Hi Brian,
My memories do not go back quite as far as yours—they do however bring fond recollections; but you are absolutely right. The '70's was the time when the industry went from totally unbrightened plating solutions, first to Sel-Rex's Q-Bath-M and from there to innumerable improvements. At that time, pyrophosphate plating was superior in terms of throwing power and properties, the military used it a lot, but had the nasty habit of causing fires. But even with pyro, you could not even dream of producing today's PCBs.
Werner


 

 

-----Original Message-----
From: Brian Ellis <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Nov 2, 2010 9:17 am
Subject: Re: [TN] Query on Copper plating


I forget the details as this was going back to about 1970 but, in a former life, we did just this kind of thing to reduce barrel cracking. However, if I remember rightly, the electrolytic flash coating was only about 5 µm. I forget which order they came in but the flash coating and the 20 µm main plating were done in different baths, one being sulphate and the other pyrophosphate. The theory behind it is that the main plating had a better throwing power, while the flash coating had a better adhesion to the electroless copper, because of epitaxial growth. 
 
Again, if my memory serves me correctly, we used this technology for only a short while, perhaps 12 months, after which it was replaced by a single bath which had sufficient quality in both aspects to no longer justify the extra step. Remember that this was in the relatively early days of through hole plating, and finding the right solution (no pun intended) was quite an adventure. 
 
I see no justification for doing this today – copper plating has come a long way in 40 years! 
 
Brian 
 
On 02/11/2010 06:16, Uppina Nagaraj wrote: 
> Hi All, 
> 
> We have a low build electroless Copper plating for Through Hole 
> metalization, which's giving around 0.5 to 0.6microns of Copper. 
> 
> The subsequent processes are pattern image printing followed by 
> pattern plating (electrolytic copper plating). 
> 
> One of our customer has a requirement to do flash Copper plating 
> (electro plating) of around 8 to 10 microns, immediately after 
> electroless Copper plating, prior to pattern image printing. 
> 
> I want some inputs on the above..... 
> 
> Is there a distinct advantage on PTH reliability by having 
> 8-10microns of electroplated copper immediately after 
> electroless Copper plating. 
> 
> Will having additional flash plating have better Thermal 
> stress&  Thermal Shock performance. 
> 
> Thanks! 
> U.Nagaraj 
> 
> 
> 
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