5 LEDs
Application Note
Sanken Electric’s light emitting diodes (LEDs) are all molded in resin molds.
When using Sanken’s LEDs, observe the following cautions:
Moisture-proof packaging of Surface Mount LEDs
1. Influence of moisture absorption on resin of surface-mount LEDs
If the resin is unusually damp, solder dipping may cause interfacial peeling.
This phenomenon, generally called “popcorn phenomenon”, occurs when a
drastic temperature change causes moisture in the resin to vaporize and to
Due to this peeling, the efficiency of light emission might worsen and the
luminosity could lower.
2. Moisture-proof packaging
Surface Mount LEDs are protected by a moisture-proof packaging (baked by
Sanken) to minimize moisture absorption by the resin before use.
Aluminum laminates with high moisture resistance are used for packaging.
Silica gel packs are enclosed in each package to further improve moisture
proof efficiency.
3. Storage after opening
Once the package has been opened, solder dipping should be carried out
within seven days.
(Pb-free devices should be reflowed within 48 hours after opening the package.)
4. Handling of Remaining Surface Mount LEDs
If some Surface Mount LEDs have not been used, put them back into the
moisture-proof packaging, seal the package completely and store it in a dry
Heat resistance of mold resin
Since an LED must emit internally generated light with high efficiency, a
highly transparent resin is used for molding. To ensure high transparency,
the molding material must be free from the additives (silica, glass fiber,
and others) that are used to improve the heat and moisture resistance of
other semiconductor components (such as transistors).
Since the resin used for LEDs generally has a low heat resistance, the
following cautions must be fully considered.
Never apply an external force, stress, or excess vibration to the terminals
(leads) at high temperature. The glass transition point of the epoxy resin
used in LEDs is about 120 to 130°C. Beyond this temperature range, the
coefficient of linear thermal expansion becomes more than double that at
room temperature, and the resin softens as well.
Under this condition, an external force or stress may budge the terminals,
and may result in disconnection of the internal wire. Figure 1 shows
reference data for the disconnection temperature and terminal load for the
SEL1010 Series.
not apply heat beyond the absolute maximum rating of the storage
temperature (100°C for ordinary LEDs, 90°C for surface-mount LEDs).
(For soldering, see the soldering conditions.)
Mechanical strength
If an excessive mechanical force is applied between the lens resin and the
terminals, the lens resin or internal connections may be damaged.
Figure 2 shows the fracture strength of the SEL1000 Series according to
the direction of the force applied to the terminals. When aligning or
forming the terminals after soldering, do not bend or twist them with a
force beyond the limits shown in Figure 2.
Figure 1 Disconnection temperature -
Terminal load
Disconnection temperature (°C)
Fracture strength (kg)
Chemical resistance
For washing after soldering, the following chemicals are recommended:
Isopropyl alcohol
Ethyl alcohol
In addition, keep the dip time within five minutes and work at room temperature.
Freon-substitute cleaning liquid
Depending on the constituents, the chemicals may discolor the resin. Make sure
that there will be no problems before use.
Figure 2 Fracture strength
Mounting method
Do not mount the LED in such a way that there is a residual stress between the
terminal and lens resin.
Electrostatic discharge (ESD) precaution
The devices with GaN / InGaN as die ingredients ara electrostatic-sensitive, so
be careful in handling them. Especially when the voltage exceeding the
absolute maximum ratings are applied to the devices, they may be damaged.
Therefore, take complete measure against ESD and surge voltages.
Terminal load (g)
Tensile direction
1. Mounting holes
Please use the printed circuit board with the same mounting hole spacing as
the LED lead pitch.
The recommended PCB hole diameters are as follows:
1. Be sure to form terminals before soldering.
2. When forming the terminals, hold tightly them at a point closer to the
lens resin than the forming position to prevent stress from being
applied between the lens resin and the terminals.
3. Form the terminals only below the tie-bar cuts (protruding part of the
4. Make the forming pitch equal to the board hole pitch.
Lead diameter
PCB hole diameter
0.9 to 1.0
1.0 to 1.1
1.0 to 1.2
2. Direct mount type
(a) Printed circuit board
Single-sided board is recommended. When using a double-sided board, do
not use thru-holes. If the direct mount type LEDs and the surface mount
devices are on the same surface of the board, insert the LEDs after the
adhesives of the surface mount devices are cured.
(b) Insertion condition
Make an insertion pressure lower but enough to insert properly. For cut and
clinch, T pattern of Panasert is recommended. When using N pattern, make
the clinching angle of the anode lead looser, but enough to hold the LED.
Standard Manual insertion of direct-mount type Automatic insertion of
direct-mount type.
Since an overcurrent may burn the LED, connect a protective resistor in
series to prevent a current over 100 mA in the case of a single-pulse
overcurrent (excluding infrared LEDs).
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