Inge ???
Not quite sure who this reply is from, or if this reply is directed at me or
not, or who 'Mr Besserwisser' or 'dear MR' are, but as for myself, I simply
responded to the pictures themselves (specifically the top one), and the
implied charge that all of this was due to gold embittlement alone.
From my previous posts, you can see that I do not believe that gold
embrittlement alone is the culprit.
I am sorry if my posts offended you, or someone else, but I thought that
this forum was a place to come and get real answers to real problems, and
not just to muse at something as a 'curiosum aurorum', unless of course,
such is clearly spelled out as the point, which in this case it was not (or
was this originally posted on Friday).
Emergency or not, lead forming and hand soldering was dictated by the part
itself, and at a minimum, anyone with good soldering skills and experience
with these kinds of parts can do good lead forming even with the tip of the
soldering iron during soldering, and if not with the tip of the iron, then
with the dentalpick or other item used to hold the lead down on the trace
while soldering.
By the way, how much do you want for that soldering pot (with all of that
solder still in it of course)?
JaMi
----- Original Message -----
From: "Hfjord" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 07, 2006 2:39 PM
Subject: Re: [TN] Gold Embrittlement
> Well Mr Besserwisser, you got no coffee today?
>
> What you see is the situation BEFORE the whole solder process had to be
> changed.
> The poor ladies, who have been hand soldering helicopters for years,
shouted
> on me and
> wondered why the joint could not be normal. Quick examination revealed
that
> the supplier
> had put on gold that would suit better for a jeweler! We had to deliver,
so
> there was nothing
> else to do than to degold all thousands transistors in a solder pot, by
> means of a simple little
> robotic.
>
> The terminations are what the supplier sells on REELS for automatic
> mounting, and we had no
> time to wait for our purchaser to search the market for a emergency
> shipping. So, we just had
> to pick them all out of the reels and degold and handsolder them as usual.
> There will be a juridic
> case, be so sure.
>
> These are low level signal amplifiers, no heat dissipated, cooling no
> problem. We use heatsinked
> transistors in other products, where heat is created. Don't you think we
> know what to do and
> how to design. We have mounted about 100,000,000 such transistors, dear
MR!
>
> The rest of your eructational pyrosis won't be met. I just showed an
> interesting case of what
> extremly thick gold on leads can cause, see it as a curiosum aurorum.
>
> If the pictures are ugly, that may mirror the spectator's sight of the
> world.
>
> Best regards
>
> Inge
>
>
> ----- Original Message -----
> From: "JaMi Smith" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, November 07, 2006 9:27 PM
> Subject: Re: [TN] Gold Embrittlement
>
>
> >I am not questioning the nasty embrittlement shown in your pictures, but
> >am
> > questioning what the heck you used to solder it with - what kind of
> > solder.
> >
> > Further I am questioning whether or not the device was operated after
you
> > soldered it and before you decided to photograph it - is this a failure
or
> > return.
> >
> > One problem that I do note, is that you have failed to properly trim and
> > form the leads prior to mounting and soldering the device.
> >
> > Typically RF transistors or amplifiers can get pretty hot, and if they
are
> > board mounted, and their ground leads, where most or all of the heat is
> > going to escape, are cut too short, and not properly formed, and not
> > properly soldered, then gold or no gold, they are going to cause normal
> > tin-lead solder to reflow during operation.
> >
> > It is vital, absolutely vital, that all ribbon leads of these types of
> > devices be completely flat on the circuit board trace before they are
> > soldered, gold or not, and it is obvious in these pictures that that is
> > not
> > the case.
> >
> > One final issue, and I am sticking my neck out here, since I do not know
> > exactly what the device is (part type and number), and I do not have any
> > data sheets, and I do not know the recommended mounting for this
> > particular
> > device. Generally speaking, RF type transistors are mounted on a Heat
Sink
> > under the PCB, with the body of the transistor going thru a hole in the
> > PCB
> > and being mounted such that the leads lay flat on the corresponding PCB
> > traces. On smaller devices such as this, it is critical that lead
forming
> > is
> > done, and that that lead forming must account for thermal expansions
over
> > the entire operational temperature range of the device, and if the
ceramic
> > case has a metal bottom, and it is soldered to the board, then the lead
> > forming must account not only for the entire operational temperature
> > range,
> > but for the soldering operation itself.
