PDIUSBH12 datasheet(26/28 Pages) PHILIPS

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Philips Semiconductors

Product specification

PDIUSBH12

USB 2-port hub

1999 Jul 22

SOLDERING

Introduction

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 is often preferred when through-hole and surface mount

components are mixed on one printed circuit board. However, wave

soldering is not always suitable for surface mount ICs, or for

printed-circuit boards with high population densities. In these

situations, reflow soldering is often used.

Through-hole mount packages

SOLDERING BY DIPPING OR BY SOLDER WAVE

The maximum permissible temperature of the solder is 260

°C;

solder at this temperature must not be in contact with the joints 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.

MANUAL SOLDERING

Apply the soldering iron (24 V or less) to the lead(s) of the package,

either 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 made for up to 5 seconds.

Surface mount packages

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.

Several methods exist for reflowing; for example, infrared/convection

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 from 215 250

°C. The

top-surface temperature of the packages should preferably be kept

below 230

°C.

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 has cured.

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.

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 to 5 seconds between 270 and 320

°C.

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