Patent Publication Number: US-2022212400-A1

Title: Method for making a metal isolator body and associated device including the same

Description:
GOVERNMENT RIGHTS 
     This invention was made with government support under classified government contract. The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of thermal isolators, and more particularly, to a method of making a thermally isolated body out of a thermally conductive metal and corresponding device including the same. 
     BACKGROUND 
     Thermal isolators are used to isolate heat sources from heat sensitive components. For example, space systems in general experience extreme changes in temperature when orbiting the earth. Extreme temperature changes can have adverse effects on heat sensitive components within the space systems. Thermal isolators block or slow the flow of heat from the heat sources to the heat sensitive components. 
     Design engineers take into account the operating temperature of the heat sensitive components when selecting the type of material to be used as a thermal isolator. Low thermal conductivity materials such as thermoplastics and ceramics are typically used as thermal isolators. 
     A problem for design engineers is that thermal isolators are often in contact with metal assemblies that make up the rest of the system. These metal assemblies include the heat sensitive components and the heat sources. Even though thermoplastics and ceramics are good thermal isolators, they have mechanical properties that are different than the metal assemblies. 
     When thermoplastic is introduced into a metal assembly as a thermal isolator, it begins to soften at high temperatures. When the high temperatures approach 200° C. the thermoplastic starts to break down. In contrast, ceramic can withstand a higher temperature limit above 200° C. but is much stiffer and more brittle than the surrounding metal components. 
     Design engineers may have to compromise system parameters of the metal assemblies, such as stiffness or operating temperature, to isolate heat sensitive components. Operating temperatures of the metal assemblies may be curtailed by thermoplastic limitations, whereas reliability of the metal assemblies may be reduced by ceramic durability limitations. 
     As an alternative to thermoplastics and ceramics, a metal such as titanium may be used as a thermal isolator because it has a lower conductivity than other metals typically found in aerospace assemblies. Even though titanium maintains the structural integrity of the metal assembly, there is a coefficient of thermal expansion (CTE) mismatch with the metal assembly. Consequently, there may be a need for a thermal isolator for a metal assembly for isolating a heat sensitive component from a heat source without compromising system parameters. 
     SUMMARY 
     A method for making a metal isolator body to be positioned between a heat sensitive component and a heat source includes obtaining at least a thermal conductivity specification and a load specification for the metal isolator body, generating a metal isolator body design including solid regions and lattice regions to meet at least the thermal conductivity specification and the load specification, and using three dimensional(3D) metal printing to form the metal isolator body based upon the metal isolator body design. 
     The 3D metal printing advantageously allows a thermal isolator to be formed out of a thermally conductive metal by being able to print the lattice regions that are used to tailor the thermal properties of the metal isolator body to meet the thermal conductivity specification. The ability to create a thermal isolator out of metal means that design engineers may no longer have to compromise system parameters, such as stiffness or operating temperature, to isolate heat sensitive components. 
     The method may further comprise obtaining a coefficient of thermal expansion (CTE) specification for the metal isolator body, and generating the metal isolator body design including solid regions and lattice regions to also meet the CTE specification. The metal isolator body may thus comprise a same metal as at least one of the heat source and the heat sensitive component. 
     The metal isolator body may comprise a cold face to be positioned adjacent the heat sensitive component, and a hot face to be positioned adjacent the heat source. The metal isolator body may have at least one fastener receiving passageway extending between the cold face and the hot face. 
     Generating the metal isolator body design may comprise forming a continuous solid region surrounding the at least one fastener receiving passageway. Generating the metal isolator body design may comprise generating the metal isolator body design to include lattice regions exposed on an outer surface of the metal isolator body to permit airflow therethrough. 
     Generating the metal isolator body design may comprise generating the metal isolator body design so that the metal isolator body has a thermal conductivity less than one tenth a thermal conductivity of a hypothetical solid metal body having a same outer shape as the metal isolator body. 
     Another aspect is directed to a method for isolating a heat sensitive component from a heat source comprising generating a metal isolator body design including solid regions and lattice regions to meet at least a thermal conductivity specification and a load specification, using three dimensional (3D) metal printing to form the metal isolator body based upon the metal isolator body design, and positioning the metal isolator body between the heat sensitive component and the heat source. 
     Yet another aspect is directed to a device comprising a housing with a heat sensitive component, a thermal isolator coupled to the housing and comprising a metal isolator body including solid regions and lattice regions to meet at least a thermal conductivity specification and a load specification, and a heat source coupled to the thermal isolator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a metal assembly with a metal isolator body positioned between a heat sensitive component and a heat source according to the invention. 
         FIG. 2  is a flowchart illustrating a method for making the metal isolator body illustrated in  FIG. 1 . 
         FIG. 3  is an upper perspective view of the metal isolator body illustrated in  FIG. 1 . 
         FIG. 4  is a lower perspective view of the metal isolator body illustrated in  FIG. 1 . 
         FIG. 5  is a close-up partial view of the lattice regions in the metal isolator body illustrated in  FIGS. 4 and 5 . 
         FIG. 6  is a flowchart illustrating a method for isolating the heat sensitive component from the heat source illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the disclosure are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     Referring initially to  FIGS. 1 and 2 , a method for making a metal isolator body  50  for a metal assembly  40  will be discussed. The metal assembly  40  includes a heat sensitive component  42  and a heat source  46 , and the metal isolator body  50  is to be positioned therebetween. 
