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 surfacemount 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

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