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July 1999

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Subject:
From:
LeRoy Forney <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 26 Jul 1999 08:52:11 -0400
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Guru Andy - Based on your "ps": How does zinc chromate passivation fit into the general picture of copper solderability?  Could it be used instead of or along with OSP coatings to reduce copper oxidation?

- LeRoy

-----Original Message-----
From:   Andy Magee [SMTP:[log in to unmask]]
Sent:   Saturday, July 24, 1999 8:08 AM
To:     [log in to unmask]
Subject:        Re: [TN] Copper oxide removal

Sulfuric is preferred over Hydrochloric for oxide removal because HCl
tends to increase in etch activity as the dissolved copper concentration
goes up with use. 10% H2SO4 will be a much more stable and reliable
process for oxide removal. Save the nitric for things like stripping
copper off your plating racks.

Andy Magee
Flex Guru - Consulting
[log in to unmask]
(937) 435-3629

ps. Initially copper foil is provided from the supplier with a zinc
chromate passivation coating to prevent oxidation. Since this angstroms
thick, relatively brittle, layer may not be uniformly intact it should
be removed with a process that will not attack the copper before
microetching. 10% H2SO4 is clearly the preferred choice over HCl, but
there are also a number of proprietary acid/surfactant mixtures that are
widely used for this.


LeRoy wrote,

Subject: Re: Copper oxide removal
Date: Fri, 23 Jul 1999 15:56:52 -0400
From: LeRoy Forney <[log in to unmask]>

My understanding of the usual oxide removal procedure is a 3-minute soak
with 5%HCl.  The goal is a very mild
etch, and I've heard that nitric acid will cause pitting instead - and
this is in line with some laboratory
oxidation studies I did some time ago.  Variability in solderability
data was much higher on aged coupons I had
treated with dilute HNO3 than on coupons treated with 5%HCl.

LeRoy
-----Original Message-----
From:   nishath yasmeen [SMTP:[log in to unmask]]
Sent:   Friday, July 23, 1999 3:34 PM
To:     [log in to unmask]
Subject:        [TN] Copper oxide removal

Hello everyone!
    Is Nitirc acid ( dilute)  a better acid than sulfuric for cleaning
the oxide on plated copper?
    Any information provided will be appreciated.

Yasmeen

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