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November 2007

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Subject:
From:
Phil Nutting <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phil Nutting <[log in to unmask]>
Date:
Wed, 28 Nov 2007 10:44:08 -0500
Content-Type:
text/plain
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text/plain (73 lines)
Roland,

In the old D-275 there was a good explanation and detail.  I'm having
trouble finding it in the new IPC documents.  This is a similar issue
I'm having.  Keep in mind that the lead to hole diameter spacing, type
of flux, preheat temp, pot temp and conveyor speed are all factors in
the soldering too. 

I'll be interested to see what other responses you get.

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roland Jaquet
Sent: Wednesday, November 28, 2007 9:05 AM
To: [log in to unmask]
Subject: [TN] Thermal Pads Dimension versus size / Copper Thickness

Dear Technetters,

I am having an issue with the very different sizes of Thermal Pads used
on a
Power PCB mix. A 4 Layer PCB with 2 Oz Copper for the inner layers and 1
Oz.
+ Plating on the outside. 

At the Soldering, the small components get too hot while solder
(Lead-Free)
does not get up high enough on the component side. 

I am wondering if there is a formula to calculate the size / shape and
dimension of the optimum Thermal Pad (Frein Thermique). 

Thank you for your input

Meilleures Salutations
Very Best Regards
Roland
 
www.PCBspecialist.com 
Roland Jaquet
14 Champ Budin
1258 Perly, GENEVA
SWTZERLAND
GSM+41-79-203-3723

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