PCA9549_1

© Koninklijke Philips Electronics N.V. 2006. All rights reserved.

Product data sheet

Rev. 01 — 11 July 2006

20 of 24

Philips Semiconductors

PCA9549

14. Soldering

14.1 Introduction to soldering surface mount packages

There is no soldering method that is ideal for all surface mount IC packages. Wave

soldering can still be used for certain surface mount ICs, but it is not suitable for fine pitch

SMDs. In these situations reflow soldering is recommended.

14.2 Reflow soldering

Reflow soldering requires solder paste (a suspension of fine solder particles, flux and

binding agent) to be applied to the printed-circuit board by screen printing, stencilling or

pressure-syringe dispensing before package placement. Driven by legislation and

environmental forces the worldwide use of lead-free solder pastes is increasing.

Several methods exist for reflowing; for example, convection or convection/infrared

heating in a conveyor type oven. Throughput times (preheating, soldering and cooling)

vary between 100 seconds and 200 seconds depending on heating method.

Typical reflow temperatures range from 215

°Cto260 °C depending on solder paste

material. The peak top-surface temperature of the packages should be kept below:

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

14.3 Wave soldering

Conventional single wave soldering is not recommended for surface mount devices

(SMDs) or printed-circuit boards with a high component density, as solder bridging and

non-wetting can present major problems.

To overcome these problems the double-wave soldering method was specifically

developed.

If wave soldering is used the following conditions must be observed for optimal results:

pressure followed by a smooth laminar wave.

Table 9.

SnPb eutectic process - package peak reflow temperatures (from

J-STD-020C

July 2004)

Package thickness

≥ 350

< 2.5 mm

240

°C+0/−5 °C

225

°C+0/−5 °C

≥ 2.5 mm

225

°C+0/−5 °C

225

°C+0/−5 °C

Table 10.

Pb-free process - package peak reflow temperatures (from

J-STD-020C July

2004)

Package thickness

2000

< 1.6 mm

260

°C + 0 °C

260

°C + 0 °C

260

°C + 0 °C

1.6 mm to 2.5 mm

260

°C + 0 °C

250

°C + 0 °C

245

°C + 0 °C

≥ 2.5 mm

250

°C + 0 °C

245

°C + 0 °C

245

°C + 0 °C