Philips Semiconductors
Product specification
8-bit serial-in/serial or parallel-out shift
register with output latches; 3-state
74HC/HCT595
SOLDERING
Introduction
SO, SSOP and TSSOP
REFLOW SOLDERING
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.
Reflow soldering techniques are suitable for all SO, SSOP
and TSSOP 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.
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).
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.
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.
WAVE SOLDERING
Wave soldering can be used for all SO packages. Wave
soldering is not recommended for SSOP and TSSOP
packages, because of the likelihood of solder bridging due
to closely-spaced leads and the possibility of incomplete
solder penetration in multi-lead devices.
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.
If wave soldering is used - and cannot be avoided for
SSOP and TSSOP packages - 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.
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.
• The longitudinal axis of the package footprint must be
parallel to the solder flow and must incorporate solder
thieves at the downstream end.
1998 Jun 04
19
NXP [ NXP ]
