In Situ Welding for Feedthrough Pad Attachment

Abstract

The present invention relates to a method for manufacturing an electrical feedthrough assembly of an electric device, the method comprising the step of: providing an electrical feedthrough assembly comprising an insulating body and at least one electrically connecting element extending through said insulating body, and joining said at least one electrically connecting element with a solderable element, wherein joining is performed by an arc welding process. The invention further relates to a respective feedthrough assembly and an electric device comprising such feedthrough assembly.

Claims

1. Method for manufacturing an electrical feedthrough assembly for an electrical device, the method comprising the step of: providing an electrical feedthrough assembly comprising an insulating body and at least one electrically connecting element extending through said insulating body, and joining said at least one electrically connecting element with a solderable element, wherein joining is performed by an arc welding process.

2. The method according to claim 1, wherein joining comprises applying a voltage to said at least one electrically connecting element or said solderable element and approaching said electrically connecting element and said solderable element.

3. The method according to claim 1, wherein said connecting element and/or said solderable element is positioned or aligned before and/or during joining by means of a gantry type fixture, wherein said connecting element and/or said solderable element is coupled to said fixture.

4. The method according to claim 1, wherein said method is automated performed.

5. The method according to claim 1, wherein said at least one electrically connecting element is designed as a wire or a pin, and comprises or essentially consists of platinum, platinum/iridium, niobium, tungsten, platinum/rhenium, or an alloy thereof.

6. The method according to claim 1, wherein said solderable element designed as a terminal block or pad, and comprises or essentially consist of nickel, copper, or an alloy thereof.

7. The method according to claim 1, wherein said insulating body comprises or essentially consists of glass or ceramic.

8. The method according to claim 1, wherein said insulating body is surrounded by a metal flange, which is brazed to said insulating body, wherein said metal flange comprises or essentially consists of titanium or a titanium alloy.

9. Electrical feedthrough assembly, comprising an insulating body, at least one electrically connecting element extending through said insulating body, and a solderable element joined to said at least one electrically connecting element, wherein said solderable element is arc welded to said at least one electrically connecting element.

10. The electrical feedthrough assembly according to claim 9, further comprising a metal flange, comprising or essentially consisting of titanium or a titanium alloy, surrounding said insulating body, wherein said flange is brazed to said insulating body, and wherein said insulating body is made of or comprises glass or ceramic.

11. The electrical feedthrough assembly according to claim 9, wherein said electrically connecting element is designed as a wire or a pin, and comprises or essentially consists of platinum, platinum/iridium, niobium, tungsten, platinum/rhenium or an alloy thereof.

12. The electrical feedthrough assembly according to claim 8, wherein said solderable element is designed as a terminal block or pad, and comprises or essentially consists of nickel, copper, or an alloy thereof.

13. Electrical device comprising, a housing, comprising or essentially consisting of titanium or a titanium alloy, and an electrical feedthrough assembly according to claim 9.

14. The electrical device according to claim 13, further comprising an electronic module or electric component, wherein at least one solderable element of said electrical feedthrough assembly is soldered to said electronic module or electric component.

15. The electrical device according to claim 13, wherein said electric device is designed as a medical device, comprising an implantable medical device, or as a battery, or a capacitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Further advantages, features and embodiments of the present invention will be explained hereinafter with reference to the drawings, in which:

[0052] FIG. 1 shows a schematic illustration of an electrical feedthrough assembly;

[0053] FIG. 2 shows an implantable medical device;

[0054] FIG. 3 shows schematic illustration of a general concept of the method of the present invention; and

[0055] FIG. 4 shows one embodiment of the method of the present invention.

DETAILED DESCRIPTION

[0056] Ceramic feedthroughs 100 are used to provide a hermetically sealed electrical path from the inside of an implantable electrical device 200 to the outside 203 (body contact side of the device). Typically, discrete wires or conductors 101 are utilized to convey electrical signals and electrical therapy from an electric pulse generator 202 to a lead, electrode or paddle or diagnostic signal the other way round. These wires 101 are often designed to be biocompatible with the blood stream for applications where the device is inside the body. Few conduction materials are body compatible, and almost none of those can be soldered using traditional tin (Sn) based alloys. This necessitates the requirement that a different material, one that is solderable to the internal electrical components 202 be connected to the discrete wires 101 in the feedthrough 100.

[0057] A typical ceramic feedthrough 100 is shown in cross section in FIG. 1. The feedthrough comprises an insulating ceramic body 102, through which a plurality of connecting pins or wires 101 extends. Typically, the pins or wires 101 are made of platinum, platinum/iridium or niobium and are brazed, particularly gold brazed, to the insulating ceramic body 102.

[0058] The insulating ceramic body 102 is usually surrounded by and brazed with a metal flange 104, preferable made of titanium or a titanium alloy, for joining the feedthrough 100 with a housing 201 of an electrical device 200 such as an implantable pulse generator. To facilitate soldering the connecting pins or wires 101 to electric or electronic components 202, solderable pads 103 are attached to the connecting pins or wires 101.

[0059] FIG. 2 shows the above mentioned typical use case for an implantable pulse generator 200 utilizing feedthrough technology 100. This implantable pulse generator 200 comprises a housing 201, typically made of titanium or a titanium alloy, wherein the feedthrough 100 is joined to the housing 201 via the flange 104 of the feedthrough 100, preferably by welding.

[0060] The implantable pulse generator 200 further comprises electronic and electric components 202 such as power source, integrated circuits, etc. to which the connecting pins 101 are soldered via the attached solderable pads 103.

[0061] One objective of the present invention is to establish an automated method of attaching pads 103 to pins 101 in feedthrough components 100, while minimizing the number of high temperature thermal exposures the components experience in fabrication. One goal of this approach is to allow for an assembly process in which the bonding of the pad 103 and pin 101 happens in the automated assembly process itself. The tooling 301, 303 utilized in the feedthrough assembly process can be designed to bring all pins 101 to the same required high voltage potential. The tooling 301, 303 can be brought very near another fixture 302 that contains the solder pads 103. The close proximity and correct current pulses can create an electrical arc. The arc, like a spark plug tip, can reach several thousand degrees, thus melting the surface of each material 101, 103. The arc and simultaneous motion of the feedthrough fixture 301 towards the pad fixture 302 will cause the two features (pad 103 and pin 101) to touch. Once touching, the arc will be quelled since the potential difference is reduced to zero. Once the arc stops, the two parts 101, 103 will solidify and since they are in direct contact, they will be welded together.

[0062] Accordingly, the present invention particularly refers to a method for directly attaching solderable pad structures 103 to typical pins 101 utilized in the construction of ceramic type feedthroughs 100. The method provides for a direct, particularly in situ, attachment of the solder pad 103 to the conductor pins 101 during the manufacturing process.

[0063] In detail, an electrical circuit is created in the assembly fixture 301, 302 to apply high voltage to each pin 101, particularly by a voltage source 303. The pad 103 is placed in an electrically connected fixture 302 (grounding side of the circuit) such that when the two fixtures 301, 302 are brought in close proximity, an electrical spark or arc is created between the fixture 301 with the feedthrough 100 and the solder pad 103. Once the two fixtures 301, 302 are brought in contact, the arc is quenched and the two surfaces (pin 101 and pad 103) will be connected. The extreme heat of the arc causes the tip of the pin 101 and pad 103 to melt, and once the arc is quenched, the two molten materials 101, 103 solidify together to form a connected structure. One main advantage of this method is that the process can take place at room temperature since the heat is locally applied to each pin/pad via the electrical arc/current. Current methods used for this process typically involve subjecting the entire feedthrough assembly 100 to a high temperature brazing furnace (1100° C.).

[0064] The process can be used several ways, however, an electrical test/assembly head is preferred that interfaces with the top or shaft of the pins. This may be a cable or wire assembly that terminates in a connector. The connector may be a block of receptacles (pin connector) that presses overtop of the pins. Particularly, the connector may have cup like shape, in which the pin rests inside the cup wall.

[0065] Advantageously, all pads 103 may be attached to the pins 100 simultaneously by contacting all feedthrough pins 100 in parallel. A fixture set 301, 302 may be provided to automate the process, in which a fixture head is movable from assembly to assembly, and with which all feedthrough pins of one assembly may be attached to corresponding pads in parallel.

