×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Gold Embrittlement in solder joints

Gold Embrittlement in solder joints

Gold Embrittlement in solder joints

(OP)
Hello,
The basic question was answered in another closed thread but I just wanted to find out a little more detail about it

How exactly and why is solder used to remove the gold plating ?
What I mean is that since gold melts at much higher temperature than solder than why would the solder remove the gold ?
Is there something else going on like a chemical reaction ?
Maybe the correct word is leaching ?
But I still don't quite understand why would gold leach out in the solder. Does this work for other metals or just gold ?

I am taking the IPC 610 training and I asked the trainer about it but he did not know exactly how that happens
I know it sounds like a stupid question but I am just curious

RE: Gold Embrittlement in solder joints

(OP)
Hello,
Thanks for the reply but that link says no document found.

Is there another link that has the information ?
 

RE: Gold Embrittlement in solder joints

RE: Gold Embrittlement in solder joints

(OP)
Hello,
Ok It's working today
From what I understand when gold is mixed with other metals it forms an alloy that has a lower melting point than pure gold

Should I assume that the gold plating on pc boards is not pure gold ?

How do I know what gold alloy is used on pc boards ?
 

RE: Gold Embrittlement in solder joints

No, gold plating is pretty darn pure (like 99.999% or better).  The gold is plated directly onto the fresh/clean copper traces.  There is a slight mixing of gold into the solder during the soldering process, but a proper process will minimize this to irrelevant levels.  And metal alloys do not necessarily have a lower melting point than the individual metals.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Gold Embrittlement in solder joints

(OP)
Sorry I am confused again
So the pure gold is plated over the copper so far it's clear

"There is a slight mixing of gold into the solder during the soldering process"

That's what I am curious about
If the pure gold melting temperature is much higher than the melted solder how does the solder mix with the gold ?
If solder can do that why not mix with the copper trace too ?

"And metal alloys do not necessarily have a lower melting point than the individual metals"

Ok. So what was the point of the link about the eutectic alloys of gold then ?
 

RE: Gold Embrittlement in solder joints

I don't understand what you are not understanding.  Some metals, like gold, form eutectics, which have lower alloy melting temperatures; others do not.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Gold Embrittlement in solder joints

(OP)
I am just going by macgyvers2000's post that seems to be contradictory to your post

He is saying that the copper traces are plated with pure gold and follows that up with a statement that implies that gold alloys do not necessarily melt at lower temperatures Of course
he did not mention specifically gold alloys

I understand that some gold alloys have lower or higher melting point than pure gold

I am just trying to figure out specifically what is the process by which gold is removed from copper traces

Perhaps I need to understand what eutectic means
You said "gold forms eutectics with many other materials"
Could you expand on that a little bit more and be a little more specific as it relates to plated gold on copper traces ?

Which material to be more specific ?
According to the statement at the link you provided
"The melting point of an alloy of two (binary) or more metals depends on the relative proportions of the ingredients"
Assuming that the gold plating is pure how can it have other materials in it to have the right proportion ?


 

RE: Gold Embrittlement in solder joints

The PCBs are plated with gold; i.e. a layer on top of the copper.

Pay less attention to the copper.

Under certain conditions, e.g. with respect to temperature and gold concentration; when tin-containing solder is applied, gold and tin will form intermetallic structures within the joint. These structures weaken the joint because they are formed differently to the solder. Note though, that this happens only under certain conditions. If you push tin and gold together with your bare hands at room temperature, it will not work.

Bear in mind that the metals do not already have to be 'alloyed' before an instance like this is possible.

I think you have enough information to explore embrittlement further.

The title of your post searched on Google brought extensive resources for you to study; e.g. http://www.semlab.com/GoldEmbrittlementofSolderJoints.pdf plus MANY more!

RE: Gold Embrittlement in solder joints

(OP)
That was interesting to read but it all seem to be at a microscopic level

What do you think of this statement that I read somewhere ?
"Gold readily dissolves in molten solder"
Is that true ?

Assuming I have a bar of gold (I don't)and I place it in a solder pot at let's say 750F
Would the gold bar dissolve completely ,just a little bit on the surface or not at all ?

RE: Gold Embrittlement in solder joints

Gold melts at nearly 2000F, so no, it's not going to completely melt at 750F... but it will mix slightly at the surface, and if the pot is stirred over a long period of time, the gold will continue to mix.  From that standpoint, the statement that gold readily dissolves in solder is misleading in its simplicity... but nevertheless, it's true from a purity standpoint.  The "microscopic" level is all that's necessary to completely taint an entire pot and make it worthless (at least as far as circuit reliability is concerned).

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Gold Embrittlement in solder joints

"That was interesting to read but it all seem to be at a microscopic level"

Gold embrittlement on a 10 inch wide solder joint (if they exist) would be the same gold embrittlement that exists in your own solder joint. If you want to disregard the microscopic level, then what you might come across on a PCB would simply be a poor solder joint with an unknown diagnosis.

RE: Gold Embrittlement in solder joints

(OP)
Thanks for the explanation
I am starting to understand the process a little bit better now
So just to make sure I understand
If gold is heated by itself to 750F nothing happens but when solder is added then some of the gold is mixed with the solder at the microscopic level?

This gold that is mixed with the solder is it melted gold, gold molecules or gold that is flaked off the pc bd ?

I am just trying to grasp the magnitude

 

RE: Gold Embrittlement in solder joints

Status, take a look at this document that I posted earlier:

http://www.sem-lab.com/GoldEmbrittlementofSolderJoints.pdf

Read the article, look at the pictures and then you should grasp the magnitude and process by which it occurs. If you have any questions afterwards, please come back.

