
--------------------------------------------------INTRODUCTIONOFPACKAGES
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4.
Mounting
Method
Package lead pins are surface treated with solder coating
or
plating to facilitate PCB mounting. The lead pins are connected
to the package
by
eutectic solder. Common connecting method
of
leads and precautions are explained as follows:
4.1
Mounting
Methods
of
Pin
Insertion
Type Package
Insert lead pins into the PCB through-holes (usually
about
4>0.8mm). Soak leads in a wave solder tub.
Lead pins held
by
the through-holes enable handling of the
package through the sqldering process, and facilitate automated
soldering. When soldering leads in the wave solder tub,
do
not
get solder on the package.
4.2
Mounting
Method
of
Surface
Mount
Type Package
Applythe specified quantity
of
solder pasteto the pattern
on
any printed board bythescreen printing method,
to
temporarily
fix the package to the board. The solder paste melts when heated
in a reflowing furnace, and package leads and the pattern
of
the
printed board are fixed by the surface tension
of
the melted
solder and self alignment.
Thesize
of
the pattern where leads are attached should be
1.1
to
1.3
times the leads' width, depending on paste material
or
furnace adjustment.
The temperature
of
the reflowing furnace
is
dependent
on
packaging material and type. Fig. 2 lists the adjustment
of
the
reflowing furnace for
FPP.
Pre-heat the furnace to
150
0
C.
Sur-
face temperature
of
the resin should be kept
at
235
0 C maximum
for
JO
minutes
or
less.
(I)
The temperature of
the
leads
should
be
kept
at
260°
for
10
minutes
or
less.
(2)
The temperature of
the
resin
should
be
kept
at
235
0
for
10
minutes
or
less.
(3)
Below
is
shown
the
temperature profile
when
soldering a
package
by
the
reflowing
method.
17
'"
"
'"
'"
0.
E
~
Fig.2
Reflowing Furnace
Adjustment
for
FPP
IUnit:mm)
Time~
Employ adequate heating
or
temperature control equipment
to prevent damage to the plastic package epoxy-resin material.
When using an infrared heater, avoid long exposure
at
tempera-
tures higher thanthe glass transition point
of
epoxy-resin(about
150
0
C),
which may cause package damage and loss
of
reliability
characteristics. Equalize the temperature inside and outside
of
packages by reducing the heat
of
the upper surface
of
the
packages.
FPP
leads may easily bend in shipment
or
during handling,
and impact solderingonto the printed board. Heat the bent leads
again with a soldering iron to reshape them.
Use
a rosin flux when SOldering, Do not use chloric flux
because the chlorine in the flux has a tendency to remain
on
the
leads and reduce reliability.
Use
alcohol, chlorothene
orfreon
to
wash away rosin flux from packages. These solvents should not
'remain on the packages for an excessive length
of
time, because
the package markings may disappear.