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Inside a Butterfly - Miniature Thermoelectric Coolers for Telecom Applications
Apr 6, 2009
Tunable lasers have become an industry standard for DWDM applications, providing flexible wavelength-routing capabilities and realizing the all-optical network. Five main basic tunable lasers structures (DFB, VCSEL, DBR, SGDBR, ECL) have one common feature - the importance of temperature stabilization for optimal operating. DWDM Lasers require precise temperature stabilization to isolate LD from ambient temperature conditions, keep wavelength stable and provide long distance transmission.
The miniature thermoelectric (Peltier) coolers, also known as solid-state heatpumps, are the most effective method to control temperature and keep the lasers at precise wavelength. “Butterfly” package with fiber pigtails is the one from two most popular transmitter packaging solutions that can be mounted on a PCB. Typical packaging solution is usually based on 14-pin hermetically sealed “Butterfly” package, that contains inside: Laser Diode (LD), Optical Isolator, Thermoelectric Cooler (TEC), Power-Monitor Photodiode and Wavelength-Monitor Photodiode.
Although 14-pin “Butterfly” package is a de-facto standard for optical fiber telecom industry, there is no strict standard for such parameters as thermoelectric cooler voltage and current. Thus, the telecom industry development has implemented an appearing of telecom oriented thermoelectric coolers family - a range of miniature thermoelectric modules with elongated shape, optimized to fit in “Butterfly” package, - and briefly standardized the electrical consumption and performance parameters.
To the moment there are six typical thermoelectric coolers, that are widely used in telecom industry and being manufactured by different companies - TE coolers with 17, 23, 29, 31, 35 and 50 couples (BiTe elements pairs inside thermoelectric cooler).
TEC Microsystems GmbH specializes in miniature cooling solutions for telecom industry and provides a complete range of TE coolers for “Butterfly” packaging solutions - 1ML06В TEC Series. The brief product map is specified below:
1ML06 Series consists of six thermoelectric cooler types - a standard range for telecom industry as it was mentioned above. The key feature, that TEC Microsystems company provides, is in a variety of combinations and manufacturing options, that extends a product range very widely:
Thermoelectric coolers of 1ML06 Series are widely used not only for DWDM transmitting laser components, but also for high-power 14xx Pump Lasers, Semiconductors Optical Amplifiers (SOAs) and other telecom products, where typical “Butterfly” or similar packages are popular.
TEC Microsystems GmbH provides miniature thermoelectric telecom coolers separately or pre-assembled in Butterfly packages, glass-to-metal or ceramics-to-metal types. The important technical advantage is that TEC Microsystems provides assembly of thermoelectric coolers in packages by soldering, using of lead-free Solder 199 (Sn-Zn, Tmelt=199ºC). With a standard internal lead-free solder for TEC (Sn-Sb, Tmelt=230ºC) the whole final sub-assembly is RoHS compliant high-temperature solution.
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The miniature thermoelectric (Peltier) coolers, also known as solid-state heatpumps, are the most effective method to control temperature and keep the lasers at precise wavelength. “Butterfly” package with fiber pigtails is the one from two most popular transmitter packaging solutions that can be mounted on a PCB. Typical packaging solution is usually based on 14-pin hermetically sealed “Butterfly” package, that contains inside: Laser Diode (LD), Optical Isolator, Thermoelectric Cooler (TEC), Power-Monitor Photodiode and Wavelength-Monitor Photodiode.
Although 14-pin “Butterfly” package is a de-facto standard for optical fiber telecom industry, there is no strict standard for such parameters as thermoelectric cooler voltage and current. Thus, the telecom industry development has implemented an appearing of telecom oriented thermoelectric coolers family - a range of miniature thermoelectric modules with elongated shape, optimized to fit in “Butterfly” package, - and briefly standardized the electrical consumption and performance parameters.
To the moment there are six typical thermoelectric coolers, that are widely used in telecom industry and being manufactured by different companies - TE coolers with 17, 23, 29, 31, 35 and 50 couples (BiTe elements pairs inside thermoelectric cooler).
TEC Microsystems GmbH specializes in miniature cooling solutions for telecom industry and provides a complete range of TE coolers for “Butterfly” packaging solutions - 1ML06В TEC Series. The brief product map is specified below:
1ML06 Series consists of six thermoelectric cooler types - a standard range for telecom industry as it was mentioned above. The key feature, that TEC Microsystems company provides, is in a variety of combinations and manufacturing options, that extends a product range very widely:
- TEC Pellet and performance parameters. TEC pellet is a BiTe element inside the thermoelectric cooler. Briefly, the number of pellets and their configuration influence on TEC electrical and performance parameters. Different pellet height provides different cooling power. TEC Microsystems GmbH with a support of RMT Ltd company provides four pellet height configurations, which covers most of typical telecom application requirements.
- TEC Ceramics. The ceramics can be Al2O3 or AlN with different thickness - standard 0.5mm or thin 0.25mm. AlN is optimal for smooth heat spreading, but as most of LD are mounted on a separate ceramics substrate, the advantage of AlN ceramics can be finally quite small in many cases. Al2O3 ceramics of regular 0.5mm thickness or thin 0.25mm is the most optimal solution. It is cost-effective, which is important in volume manufacturing applications.
- TEC ceramics surface can be blank or metallized depending of customer’s further mounting method. Metallization is based on Ni only plaiting or Au over Ni. Additionally metallized surfaces can be pre-tinned with different solder types to make further mounting more convenient.
- Customized Au patterns can be applied on TEC cold side for mounting of LD, photodiode and thermistor directly on thermoelectric module ceramics
Thermoelectric coolers of 1ML06 Series are widely used not only for DWDM transmitting laser components, but also for high-power 14xx Pump Lasers, Semiconductors Optical Amplifiers (SOAs) and other telecom products, where typical “Butterfly” or similar packages are popular.
TEC Microsystems GmbH provides miniature thermoelectric telecom coolers separately or pre-assembled in Butterfly packages, glass-to-metal or ceramics-to-metal types. The important technical advantage is that TEC Microsystems provides assembly of thermoelectric coolers in packages by soldering, using of lead-free Solder 199 (Sn-Zn, Tmelt=199ºC). With a standard internal lead-free solder for TEC (Sn-Sb, Tmelt=230ºC) the whole final sub-assembly is RoHS compliant high-temperature solution.
