Hi all,

there is a very wide variety of BTCs with power pads, so as in most cases "it 
depends", mostly on pitch and distance between thermal pad and peripheral 
pads and the solder mask clearance whether the concept of direct 
connection between peripheral pads and power pad would cause a risk of 
solder draining and thus unreliable solder joints. 

Additionally for components with very fine pitches - 400µm and less - the 
thickness of solder mask on traces changes the topology of the local 
surface around the BTC which may have some influence on the amount of 
solder paste printed and may cause some elevation of the component body 
and again has some influence on the solder joint hight and therefore 
reliability.

So in general it would be safer to avoid direct connection between 
peripheral pads and thermal pads. Unfortunately there is no easier answer.

Mit freundlichen Grüßen/Best regards

Rainer Taube

FED Director Standardisation
Master IPC Trainer (IPC-A-610)

TAUBE ELECTRONIC GmbH
Nostitzstraße 30
10965 Berlin
Tel.: ++49 (0)30 6959 2511
Fax: ++49 (0)30 6942 338
e-mail: [log in to unmask]
http://www.taube-electronic.de

Geschäftsführer/CEO: Rainer Taube
Amtsgericht/Trade Register: Berlin HRB 95715 B
USt.-ID/VAT: DE 814229848
Nostitzstraße 30
10965 Berlin


Am 2 Mar 2015 um 10:49 hat Jack Olson geschrieben:

> I may have misunderstood, but I thought I heard someone at the
> APEX
> conference imply that it was not a good practice to tie GROUND PINs
> of
> "Bottom Terminated Components" directly to the grounded THERMAL
> PAD
> underneath the device.
> Did I hear that right?
> I should have asked when I had the chance, but I got distracted.
> 
> 
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