Well and simply put Lee. I concur.

Add to the bare pwb plating concern a concern about solder joint 
acceptability for uVia in pad.  As the uVia aspect ratio increases past 
0.5:1 the likelihood of voids in solder joints increases.

The shape/slope/quality of the uVia wall and quality of uVia plating 
becomes critical. It gets more difficult to maintain uVia form that assures 
solder quality.

Put another way, the solder joint becomes increasing sensitive to uVia 
shape and roughness. It becomes increasingly likely you'll have 
unacceptable solder voids due to outgassing from the uVia.

If it wasn't such a huge distribution I'd attach some photos to illustrate 
the effect.


dw


At 08:37 AM 11/20/2007, Lee parker wrote:
>Sherif
>
>The real issue with laser drilled holes is plating the via which is usually
>blind. Aspect ratios above 0.8 become a challenge which is even more
>impacted by the diameter of the hole. The hole you suggested has a aspect
>ratio of 1.0, the quality of the plating will be problematic.
>
>Best regards
>
>Lee
>
>J. Lee Parker, Ph.D.
>JLP Consultants LLC
>804 779 3389
>
>
>
>----- Original Message -----
>From: "Sherif Refaat" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Monday, November 19, 2007 10:18 AM
>Subject: [TN] Laser drilling limitations
>
>
> > Hi Technetters;
> >
> > What is a practical maximum via hole diameter and depth manufactured using
> > Laser ablation? I would say these should be 0.006" and 0.006". Any
> > different
> > opinions?
> >
> > Sherif,
> >
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