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Re: Tutorial about IPC-7531A


On Thu, 2 Sep 2010, Brian F. G. Bidulock wrote:

Looking at an entry for a BGA below (wrapped) from BGA7351B.plb09

Ahem... I've only done CHP component till now :D

Many of the XML'ish attributes appear self-explanatory: (all decimal
units appear to be in MM, and integer units are 10 nanometers.  These
probably correspond to fields in the calculator.

Exactly. There's a risk that the decimal unit are in the 'configured
unit', but IPC seems to do all its work in metric.

    dflt="1" <- default is pin 1?

No, it's the 'use default' not 'user' radio button

    cyd_xs="1" <- courtyard excess?

Exactly, nominal for BGA is 1mm

 BGA; <- specifies format of following fields...
     1; <- ????

It seems a revision level indicator. For CHP it's always 0 except for
CLED which were added later and have 1. It seems that the viewer ignores

     0 1 4 1 4 1 26 3 7 1 3 1 3 1 2 1 1 1 1 1 2 1 3 1 3 1 7 3 26 1 4
       1 4 1; <- some way of spec'ing the 21 missing balls in the grid?

Probably yes. But I prefer to analyze first the 'easy' component to
better get in their mindset. Also BGA have different rules (they don't
have fillet targets, only pad size proportions depending on pitch).

Well, that's the idea anyway....

You're right. I'm doing the analysis component by component, you have to
be patient :D

Lorenzo Marcantonio
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