     The metal assembly  40  is not limited to any particular system or setup. As an example, the metal assembly  40  may be part of a satellite where the heat sensitive component  42  is a processor within a transceiver card carried by a metal housing  41 , and the heat source  46  is the skin of the satellite. As the skin of the satellite is exposed to sunlight, the skin becomes the heat source  46 . The metal housing  41  is in contact with the thermal isolator  50  which is in contact with the skin of the satellite, i.e., the heat source  46 . 
     In the illustrated flowchart  20 , the method includes, from the start (Block  22 ), obtaining at least a thermal conductivity specification and a load specification for the metal isolator body  50  at Block  24 , and generating a metal isolator body design at Block  26 . The metal isolator body design includes solid regions  52  and lattice regions  54  to meet at least the thermal conductivity specification and the load specification. Three dimensional (3D) metal printing is used at Block  28  to form the metal isolator body  50  based upon the metal isolator body design. The method ends at Block  30 . 
     The 3D metal printing advantageously allows a thermal isolator to be formed out of a thermally conductive metal by being able to print the lattice regions  52  that are used to tailor the thermal properties of the metal isolator body  50  to meet the thermal conductivity specification. 
     In addition to designing the metal isolator body  50  to meet a thermal conductivity specification and a load specification, the method may further include obtaining a coefficient of thermal expansion (CTE) specification for the metal isolator body  50 . The metal isolator body design is generated to also meet the CTE specification. 
     The metal isolator body  50  may thus be formed from a same metal as at least one of the heat source  46  and the heat sensitive component  42 . The ability to create a thermal isolator out of the same metal that may be used to form the rest of the metal assembly  40  means that design engineers may no longer have to compromise system parameters, such as stiffness or operating temperature, to isolate heat sensitive components  42 . 
     An example metal isolator body  50  will now be discussed in reference to  FIGS. 3-5 . The illustrated metal isolator body  50  is designed to meet a thermal conductivity specification and a load specification. The solid regions  52  allow the metal isolator body  50  to meet the load specification, while the lattice regions  54  provide strength but also allow the metal isolator body  50  to meet the thermal conductivity specification. The metal isolator body  50  may have other sizes or shapes as will be appreciated by those skilled in the art. The orientation and positioning of the solid and lattice regions  52 ,  54  will be based on the predetermined thermal conductivity and load specifications supporting the intended application of the metal isolator body  50 . 
     The metal isolator body  50  includes a cold face  62  to be positioned adjacent the heat sensitive component  42 , and a hot face  66  to be positioned adjacent the heat source  46 . The solid regions  52  correspond to fastener receiving passageways  60  extending between the cold face  62  and the hot face  66 , where a continuous solid region  52  surrounds each fastener receiving passageway  60 . 
     The lattice regions  54  are exposed on an outer surface of the metal isolator body  50  to permit airflow therethrough. The lattice regions  54  include metal lines or sections  70  coupled together with square or diamond-shaped spaces  72  left between, as best illustrated in  FIG. 5 . The square or diamond-shaped spaces  72  advantageously may define an overwhelming majority of the volume of the metal isolator body  50 . The conductivity of air is several orders of magnitude lower than that of most metals which allows the metal isolator body  50  to function as a thermal isolator. Of course, the metal isolator body  50  may also be used in a vacuum environment, such as in space. The 3D printing allows geometries such as the lattice regions  54  to be obtained. Without 3D printing, forming lattice regions in a metal isolator body may be extremely difficult. A powder bed fusion (PDF) process may be used for 3D printing. Powder bed fusion includes the following commonly used printing techniques: direct metal laser sintering (DMLS), electron beam melting (EBM), selective heat sintering (SHS), selective laser melting (SLM) and selective laser sintering (SLS). The powder bed fusion (PBF) methods use either a laser or electron beam to melt and fuse material powder together. Of course, other 3D printing techniques may be used, as readily appreciated by those skilled in the art. 
     As readily understood by those skilled in the art, thermal conductivity is the property of a body to conduct heat. Heat transfer occurs at a lower rate across a body of lower thermal conductivity than across a body of higher thermal conductivity. For comparison purposes, the illustrated metal isolator body  50  may have a have a thermal conductivity less than one tenth a thermal conductivity of a hypothetical solid metal body having a same outer shape as the metal isolator body. 
     Another aspect is directed to a method for isolating the heat sensitive component  42  from the heat source  46 . Referring now to the flowchart  100  illustrated in  FIG. 6 , the method includes, from the start (Block  102 ), generating a metal isolator body design including solid regions  54  and lattice regions  52  to meet at least a thermal conductivity specification and a load specification at Block  104 . Three dimensional (3D) metal printing is used at Block  106  to form the metal isolator body  50  based upon the metal isolator body design. The method further includes positioning the metal isolator body  50  between the heat sensitive component  42  and the heat source  46  at Block  108 . The method ends at Block  110 . 
     Yet another aspect is directed to a device  40  comprising a housing  41  with a heat sensitive component  42 , and a thermal isolator coupled to the housing and comprising a metal isolator body  50  including solid regions  52  and lattice regions  54  to meet at least a thermal conductivity specification and a load specification. A heat source  46  is coupled to the thermal isolator. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.