> >
> > Finally, these devices must be hand soldered, and hand soldered by
someone
> > who knows how to solder these types of devices.
> >
> > Simply from observing the pictures, I would say that the ground leads
are
> > way too short to transfer the heat that whoever required the large holes
> > knew was going to be there, and that the leads were not properly formed,
> > and
> > that whoever soldered the leads did not know how to solder them, and
spent
> > way too much time on the solder joint, thus the excessive embrittlement
> > (once again, I am not arguing the embrittlement issue itself, but this
> > appears to be excessive).
> >
> > Please remember that tin-lead solder is an exceptionally poor electrical
> > conductor, and that it's conductivity is only 16% to 18% that of copper,
> > and
> > that its thermal conductivity is equally as bad. This means that if you
> > install any ribbon lead device such as this, whether it is an RF
> > transistor
> > or amplifier or not, that if the leads are just 'hanging out there',
with
> > lots of solder between them and the trace on the board, which in terms
of
> > both current and thermal flow is now a resistor, then the device will
very
> > quickly get hot enough to reflow the solder on the leads.
> >
> > Any and all of the above are probably contributors to why these pictures
> > look soooooooo ugly!
> >
> > Yes, there is gold embrittlement, but I saying that this is not just
gold
> > embrittlement, but that there is more to the issue of the joints shown
in
> > these pictures.
> >
> > Even when hand soldering a device such as this, and even if the leads
are
> > properly formed, it is good practice, and common practice, to hold the
> > lead
> > firmly against the trace during soldering with something such as the tip
> > of
> > a dental pick, or some other similar object (even a wooden toothpick or
> > the
> > wooden end of an alcohol swab) that will not interfere with the flow of
> > solder, or thermally interfere, but that can he held there completely
> > still
> > until the solder joint has thoroughly cooled.
> >
> > In other words, what I am saying, is that in this case, even if all the
> > gold
> > were removed from the leads prior to soldering, you would still have
> > problems with them, which at best would be cold solder joints at
> > installation, and/or reflow during operation.
> >
> > Forgive me, but these solder joints look like crap, to put it bluntly
(and
> > mildly), irrespective of the gold embrittlement.
> >
> > JaMi
> >
> >
> > ----- Original Message -----
> > From: "Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Monday, November 06, 2006 12:59 AM
> > Subject: Re: [TN] Gold Embrittlement
> >
> >
> > Agree,
> > We degold all microwave SMT small outline transistors ("helicopters"),
> > because we had catastrophic gold embrittlement problems. The solder
> > joints were so brittle, that the leads lifted from the pad in the temp
> > cycle tests. We measured as much as 15 micrometers of gold! The
> > semiconductor manufacturer meant, that it is a problem to have control
> > on the gold process on such small parts. What nonsense! Anyway, we are
> > today suspiscious with many gold plated parts and do degolding rather
> > than getting embrittlement.
> >
> > I'll send some pictures to Steve, so you can see what can happen.
> > Horror!
> >
> >
> > Inge
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
> > Sent: den 2 november 2006 23:06
> > To: [log in to unmask]
> > Subject: Re: [TN] Gold Embrittlement
> >
> > Hi Amol,
> > I you have imersion Au, Au-embrittlement is not a problem because there
> > is not enough Au. Be careful, however, if your PCBs come from China; I
> > have seen much thicker Au-layers than are possible with iAu.
> > Calculating the wt% of Au in a soldert joint is an exercise in futility,
> > because you have to make the assumption--frequently not warranted--that
> > the SnAu-IMCs are uniformally distributed.
> > In cases where you suspect thicker Au [and for the matter Ag; which is
> > equally as bad as Au in causing SJ-embrittlement] deposits, the safest
> > course of action is to wash the Au (Ag) off by tipping.
> >
> > Werner
> >
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