PIP202-12M Datasheet, PDF (15/20 Pages) NXP Semiconductors – DC to DC converter powertrain

Philips Semiconductors
PIP202-12M
DC to DC converter powertrain
15. Soldering
15.1 Introduction to soldering MLF packages
The MicroLeadFrame package (MLF) is a near Chip Scale Package (CSP) with a
copper leadframe. It is a leadless package, where electrical contact to the printed
circuit board is made through metal pads on the underside of the package. In addition
to the small pads around the periphery of the package, there are large pads on the
underside that provide low thermal resistance, low electrical resistance, low
inductance connections between the power components inside the MLF package and
the PCB. It is this feature of the MLF package that makes it ideally suited for VRM
applications.
Electrical connection between the package and the printed circuit board is made by
printing solder paste on the printed circuit board, placing the component and
reflowing the solder in a convection or infra-red oven. The solder reflow process is
shown in Figure 18 and the typical temperature profile is shown in Figure 19. To
ensure good solder joints, the peak temperature T_p should not exceed 220° C for thin
packages such as MLF, and the time above liquidus temperature should be less than
1.25 minutes. The maximum temperature can be increased for lead free solder. The
ramp rate during preheat should not exceed 3 K/s. Nitrogen purge is recommended
during reflow.
SOLDER PASTE
PRINTING
POST PRINT
INSPECTION
COMPONENT
PLACEMENT
PRE REFLOW
INSPECTION
REFLOW SOLDERING
POST REFLOW INSPECTION
(PREFERABLY X-RAY)
REWORK AND
TOUCH UP
03aj25
300
Temp
(°C)
Tp
200
Tr
Te
1 min max
03aj26
1.25 min max
100
rate of rise of
temperature < 3 K/s
0
0
1
2
3
time (minutes)
Fig 18. Typical reflow soldering process flow.
Fig 19. Typical reflow soldering temperature profile.
9397 750 10031
Product data
Rev. 01 — 15 July 2002
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
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