Bill,Poh: First of all I'm assuming the "OCC" term used is the same as
the more commonly used name OSP. Also the "Entek 160" reference is actually
ENTEK 106 or 106A.
        This material and other OSP's will not chemicaly react with gold to form
a coating.They only react with the exposed copper. It is an organic coating
based on azole chemistry. This chemistry forms polymeric complex with the copper
surface thru covalent bonding.
        If the bare board fabricator during the OSP coating operation does not
control the micro etch time and chemistry correctly in conjunction with a post
acid dip a "bloom" will form on the gold. This originates at the copper/gold
interface. It is a result of a type of galvanic reaction called Bimetallic
Corrosion. This bloom will react with the OSP to create a film formation. This
is probably what you are seeing.

                                                regards
                                                        Michael Barmuta
                                                        Staff Engineer
                                                        Fluke Corp.
                                                        Everett Wa.
                                                        425-356-6076




On Thu, 10 Dec 1998 08:09:17 -0800 Bill Davis wrote:

> From: Bill Davis <[log in to unmask]>
> Date: Thu, 10 Dec 1998 08:09:17 -0800
> Subject: Re: [TN] OCC coating on gold-finger
> To: [log in to unmask]
>
> We have had to use polyimide tape on the gold fingers when using Entek
> 160 OSP materials.
>
> The major problem we have found is that the OSP isn't consistent from
> board to board- some boards have 5000 angstroms others have 2000 (target
> 3200). The higher end thickness tend not to burn off and have caused us
> problems. Our boards are used in standard PC systems, typically in the
> AGP slot, so we don't have a lot of amperage to burn through any
> residual during use either. Thus, any residual OSP is detrimental in our
> case.
>
> I have seen one company use a re-useable rubber boot  to cover the
> fingers during application and solder, but this company was highly
> integrated and produced its own boards and assembled its own products.
>
> Regards,
> > Bill Davis, Ph.D.
> > Diamond Multimedia Systems
> > Senior Scientist
> > Tel. 408.325.7868
> > Cell. 408.888.5650
> > e-mail: [log in to unmask]
> >
> >
>
>
> -----Original Message-----
> From: Poh Kong Hui [mailto:[log in to unmask]]
> Sent: Thursday, December 10, 1998 7:20 AM
> To: [log in to unmask]
> Subject: [TN] OCC coating on gold-finger
>
>
> Hi Technetters,
>
> Pardon my innocence. I am very curious to find out whether there is
> taping or masking need to be done on the goldfinger before applying
> the OCC material.
>
> I understand that OCC can act as an insulator. So if there is no
> masking on goldfinger, will the heat from the reflow oven able to
> completely burn off the OCC material ?
>
> Could you pls advise me.
>
>
> Poh
>
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