Thank you, Paul
David Tremmel
-----Mensaje original-----
De: TechNet [mailto:[log in to unmask]] En nombre de Paul Reid
Enviado el: Friday, June 08, 2007 4:38 PM
Para: [log in to unmask]
Asunto: Re: [TN] Z-axis expansion
Hi David,
I have some numbers for you but I have to preface them with two caveats.
1. We do not measure the CTE of the PTHs alone. The PTHs are usually
attached to a dielectric so the copper CTE I will give is that of pure
copper form literature.
2. We measure the CTE of fabricated PWBs, never dielectric alone. The
numbers give will include the copper ground planes and therefore be less
that the measure CTE of raw laminate. The more copper in the stack up the
lower the CTE.
Cu's CTE is approximately 17 ppm/°C, no Tg, CTE is relatively constant until
the copper melts.
Dielectric in the PWB before Tg ~15 to 30 ppm/°C
Dielectric in the PWB after Tg ~ 150 to 300 ppm/°C
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1
613 596 4244 ext. 229
[log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of David Tremmel
Sent: Friday, June 08, 2007 3:13 PM
To: [log in to unmask]
Subject: [TN] Z-axis expansion
Hello,
I have seen comments regarding z-axis expansion that boards and components
experience during reflow; would any of the gurus care to give some numbers?
Such as the copper in the vias has such-and-such expansion versus a High Tg
FR4 which has such-and-such z-axis expansion. (I am sure someone is going
to correct me because I did not use the correct terms).
Thank you in advance,
David Tremmel
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