Topics

'Solder Rot'

Tim Phillips
 

from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination with
a jewellers loupe and bright light showed a bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had
'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim

EricJ
 

It absolutely does. I was just reading a paper about this the other day. Several factors contribute to circuit failure due to aging. One being that the solder bond weakens apparently due to inter-metallic layer growth over time. There was a whole section dedicated to testing shear strength of aged surface mount joints. Leaded solder did much better than lead-free at retaining bond strength in those cases.

Several other factors mentioned and tested were the weakening of foil layers' (tracks and pads) adhesion to the boards (roughly halved over time), vias coming loose and separating from the fiberglass surface of the boards (apparently very common on heavy copper sections of the board due to thermal expansion of the copper and vias during soldering) and cracking and "tearing" of aged through-hole solder joints.

--Eric

On Jan 6, 2020 6:32 AM, Tim Phillips <timexucl@...> wrote:




from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination
with
a jewellers loupe and bright light showed a  bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had

'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim





Geoffrey Thomas
 

I would guess it had not been soldered correctly from the factory. I've had a intermittently faulty HP monitor that had the same problem, the component lead just hadn't "wetted" correctly. One soldered joint later, perfect.

Geoff.

On 06/01/2020 12:32, Tim Phillips wrote:
from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination with
a jewellers loupe and bright light showed a bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had
'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim

Tam Hanna
 

Hello Eric,
May I ask for you to provide me a link or reference to the paper?

Tam
---
With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 14k other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/

KB6NAX
 

Tim, I think what you are describing is poorly formed solder joints that
could not withstand the forces of installing/removing transistors. No,
solder does not normally "crystalize", but could be grainy and weak due to inadequate
melt temperature when the soldering was done or excessive oxidation of metals prior to soldering. A process control excursion
at the factory, unusual for Tektronix.

Arden

from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination with
a jewellers loupe and bright light showed a bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had
'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim <
..............

greenboxmaven
 

I am very surprised at Tektronix having this sort of problem. I worked a few years at a vintage sound equipment botique as a retirement job, and aged solder joints were a very common and serious problem. Kenwood gear, both sound and ham, was the worst for this problem, but it occurred elsewhere as well. Reheating all of the connections and adding a small dab of well fluxed solder was all that was needed in many cases to bring a dead or poorly performing rig back to life. For through hole solder joints, I like to warm them up, push a piece of small stranded wire through, flow the solder well, and then trim the wire. Over 40 years ago, I was given a couple dozen Monroe/ Litton desktop calculators with Nixie tube displays. They all had unreal faults, and all but one were fully restored by putting wires in the through hole connections and reheating the others.

Bruce Gentry, KA2IVY

On 1/6/20 8:10 AM, EricJ via Groups.Io wrote:
It absolutely does. I was just reading a paper about this the other day. Several factors contribute to circuit failure due to aging. One being that the solder bond weakens apparently due to inter-metallic layer growth over time. There was a whole section dedicated to testing shear strength of aged surface mount joints. Leaded solder did much better than lead-free at retaining bond strength in those cases.

Several other factors mentioned and tested were the weakening of foil layers' (tracks and pads) adhesion to the boards (roughly halved over time), vias coming loose and separating from the fiberglass surface of the boards (apparently very common on heavy copper sections of the board due to thermal expansion of the copper and vias during soldering) and cracking and "tearing" of aged through-hole solder joints.

--Eric

On Jan 6, 2020 6:32 AM, Tim Phillips <timexucl@...> wrote:



from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination
with
a jewellers loupe and bright light showed a bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had

'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim





EricJ
 

Hi Tam,

It is National Physical Laboratory's "Good Practice Guide #136."

--Eric

On Jan 6, 2020 10:04 AM, Tam Hanna <tamhan@...> wrote:




Hello Eric,
May I ask for you to provide me a link or reference to the paper?

Tam
---
With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 14k other followers by visiting the Crazy
Electronics Lab at https://www.instagram.com/tam.hanna/





Roy Thistle
 

On Mon, Jan 6, 2020 at 08:19 PM, EricJ wrote:


National Physical Laboratory's "Good Practice Guide #136.
Hi Tam, Hi Eric .et al.:
Just a caveat... this N.P.L. article is referring to mostly low volume automated soldering (using expensive soldering machines, such as laser soldering)… for instruments (and their associated components) meant to operate at high temperatures (that is instruments operating at 180 to 300 centigrade.)… according to the article's introduction, at least.
How much traction the information presented there bears upon the stuff we deal with in this forum... well, would we still be in Kansas?
Despite the above restriction... there are some really cool pictures.
Best regards and wishes.
Roy
P.S. Eric thanks for sharing this great link, and this information...always appreciated. Best regards.

