Hello members,

I would like to consult the following questions:

IPC-7351 define “courtyard excess” for placement density level A (most), B
(nominal) and C (least). And according to Note 3 on page 1, courtyard
excess defined in IPC-7351 are for reflow soldering.

In prototyping, I however need to ask a solderer to manually solder the
chips/components. For C (least) level density by which the minimum
courtyard excess is 0.1mm → between two components is 0.1 × 2 = 0.2mm = 8mil,
and assume this 8mil distance is between two closest pads on different
components, is this too close for a manual solderer to solder properly?

There are two aspects to consider:

   1. Solder mask is always needed to prevent bridging. If the separation
   is only 8mil, and considering that solder mask has expansion which at least
   ≥ 1mil, so that the maximum remaining width for solder mask sliver is
   only about 8-2×1=6 mil. Is this narrow sliver wide enough to prevent
   bridging?
   2. Even if we could ignore the solder mask width issue, or that it turns
   out 6mil width is enough for solder mask sliver, we still need to ascertain
   that 8mil separation could be handled without difficulty by human hand. Is
   it very difficult for an experienced solderer to do this? How about a
   solderer of average skill level?

Thanks and regards,
Jian Lin

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