Could somebody tell me what a type 3, class 2 PWB isaccording to IPC 6012?
Got a problem here with some boards that have annular ring on some holes that is
less than .002", some only about half.
Us lowly uneducated production types think this is unacceptable. But we have
always refered to IPC 600. The QE. however feels that IPC 600 does not apply
since it is not designated on the drawing. He says they should be acceptable
under 6012 but we don't have a copy.
 How does everyone else feel about using these boards? This is a goofy program
anyway. We are "fixing" what the Q.E. calls voids in the solder that are
actually the open ends of hollow connector pins.
 Thanks
Charles Caswell

Charles,

Class 2 requirements in 6012A table 3-5 Minimum Internal and External Annular
Ring states:
For Class 2 PTH, 90 deg. breakout of the hole from land is allowed when visually
assessed. For external lands, the land/conductor junction SHALL NOT be reduced
below the allowable width reduction in 3.5.3.1 The conductor junction should
never be less than 0.002 inches or the minimum line width, whichever is smaller.

For Class 3 PTH, The minimum external annular ring SHALL NOT be less than 0.002
inches. The minimum functional internal annular ring SHALL NOT be less than
0.00098 inches.

The minimum external annular ring may have 20% reduction of the minimum annular
ring due to defects such as pits, dents, nicks, pinholes, or splay in the
annular ring of isolated areas.

Section 3.5.3.1Conductor Width Reduction states: Allowable reduction of the
minimum conductor width (specified or derived) due to isolated defects (i.e edge
roughness, nicks, pinholes and scratches) which expose base material SHALL NOT
exceed 20% of the minimum conductor width for Class 2 and 3.

It would be hard for me to say good or bad without knowing what the annular ring
dimension should be (did you loose 20% of conductor width) or without seeing the
board. If you have any that are less than the 0.002 then they are indeed out of
specification and the others are right on the border.

I hope this information helps. I suggest purchasing a copy of the IPC 6012A
valuable information inside.


Regards,
Richard Carruth
Quality Eng.
LaBarge Inc.
Ph# 918-459-2346

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