Philips Semiconductors

Product specification

PTN3500

Maintenance and control device

2001 Jan 17

12

SOLDERING

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).

DIP

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

has been pre-heated, forced cooling may be necessary immediately

after soldering to keep the temperature within the permissible limit.

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.

SO and SSOP

Reflow soldering

Reflow soldering techniques are suitable for all SO and SSOP

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.

Several techniques exist for reflowing; for example, thermal

conduction by heated belt. Dwell times vary between 50 and 300

seconds depending on heating method. Typical reflow temperatures

range from 215 to 250

°C.

Preheating is necessary to dry the paste and evaporate the binding

agent. Preheating duration: 45 minutes at 45

°C.

Wave soldering

Wave soldering is not recommended for SSOP 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, the following conditions

must be observed:

followed by a smooth laminar wave) soldering technique

should be used.

parallel to the solder flow and must incorporate solder

thieves at the downstream end.

Even with these conditions, only consider wave soldering

SSOP packages that have a body width of 4.4 mm, that is

SSOP16 (SOT369–1) or SSOP20 (SOT266–1).

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.

Maximum permissible solder temperature is 260

°C, and maximum

duration of package immersion in solder is 10 seconds, if cooled to

less than 150

°C within 6 seconds. Typical dwell time is 4 seconds at

250

°C.

A mildly-activated flux will eliminate the need for removal of

corrosive residues in most applications.

Repairing soldered joints

Fix the component by first soldering two diagonally opposite end

leads. Use only a low voltage soldering iron (less than 24 V) 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 to 5 seconds

between 270 and 320

°C.

code 9398 393 40011.