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March 2012

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From:
Paul Reid <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Paul Reid <[log in to unmask]>
Date:
Mon, 26 Mar 2012 15:11:27 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (244 lines)
Hi Mark,

I just want to warn you that the difference between a void due to a
bubble and void due to poor electroless coverage is very subtle. I
rarely find that the bubble causes the problem. More often than not the
cause is poor electroless coverage rather than a bubble. Of course the
poor electroless coverage could be due to a bubble.

There should be no nickel corrosion due to the void. The nickel and gold
should be continuous up to the void. But having a void could cause what
we call "nickel acceleration" in thermal cycle type of reliability
testing. When nickel is not continuous it can focus stress into the
areas where there is no nickel causing cracks early in thermal cycle
testing. This could result in failure in assembly or reduction of field
life in the end use environment.

Ian is correct. It would be best to post a picture and let us see what
you are looking at.

I will say that the vibration is a good idea but make sure the vibration
is in the direction of the though hole or side ways to the rack not in
the direction of the rack.


Sincerely,  

 

Paul Reid 

Program Coordinator  

PWB Interconnect Solutions Inc. 
235 Stafford Rd., West, Unit 103 
Nepean, Ontario Canada, K2H 9C1 

613 596 4244 ext. 229  

Skype paul_reid_pwb 
[log in to unmask] 

 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna
Sent: March 26, 2012 1:39 PM
To: [log in to unmask]
Subject: Re: [TN] Fw: [TN] plating void

photos would be great -- nooks and crannies are generally problematic in
a 
plated hole -- good vibration is important in electroless -- assuming a 
standard thickness, your aspect is only 6:1, so no rocket science -- 
viscosity can also be an issue -- there are additives to reduce surface 
tension and improve wetting in holes -- but again, for 6:1 this is
pretty 
bread-and-butter plating -- but best to get a nice microsection view --
a 
little concerned about the nooks etc 



From:
drilbert <[log in to unmask]>
To:
TechNet E-Mail Forum <[log in to unmask]>, Ian Hanna <[log in to unmask]>
Date:
26/03/2012 01:32 PM
Subject:
Re: [TN] Fw: [TN] plating void



Thanks Ian.  I will send a picture. 
The part has certain nooks and crannies where the voids tend to occur. 
From your input it sounds like bubbles are a common process risk with 
plating baths that we must pay attention to and manage how to prevent. 
The vibration in place may need to be reconfigured or replaced.  It
seems 
weak.  I couldn't feel much vibration translating into the rack.
 
Mark Julstrom

From: Ian Hanna <[log in to unmask]>
To: [log in to unmask] 
Sent: Monday, March 26, 2012 6:44 AM
Subject: Re: [TN] Fw: [TN] plating void

thanks dwight -- yes -- a picture is worth many many words -- 

mark,
the simplest explanation is electroless copper voiding via bubbles -- 
bubbles are very much a part of the process -- the trick is not to let 
them collect in the small holes -- vibration helps -- there is a whole 
science behind that -- rack/bar vibration electric/air -- i once found
my 
(rack) air vibrators in one shop were worn out -- they made lots of
noise 
still, but running a vibrometer, they didn't actually do much anymore --

don't have any numbers tho, just anecdotes now for this.  we replaced
the 
worn out units and life was good -- also -- be very careful if you try
to 
do a web-search on this topic...i learned that the hard way also... 

the good news is that this mode is fairly black and white -- if there is
a 

(full) bubble void, you see it, if there is none it passes -- you won't 
get half a bubble void...

i would want to confirm the root cause just to be safe - but the exposed

laminate is a fair indicator 




From:
Dwight Mattix <[log in to unmask]>
To:
<[log in to unmask]>
Date:
23/03/2012 04:42 PM
Subject:
Re: [TN] Fw: [TN] plating void
Sent by:
TechNet <[log in to unmask]>



Looks like you missed part of what Ian was saying there...

Let me try to expand on that:
It could have been
a) skipped by electroless Cu plating and therefore not 
electrolytically plated at all.
b) If it was first plated fine by electroless and then successfully 
electrolytic plated. It could then be etched out down to base 
dielectric if there was skip in the etch resist plating.

In either case it would show a bare dielectric in the hole wall. They 
will have different copper shape leading into the void though 
depending on source of the missing copper.

Once more with feeling: A picture is worth a thousand words. Of a 
cross-section that is...


At 01:18 PM 3/23/2012, [log in to unmask] wrote:
>It is a base dielectric material.  The plating portion of the wet 
>process begins with an electroless Cu bath.
>
>
>
>----- Forwarded Message -----
>From: Ian Hanna <[log in to unmask]>
>To: "[log in to unmask]" <[log in to unmask]>
>Sent: Friday, March 23, 2012 12:47 PM
>Subject: Re: [TN] plating void
>
>do you mean base dielectric material, or base copper material -- an 
>electrolytic  copper plating void will still leave the base copper 
>intact  if it is caused by a bubble -- what is the shape of the 
>edges, is it tapered or rounded -- is the void in the centre of the 
>hole or towards the outside? any photos? could be electroless copper 
>void electrolytic copper void tin void dry-film residue
>From:  "[log in to unmask]" <[log in to unmask]>
>To:  <[log in to unmask]>
>Date:  23/03/2012 03:41 PM
>Subject:  [TN] plating void
>Sent by:  TechNet <[log in to unmask]>
>
>________________________________
>I'm looking for input on the following plating defect.
>
>I observe a plating void that occurs on a Cu plated feature with 
>ENIG finish.    The void goes down to the base material.  The defect 
>is typically .002 diameter.  The feature size is .010 across.  The 
>parts run on a manual plating line and hang on a small plating rack.
>
>The plating engineer believes the root cause of the void is a bubble 
>on the part during plating.  The action plan includes implementing 
>stronger vibration on the part in the plating bath.
>
>I have two questions.
>1.  How much vibration is typically needed to avoid developing a 
>bubble on a part during plating?
>2.  For this plating void defect, is it possible that Ni corrosion 
>or other reliability concerns would eventually develop if defective 
>parts escaped?
>
>Thank you,
>
>Mark Julstrom
>
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