Jean-Paul
 

Besides this problem you have "tin disease" in very cold climates and "tin whiskers" for very close spaced solder connections and at higher voltages.

Jon

EricJ
 

Hi,

Actually I think the problem is likely even MORE prevalent when hand soldering. The intermetallic layer growth not only occurs due to aging but also happens when a joint is heated longer and/or hotter than it ought to be, which I am sure happens with some guys soldering at home. Those joints will be starting with a handicap right off the get-go. If the problem takes 10 or more years to manifest I suppose most won't worry about it.

I don't know if you have heard about Metcal's new soldering station with the LEDs that tell you when to remove the iron from the joint; it actually monitors the amount of heat applied to a joint and for how long to try to optimize that intermetallic layer thickness.

--Eric

On Jan 7, 2020 3:37 AM, Roy Thistle <roy.thistle@...> wrote:




On Mon, Jan  6, 2020 at 08:19 PM, EricJ wrote:


National Physical Laboratory's "Good Practice Guide #136.
Hi Tam, Hi Eric .et al.:
Just a caveat... this N.P.L. article is referring to mostly low volume
automated soldering (using expensive soldering machines, such as laser
soldering)… for instruments (and their associated components) meant to
operate at high temperatures (that is instruments operating at 180 to 300
centigrade.)… according to the article's introduction, at least.
How much traction the information presented there bears upon the stuff we
deal with in this forum... well, would we still be in Kansas?
Despite the above restriction... there are some really cool pictures.
Best regards and wishes.
Roy
P.S. Eric thanks for sharing this great link, and this
information...always appreciated. Best regards.





DaveH52
 

That's not a new concept. Thermal cycling produces stresses in the solder, and eventually it will fail, especially leadless parts. Leaded components provide some stress relief in the leads.. If you google solder joint cracking, you will find a wealth of information, including
https://www.dfrsolutions.com/predicting-fatigue-of-solder-joints
Dave

Roy Thistle
 

On Tue, Jan 7, 2020 at 11:44 AM, DaveH52 wrote:


you will find a wealth of information, including
https://www.dfrsolutions.com/predicting-fatigue-of-solder-joints
Thanks for that link DaveH53 (Dave?).
From the paper (buried in the long introduction) , "The purpose of this paper is to provide a better understanding of the relevance of standard strain energy based models for low cycle fatigue of solder joints in predicting the behavior of standard SMT packages subjected to a very high number of power cycles.", where the paper leads me to believe "... a very high number of power cycles." is something like 250,000.
There is also some discussion about this being a significantly higher than room temperature phenomenon.
I have definitely experienced thermally induced strain in poorly designed laptops where heat/temperatures are a problem.
While very interesting... to me at least... and I'd like to hear more...I'd venture that for a lot of the stuff discussed on this list, failures due to the phenomena, discussed in the paper, are not an issue, for many of us?
Best regards, best wishes.
Roy

Dave Seiter
 

And the occasional rare problem like silver whiskers.  Only seen that one once; probably due to a long time in a unusual atmosphere. 
-Dave

On Tuesday, January 7, 2020, 05:00:23 AM PST, Jean-Paul <jonpaul@...> wrote:

Besides this problem you have "tin disease" in very cold climates and "tin whiskers" for very close spaced solder connections and at higher voltages.

Jon

KB6NAX
 

Copper tracks on aqueous cleaned boards can form between traces. I once found one that was over an eighth inch long. -Arden

Eric
 

Speaking of solder joints what do you guys think about Hakko's Hot N2 gas shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas flush of the area to prevent oxidation inside the solder joint. I guess the idea is MIG welding for soldering?

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Ken Eckert
 

Same idea as making a thermocouple, except you use argon

On Wednesday, January 8, 2020, Eric <ericsp@...> wrote:

Speaking of solder joints what do you guys think about Hakko's Hot N2 gas
shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas flush
of the area to prevent oxidation inside the solder joint. I guess the idea
is MIG welding for soldering?

