Philips PNX2000 13. Soldering

Product data Rev. 03 – 23 August 2004 27 of 31

Philips Semiconductors PNX2000

Audio video input processor

13. Soldering

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 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. In these situations reflow soldering is

recommended.

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 and 200 seconds depending on heating method.

Typical reflow peak temperatures range fro m 215 to 270 °C depending on solder paste

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

•below 220 °C (SnPb process) or below 245 °C (Pb-free process)

—for all BGA and SSOP-T packages

—for packages with a thickness ≥ 2.5 mm

—for packages with a thickness < 2.5 mm and a volume ≥350 mm3 so called

thick/large packages.

•below 235 °C (SnPb process) or below 260 °C (Pb-free process) for packages with a

thickness < 2.5 mm and a volume < 350 m m 3 so called small/thin packages.

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

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:

•Use a double-wave soldering method comprising a turbulent wave with high upward

pressure followed by a smooth laminar wave.

•F o r packages with leads on two sides and a pitch (e):