Micropak Manufacturing Guidelines

Process tolerance guidelines
The Recommended Land Pattern depicted in the Dimensions page has a 0.3mm wide pad consistent with 0.5mm pitch leaded components. Fine pitch leaded components often do not use a solder mask between pads. If a solder mask is to be used between pads, then depending on manufacturing tolerance the 0.3mm pad dimensions may not allow sufficient solder mask line width to insure good manufacturability. The drawing below illustrates results for PC board land pad dimensions for a specific set of manufacturing process tolerances. In this example, the solder mask registration tolerance is +/- 3mils. Given these tolerances, a solder pad of 0.25mm x 0.4mm can be used that will allow solder mask dimensions with reasonably achievable 4mil line widths. The pad dimensions of 0.25mm x 0.4mm are slightly larger than the lands on MicroPak. The larger pads, 0.3mm x 0.49mm, shown in the Recommended Land Pattern depicted in the Dimensions page would require narrower solder mask lines or no solder mask.  Industry standard 5mil thick laser cut solder stencil is recommended.

The figure above shows

• Design using solder mask line of 4mils and a +/-3mils registration tolerance gives a pad size of 0.25mm.
• Component can be shifted horizontally +/-1mil and still be on solder pad.
  

Solder stencil guidelines

• Non solder mask defined (NSMD) land pads are recommended for customer’s PCB for highest solder joint reliability.

The information described herein is preliminary.