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greenboxmaven
 

An interesting idea. Does it use a cylinder of compressed nitrogen or the exhaust of an oxygen concentrator? I can imagine the AudioPhools right now, arguing over where and when the nitrogen came from, or if argon or xenon would make the joint sound better.

Bruce Gentry, KA2IVY

On 1/8/20 11:06 PM, Ken Eckert wrote:
Same idea as making a thermocouple, except you use argon

On Wednesday, January 8, 2020, Eric <ericsp@...> wrote:

Speaking of solder joints what do you guys think about Hakko's Hot N2 gas
shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas flush
of the area to prevent oxidation inside the solder joint. I guess the idea
is MIG welding for soldering?

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Ken Eckert
 

It has to be an inert gas, you are trying to keep the joint/work zone in a
oxygen free environment

On Thursday, January 9, 2020, greenboxmaven via Groups.Io <ka2ivy=
verizon.net@groups.io> wrote:

An interesting idea. Does it use a cylinder of compressed nitrogen or the
exhaust of an oxygen concentrator? I can imagine the AudioPhools right now,
arguing over where and when the nitrogen came from, or if argon or xenon
would make the joint sound better.

Bruce Gentry, KA2IVY


On 1/8/20 11:06 PM, Ken Eckert wrote:

Same idea as making a thermocouple, except you use argon

On Wednesday, January 8, 2020, Eric <ericsp@...> wrote:

Speaking of solder joints what do you guys think about Hakko's Hot N2 gas
shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas
flush
of the area to prevent oxidation inside the solder joint. I guess the
idea
is MIG welding for soldering?

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Eric
 

It uses an air compressor that passes through a N2 generator that is
supposed to get it to 99.99% and it is all really low pressure. The whole
system runs at 3 to 5 psi

On Thu, Jan 9, 2020, 9:58 AM Ken Eckert <eckertkp@...> wrote:

It has to be an inert gas, you are trying to keep the joint/work zone in a
oxygen free environment

On Thursday, January 9, 2020, greenboxmaven via Groups.Io <ka2ivy=
verizon.net@groups.io> wrote:

An interesting idea. Does it use a cylinder of compressed nitrogen or the
exhaust of an oxygen concentrator? I can imagine the AudioPhools right
now,
arguing over where and when the nitrogen came from, or if argon or xenon
would make the joint sound better.

Bruce Gentry, KA2IVY


On 1/8/20 11:06 PM, Ken Eckert wrote:

Same idea as making a thermocouple, except you use argon

On Wednesday, January 8, 2020, Eric <ericsp@...> wrote:

Speaking of solder joints what do you guys think about Hakko's Hot N2
gas
shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas
flush
of the area to prevent oxidation inside the solder joint. I guess the
idea
is MIG welding for soldering?

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greenboxmaven
 

That is what I thought it would do. The "generator" is a seperator. The common ones used for medical and welding seperate the oxygen and release the nitrogen back to the atmosphere. In this case, the same equipment could be used, but the nitrogen would be collected and used and the oxygen released back to the atmosphere.

Bruce Gentry, KA2IVY

On 1/9/20 10:23 AM, Eric wrote:
It uses an air compressor that passes through a N2 generator that is
supposed to get it to 99.99% and it is all really low pressure. The whole
system runs at 3 to 5 psi

On Thu, Jan 9, 2020, 9:58 AM Ken Eckert <eckertkp@...> wrote:

It has to be an inert gas, you are trying to keep the joint/work zone in a
oxygen free environment

On Thursday, January 9, 2020, greenboxmaven via Groups.Io <ka2ivy=
verizon.net@groups.io> wrote:

An interesting idea. Does it use a cylinder of compressed nitrogen or the
exhaust of an oxygen concentrator? I can imagine the AudioPhools right
now,
arguing over where and when the nitrogen came from, or if argon or xenon
would make the joint sound better.

Bruce Gentry, KA2IVY


On 1/8/20 11:06 PM, Ken Eckert wrote:

Same idea as making a thermocouple, except you use argon

On Wednesday, January 8, 2020, Eric <ericsp@...> wrote:

Speaking of solder joints what do you guys think about Hakko's Hot N2
gas
shielded soldering irons? The idea is to use a 99.99% pure Hot n2 gas
flush
of the area to prevent oxidation inside the solder joint. I guess the
idea
is MIG welding for soldering?

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