Notes on Handling Laser Diodes

Unlike normal transistors and integrated circuits, special care must be given to the following points when handling laser diodes.

5.2.1.1 Eye Protection against Laser Beams

Take care not to allow laser beams to enter your eyes under any circumstances. Using safety goggles that block laser beams is strongly recommended when performing inspection or measurement of a laser diode in the emitting state.

Be sure to observe the laser safety standards specified by IEC60825-1 and JIS standard C6802 “Safety of Laser Products.”

Warning labels such as those shown in Fig. 5-8 below are noted in the product specifications.

For details, see IEC60825-1.

Fig. 5-8 Examples of labels listed in the product specifications Class 3B

Class 4

5.2.1.2 Gallium Arsenide

Laser diodes (except for blue and violet laser diodes) use gallium arsenide (GaAs). This is not a problem for normal use, but GaAs produces poisonous gas when it reacts with acids or steam. Therefore, never crush, heat to the maximum storage temperature or higher, or place a laser diode in your mouth.

In addition, the following disposal methods are recommended when disposing of this product.

1) Engaging the services of a contractor certified in the collection, transport and intermediate treatment of items containing arsenic.

2) Managing the product through to final disposal as specially managed industrial waste which is handled separately from general industrial waste and household waste.

5.2.1.3 Electrical Stress

Laser diodes (LD elements) are one of the most sensitive to electrical stress among semiconductor products, so sufficient care should be taken for handling. It is recommended to monitor the optical power output using the photodiode built into the laser diode or an external photodiode, and to drive the laser diode at a constant power output within the range that does not exceed the recommended power output. When driving at a constant current, the design should take into account the increase in power output at low temperatures in consideration of the temperature dependence of the I-L characteristics.

The Sony Semiconductor Business Unit provides consulting services with the aim of supporting measures for trouble caused by electrical stress at the customer’s premises. Please contact your Sony sales representative when necessary.

(1) Overcurrent and surge current

The laser diode life becomes shorter as the operating optical power output increases. The life cannot be assured when used under conditions that exceed the recommended conditions, so use within the recommended conditions range. In addition, note that if the optical output power exceeds the absolute maximum rating even for an instant, the laser diode may be damaged, which may shorten the life or in the worst case lead to the immediate stop of oscillation. Of the different kinds of damage due to electrical stress, the most common is damage caused by optical power output in excess of the absolute maximum rating. The mechanism is that

“excessive light emission causes the light emission facet to become excessively hot, resulting in structural breakdown of the light emission area.”

<Main causes of overcurrent and surge current>

a. Power supply (excessive overshoot of power-on current, etc.)

b. Adjustment errors (optical output power adjustment knob overrun, etc.)

c. Electrical leakage or inter-line potential difference factors (current flowing simply when a connection is made, etc.)

d. Static electricity (charge carried by the laser diode, charges carried by the human body or other surrounding items, etc.)

e. Connection defects (chattering, etc.)

f. Work errors (circuit cut-off while the power is on, etc.)

g. Operating conditions (used under conditions that exceed the recommended conditions, etc.)

(2) Static electricity

Care should be taken as static electricity as this is cause of surge current flowing to the laser diode.

When static electricity flows in a laser diode, the conditions and the damage mechanism are the same as those of overcurrent. There are various methods for dealing with static electricity depending on the situation, but the basic approaches are as follows in consideration of cost effectiveness.

a. Prevent charges accumulated as static electricity from flowing to laser diode leads.

b. When static electricity cannot be prevented from flowing, implement protective countermeasures and limit the flowing current.

c. Reliably ensure that the laser diode anode and cathode are always the same potential when the power is off.

d. Suppress the generation of static electricity, or eliminate the charge.

* Special care should be taken for static electricity carried by the package of resin package products.

5.2.1.4 Contamination (dust and dirt)

1) Care should be taken to prevent dust and dirt from adhering to the window glass of products, as this may result in reduced optical power output or light emission pattern deformation.

a. Do not touch the window glass.

b. Use an air blower or other non-contact method to remove dirt adhered to the window glass.

Care should be taken when cleaning as mist or other substances in the air may cause secondary contamination, contact by the nozzle may scratch the window glass, or static electricity generated by the air blower may result in ESD breakdown of the product.

2) Care should be taken for the ambient conditions, as corrosive gas or other harmful gases (outgas from the adhesive, etc.) may have an adverse effect on products.

3) The internal elements of open package products may be contaminated if foreign matter (adhesive, solvent, dust, etc.) enters the inside of the package, so take care to prevent the entry of foreign matter. Contamination of the laser diode facet, photodiode light receptor surface or other parts may cause the characteristics to deteriorate.

5.2.1.5 Mechanical Stress

When products are damaged by mechanical stress, leaks from the window glass or airtight parts may cause a

drop in hermeticity, or the laser element and internal connections may be damaged. As a result, product life may be significantly shortened or characteristics may deteriorate.

(1) Outer lead bending

Products with outer leads should be handled with care to prevent lead bending. Damage to the insulating glass at the base of the outer leads may cause a drop in hermeticity.

(2) Outer lead pull-out

Pulling strongly on the outer leads of products with outer leads may cause the leads to fall out, or pressing in strongly may cause the leads to cave in. In particular, the outer leads of a mounted laser diode should be completely freed before pulling out the laser diode.

(3) Package damage

Care should be taken as applying strong force to the laser diode package may cause adhered materials to delaminate, or the package may deform or become chipped or cracked.

(4) Window glass, lens and other glass damage

Applying strong force to the window glass, lens or other glass parts of laser diodes may damage, soil, crack or cause the glass to fall out. In addition, applying strong force to the package may deform the package and cause the window glass, lens or other glass parts to crack or fall out.

(5) Internal element damage

Using tweezers or allowing other items to enter the inside of open package products may damage the internal elements, so take care not to allow these items to enter the inside of the package.

5.2.1.6 Thermal Stress

(1) Operation under a high-temperature environment

The laser diode life becomes shorter as the operating case temperature increases. Care should be taken as the life cannot be assured when used under temperature conditions that exceed the recommended conditions.

(2) Heating due to soldering

Care should be taken as excessive heating during soldering may cause the internal elements of laser diodes to deteriorate.

5.2.1.7 Condensation

(1) Optical path obstruction

When laser diodes are moved quickly from a low-temperature environment to a room temperature or high-temperature environment, condensation may temporarily form on the glass surfaces. Care should be taken as

this may cause the product characteristics to deteriorate temporarily or dirt to adhere to the window glass surface.

(2) Electrochemical reactions

When open package products are operated in the condition with condensation, electrochemical reactions may cause the product characteristics to deteriorate. Avoid use in the condition with condensation.

Customers are requested to visually inspect laser diodes before handling, and to use laser diodes safely and properly.