The way to determine if this is a significant line is to compare the
interface of the interconnection with the electroless copper (or direct
metalization) in an area above the knee of the hole. Follow the interface
from the top of the pad down to the knee of the hole. This area will be
considered the control and establish the standard interface condition for
the evaluation of the internal interconnection. Review the line between the
foil, electroless copper (or direct metalization) and the electrolytic
copper above the knee of the hole. If the condition at the internal layer
is generally the same as the lines of demarcation above the knee the hole
(although the line may be thinner), then probably is not a problem. If the
line is thicker at the internal interconnection, or if there are discernable
inclusions, then there may be a problem and more evaluation is indicated.
You will be trying to differentiate between a good interconnection vs. drill
smear, or pull away.
Drill smear has to be under the electroless layer while hole wall pull away
may be under the electroless layer or between the electroless and the
electrolytic plating. Try using the highest power to determine where the
line occurs within the interconnection structure. Some electroless coppers
stain dark with a micro-etch and some days the micro-etch is more aggressive
than others. Variability is, unfortunately, the norm so experience counts
in evaluating interconnection interfaces.
Solder float tests and other thermal cyclic methods may be used to determine
the relative robustness of the interconnection. Microscopic examination
will only give an indication of process quality (and microsection quality)
but is not an object method of discerning reliability. Solder float tests
and other thermal cyclic methods may determine the relative robustness of
the internal interconnection.
-----Original Message-----
From: Pete menuez [mailto:[log in to unmask]]
Sent: Tuesday, January 11, 2005 8:08 AM
To: [log in to unmask]
Subject: Re: [TN] Inner layer to barrel connection quality
This is probably a normal (acceptable) condition. As to why earlier
sections showed no demarcation line and this one did may be the amount of
etch used to expose the demarcation line. Some shops like to etch as little
as possible - to just expose the demarcation - so they don't discolor the
electroless. Electroless copper, if this is what was used, may turn black
making the connection look separated.
It is always a good idea to review the sections prior to etch to see if
there is any separation. Some one may want to challenge me on this but
generally if you have post separation you will see it before etch. (An
exception to this is if the cross section grinding smeared copper across the
interface hiding the separation.)
pete
>From: "Finks, Tim (Healdsburg)" <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>, "Finks, Tim
>(Healdsburg)" <[log in to unmask]>
>To: [log in to unmask]
>Subject: [TN] Inner layer to barrel connection quality
>Date: Mon, 10 Jan 2005 14:15:29 -0800
>
>I have PTH cross-section images which show a visible interface between
>inner
>layer foils and the PTH plating. Earlier, similar, board cross-sections
>show
>no discernable interface - the inner layer foil and the barrel plating
>appear to be integral.
>
>What should I see when I have an acceptable PWB?
>
>
>
>Regards,
>
>Tim Finks
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
>To unsubscribe, send a message to [log in to unmask] with following text in
>the BODY (NOT the subject field): SIGNOFF Technet
>To temporarily halt or (re-start) delivery of Technet send e-mail to
>[log in to unmask]: SET Technet NOMAIL or (MAIL)
>To receive ONE mailing per day of all the posts: send e-mail to
>[log in to unmask]: SET Technet Digest
>Search the archives of previous posts at: http://listserv.ipc.org/archives
>Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
>for additional information, or contact Keach Sasamori at [log in to unmask] or
>847-615-7100 ext.2815
>-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
