It's not just a matter of meeting industry standards but of supply portability and high vs low volume build rules.
Hence the creation and maintenance of sets of different internal pwb constraints tables for different classes of pwb which also have to reflect where they'll be sourced. The routing rules for high volume full build 0.65 - 1.2mm thick ELIC type stackups with uVia only outerlayers and no core vias are not the same as rules for 2mm thick 3n3 with uVia stacked on core via and uVia + PTH on outers which are not the same as 5mm thick flipdrilled probecard or loadboard routing rules. Each rule set has rules for areas that are way over the IPC lines but fall within the needs of the app.
dw
Sometimes under battle field emerging technology conditions intelligent disregard of orders IPC standards is called for (just be sure to keep good notes for your inevitable court martial). ;)
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Wednesday, October 21, 2015 10:20 AM
To: [log in to unmask]
Subject: Re: [TN] IPC-A-610
Doug,
"thou shall not do this" are very hard to define. Nothing can replace mentor and training plus hands on for design. the std should define minimum requirements of "you must do this"... hard to define all the stupid mistake that pop out of some of the newbie's head... like the dead bug (pinout were mirror image flipped... so you have to mount the part facing sky and hard wire each pin.. don't laugh, it happened twice - prototype, and later rev, someone decided to get the rev 0 dwg and modify other area of layout ... - thanks god it is a long time ago).
jk
> Dwight,
>
> As a suggestion, if you have DfM guidelines that work, you might make
> them available to Gary Ferrari, who leads the IPC-2221 and -2222
> design standards. The more we manufacturing people can do to let
> designers know what causes is pain, the better off we will be.
>
>
> Doug Pauls
> Principal Materials and Process Engineer Rockwell Collins
>
> On Wed, Oct 21, 2015 at 9:47 AM, Mattix, Dwight
> <[log in to unmask]<mailto:[log in to unmask]>>
> wrote:
>
>> Edit to add:
>> Got a whole 'nother set of design for assembly Mfg Eng guidelines and
>> assembly quality workmanship guidelines to fill gaps (we perceive) in
>> IPC workmanship guidelines.
>>
>> Back in the basestation days... We had an internal circuit assembly
>> rework and repair document I published that harmonized our allowed
>> repair/rework methods, IPC workmanship and customer (Nortel at the
>> time) rework&repair standards. An interesting Venn diagram problem,
>> that was.
>>
>> -----Original Message-----
>> From: Mattix, Dwight
>> Sent: Wednesday, October 21, 2015 7:40 AM
>> To: [log in to unmask]<mailto:[log in to unmask]>; 'Peter G. Houwen' <[log in to unmask]<mailto:[log in to unmask]>>
>> Subject: RE: [TN] IPC-A-610
>>
>> "I couldn't solder it right, it's precluded by your design".
>>
>>
>> Fwiw, It's a pwb fab note. Not an assembly level note. So, your
>> concern is valid but mute. :)
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter G. Houwen
>> Sent: Wednesday, October 21, 2015 7:00 AM
>> To: [log in to unmask]<mailto:[log in to unmask]>
>> Subject: Re: [TN] IPC-A-610
>>
>> 'A note "Shall meet IPC Class x ,blah blah, except where precluded by
>> original design" doesn't sound like the correct approach to me - it
>> could unintentionally result in the designer not getting vital
>> feedback from the fabricator and assembler.'
>>
>> James makes a good point. It also makes it easy for the assembler to
>> say "I couldn't solder it right, it's precluded by your design".
>> Much better to add "Except as noted", then make sure it's noted.
>> Makes for better design discipline and is more likely to get a
>> response from manufacturing if you accidentally missed something.
>>
>> Pete
>>
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