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October 2008

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Thu, 9 Oct 2008 19:12:40 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (164 lines)
There are a few possibilities here - whether the pads were degraded by the
multiple cycling or not and / or any good to start with, and secondly if a
bare board shows the same issues; whether there is contamination only on the
pads such as would be the case in a bad resist develop / strip process.

Either way putting a bare board through will throw some light on the issue

John Burke

(408) 515 4992


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
Sent: Thursday, October 09, 2008 6:23 PM
To: [log in to unmask]
Subject: Re: [TN] PCB pad non-wetting issues

The question is why it only happened on the solder side pads (believed
that solder flow through PTH barrel and fillets formed on the
component/top side of the board). Either black pad issue on the solder
side or the wetting/contact time is too long at wave soldering process.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani
Sent: Thursday, 9 October 2008 10:54 PM
To: [log in to unmask]
Subject: Re: [TN] PCB pad non-wetting issues

No, this is a good suggestion. I will propose it based on the PCB
pricing and failure rate.

Thank you,
Paymon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: October 9, 2008 10:25 AM
To: [log in to unmask]
Subject: Re: [TN] PCB pad non-wetting issues

Have you tried running a bare board through to confirm/eliminate the
heating
cycles?



John Burke

(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani
Sent: Thursday, October 09, 2008 6:57 AM
To: [log in to unmask]
Subject: [TN] PCB pad non-wetting issues

Hello All,

 

We are experiencing a pad non-wetting issue for the though-hole
component pads ONLY! The PCB goes through few heat cycles with top and
bottom side assembly during at SMT process and then through-hole
assembly at wave process. The problem is found at Wave process. The Pb
solder does not wet to the through-hole component pads on the solder
side only! An SEM/EDS evaluation revealed high concentration of P in the
Nickel and Nickel/Tin intermetalic layer of 11% to 21%. I would like to
ask anyone if they have experienced a similar defect in the past. What
is the Root Cause?

 

Thank you in advance,

Paymon


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