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© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

Product data sheet

Rev. 01 — 13 October 2005

13 of 17

Philips Semiconductors

PCK9447

3.3 V/2.5 V 1 : 9 LVCMOS clock fan-out buffer

12. Soldering

12.1 Introduction to soldering surface mount packages

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 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.

12.2 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 peak temperatures range from 215

°Cto270 °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 BGA, HTSSON..T and SSOP..T packages

– for packages with a thickness

≥ 2.5 mm

– for packages with a thickness < 2.5 mm and a volume

thick/large packages.

°C (SnPb process) or below 260 °C (Pb-free process) for packages with a

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

12.3 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.

– larger than or equal to 1.27 mm, the footprint longitudinal axis is preferred to be

parallel to the transport direction of the printed-circuit board;