jim Adney]

On Wed, 3 Sep 2008 10:00:20 +0100 "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

The whole situation has become very complex, with two technologies now
competing on geographical grounds. I guess if all your work, and that of
your friend's place, is US based, and not for export over here, then you
have no need to switch to RoHS approved components and solder, except maybe
on the grounds of the caveat regarding not mixing solder types. By this I
mean that I guess gear manufactured in lead-free technology is pouring into
the US from the far east, but the fact that you have no *requirement* to
preserve its lead-free status, probably means that it is getting repaired,
for the most part, with leaded solder, which may not be the best thing for
long term reliability. Not that this technology is reliable in the first
place, of course ... !! d;~}

I certainly don't know all the legal ins and outs, but my previous
employer certainly made things that were shipped to all parts of the
world. It was custom scientific gear, however, and certainly not any
kind of a commercial mass-marketed product, so it remains exempt. They
report that the exemptions get stricter every year, so they expect to
have to deal with RoHS eventually and are just hoping for now that it
remains a far distant problem.

My friend did check with one of the techs today and was told that they
have occasionally had to repair lead free boards that had come as part
of more commercial products. He reports that it was quite hard to get
the dead RoHS parts out of the board.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Eeyore]

Arfa Daily wrote:

Almost invariably, when I receive them, someone has already 'had
a go'.

May The Lord save us ! ;~)

Graham

 

[Eeyore]

Arfa Daily wrote:

"Eeyore" wrote in message
Arfa Daily wrote:

Thinking about it, the leads went E-B-Scr-space-C. It was probably one of
those fortuitous 'mistakes' where I was measuring the collector voltage,
and the meter probe slipped ...

Unlike me designing power amps where a similar slip tends to result in a
lot of magic smoke being let out.

Oh I had to work on them too ! Our company was responsible for background
music machines that were rented out ro shops etc. They used a sort of
cassette tape that was endless (!) in that it wound off the centre and back
on to the outside. Bit like an 8 track mechanism, but only had four tracks,
as I recall. Anyways, they had a bloody great amplifier built into them,
based on 2N3055s. Being an early design, there was no protection or bias
stabilization, and you only had to bring a 20k / volt meter near to some
points to get them to run away, releasing their magic smoke ... Happy days.
It's back when engineers learnt the business properly d:~}

An, the days of 50uA meter movements. I do still have a small one and even found
a leather BT case designed for it on the local market.

Graham