[0066] Alternatively, parallel fixture heads may be provided, with which a plurality of feedthrough assemblies may be manufactured in parallel, particularly facilitating a higher throughput manufacture.

[0067] FIG. 3 shows an illustration of the principal approach to connect the pads to the pins. Here, each pin 101 of a feedthrough assembly 100 is connected to a voltage source 303. The solderable pads 103 to be joined are attached or coupled to a fixture 302, by with the solderable pads 103 can be positioned to and aligned with the pins 101. Advantageously, the fixture 302 is made of an electrically conductive material and may serve as a ground electrode. Joining of pins 101 and pads 103 is conducted by applying a current to the pins 101 and moving the pins 101 and the fixtures 302 towards each other as indicated by the arrows. At a certain distance, an arc will emerge between an individual pin 101 and a corresponding pad 103, whereby the tip of the pin and the solderable pad begins to melt. Upon further approaching, the pin 101 and the pads contact each other, whereby the arc is quenched and a metallurgical connection forms.

[0068] FIG. 4 illustrates one preferred embodiment of the method of the present invention. Therein it is envisioned to couple an overhead X-Y-Z gantry type fixture 301 or machine with an electrical pulse control circuit 303. The overhead gantry type fixture 301 is preferable movable in all three spatial dimensions as indicated by the arrows X and X-Y. Furthermore, the overhead gantry type fixture 303 preferably has connector like features 304, by which the pins 101 on the feedthrough 100 can engage the electrical connections within the fixture 301. Spring contacts 304, for example, may be used to connect the pins 101 with the gantry type fixture 301. A control circuit 303 that is configured to control the electrical voltage and pulse parameters may be used to ramp the potential up in each pin 101 circuit. The time, pulse frequency and amount of current are preferably controllable. The specific parameters for voltage, frequency and current flow depends on the specific material sets being used (pin type, pad type and geometry).

[0069] Preferably, an automated test cell or placement robotic cell may be used to pick up the fixtures 303, 302, each feedthrough 100, and control the motion, e.g. in X-Y-X directions, of the process. Advantageously, the electrical high voltage test equipment often used for these types of components may be used to thus combine processes. This automation is particularly useful to reduce manufacturing labor and cost and to provide high volume manufacturing.

[0070] The present invention particularly provides the following advantages:

[0071] In typical feedthrough manufacturing, the pads 103 are attached to the pins 101 via brazing. The method of the present invention allows for the feedthroughs to be made using a single pass in the high temperature process (gold to ceramic and gold to pin melting). Today, the bulk of the feedthroughs go into the brazing furnace for a second pass to attach the pins 101. Thus reducing labor, cost and stress on the components may be achieved with the method of the present invention. In addition, pad types with different finishes may be attached to the pin without damaging the solderable surface.

[0072] The manufacturing process as described above may be combined with voltage testing, e.g. of the pins 101. Advantageously, the same equipment may be used for manufacturing and testing.

[0073] The method of the present invention may be automated, particularly as welding occurs in situ in the assembly process.

[0074] Simplification of brazing steps is possible with this approach, since at present the brazing is done in two steps as described above. Typically, components are placed into a crucible fixture and sent into the braze furnace to make the basic feed through assembly. A second fixture is used to load the pads on top of the pins and then the parts are put back into the braze furnace a second time. The fixtures and process are complicated due to the many small parts of the fixture. With the method of the present invention, only one brazing step is necessary. Advantageously, due to omitting further brazing steps, thermal stress on the feedthrough assembly may be minimized, particularly since high temperature occurring during the arc welding step are limited to the pin/pad area itself, while the flange/ceramic portion of the assembly may remain at ambient temperature.

[0075] The method of the present invention may be applied to multiple types of feedthroughs 100, for example, comprising ceramic as well as glass constructions 102. Thus, the method of the present invention is also applicable for battery and capacity electrode attachment in addition to ceramic feedthroughs for module assembly.

[0076] The inspectability of the pin to pad connection is retained by the method of the present invention, as the pin to pad 360 degree fillets are visible.

[0077] The method of the present invention is independent of the design of the feedthroughs, unlike laser welding processes, since there is no shadowing or beam path constrictions.

[0078] Multiple pins and pads can be joined simultaneously. This process can be massively parallel.

[0079] 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 teachings of the disclosure. 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, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.