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June 2007

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Subject:
From:
Colin McVean <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Colin McVean <[log in to unmask]>
Date:
Tue, 26 Jun 2007 07:38:15 +0100
Content-Type:
text/plain
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text/plain (173 lines)
UL makes it's money twice with this one - It first approves the laminate
at the laminate manufacturer, with MOT's (maximum operating temperature)
then further approves the MOT at the PCB fabricator. The two values do
not necessarily match up dependant on how the fabricator builds his
boards. I have seen some instances of 130oC laminate approved at
fabricators to only 105oC. Best to check in the first instance with the
PCB supplier to check what they have in terms of approvals.

UL also tests minimum board thickness, maximum un-pierced ground plane,
minimum track width, maximum copper thickness, bond strength as well as
flammability.

Rgds

Colin W.T. McVean M.Inst.C.T                                
Production Manager
 
 
Artetch Circuits Ltd  (www.artetch.co.uk)
Direct Dial      01903 712926
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Skype: colin.artetch                                           
40th Anniversary 1967 - 2007
P Before printing , please think about the Environment       
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna
Sent: 25 June 2007 18:45
To: [log in to unmask]
Subject: Re: [TN] UL specification on temp rating for bare board
material

UL lists a 'maximum operating temperature' for listed circuit boards --
in the old days this was usually 105C -- now its usually 130C for FR-4--
again, this has to do with the safety of the materials more than the
electrical performance of a finished board...

how many layers is your design?  Spec'ing tg170 on an 8-layer shouldn't
impact price very much but the same call-out could add substantial cost
to a double-sided build...

ian



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brooks,Bill
Sent: Monday, June 25, 2007 1:32 PM
To: [log in to unmask]
Subject: Re: [TN] UL specification on temp rating for bare board
material

Here's a good description of the 94V spec.. 

http://www.boedeker.com/bpi-ul94.htm



Cheers, 

Bill



-----Original Message-----
From: Ted Tontis [mailto:[log in to unmask]] 
Sent: Monday, June 25, 2007 9:31 AM
To: [log in to unmask]
Subject: Re: [TN] UL specification on temp rating for bare board
material

My employer is telling me that UL specifies the opperating tempature of
the
PCB material. From what I understand UL only specifies the flame rating
and
voltage rating. Proper opperating tempature is provided by the
manufacture
of the lamanate? Thats my question does UL specifiy the opperating
tempature
of the PCB lamanet?

Here is what is stated on the old drawings.

1. CIRCUIT BOARDS MUST CONFORM TO UL 94 VERTICAL FLAME TEST AND UL796
2. MATERIAL:  0.062 +/- .006 THICK FR-4 LAMINATE - 2 LAYERS

Here is what I have
2. Fabercate PCB in accordance to IPC-6012A Class 2; per IPC-6011 using
the
customer supplied data files.
3. Materials:
A) Laminate and prepeg (B-stage) to be in accordance with IPC-4101/23 or
IPC
4101/24. Material must meet UL 94V-0
Flammability rating with a Tg rating of 170 or greater is recommended.
Finished thickness shall be .062 +/- .006
B) Copper foil to be in accordance with IPC-MF-150. Unless other wise
specified, all copper weight for inner signal layers
to be 35um (1 oz). For outer layers 71um (2 oz). Copper weight is to be
considered "finished copper weight"

I do not have a copy of UL 796 nor does my employer. I have no idea what
that is or if thats where the temp rating comes from. I am pretty sure
the
guy is just cutting cost where ever he can and this is just one more
place
to cut them. I have just never heard of UL making recomendations for
opperating tempatures of PCB lamate material.
Thank you,

Ted

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