P83C524 datasheet(71/76 Pages) PHILIPS

71 / 76 page

1997 Dec 15

Philips Semiconductors

Product speciﬁcation

8-bit microcontrollers

P83C524; P80C528; P83C528

27 SOLDERING

27.1

Introduction

There is no soldering method that is ideal for all IC

packages. Wave soldering is often preferred when

through-hole and surface mounted components are mixed

on one printed-circuit board. However, wave soldering is

not always suitable for surface mounted ICs, or for

printed-circuits with high population densities. In these

situations reflow soldering is often used.

This text gives a very brief insight to a complex technology.

A more in-depth account of soldering ICs can be found in

our

“IC Package Databook” (order code 9398 652 90011).

27.2

DIP

27.2.1

SOLDERING BY DIPPING OR BY WAVE

The maximum permissible temperature of the solder is

260

°C; solder at this temperature must not be in contact

with the joint for more than 5 seconds. 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 plastic body must not exceed the

specified maximum storage temperature (Tstg max). 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.

27.2.2

REPAIRING SOLDERED JOINTS

Apply a low voltage soldering iron (less than 24 V) to the

lead(s) of the package, 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.

27.3

PLCC and QFP

27.3.1

REFLOW SOLDERING

Reflow soldering techniques are suitable for all PLCC and

QFP packages.

The choice of heating method may be influenced by larger

PLCC or QFP packages (44 leads, or more). If infrared or

vapour phase heating is used and the large packages are

not absolutely dry (less than 0.1% moisture content by

weight), vaporization of the small amount of moisture in

them can cause cracking of the plastic body. For more

information, refer to the Drypack chapter in our

“Quality

Reference Handbook” (order code 9397 750 00192).

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,

infrared/convection heating in a conveyor type oven.

Throughput times (preheating, soldering and cooling) vary

between 50 and 300 seconds depending on heating

method. Typical reflow peak temperatures range from

215 to 250

°C.

27.3.2

WAVE SOLDERING

27.3.2.1

PLCC

Wave soldering techniques can be used for all PLCC

packages if the following conditions are observed:

• A double-wave (a turbulent wave with high upward

pressure followed by a smooth laminar wave) soldering

technique should be used.

• The longitudinal axis of the package footprint must be

parallel to the solder flow.

• The package footprint must incorporate solder thieves at

the downstream corners.

27.3.2.2

QFP

Wave soldering is not recommended for QFP packages.

This is because of the likelihood of solder bridging due to

closely-spaced leads and the possibility of incomplete

solder penetration in multi-lead devices.

If wave soldering cannot be avoided, for QFP

packages with a pitch (e) larger than 0.5 mm, the

following conditions must be observed:

• A double-wave (a turbulent wave with high upward

pressure followed by a smooth laminar wave)

soldering technique should be used.

• The footprint must be at an angle of 45° to the board

direction and must incorporate solder thieves

downstream and at the side corners.

CAUTION

Wave soldering is NOT applicable for all QFP

packages with a pitch (e) equal or less than 0.5 mm.

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