With regards to copper type, since most of my boards are double sided with through hole, the ductility of the copper is very important due to the number of heat excursion the board will see (top, bottom, through-hole, possible touch-up). Both H or S will suffice, but preferred is S. Why? "S" is better suited for high frequency circuits (signal integrity reasons) as it has lower surface roughness because of the way it is deposited and it permits thinner dielectrics. But then it can cost a bit more for the added benefits, always a trade off. A good article that was in PCD&F is at
pcdandf.com/cms/images/stories/mag/0505/0505hilburn.pdf
In regards to specifying laminate thickness, I do it because it's rare for me to do a board that isn't RF/Mixed-signal or is multi-layer. Also I generally specify laminate thickness with a realistic tolerance per layer and finished overall thickness with tolerance. This ensures that my final product is consistent no matter who the vendor is. When I do that, I can also than calculate what the impedances are for the traces and adjust them as needed (usually a little large) so that the vendor can adjust them to meet my requirements for the design as specified on the drawing (if required).
It all requires more upfront planning and thinking through the whole design process along with also anticipating what the vendor will do.
Hope this helps,
Take Care,
-Jeffrey
Jeffrey A. Jenkins CID+/CIT
Sr. PCB/CAD Designer
L-3 Communications - Linkabit Division - San Diego
Office: 858-552-9832
Fax: 858-535-3680
Email: [log in to unmask]
From: Jack Olson [mailto:[log in to unmask]]
Sent: Wednesday, May 19, 2010 6:16 PM
To: Jenkins, Jeffrey A @ LINKABIT
Cc: [log in to unmask]
Subject: Re: [DC] My first RoHS circuit board!
veeerrryyyyy innnnnterestinggggggg......
Thanks for the example, I noticed you are asking for a "S" material,
(HIGH TEMP ELONGATION)
and I am only familiar with "C"
(ELECTRO-DEPOSITED)
which makes sense. In fact, in Werner's workshop he recommends a grade 3 foil.
("How to Specify PCBs to Reliably Survive the RoHS-Mandated Lead-Free Soldering Process")
I'm not sure how to say it without having to specify the laminate thicknesses as well.
or maybe I should?
(for my current design the actual laminate choices don't matter, just the quality)
and I'm curious why you want "S" instead of "H" (reverse treat? why is that important?)
surfin' the learnin' curve,
Jack
On Tue, May 18, 2010 at 5:46 PM, <[log in to unmask]> wrote:
Jack,
Congrats, I'm envious;)
If you are going with a general material call-out such as IPC4101/126 which lets the vendor select the final used material, I would recommend adding a sub note within the material call-out note indicating "non-dicy material required" along with any other requirements. Better to be clear from the beginning what is expected, because it should be assumed the vendor will select the lowest cost material to complete the job, and this may not be what you want.
If you select the material, one I'd recommend for most general FR-4 usage would be Isola 370HR which seems to be a pretty good choice and /126 approved (but always confirm intended material with vendor if it meets requirements.). No matter the choice what I do is say something similar to below:
4. Isola 370HR Series material IAW with IPC-4101C/126 or equivalent as specified below with approval of "Customer name" Prior to usage:
-LAMINATE MATERIAL: L-126-****-S**/S**-*-* IAW IPC-4101C/126.
-PREPREG MATERIAL: P-126 IAW IPC-4101C/126.
**** SEE LAYER CONFIGURATION
** SEE STACK-UP FOR COPPER THICKNESS REQUIREMENTS.
* BEST CLASS OF MATERIAL AVAILABLE, AS DETERMINED BY VENDOR.
If I'm not specing the material, I omit the first line. But in general they will go with your choice if it's available and as written it leaves the door open to alternative material after review.
If there are any questions, please feel free to contact me.
Take Care,
-Jeffrey
Jeffrey A. Jenkins CID+/CIT
Sr. PCB/CAD Designer
L-3 Communications - Linkabit Division - San Diego
Office: 858-552-9832
Fax: 858-535-3680
Email: [log in to unmask]
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: Tuesday, May 18, 2010 2:29 PM
To: [log in to unmask]
Subject: [DC] My first RoHS circuit board!
Well, we avoided it as long as we could, but now I have to design for RoHS compliance.
I'm basically following Werner's recommendations (which don't conflict with anyone else's as far as I know), but I'm confused about one aspect of material:
Several sources have stated that its better to use "NON-DICEY" material, but none of the IPC-4101 slash sheets mention dicy or non-dicy (or dicyandiamide).
If we are trying /126 material, do we still have to specify non-dicy?
thanks,
Jack
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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
---------------------------------------------------------------------------------
|
