Well, maybe I wasn't clear, (or maybe my thinking is way off-base!),
but our bare boards are currently manufactured as Class 2 except for two
notes where
1) we don't allow drill break-out from the pads and
2) we want thicker plating in the holes.
(1mil desired with no value less than 0.8, instead of 0.8mil desired with
no value less than 0.7)
Those two requirements are easily understood by our suppliers.
If we are confident that we are getting good class 2 boards, then we want
all the benefits of a robust assembly process, so we specify class 3 for
our assemblies and we are willing to pay whatever that costs.(at this point
the bare board is just another component in the assembly BOM).
A previous comment noted something about what my customers require, but in
this case I AM the customer and have to specify whatever we need, so I'm
willing to switch to Class 3 Bare Boards if I need to.
(but I have a doubt that a supplier is going to do anything much
differently for class 3 than he would for class 2, we just have to pay more
for testing and documentation)
Anyway, if it's a rule then it's a rule, but your comment that "The use of
one class for a specific characteristic does not mean that all other
characteristics must meet the same class" seems to support our scheme over
the statement in the "IPC Checklist" page 8.
thanks,
Jack
.
On Thu, Apr 25, 2019 at 6:09 AM McGlaughlin, Jeffrey A <
[log in to unmask]> wrote:
> Jack -
>
> From 600F section 1.4 "Acceptability criteria in this document have
> separated so that printed board product may be evaluated to any one of the
> three classes. The use of one class for a specific characteristic does not
> mean that all other characteristics must meet the same class. Selection
> should be based on minimum need..."
>
> So how do you classify the bare board as Class 3?
>
> Onward through the fog,
> Jeffrey
>
> Jeffrey McGlaughlin, C.I.D.
> Engineering Designer
> ST RE Str Eng & Analysis
> Office: 614.424.7582| Fax: 614.458.7582
> [log in to unmask]
>
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>
> -----Original Message-----
> From: DesignerCouncil <[log in to unmask]> On Behalf Of Jack Olson
> Sent: Wednesday, April 24, 2019 10:55 AM
> To: [log in to unmask]
> Subject: [DC] Bare Board Class must be >= Assembly Class?
>
> Message received from outside the Battelle network. Carefully examine it
> before you open any links or attachments.
>
> Greetings,
>
> I stumbled into a checklist on the IPC
> website,
> http://www.ipc.org/4.0_Knowledge/4.1_Standards/PCBA-Checklist18.pdf
>
> and on page 8 is a statement I have never heard before.
>
> "Please NOTE that the final performance class for printed board
> assemblies (assembled,soldered, cleaned and tested) cannot be any
> greater than the performance class called out for the bare printed
> board. That is, in order to obtain a Class 3 with the assembly printed
> board assembly, an IPC Class 3 recognition of the bare printed board
> (anything with a Class 2 or 1 with the bare printed board prevents
> obtaining a Class 3 with the printed board assembly) must be first
> obtained."
>
> Does anyone know which IPC document this came from?
>
>
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