TDA8024 datasheet(26/29 Pages) PHILIPS

26 / 29 page

2004 July 12

Philips Semiconductors

Product speciﬁcation

IC card interface

TDA8024

15 SOLDERING

15.1

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.

15.2

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

°C to 270 °C depending on solder paste material. The

top-surface temperature of the packages should

preferably be kept:

• below 225 °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

≥ 350 mm3 so called thick/large packages.

• below 240 °C (SnPb process) or below 260 °C (Pb-free

process) for packages with a thickness < 2.5 mm and a

volume < 350 mm3 so called small/thin packages.

Moisture sensitivity precautions, as indicated on packing,

must be respected at all times.

15.3

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:

• Use a double-wave soldering method comprising a

turbulent wave with high upward pressure followed by a

smooth laminar wave.

• For packages with leads on two sides and a pitch (e):

– 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;

– smaller than 1.27 mm, the footprint longitudinal axis

must be parallel to the transport direction of the

printed-circuit board.

The footprint must incorporate solder thieves at the

downstream end.

• For packages with leads on four sides, the footprint must

be placed at a 45

° angle to the transport direction of the

printed-circuit board. The footprint must incorporate

solder thieves downstream and at the side corners.

During placement and before soldering, the package must

be fixed with a droplet of adhesive. The adhesive can be

applied by screen printing, pin transfer or syringe

dispensing. The package can be soldered after the

adhesive is cured.

Typical dwell time of the leads in the wave ranges from

3 seconds to 4 seconds at 250

°C or 265 °C, depending

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

A mildly-activated flux will eliminate the need for removal

of corrosive residues in most applications.

15.4

Manual soldering

Fix the component by first soldering two

diagonally-opposite end leads. Use a low voltage (24 V or

less) soldering iron applied to the flat part of the lead.

Contact time must be limited to 10 seconds at up to

300

°C.

When using a dedicated tool, all other leads can be

soldered in one operation within 2 seconds to 5 seconds

between 270

°C and 320 °C.

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