SI8457DB Datasheet, PDF (9/11 Pages) Vishay Siliconix – P-Channel 12 V (D-S) MOSFET

AN824
Vishay Siliconix
TABLE 1
Main Parameters of Solder Bumps in MICRO FOOT Designs
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{MICRO FOOT CSP}
Bump Material
Bump Pitch* Bump Diameter*
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{MICRO FOOT CSP MOSFET}
0.8
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MICRO FOOT CSP Analog Switch
Eutectic Solder:
63Sm/37Pb
0.5
MICRO FOOT UCSP Analog Switch
0.5
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{* All measurements in millimeters}
0.37-0.41
0.18-0.25
0.32-0.34
Bump Height*
0.26-0.29
0.14-0.19
0.21-0.24
MICRO FOOT’S DESIGN AND RELIABILITY
As a mechanical, electrical, and thermal connection between
the device and PCB, the solder bumps of MICRO FOOT
products are mounted on the top active surface of the die.
Table 1 shows the main parameters for solder bumps used in
MICRO FOOT products. A silicon nitride passivation layer is
applied to the active area as the last masking process in
fabrication,ensuring that the device passes the pressure pot
test. A green laser is used to mark the backside of the die
without damaging it. Reliability results for MICRO FOOT
products mounted on a FR-4 board without underfill are shown
in Table 2.
TABLE 2
MICRO FOOT Reliability Results
Test Condition C: −65_ to 150_C
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{Test condition B: −40_ to 125_C}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{121_C @ 15PSI 100% Humidity Test}
>500 Cycles
>1000 Cycles
96 Hours
The main failure mechanism associated with wafer-level
chip-scale packaging is fatigue of the solder joint. The results
shown in Table 2 demonstrate that a high level of reliability can
be achieved with proper board design and assembly
techniques.
BOARD LAYOUT GUIDELINES
Board materials. Vishay Siliconix MICRO FOOT products are
designed to be reliable on most board types, including organic
boards such as FR-4 or polyamide boards. The package
qualification information is based on the test on 0.5-oz. FR-4
and polyamide boards with NSMD pad design.
Land patterns. Two types of land patterns are used for
surface-mount packages. Solder mask defined (SMD) pads
have a solder mask opening smaller than the metal pad
(Figure 3), whereas on-solder mask defined (NSMD) pads
have a metal pad smaller than the solder-mask opening
(Figure 4).
NSMD is recommended for copper etch processes, since it
provides a higher level of control compared to SMD etch
processes. A small-size NSMD pad definition provides more
area (both lateral and vertical) for soldering and more room for
escape routing on the PCB. By contrast, SMD pad definition
introduces a stress concentration point near the solder mask
on the PCB side that may result in solder joint cracking under
extreme fatigue conditions.
Copper pads should be finished with an organic solderability
preservative (OSP) coating. For electroplated
nickel-immersion gold finish pads, the gold thickness must be
less than 0.5 mm to avoid solder joint embrittlement.
Copper
Solder Mask
www.vishay.com
2
FIGURE 3. SMD
Copper
Solder Mask
FIGURE 4. NSMD
Document Number: 71990
06-Jan-03