Agree that its low producibility, however, some industry capability does exist for drilling and metallization of a 6 mil hole on a 62 mil pad with external annular ring exceeding tangency.
Joey Rios
MIT Kavli Institute
Cambridge, MA
Sent from my iPhone
> On Feb 18, 2016, at 7:48 PM, Mathis, Louis (SSA R4) <[log in to unmask]> wrote:
>
> A 6 mil drill in a 12 mil pad will not meet the design requirements in IPC-2221, paragraph 9.1.1. Even using the Level C fabrication allowance, the minimum pad would be .0179 plus the tolerance of the drill diameter.
>
> --
> Louis Mathis
> Member of the Technical Staff
> Cobham Microelectronic Solutions
> T : +1 858-505-3151
>
> Please consider the environment before printing this email
>
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Ron Olinyk
> Sent: Thursday, February 18, 2016 3:56 PM
> To: [log in to unmask]
> Subject: [DC] Mechanical drill -6mil aspect ratio
>
> ** Please note that the Sender of this email is from outside the Cobham NA IT Hub **
>
> Does anyone know what the typical aspect ratio would be for a 6mil
> (0.152mm) drill in FR4 would be?
> Can a 6mil drill be used as a full drill-thru on 0.062 thick circuit board? -which I think would be a 10:1 aspect ratio...
>
> I've got a design with a 0.5mm uBGA (169 pin, full array) that i want to do fanout vias between pads. I'm using a 8.7mil BGA pad and planning on a fanout via with a 12mil pad and 6mil drill. I originally set this up as a blind via from top to inner1 layer, which works, but I am quickly running out of available via room around the BGA for connecting signals, power/gnd, ect. I'm using an 8mil drill elsewhere on the board which I know is doable on a 0.062 board -just not sure if 6mil is doable -and with a 3mil annular ring!
>
> Any advice greatly appreciated.
> Thanks
> Ron
>
>
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