We all know that QSI laser diodes have a heavy market share, so do you know the quality of QSI products? Today, Longxingda Technology, as the general agent of QSI China, will give you a brief introduction.

1. Analysis of heat dissipation performance of QSI laser diode

The heat dissipation performance is directly related to the stability, life and output performance of laser diode. If the heat dissipation is insufficient and the device temperature is too high, the threshold current will increase, the efficiency will decrease, the emission wavelength will drift and even fail.

The following is a comprehensive analysis of QSI in heat dissipation design, temperature index and practical temperature performance based on public information.

1. Temperature specification and packaging form on the product

In QSI's red laser diode products (635-680 nm), many models indicate that the ambient/maximum working temperature is 50 C ~ 70 C, and some low-power models are 40-50 C.

In the infrared band (780-940 nm, etc.), there are also many models with the highest working temperature of 60 °C, 80 °C or higher.

The packaging forms are generally TO-33, TO-56, TO-18, Lead-Frame and other standard metal small packages. The metal package is helpful for the heat to be led out of the laser diode chip and dissipated to the external environment or the device shell through the pin or base.

2. Limitations and challenges of heat dissipation

Although QSI embodies a good design in terms of the working temperature of packaging and labeling, there are still the following heat dissipation challenges to pay attention to:

Power and heat density: When high light power or large current mode (especially continuous wave CW mode), the heat generated is not small. If the thermal resistance between the device chip and the bottom of the package and the heat sink is large, or the external environment is not good, the temperature will easily accumulate.

Temperature drift and efficiency attenuation: Like other laser diodes, with the temperature rising, the threshold current and slope efficiency decrease, and the emission wavelength may drift towards long wavelength, which will affect the stability and optical performance.

Limitation of heat dissipation path: In a small package, the surface area available for contact heat dissipation is limited, and the thermal resistance with the electrical connection structure can not be ignored.

Generally speaking, QSI laser diode is at the top level in heat dissipation design.

Second, QSI laser diode quality evaluation

Quality covers many dimensions: stability, consistency, life, reliability, safety and so on. The following is a comprehensive evaluation of quality based on public information and QSI brand characteristics generally recognized by the industry.

1. Stability and consistency

The benchmark indexes of the same model in different batches (such as threshold current, light output, wavelength, slope efficiency, etc.) have clear minimum-typical-maximum values in the specification table, which shows that the control consistency in the production process is good. For example, model QL85J6S-A/B/C-L has a typical output power of 40 mW in 850 nm band and an operating temperature range of-10 ~+60 C.

2. Life and reliability

Although there may not be a life test curve for each model in the public information, some sales channels mention descriptions such as "Life over 8000 hours at high temperature of 50 °C".

The agreement between the brand and the agent and the product standard generally have the test requirements of high temperature resistance, high humidity, impact resistance and ESD (electrostatic discharge). For example, the data sheets of QSI models clearly indicate its storage temperature, reverse voltage tolerance, photoelectric monitoring diode and other additional functions to ensure long-term reliability.

3. Security and protection mechanism

Most models have PD, which can realize APC or similar automatic power control/monitoring function to avoid overdrive. For example, this feature is found in the QL85J6S-A/B/C-L model.

There are often "absolute maximum rated" parameters in specifications, including maximum reverse voltage, maximum working temperature, storage temperature range, etc., to remind users not to exceed these limits. This helps to prevent damage caused by misuse.

4. Performance indicators (threshold current, slope efficiency, wavelength stability, etc.)

The slope efficiency of several models of optical power vs current has clear data. For example, model QL85J6S-A/B/C-L has a slope efficiency of about 0.6-0.9 mW/mA under the condition of 40 mW output power.

The change of wavelength drift with temperature is generally within the controllable range. There is a big boundary between the product labeling working temperature range (Topr) and the storage temperature range, such as-10 C to+60-70 C, to adapt to the environmental temperature change.

Third, summary of advantages and suggestions

Based on the above analysis of heat dissipation and quality, the following are the main advantages of QSI laser diode and suggestions for attention in practical use.

advantage

The metal package supports good thermal conductivity, and the package is standardized, which is convenient for assembling the radiator or the metal bottom plate.

The reasonable temperature range is wide, and some models can support the ambient temperature of 70-85 °C, which means that they can still work in harsh environments.

Good reliability, high production consistency, monitoring diode and protection specifications, which is helpful to system stability.

The performance is stable, the threshold current, output power and slope efficiency are clear in the product parameters, and customers can design the drive and heat dissipation according to the data sheet.

Suggestions/Precautions

When used in high power or continuous wave mode, it should be matched with good heat dissipation design, such as heat sink, heat sink or heat dissipation bottom plate, and good heat conduction materials.

Be careful not to exceed the maximum working temperature and rated current indicated in the data sheet, so as to avoid performance attenuation or failure caused by heat accumulation.

Prevent thermal mechanical stress (such as temperature control of solder joint and bottom plate) and electrostatic discharge (ESD) from damaging the chip and package during welding or assembly.

In the application of pursuing long life, we can consider slightly reducing the light output or running at a slightly lower current to increase the derating and reduce the heat load.

Generally speaking, QSI laser diode performs well in heat dissipation performance and quality, and it is an option with high quality and good reliability in the industry. If the cooling system is designed reasonably and the operating conditions are controlled, its stability and service life can meet the high-demand applications.