Patent Publication Number: US-10763647-B2

Title: Ground contact integrated into welding protection strip

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority, under 35 U.S.C. § 119, of European application EP 17185502.6, filed Aug. 9, 2017; the prior application is herewith incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an assembly, particularly in the form of an implantable medical device such as cardiac pacemaker, particularly an implantable leadless pacemaker (iLP) or a loop recorder. 
     Usually, an electronic circuit of such an assembly has to make electronic contact with a surrounding housing (ground potential). 
     In the prior art, such contacts are e.g. established by using a separate ground pin connected via a small wiring band to the circuit. As a consequence enough installation space has to be provided in order to fit this type of a connection into the housing of the assembly/medical device. Thus, less installation space is available for actual components of the circuit. Further, costs for such small wiring bands are not negligible. Furthermore, the handling of such wiring bands often leads to problems such as faulty electrical contacts and frequently requires time consuming manual correction/adjustment. 
     Furthermore, U.S. Pat. No. 8,968,919 B2 discloses welding strips that are used as electrical connection devices for contacting battery cells. 
     SUMMARY OF THE INVENTION 
     Based on the above, the problem to be solved by the present invention is to provide an improved way of providing an electrical connection between a ground connection of an electronic circuit and a housing enclosing the circuit. 
     This problem is solved by an assembly having the features of the main apparatus claim as well as by a method having the features of the main method claim. Preferred embodiments of these aspects of the present invention are stated in the corresponding sub claims and are described below. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, an assembly, comprising: 
     a) a housing defining an internal space of the assembly, 
     b) an electronic circuit arranged in the internal space, and 
     c) a protection strip arranged in the internal space for protecting the electronic circuit against external influences. 
     Wherein according to the present invention, the protection strips forms a ground conductor that is electrically connected to the housing and to a ground connection of said electronic circuit. 
     Thus, the present invention integrates the function of electrically connecting the circuit to the housing into the already existing protection strip so that special components such as a separate ground pin and an associated wiring band can be omitted. Besides the fact that the number of parts is reduced also installation space is saved and can be used for further components of the actual circuit. Alternatively, the free installation space provides the possibility to further miniaturize the assembly. 
     Particularly, the assembly can be or can form part of a medical device, particularly an implantable medical device, a cardiac pacemaker, particularly an implantable leadless pacemaker (iLP), or a loop recorder etc. 
     Further, particularly, in an embodiment the protection strip is configured to protect the electronic circuit against temperature influences, particularly external heat (see also below). 
     Further, according to an embodiment of the assembly according to the present invention, the housing comprises two housing parts, particularly shells, wherein each housing part comprises a circumferential boundary area, wherein the boundary areas are connected to form the housing. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the housing parts are connected via a welding seam that connects the boundary areas. The welding seam may be formed using laser welding or another suitable technique. 
     Further, according to an embodiment of the assembly according to the present invention, the protection strip is configured to protect the electronic circuit against external influences generated upon welding of the welding seam. Such influences can be heat that is generated by the welding process as well as welding material splatter. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the protection strip is arranged such that in the internal space it overlaps with both boundary regions on an inside of the housing, which inside faces the electronic circuit. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the protection strip comprises a wing protruding from an elongated portion of the protection strip that extends along the circumferential boundary area of the first housing part, which wing is particularly bent down towards the ground connection and connected, particularly welded, to the ground connection of the electronic circuit so that the wing stands in electrical contact with the ground connection. 
     Particularly, in an embodiment, the electronic circuit is arranged on a substrate, which can be formed by a printed circuit board (PCB). Particularly, the ground connection can be formed by a contact pad that is arranged on the substrate. 
     Further, particularly, the protection strip extends along a periphery of a substrate, particularly a printed circuit board, which substrate carries the electronic circuit. 
     Further, particularly, according to an embodiment the protection strip may comprise two opposing ends, wherein the respective end is in electrical contact with a sleeve that protrudes through a through hole of the housing out of internal space of the housing, wherein particularly the through hole is formed by a first and a second recess, wherein the first recess is formed in the boundary area of the first housing part, and wherein the second recess is formed in the boundary area of the second housing part. 
     According to an embodiment of the present invention, the sleeve is configured as a feedthrough flange which is welded to the housing. The sleeve can for instance be configured to contain the connection pin and/or guide an antenna of the assembly, e.g. a silicone antenna. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the housing or the housing parts is/are formed out of or comprises titanium. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the protection strip is formed out of or comprises metal alloy material, for instance constantan. 
     Furthermore, according to an embodiment of the assembly according to the present invention, the ground connection (e.g. ground connection pad on substrate/PCB of electronic circuit) is formed out of or comprises metal alloy material, for instance constantan. 
     According to an embodiment of the present invention, the protection strip and the ground connection are made of similar materials in order to allow connecting them via a welding process (e.g. laser welding). 
     Yet another aspect of the present invention relates to a method for producing an assembly, particularly an assembly according to the present invention. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a method which comprises the steps of: 
     a) providing a first and a second housing part, an electronic circuit, and a protection strip, 
     b) mounting the protection strip to the first housing part, so that the protection strip is in electrical contact with the first housing part, 
     c) arranging the electronic circuit in an internal space of the first housing part, 
     d) establishing an electrical connection between the electronic circuit and the protection strip, 
     e) arranging the second housing part on the first housing part, and 
     f) connecting the first housing part to the second housing part so as to form a housing which hermetically seals said electronic circuit. 
     Furthermore, according to an embodiment of the method according to the present invention, establishing the electrical connection between the electronic circuit and the protection strip comprises the steps of: bending a wing of the protection strip towards a ground connection (e.g. ground connection pad, see above) of the electronic circuit, which wing particularly protrudes from an elongated portion of the protection strip that extends along a circumferential boundary area of the first housing part, and connecting, particularly welding, the wing to the ground connection so that the wing stands in electrical contact with the ground connection of the electronic circuit. 
