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November 2007

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Subject:
From:
"Simonik, Dave R. (David)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Simonik, Dave R. (David)
Date:
Wed, 21 Nov 2007 10:25:09 -0500
Content-Type:
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Sherif;

  We've been laser drilling since 1997, and we laser drill .012"
diameter vias from layer 1 - 3 on a daily basis. Our typical laser vias
are 5 to 6 mil diameter vias for layer 1 to 2 connections, and 10 to 12
mil diameter vias for layer 1 - 3 connections. We have even laser
drilled 16 mil diameter vias down to layer 4 for one of our customers.
This hole size and depth are no problem for a laser drill, either Uv
alone, or Uv/Co2 combination. 

Dave Simonik
Laser Process Technician
Sanmina-SCI Corp.
Owego Division

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sherif Refaat
Sent: Tuesday, November 20, 2007 2:47 PM
To: [log in to unmask]
Subject: Re: Laser drilling limitations

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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