Kevin.
Thanks. This operation is a bit new for us. Sounds easy enough, but in reality...? Wonder if same method can be used for solder filled heat transfer vias.
best
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: måndag 9 november 2009 13:11
To: [log in to unmask]
Subject: Re: [TN] Via fill for heat transfer
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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