Philips Semiconductors
Product specification
PDIUSBH12
USB 2-port hub
1999 Jul 22
26
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
S
OLDERING
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 (T
stg(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.
M
ANUAL
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
R
EFLOW
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.
W
AVE
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.
M
ANUAL
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.
