IR3523

Page 35 of 37

June 20, 2008

SOLDER RESIST

• The solder resist should be pulled away from the metal lead lands by a minimum of 0.06mm. The solder

resist mis-alignment is a maximum of 0.05mm and it is recommended that the lead lands are all Non

Solder Mask Defined (NSMD). Therefore pulling the S/R 0.06mm will always ensure NSMD pads.

• The minimum solder resist width is 0.13mm.

• At the inside corner of the solder resist where the lead land groups meet, it is recommended to provide a

fillet so a solder resist width of ≥ 0.17mm remains.

• The land pad should be Solder Mask Defined (SMD), with a minimum overlap of the solder resist onto

the copper of 0.06mm to accommodate solder resist mis-alignment. In 0.5mm pitch cases it is allowable

to have the solder resist opening for the land pad to be smaller than the part pad.

• Ensure that the solder resist in-between the lead lands and the pad land is ≥ 0.15mm due to the high

aspect ratio of the solder resist strip separating the lead lands from the pad land.

• The single via in the land pad should be tented or plugged from bottom boardside with solder resist.