Let's not forget the world wide problem with "black pad" and the immersion
gold process. A problem that results in completely random instances of
contamination that results in nonwetting of solder to the land pad. This
becomes very inconvenient at a BGA as the open that is created is not
identifiable with xray including 5DX. It is bad enough that we often
recommend that OEM's go back to HASL until it is eliminated from fabs.

Dorothy Lush

> ----------
> From:         Andrew Hoggan[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Andrew Hoggan
> Sent:         Wednesday, July 11, 2001 2:27 PM
> To:   [log in to unmask]
> Subject:      Re: PCB surface finishes
>
> Possibly the concern comes through a lack of control in applying immersion
> gold compared to other forms of plating. If there is too much gold, then
> the
> intermetallic formed on soldering would potentially interfere with the
> solder joint integrity, potentially causing fracture. I couldn't speculate
> further without more information on your concern.
>
> Andrew Hoggan
> BBA Associates Ltd
> www.bba-associates.com
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Shoukai Zhang
> Sent: Wednesday, July 11, 2001 10:27
> To: [log in to unmask]
> Subject: [TN] PCB surface finishes
>
>
> Dear TechNetters:
>
> As we know that the preferred metal surface finishes are HASL, EN/IG
> (Electroless Nickel and Immersion Gold, and OSP etc.
>
> It's reported that EN/IG(also called immersion gold) suface may lead
> unreliable solder joint for BGA component,  and suggest do not use
> immersion gold for designs that have BGAs.
>
> Please give your advices.
>
> Thanks with best regards,
> Zhangshoukai, PE, Huawei Technologies.
>
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