Thermoelectric cooler

• US 5,441,576 A
• Filed: 05/24/1994
• Issued: 08/15/1995
• Est. Priority Date: 02/01/1993
• Status: Expired due to Fees

• Current Assignee: Marlow Industries, Inc. (Coherent Corp.)
• Original Assignee: Fry's Metals Incorporated (Element Solutions Inc)
• Inventors: Bierschenk, James L., Howarth, Richard A., Socolowski, Norbert J.
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): CARROLL, CHRISMAN DION
• Application Number:
  US08/248,537
• Time in Patent Office: 448 Days
• Field of Search: 136/203, 136/204, 136/224, 136/225, 136/237
• US Class Current: 136/203
• CPC Class Codes: H10N 10/13 characterised by the heat-exchanging means at the junction
• CPC Class Codes: H10N 10/817 the junction being non-separable, e.g. being cemented, sintered or soldered

Abstract

A thermoelectric heat pump which is resistant against thermal stresses incurred during thermal cycling of Thermal Cyclers or the like between cold and hot temperatures of about 0° C. at a ramping rate up to about 1° C. per second has improved joints between the thermoelements and electrical conductors which have low electrical resistance and which substantially reduce fractures during thermal cycling. The joints include a tin-silver-indium solder containing by weight about 95% tin, 3.5% silver, and 1.5% indium, or a tin-silver-cadmium solder containing by weight about 95.5% tin, 3.5% silver, and 1.0% cadmium. A robust nickel diffusion barrier between the joints and thermoelectric elements ends provides additional improvement against joint fracture.

Claims

1. A thermoelectric heat pump for a thermal cycler comprising:

first and second type thermoelectric legs;

tin-silver-indium or tin-silver-cadmium bonding means connected to the first and second type thermoelectric legs being cycled alternately between cold and hot temperatures of about 0°

C. up to about 100°

C. at a ramping rate of about 1°

C. per second;

conductive tab means attached to the bonding means for connecting the legs in series to form a thermocouple, and

insulator means connected to the conductive tab means for preventing shorts when the thermoelectric heat pump is connected to a sample holder of a thermal cycler.

2. A thermoelectric heat pump according to claim 1 wherein the solder is about 95 weight percent tin, 3.5 weight percent silver, and 1.5 weight percent indium.

3. A thermoelectric heat pump according to claim 1 wherein the solder is about 95.5 weight percent tin, 3.5 weight percent silver, and 1.0 weight percent cadmium.

4. A thermoelectric heat pump for a thermal cycler or the like comprising:

first and second different type thermoelectric legs having first and second opposing ends, and first and second diffusion barriers formed on the first and second opposing ends;

bonding means operatively formed on the diffusion barriers of the opposing ends of the thermoelectric legs; and

conductive tab means attached to the bonding means for connecting the legs in series to form a thermocouple;

said bonding means comprising a tin-silver-indium solder or tin-silver-cadmium solder for providing a thermoelectric heat pump being cycled between low and high temperatures of about 0°

C. up to about 100°

C. at a rate of 1°

C. per second.

5. A thermoelectric cycler comprising:

a sample holder means for holding samples;

an improved thermoelectric heat pump operatively connected to the sample holder means for thermal cycling the sample holder between about 0°

C. and 100°

C. at a ramping rate of about 1°

C. per second, said thermoelectric heat pump including different type thermoelectric legs having first and second opposing ends, diffusion barriers formed on the first and second opposing ends, first and second arrays of conductor tab means, and a bonding means having a tin-silver-indium or a tin-silver-cadmium solder means for connecting the opposing ends of the thermoelectric legs and arrays of conductor tab means with the diffusion barrier material there between for forming thermoelectric couples, the tin-silver-indium or tin-silver-cadmium solder means being resistant to thermal stresses during the thermal cycling at the ramping rate whereby the number of cycles to failure of the thermoelectric heat pump is increased;

a power supply means connected to the thermoelectric couples for supplying a dc current to the thermoelectric couples for producing alternating cold and hot effects; and

a controller means connected to the power supply means for controlling the polarity of the dc current applied to the thermoelectric couples, for cycling the thermal cycler and setting the ramping rate.