Lee and Dwight;

Thanks for your response.

I understand your point. However my question is regarding diameter and depth 
not the aspect ratio (though I understand they are related). In a specific 
application the hole dia. is 0.013" and the depth is 0.009" so the aspect 
ratio is below .7 : 1. Would such a relatively large hole be OK for Laser 
drilling. There are other smaller holes 0.006" dia. and 0.004" depth on the 
same board which are OK to Laser drill. But the designer is asking for the 
larger ones also to be Laser drilled (instead of other methods of drilling 
the holes) to save on cost and stream line the process.

Sherif,
----- Original Message ----- 
From: "Dwight Mattix" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 20, 2007 2:10 PM
Subject: Re: [TN] Laser drilling limitations


> 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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