Philips Semiconductors

PCF85103C-2

256

Product data

Rev. 04 — 22 October 2004

15 of 20

9397 750 14218

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

14. Soldering

14.1 Introduction

This text gives a very brief insight to a complex technology. A more in-depth account

of soldering ICs can be found in our

Data Handbook IC26; Integrated Circuit

Packages (document order number 9398 652 90011).

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

preferred when through-hole and surface mount components are mixed on one

printed-circuit board. 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. Driven by legislation and environmental forces the worldwide use of

lead-free solder pastes is increasing.

14.2 Through-hole mount packages

14.2.1

Soldering by dipping or by solder wave

Typical dwell time of the leads in the wave ranges from 3 to 4 seconds at 250

°C or

265

°C, depending on solder material applied, SnPb or Pb-free respectively.

The total contact time of successive solder waves must not exceed 5 seconds.

The device may be mounted up to the seating plane, but the temperature of the

If the printed-circuit board has been pre-heated, forced cooling may be necessary

immediately after soldering to keep the temperature within the permissible limit.

14.2.2

Manual soldering

Apply the soldering iron (24 V or less) to the lead(s) of the package, either below the

seating plane or not more than 2 mm above it. If the temperature of the soldering iron

bit is less than 300

°C it may remain in contact for up to 10 seconds. If the bit

temperature is between 300 and 400

°C, contact may be up to 5 seconds.

14.3 Surface mount packages

14.3.1

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.

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 and 200 seconds depending on heating method.

Typical reflow peak temperatures range from 215 to 270

°C depending on solder

paste material. The top-surface temperature of the packages should preferably be

kept:

°C (SnPb process) or below 245 °C (Pb-free process)

– for all the BGA and SSOP-T packages