PCD3359A Ver la hoja de datos (PDF) - Philips Electronics

Número de pieza

componentes Descripción

Fabricante

PCD3359A

8-bit microcontroller with DTMF generator and 128 bytes EEPROM

Philips Electronics 

Philips Semiconductors

8-bit microcontroller with DTMF

generator and 128 bytes EEPROM

Product specification

PCD3359A

21 SOLDERING

21.1 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 “Data Handbook IC26; Integrated Circuit Packages”

(order code 9398 652 90011).

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.

21.3.2 WAVE SOLDERING

21.3.2.1 LQFP

Wave soldering is not recommended for LQFP 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.

21.2 DIP

21.2.1 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.

21.2.2 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.

21.3 LQFP and SO

21.3.1 REFLOW SOLDERING

Reflow soldering techniques are suitable for all LQFP and

SO packages.

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.

CAUTION

Wave soldering is NOT applicable for all LQFP

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

If wave soldering cannot be avoided, for LQFP

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.

21.3.2.2 SO

Wave soldering techniques can be used for all SO

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 end.

21.3.2.3 Method (LQFP and SO)

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.

1998 May 11

30

Share Link: