I have not used it personally Richard, I guess you are clocking at
10GHz, I did a fast search on the net, and it would seem that adhesion
is a known problem which is apparently addressed by increasing the
copper roughness.
Here is a link to a forum:
http://www.qsl.net/wb6tpu/si-list4/0407.html
Here is an excerpt from the thread:
===================================================================
One point to keep in mind: the dielectric is not the only
limiting factor at the higher frequencies; the conductor
loss generally becomes a bigger factor with the materials
that with standard FR4. I'm not sure of the details, but
to obtain the same peel-strength with the non-FR4 materials,
some (not all) of the materials use a larger toothing profile
(i.e., surface roughness) than FR4, which can really eat away
at your signals. So, even though your dielectric losses
are better, the rougher metal increases your conductor
loss. When looking at the various materials, be sure
to keep this in mind.
===================================================================
Hope this helps.
John
John Burke
Senior Manager - Operations , Optichron
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, January 19, 2006 2:09 PM
To: [log in to unmask]
Subject: Re: [TN] PWB SMT pad retention
The boards are made of Rogers 4350
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sherif Refaat
Sent: Thursday, January 19, 2006 11:31 AM
To: [log in to unmask]
Subject: Re: [TN] PWB SMT pad retention
Hi Richard,
What kind of laminate is that? I had similar problem, few years ago,
repairing boards built using "Thermount" (Aramid). That was one of the
draw backs of this laminate. The new version of "Thermount" suppose to
be better in terms of peel strength, but I don't know if it is close
enough to that of FR4.
Sherif Refaat,
----- Original Message -----
From: "Stadem, Richard D." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, January 19, 2006 11:42 AM
Subject: [TN] PWB SMT pad retention
Hi, Folks,
Is there a standard that specifies how well SMT pads should adhere to
the pwb? By pads I mean BGA pads that have no trace attachment, and I.C.
(gullwing) pads.
A client has circuit boards with pads that come off extremely easily
during standard rework and reflow processes. It is not limited to the
BGA pads, many other unused I.C. lead pads are also being found out of
place in the solder joints after reflow, and are easily peeled away. The
pads are not tiny flip chip pads, but standard .035" diameter pads and
rectangular .020" by .030" pads. The reflow peak temperature is only 210
deg. C for about 40 seconds. The rework is at 200 C. for 30 seconds.
Also, any speculation on the cause? This problem is limited to a single
PWB part number.
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