Jian,

it depends...very much depends in this case...on a number of conditions,
such as

a. The size and the shape of the iron tip
b. The used solder wire gauge and the necessary amount of solder.
c. The used temperature of the tip
d. The used flux
e. The size of the pads
f. The quality of the finish (wetting angle)
g. The surface cleanliness of the board
h. The type of components
i.  and more conditions that I don't see instantly
j. and of course the operator's skill
k. just came to think or maximum system voltages and type of media (RF, LF,
DC ..)

I've seen our guys solder 10 mil space without any problems, and I've also
rejected boards with near-shortage solder joints. In my opinion, there is
only one way to give answer: run a test series, and freeze every operator
sequence if the result is good. If not, adjust the parameters one by one
until you can safely repeat the processs.

It's amazing how separating a 5 to 10 mil space can be if all parameters of
the board are OK, and vice versa, it can be a hell to avoid bridging.

Hope you got inspiration to go on with your process evaluation. Soldering
is an ART !

Inge

On 29 January 2012 12:59, Jian Lin <[log in to unmask]> wrote:

> 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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