If this topic is being revised, I would suggest that we distinguish between
two types of marking.
1). Tracking and Identification (and maybe polarity) is essential, and must
be legible
2). Reference Designators may be present but are not essential

As circuit board designers, quite often we find ourselves removing over half
the reference designators because there is simply not enough room for them.
But as an attempt to be helpful to anyone down the line we try to put as
many as we can, and inevitably there will be some grey area where we know it
might not come out right, like over a via that has mask encroached up to the
drilled hole. This is not going to look good in the finished product, but
even if only the "43" is visible on component "C143", and even if everyone
agrees that seeing a RefDes for C143 is not essential, it may be helpful to
someone working in the lab or whatever.

I don't think our attempt to add extra info for non-essential nomenclature
should penalize us with possible rejects. Knowing that all I have to do is
remove ALL the reference designators to guarantee a conforming product will
only encourage me to take the easy way out and remove the silkscreen
altogether. hey, no rejects!

Jack (aka "the new guy")


On Wed, Jun 16, 2010 at 1:54 PM, Dupriest, Don <[log in to unmask]>wrote:

> Hi Wendi, I would say yes it applies to component marking (reference
> designators).  Examples in 600 mostly reflect numbering (like traceability)
> but one example photo shows a component symbol.  As to legibility; I would
> prescribe to if you can interpret the letters or symbol with 2X it is fine.
>  However, this section probably could stand some more work.  One thing we
> have noticed is 6012 does not specifically address adhesion for marking like
> solder mask is covered in 600 and 6012.  It references a permanency
> requirement so one would assume tape test and/or solvent resistance would be
> applicable.  But a tape test may be too difficult to pass for some really
> small feature sizes/designator letters.
>
> Guess just another thing to add to the committee to do list.
>
> C. D. (Don) Dupriest
> Lockheed Martin - MFC
> Advanced Manufacturing Technology
> member of:
> Production Technical Excellence Staff
> Ph. 972/603-7724 fax: 972/603-9052
> Email: [log in to unmask]
>
>
>
> -----Original Message-----
> From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Wendi Boger
> Sent: Wednesday, June 16, 2010 1:05 PM
> To: [log in to unmask]
> Subject: [IPC-600-6012] Legibility of Marking
>
> Everyone,
>
>
>
>    Does section 2.8 Marking in IPC-A-600 apply to Legend (component
> mark)?    We are increasingly seeing designs with very small legend
> features causing discussions at final inspection as to whether they meet
> the requirement for legibility.  From what I understand legible means at
> no more than 2x you can understand what the symbols are.  Fussiness and
> filled in holes in letters are allowed if you can tell what the letter
> is.
>
>
>
>    Would appreciate some guidance on this.
>
>
>
> Thanks,
>
> Wendi
>
>
>


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