SOLDERING RECOMMENDATION
The soldering process causes considerable ther-
mal stress to a semiconductor component. This
has to be minimized to assure a reliable and ex-
tended lifetime of the device. The PowerSO-10
package can be exposed to a maximum tempera-
ture of 260°C for 10 seconds. However a proper
soldering of the package could be done at 215°C
for 3 seconds. Any solder temperature profile
should be within these limits. As reflow techniques
are most common in surface mounting, typical
heating profiles are given in Figure 1,either for
mounting on FR4 or on metal-backed boards. For
each particular board, the appropriate heat profile
has to be adjusted experimentally. The present
proposal is just a starting point. In any case, the fol-
lowing precautions have to be considered :
- always preheat the device
- peak temperature should be at least 30 °C
higher than the melting point of the solder
alloy chosen
- thermal capacity of the base substrate
Voids pose a difficult reliability problem for large
surface mount devices. Such voids under the
package result in poor thermal contact and the
high thermal resistance leads to component fail-
ures. The PowerSO-10 is designed from scratch to
be solely a surface mount package, hence symme-
try in the x- and y-axis gives the package excellent
weight balance. Moreover, the PowerSO-10 offers
the unique possibility to control easily the flatness
and quality of the soldering process. Both the top
and the bottom soldered edges of the package are
accessible for visual inspection (soldering menis-
cus).
Coplanarity between the substrate and the pack-
age can be easily verified. The quality of the solder
joints is very important for two reasons : (I) poor
quality solder joints result directly in poor reliability
and (II) solder thickness affects the thermal resis-
tance significantly. Thus a tight control of this pa-
rameter results in thermally efficient and reliable
solder joints.
Fig. 1 :
Typical reflow soldering heat profile
Time (s)
Temperature ( C)
0 40 80 120 160 200 240 280 320 360
0
50
100
150
200
250
o
215 C
o
Soldering
Preheating
Cooling
245 C
o
Epoxy FR4
board
Metal-backed
board
TLPxxM/G/G-1
12/14
