Jacob,

Actually IPC 6012 states the opposite, vias may be completely plugged.
If you have access to 6012 look at table 1-1 for plated holes (including
vias).

When plating is not desired in vias the requirement is typically to tent
them with solder mask.

Franklin


"" wrote:

>
>
> Technetter,
>
> 1) Is there any spec that says no solder is allowed in via holes
> (<22mil) especially the HASL boards?
>
> I've encountered a numerous of HASL boards with this problem. Due to
> the solder in via hole, solder lump will start to form at the annular
> ring of the via holes & it causes uneveness solder paste printing as
> well as posibilities of damaging the solder paste stencil. The solder
> lump will only form after the first IR reflow & with the via hole
> facing downward. When it's going for its second round of SMT, the
> problem start to appear, bridging.
>
> 2) Is there any recommended solutions to this problem?
>
> Another input, most of these boards were plugged either from the
> primary or the secondary side. In my case, we'll always mount the
> plugged side first & then followed by the other side.
>
> 3) Is there such a design rule that the process has to go the other
> way round? Meaning, mount on the unplugged side first insteads of the
> plugged side.
>
> Regards,
>
> Jacob Pao (SQE)
>

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