See section 9.1.2 of IPC-2222 for the calculations that were in
IPC-D-275.

The basic formula is: pad diameter x.6 / # of webs not to exceed 2mm for
all webs in 2 oz copper [4mm in 1oz Cu]

Jeffrey McGlaughlin, CID 
Engineering Designer EAS 
4-2-50 room 
x-7582 Phone 
(614)458-7582 Fax 



  

-----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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