Hello All,

I am trying to determine the exact meaning of the IPC spec 2221
sections 9.1.2 thru 9.1.4 and have many questions hopefully
someone  can answer.

From section 9.1.2 "A".

1. Is maximum hole size the drilled size or the finished hole size ?
2.  The annular ring uses a 0.05 MM value for the annular ringsize.
In table 9.2 in spec IPC2221 0.05mm is for external Supported annular rings
shouldn't the value be 0.03mm since the plane is an internal layer ?

From Section 9.1.3 Figure 9.1.

1. The .25MM minimum for the nonfunctional land is this what should be
used to create the outer ring size on a thermal connection ?

2. Is the value "B" - standard manufacturing allowance the same as
fabrication allowance ?

3. For value "A" - electrical clearance - how are these values determined ?


From section 9.1.3.1.

1. In figure 9-2 on the bottom right side is shows A + B see fig 9-3.
Shouldn't that be
figure 9-1 ? Also why is this even mentioned if the clearance area is
determined by
hole diameter and fabrication allowance ?

2. Is the hole diameter (max) the finished hole size of the drill size ?

Lenny ALexman

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