Philips TDA8950 User Manual download pdf (Page 36)

Preliminary data sheet Rev. 01 — 9 September 2008 36 of 39

NXP Semiconductors

TDA8950

2 × 150 W class-D power ampliﬁer

15.4 Reﬂow soldering

Key characteristics in reﬂow soldering are:

• Lead-free versus SnPb soldering; note that a lead-free reﬂow process usually leads to

higher minimum peak temperatures (see Figure 31) than a SnPb process, thus

reducing the process window

• Solder paste printing issues including smearing, release, and adjusting the process

window for a mix of large and small components on one board

• Reﬂow temperature proﬁle; this proﬁle includes preheat, reﬂow (in which the board is

heated to the peak temperature) and cooling down. It is imperative that the peak

temperature is high enough for the solder to make reliable solder joints (a solder paste

characteristic). In addition, the peak temperature must be low enough that the

packages and/or boards are not damaged. The peak temperature of the package

depends on package thickness and volume and is classiﬁed in accordance with

Table 11 and 12

Moisture sensitivity precautions, as indicated on the packing, must be respected at all

times.

Studies have shown that small packages reach higher temperatures during reﬂow

soldering, see Figure 31.

Table 11. SnPb eutectic process (from J-STD-020C)

Package thickness (mm) Package reﬂow temperature (°C)

Volume (mm

)

< 350 ≥ 350

< 2.5 235 220

≥ 2.5 220 220

Table 12. Lead-free process (from J-STD-020C)

Package thickness (mm) Package reﬂow temperature (°C)

Volume (mm

)

< 350 350 to 2000 > 2000

< 1.6 260 260 260

1.6 to 2.5 260 250 245

> 2.5 250 245 245

1 2 ... 31 32 33 34 35 36 37 38 39

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Philips TDA8950 User Manual Page 36