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November 2009

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Subject:
From:
"Glidden, Kevin" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Glidden, Kevin
Date:
Mon, 9 Nov 2009 07:10:46 -0500
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Inge,

Good Morning.

Planarization is one of the steps for via filling that is done as part of the PCB fab process.  After the via is resin filled and cured, the PCB surface is planarized with an orbital wet sanding machine.  There is not much "sanding" to do if the plugging material is applied via roller coater, which creates a smoother surface at application than a squeegee printed filler.


Kevin

-----Original Message-----
From: Inge [mailto:[log in to unmask]]
Sent: Saturday, November 07, 2009 4:16 AM
To: Glidden, Kevin; TechNet E-Mail Forum
Subject: Re: [TN] Via fill for heat transfer

Kevin,
how do you perform the planarization in practice?
/Inge


----- Original Message -----
From: "Glidden, Kevin" <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"
<[log in to unmask]>
Sent: Friday, November 06, 2009 8:37 PM
Subject: RE: [TN] Via fill for heat transfer


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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