"If gold is heated by itself to 750F nothing happens but when solder is added then some of the gold is mixed with the solder at the microscopic level?" In a proverbial nut shell, yes.

RE: Gold Embrittlement in solder joints

(OP)
I read that article before but it's hard to determine how much gold is there It's also hard to tell which shade of gray is the gold

If that was a copper trace that was plated with gold does all of the gold come of or gets mixed with the solder in one application ?
If only a small microscopic amount is mixed with the solder I would imagine it would take a long time to remove all of it

Is the procedure in IPC 610 to add solder and the remove it and doing that twice enough to remove all the gold ?
 

RE: Gold Embrittlement in solder joints

Status, extracting the gold on such a scale would take more than a long time and is not practical. One would be better off creating a new joint.

I am not familiar with IPC 610, and given you are on a course for such; would it not be wiser to ask your trainer?

RE: Gold Embrittlement in solder joints

If the objective is to recover gold, then there are chemical processes that are more effective and selective.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Gold Embrittlement in solder joints

(OP)
The objective is not to extract gold but to remove the gold from the plated surface where something is going to be soldered to
This would be from at least 95% of surface to be soldered to

I did ask the trainer but he did not have an answer at the time and he said that he will get back to me and I thought maybe I can research it myself in the meantime

I found it hard to believe at the time that just by tinning a gold plated surface the gold would be gone so easily without actually melting the gold

Someone said in a previous post with the same title that tinning the gold plated surface and removing it by wicking it off with solder wick is acceptable while the instructor said this must be done twice maybe as an extra step in case not all of the gold was removed in the first step

I don't have the manual with me but I don't think IPC 610 specifies what method to use to remove the gold
I read somewhere else that a double dip (two solder pots) immersion or the use of a flowing solder wave is the way to go

I guess the only way to find out for sure is to use a method and somehow analyze the solder joint under a powerful microscope to determine how much if any gold is left in the solder joint

I want to thank everyone for their comments on this subject  

RE: Gold Embrittlement in solder joints

Duh?  

Does someone think that the gold plating is somehow bad?  Can you really imagine doing this on every single solder joint?  

Wouldn't this be a total waste of time and money?  And wouldn't someone think that it might be more efficient to not have gold there in the first place, if all you're going to do is to remove it immediately prior to soldering?

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Gold Embrittlement in solder joints

(OP)
I totally agree with the waste of money but I guess when you work for NASA price is not a factor
Where do you think those $700 hammers come from ?


Actually we did receive a small quantity  of bds (not for NASA) that were plated with gold by accident and we ended up using it as is just soldering to it normally and haven't had any returns because of any joint failure  

RE: Gold Embrittlement in solder joints

IPC610 allows for that, so long as you have documentation of no solder issues.

Frankly, it seems to be a perfectly stupid idea.  Every additional second of heat on every joint is just increasing the probability of failure from other problems.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Gold Embrittlement in solder joints

(OP)
I agree but we can't do anything about it just follow the rules like a bunch of lemmings  

RE: Gold Embrittlement in solder joints

So your intent is to remove the gold plating from certain locations by applying solder and sucking it up?  That's not going to work, not by a loooooong shot.  You would need to apply/remove that solder several million (billion? trillion?) times to even come close to removing all of the gold.  Doing it twice, you're just going to piss off the plating, not get rid of it.

You have three choices: 1) Don't put it there in the first place (masking is easy as pie during the plating process), 2) Remove it by chemical means (not ideal by a long shot, and messy, possibly dangerous/toxic), 3) Remove it by mechanical means (such as sandpaper tubes on a Dremel).
 

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Gold Embrittlement in solder joints

(OP)
That's not my intent.
That is the instruction according to the IPC 610 standard
and the instructor

I understand your point and I have not removed any gold from any pc bd I was just trained on the IPC 610 so I was just curious about the process in theory only not in reality.
 

RE: Gold Embrittlement in solder joints

"I understand your point and I have not removed any gold from any pc bd I was just trained on the IPC 610 so I was just curious about the process in theory only not in reality."


There is no real gold out there any place in industry.
Real gold is in gold nuggets only. Close to 100% gold.

Jewelry gold and industrial (watch cases etc.)are a tin-copper alloy with only a trace of real gold in it.
The gold content is less than 1/1000 of one percent even in
gold bullion coins.

Specific gravity of tin can be increased to match that of gold by melting the tin and letting it cool down on air--repeatedly.  I am ready to do that experiment here at home and have a way to check specific gravity as well.

I learned this from God (who now wants to be called Voynich)
at age 4, looking at my real tin soldiers I was playing with.

So, now I want to prove it to myself.

I own a few gold nuggets purchased from ebay, they look like crap, not shiny like gold, but that proves they really are gold.


So, you are really not dealing with gold at all, but with compressed tin at 99 % or so.  That golden tin has similar qualities to real gold, and its usefulness has been established.

Since you don't believe this, there is no point in writing any more than this.


Voynich  (psychic reading)




 

RE: Gold Embrittlement in solder joints

"Since you don't believe this, there is no point in writing any more than this."

But what about the cold fusion possibilities?  

RE: Gold Embrittlement in solder joints

Wow! So my tin jewelery I mail in that safe and secure envelope to "Cash for Gold" is going to be a heck of a deal!

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

RE: Gold Embrittlement in solder joints

(OP)
Looks like we are getting a little bit off the subject
I was only asking about the gold plating on pc boards
I was not referring to jewelery or any other gold

I found another good link that explains the type of plating
and it's many uses
http://en.wikipedia.org/wiki/Gold_plating

RE: Gold Embrittlement in solder joints

Actually, the IPC link I posted has some very detailed data on the layer construction; it would probably be quite educational.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources