> Hi Jack - Happy Birthday Jack - Live long and prosper!

> On 28 May 2020, at 17:52, Jack Olson <[log in to unmask]> wrote:
> 
> don't forget, there is a difference between the drill size and the finished
> plated hole diameter.
> (just trying to help)
> 
> On Tue, May 26, 2020 at 12:34 PM <[log in to unmask]> wrote:
> 
>> Jack,
>> 
>> My PCB supplier can drill to 6 mil with a tolerance of +/-2mil.  That
>> allows me to have a pad of 14mil and meet the minimum of 2mil outer annular
>> ring for IPC-6012 Class 3.
>> 
>> I could use laser microvias and buried vias but there is a significant
>> cost going that way.
>> 
>> My preference is to use a 6mil drilled via but I'm not sure that will
>> qualify for Class 3.
>> 
>> Anyone know if there are exemptions that allow a 6mil via for Class 3.
>> 
>> Thanks all,
>> 
>> Larry
>> 
>> -----Original Message-----
>> From: TechNet <[log in to unmask]> On Behalf Of Jack Olson
>> Sent: Tuesday 26 May 2020 18:24
>> To: [log in to unmask]
>> Subject: Re: [TN] IPC Class 2 v 3
>> 
>> On Fri, 22 May 2020 16:54:20 +0100, Larry Brophy <[log in to unmask]>
>> wrote:
>>> 
>>> Sorry I have another question and it is again to do with what you have
>>> said , it is a conflict between the two specifications.
>>> We need to use a micro BGA.  Based on our PCB manufactures capabilities
>>> in the BGA area we need to use a blind via drilled at 6mil with a 14mil
>>> pad to guarantee a 2mil annular ring.
>>> But IPC-2221 states that the smallest blind via is 8 mil.  Table 9-4.
>>> This is just another design guide v IPC-6012 issue?
>> 
>> I thought Table 9-4 referred to the minimum mechanically DRILLED hole
>> size, (laser can be smaller diameter?) but after reviewing the document, it
>> does not seem clear to me.
>> (good question, but I only have the 2221C Working Draft OCT2013 to look at
>> right now)
>> 
>>