Inge,
I would fill the vias completely, and have them planarized and capped. This prevents the solder thieving and eliminates air pockets in the fill, or the risks of a tented via on one side. I am not sure of the limitation on plugging in such a small via - what is the aspect ratio? Smaller vias might be candidates for electroplating plugging.
-----Original Message-----
From: Inge [mailto:[log in to unmask]]
Sent: Friday, November 06, 2009 1:18 PM
To: [log in to unmask]
Subject: Re: [TN] Via fill for heat transfer
Hey there,
I've a q about via fill for LGA, small ones, package 5x5 millimeters and 8
I/Os, teflon one layer on thick brass back. Heat transfer vias 0.5 mm. How
do you fill them before mounting the LGAs? Halfways, even or overfilled? If
the solder volume is too meagre, there will not be a good SJ against the LGA
heat sink (under side), if you have too much solder, you may get
overbridging. There are five vias for the contact with the heat sink, four
vias in a square and one in the middle. We solder same size of packages with
J-leads on the same board, and they become perfect, but the LGAs get varying
result.
/Inge
PS. I regret the deplorable incident in Austin. Bad, very bad in many
aspects, both socially and politically. The human nature is really
unpredictable.
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