IP4855CX25 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 2 — 24 May 2013 25 of 30
NXP Semiconductors
IP4855CX25
SD 3.0-compliant memory card integrated dual voltage level translator
16. Design and assembly recommendations
16.1 PCB design guidelines
For optimum performance, use a Non-Solder Mask PCB Design (NSMD), also known as a
copper-defined design, incorporating laser-drilled micro-vias connecting the ground pads
to a buried ground-plane layer. This results in the lowest possible ground inductance and
provides the best high frequency and ESD performance. For this case, refer to Table 17
for the recommended PCB design parameters.
[1] OSP: Organic Solderability Preservation
FR4: Flame Retard 4
16.2 PCB assembly guidelines for Pb-free soldering
Table 17. Recommended PCB design parameters
Parameter Value or Specification
[1]
PCB pad diameter 250 m
Micro-via diameter 100 m (0.004 inch)
Solder mask aperture diameter 325 m
Copper thickness 20 m to 40 m
Copper finish AuNi or OSP
PCB material FR4
Table 18. Assembly recommendations
Parameter Value or Specification
Solder screen aperture diameter 290 m
Solder screen thickness 100 m (0.004 inch)
Solder paste: Pb-free SnAg (3 % to 4 %) Cu (0.5 % to 0.9 %)
Solder/flux ratio 50/50
Solder reflow profile see Figure 15
