ECMF02-2BF3 Datasheet - Clarification on Stencil Opening Shape

[rafi]

Hi ST Team,

 for the ECMF02-2BF3 and have a question regarding the recommended stencil opening. In the datasheet, the stencil aperture is specified as 220 µm, but it is not clear whether the aperture should be: Square (220 µm × 220 µm)  or  Round (220 µm diameter)

[Peter BENSCH]

Welcome ​@rafi, to the community!

Well, the datasheet, section 5, fig. 14, shows the correct shape for stencil: 220µm square:

A common practice for BGAs is to use square stencil apertures, possibly with rounded corners. The square has the advantage that, for the same nominal diameter, it often delivers slightly more solder paste volume than a circle. If the datasheet specifies a stencil opening as a square with the same side length as the recommended pad diameter, this is usually to be understood as a nominal recommendation, not as a mandatory 1:1 geometry. In practice, this is often further adjusted to suit the paste volume and reflow reliability.

Hope that helps?

Regards
/Peter