spec number is not arbitrary - it got tons of work behind it -  
reliability test vs cleanliness vs space clearance vs voltage bias,  
dry vs web soldermask, etc. etc. for example, C4 flip chip on board  
would have different value than spec - you need to develop your own  
now (old spec is based on many hard work of research lab, such as  
ATT, IBM, Motorola, etc.etc.).  To say it is arbitrary - you need dig  
more deep (google only have info after 90s, you miss a lot if you  
depend only on google).  IMHO.  you got old number - a good start,  
depend upon what your product is and how it is made (make huge  
difference if it touched by human hand).  Best of luck.
jk
On Apr 5, 2019, at 9:50 AM, Craig Sullivan wrote:

> Lloyd,
>
>
>
> Thank you. Yes I know I have to do the work and I am participating  
> in the webinar.
>
>
>
> The question was generic in nature to see which document (obsolete  
> or not) those limits originally came from, because right now it  
> seems the numbers were arbitrarily chosen here many years ago. I  
> don’t find it in the old  IPC documents I have so, my research  
> continues.
>
>
>
> Craig Sullivan
>
> Quality Engineer
>
> IT Administrator
>
> Phone:  (607) 266-0480 x115
>
> Fax:  (607) 266-0482
>
> Email: [log in to unmask]
>
> Web:  www.mplinc.com <http://www.mplinc.com/>
>
>
>
> MPL, Inc.
>
> 41 Dutch Mill Road  |  Ithaca  |  NY  |  14850
>
> An ISO 9001:2015 Certified and ITAR Registered Company
>
> IPC member since 2004
>
>
>
>
>
> From: lduso - Diamond-MT.com [mailto:[log in to unmask]]
> Sent: Friday, April 05, 2019 9:37 AM
> To: TechNet E-Mail Forum; Craig Sullivan
> Subject: Re: [TN] Old cleanliness documentation
>
>
>
> Craig
>
>
>
> All the numbers are gone from the IPC. The short answer is, you  
> need to set a limit based on how clean your boards need to be. In  
> other words, you need to do the work to gather the data.
>
>
>
> Doug Pauls conducted some great classes on the new IPC amendment  
> and will surely be on here shortly to comment as well. I do believe  
> Mike Konrad from Aqueous Technologies is also doing a webinar  
> specifically addressing this on the 16 April.
>
>
>
> Lloyd Duso
>
> General Manager
>
> Diamond-MT
> (814) 535-3505
>
> www.Diamond-mt.com
>
>
>
>
>
> On Fri, Apr 5, 2019 at 8:33 AM Craig Sullivan  
> <[log in to unmask]> wrote:
>
> Good Morning Everyone,
>
>
>
> I have inherited the task of monitoring and analyzing our cleanliness
> testing process. As I am looking through old records I see cleanliness
> pass/fail limits of ~14 ug/in^2 for class 2 and ~6.5 ug/in^2 for  
> class 3.
> Can anyone tell me what IPC document this was actually in? I cannot  
> seem to
> find it.
>
>
>
> I'm changing to match the J-STD-001 limits of 1.56 ug/cm^2 and  
> we've always
> been well below any of these "limits", but everyone I have asked  
> has no idea
> where the above numbers (14 & 6.5) came from, other than to say "IPC".
> Anyone know?
>
>
>
> Craig Sullivan
>
> Quality Engineer
>
> IT Administrator
>
> Phone:  (607) 266-0480 x115
>
> Fax:  (607) 266-0482
>
> Email:  <mailto:[log in to unmask]> [log in to unmask]
>
> Web:   <http://www.mplinc.com/> www.mplinc.com
>
>
>
> MPL, Inc.
>
> 41 Dutch Mill Road  |  Ithaca  |  NY  |  14850
>
> An ISO 9001:2015 Certified and ITAR Registered Company
>
> IPC member since 2004