All,
 I have been watching this discussion with interest and unless I missed some posts have found only 2 answers to the original question. Can I assume that not many companies are using "via in pad"? Is there a reliability issue with this design practice? Any responses are welcome.

Thanks,

Geoff Kishpaugh
Motorola Inc.
1900 Winchester Rd, IL-46
Libertyville, IL, 60048
Phone: 847-523-0067
Fax:   847-523-0078
email: [log in to unmask]

------------------------------------------

Hi Leonard,

We typically see blind vias up to .013 drilled size in .030 x .060 pads. You should actually put
the via towards the end of the pads, rather than the center. Board thickness does make a
difference and the ratio of board thickness to drilled hole size (aspect ratio) should not
exceed 10:1 for blind or thru-vias drilled with conventional equipment and 1:1 for controlled
depth laser drilling, where the drilled via size can go down to .006 inches. The aspect ratios
mentioned are only for the "blind" portion being drilled and not the thickness of the entire
board.

You may contact me offline at 817-481-7281 should you have additional questions or wish to
discuss this further.

Regards,

Keith Larson
Circuit Technology Inc.

-----Clip------

Leonard;
The only large company to use via in land on a regular
basis is Lucent, they have the process down pat.
The trick is to figure how much solder you going
to lose to the hole.
It real helps on high density boards.
Lou
-----Clip------

Leonard Toohey wrote:

> What is the state of the industry regarding putting
> vias in the center of SMT discrete device pads?
>
> I am mainly wanting to know about 0603, 0805 and 1206 devices.
> Is board thickness a factor?
> What about via hole size?
>
> Thanks,
>
> Leonard Toohey
> [log in to unmask]
> 12303 Technology Blvd.
> Austin, TX 78727
> Ph(512) 257-5423
> Fx(512) 249-7236
> http://www.netspeed.com

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