 
| Subject: | |
| From: | |
| Reply To: | |
| Date: | Mon, 1 Aug 2011 07:10:38 -0700 |
| Content-Type: | text/plain |
| Parts/Attachments: |
|
|
I think mostly for fill.
As an example, 1080 prepreg starts at about 3.5 mils and after pressing is about 2.5 mils.
This means there is about 0.5 mils per side to fill in etched areas on adjacent layers.
That is less than 1/2 oz copper (currently IPC considers 1.2 mil thickness per oz).
Poor fill will aid in delamination and poor reliability.
Use of 2 sheets will allow more resin to flow towards needed fill areas giving better bonding.
Also resin content on thinner prepregs is usually higher allowing more resin flow to use for fill
A Designers understanding of why
Frank N Kimmey CID+
Manager - PCB Design
Powerwave Technologies Inc
Mobile - 916-670-0645
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
Sent: Sunday, July 31, 2011 6:50 PM
To: [log in to unmask]
Subject: [TN] PCB dielectric - 2 layers prepreg
Hi All,
In one of the Class 3/A Exception Requirements, it
indicates that for "Dielectric Thickness of 0.089 mm [0.0035 in] minimum
with 2 layers prepreg if not specified on drawing.", what is the reason
to use 2 layers prepreg, what is the advantage over a single layer?
Thanks.
Regards
GA Tan
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
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
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
Click the following link to report this email as spam: https://www.mailcontrol.com/sr/moVsLKrorhXTndxI!oX7UtQCCy0vBYELBZ7xqNTLKfpg3ldzu73O9wL!uy7VmyAUIUzfroeKbgFhUYCj!eKynw==
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
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
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
|
|
