Display Your Know How: Footprints

B is better (Per IPC7093A) but the corners should have a radius of at least the diameter of the solder power.  This will help in the paste release.  Also the Pas to pad area needs to be calculated - target is between 50% and 80% to avoid voids.  There are no thermal via;s shown, the paste areas need to be such that these vias area avoided best as possible.

B is better (Per IPC7093A) but the corners should have a radius of at least the diameter of the solder power.  This will help in the paste release.  Also the Pas to pad area needs to be calculated - target is between 50% and 80% to avoid voids.  There are no thermal via;s shown, the paste areas need to be such that these vias area avoided best as possible.

Thanks Wild - I found your points very interesting! Upon rereading, can you clarify your meaning of solder "power". Are you referring to solder ball size here? Just for my own education - I would be interested to know thanks! 

Here is a link to The company AIM website that has details on Solder Powder:
aim alloys

BTW - the SAC305, SAC405, SAC505 - the first digit is the Power Size.  So SAC305 is the type 3 with diameters ranging from 25-45um

I had tried to post a reply but Cadence flagged it as spam.
Go to the AIM site (www.aimalloys.com/products/solder-powder) and there is a description of solder powder.
The photo shows the powder size, you can see that SAC305 has a powder ball size of 25 to 45um, 4 and 5 also shown.

Second post was also flagged as spam.
Just search on Solder Powder, pictures and websites such as AIM alloys with give you a good description.
Note SAC305 uses type 3 powder ball size which is 25 to 45um, type 4 is 20 to 38 um and type 5 is 15 to 25 um.

Yes any external links are automatically flagged for site safety reasons. These are approved now after review.