     Furthermore, according to an embodiment of the method according to the present invention, the protection strip is arranged along the boundary area of the first housing part on an inside of the first housing part so that the protection strip protrudes past the boundary area of the first housing part, particularly so as to be able to also overlap with the boundary area of the second housing part once the second housing part is arranged on the first housing part so that their boundary areas are arranged on one another. 
     Furthermore, according to an embodiment of the method according to the present invention, the protection strip is welded to the first housing part, particularly to the boundary area of the first housing part. Laser welding can be applied to weld the protection strip to the boundary area of the first housing part. 
     Furthermore, according to an embodiment of the method according to the present invention, the second housing part comprises a circumferential boundary area, wherein the circumferential boundary area of the second housing part is welded to the circumferential boundary area of the first housing part to form a housing that encloses the electronic circuit, wherein the protection strip protects the electronic circuit upon welding of the first housing part to the second housing part. 
     Integrating the ground contact into the welding protection strip saves installation space, which may be used to reduce the overall size of the assembly/housing or may provide additional space for electrical components.  FIG. 4  shows the free installation space in case of a medical monitoring device. The usual ground connection (e.g. pin) according to the prior art would be located in the space marked by the ellipse. This space can now be used completely by other components. Furthermore, the additional wing of the protection strip almost constitutes no extra cost since the basic shape is realized using a cutting, etching or pressing process. Furthermore, a wiring band can be omitted that would be needed to connect said pin to the ground connection of the circuit. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a ground contact integrated into a welding protection strip, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagrammatic, perspective view of a first (lower) and a second (upper) housing part of a housing of an assembly according to the present invention as well as a protection strip connected to the first housing part; 
         FIG. 2  is a perspective view of the first housing part of  FIG. 1  and an electronic circuit arranged in the first housing part, wherein a wing of the protection strip protrudes upwards; 
         FIG. 3  is a perspective view of the assembly of  FIG. 2  with the wing bent downwards onto a ground connection of the electronic circuit; and 
         FIG. 4  is a top view of the assembly shown in  FIGS. 1 to 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown in conjunction with  FIGS. 2 to 4  an assembly  1  according to the present invention. The assembly  1  comprises a housing  10  ( FIG. 1  indicates the two housing parts  11 ,  12  forming housing  10 ), which housing  10  defines/encloses an internal space  2  of the assembly  1 . The assembly  1  further comprises an electronic circuit  20  arranged in the internal space  2 , and a protection strip  30  arranged in the internal space  2  for protecting the electronic circuit  20  against external influences. According to the present invention, the protection strip  30  forms a ground conductor that is electrically connected to the housing  10  and to a ground connection  21  of the electronic circuit  20 . 
     Particularly, the electronic circuit  20  is arranged on a substrate  22 , here in the form of a printed circuit board, wherein the ground connection  21  is formed as a pad  21  arranged on the substrate  22 . 
     As indicated in  FIG. 1 , the housing  10  comprises two housing parts  11 ,  12 , here e.g. formed as shells  11 ,  12 , wherein each housing part  11 ,  12  comprises a circumferential boundary area  11   a ,  12   a , which boundary areas  11   a ,  12   a  are to be connected by a welding seam  13  which may be generated using laser welding. The position of the seam  13  is indicated in  FIG. 4 . Particularly, the protection strip  30  is configured to protect the electronic circuit  20  against external influences such as heat and welding material splatter generated upon welding of the welding seam  13 . 
     In order to protect the circuit  20 , the protection strip  30  is particularly arranged such in the housing  10  that it extends around the periphery of the substrate  22  of the electric circuit  20 . The protection strip  30  overlaps both boundary areas  11   a ,  12   a  of the housing parts  11 ,  12  and thus covers a gap between these boundary areas  11   a ,  12   a  from an inside  10   a  of the housing  10  when the boundary areas  11   a ,  12   a  are arranged on one another (e.g. by lowering the second housing part  12  down to the first housing part  11  as indicated by the arrow in  FIG. 1 ). This position of the protection strip  30  can be achieved by connecting, particularly welding, the protection strip  30  to the first housing part  11  such that it protrudes beyond the boundary area  11   a  of the first housing part  11  as shown in  FIG. 1 . 
     For electrically contacting the ground connection  21  of the electronic circuit  21 , the protection strip  30  comprises a wing  31  that protrudes from a portion  32  of the protection strip  30  that extends along the circumferential boundary area  11   a  of the first housing part  11 . This wing is bent downwards (see  FIGS. 2 and 3 ) and is then connected, particularly welded, to the ground connection  21  of the electronic circuit  20  so that the wing  31  stands in electrical contact with the ground connection  21 . 
     Further, additionally, as shown in  FIGS. 1 to 4  the protection strip  30  may comprise two opposing ends  33 ,  34 . A respective end  33 ,  34  is in electrical contact with a sleeve  50  that protrudes through a through hole  51  of the housing  10  out of internal space  2  of the housing  10 . The through hole  51  is formed by a first recess  52  and a second recess  53 . The first recess  52  is formed in the boundary area  11   a  of the first housing part  10 , and the second recess  53  is formed in the boundary  12   a  area of the second housing part. When the two housing parts  11 ,  12  are connected to each other the two recesses  52 ,  53  meet and form the through hole  51  for the sleeve  50 . 
     Integrating the ground conductor into the protection strip  30  as described herein frees installation space as indicated in  FIG. 4  by the ellipse. This additional installation space can be used for further electrical components. Alternatively, the overall size of the housing  10  can be reduced. 
     It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.