US 20020022382 A1
This invention concerns improvements in fuel cell fabrication. Arrays of independent acting compliant electrical contacts are incorporated within a fuel cell which improve fuel cell Bi Polar Separator Plate (bipolar separator plate) which improve fuel cell operation by creating uniform and intimate electrical contact with the adjacent membrane electrode assembly (Membrane electrode assembly). These compliant electrical contacts provide substantial uniform internal pressure distribution and substantially uniform electrical contact. In one embodiment, the array of compliant electrical contacts are in the form of a plurality of metal springs of various configurations which are electrically and mechanical contacted to a conducting base plate. In another embodiment the array of compliant electrical contacts are in the form of a plurality of small metal pins or rods which are electrically and mechanically contacted to a conducting base plate.
1. An array of independently acting compliant electrical contacts within a fuel cell electrode which improve fuel cell operation and performance by providing substantially increased and optimized surface area for increased electrical contact between the compliant contact attached to the conducting plate and bipolar separator plate and membrane electrode assembly, substantial uniform internal compressive loads and distribution resulting from the independent action of the compliant electrical contacts when the fuel cell stack is compressed.
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30. The compliant electrical contacts (springs) wherein the thickness of the shaped metal strip is between about 0.001 in. and 0.090 in.
31. The individual compliant electrical contact wherein the width of the shaped metal strip is between about 0.020 in. and 1.0 in.
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 This application is a continuation-in-part of U.S. Ser. No. 60/226,471, filed Aug. 18, 2000 which is incorporated herein by reference in its entirety.
 1. Field of the Invention
 This invention concerns compliant electrical contacts for fuel cell use to create, adjust and distribute internal forces and loads to optimize contact area to increase fuel cell performance. In a number of embodiments, an array of metal springs of different shapes and configurations contact the adjacent electrode. In another embodiment, a series of electrical contact points similar to a “bed of nails” is used to adjust forces and pressure.
 2. Description of the Related Art
 Fuel cells are energy conversion devices that use hydrogen, the most abundant fuel on earth, and oxygen from the air, to create electricity through a chemical conversion process, without combustion and without harmful emissions. The voltage and current output depends on the number of cells in the stack, total active surface area and efficiency. The basic process, for a single cell, is shown in FIG. 1.
 Traditional fuel cell stacks 1, see FIG. 2, are made of many individual cells 2, see FIG. 3, which are stacked together. The ability to achieve the required gas and liquid sealing and to maintain intimate electrical contact has traditionally been accomplished with the use of relatively thick and heavy “end plates” (3, 4) with the fuel cell stack 5 held together by heavy tie-rods or bolts 6 and nuts 7 (or other fasteners) in a “filter-press” type of arrangement, see FIGS. 2 and 4. Disassembly and analysis of fuel cell stacks built by traditional and other methods reveals evidence of incomplete electrical contact between bipolar separator plates (BSPs) 8 and the membrane electrode assembly (MEAs) 9, which results in poor electrical conduction, lower cell performance, often along with evidence of gas and liquid leakage.
 The traditional method of assembly of Proton Exchange Membrane (PEM) fuel cells requires several parallel and serial mechanical processes that must be accomplished simultaneously for each individual cell, see FIG. 3.
 1. The Membrane Electrode Assembly (MEA) 9 must be sealed to the Bipolar Separator Plates (BSPs) 8 at each plate/MEA interface, via a gasket 10A and 10B.
 2. The fuel, oxidizer and coolant manifolds 11, 11A and 11B are all required to be sealed at the same time during fabrication as the MEA is sealed to the BSP.
 3. The BSPs 8 must be in intimate electrical contact with the electrode assembly 9, across its entire surface area, at all times for optimum performance.
 As the traditional fuel cell stack 1 is assembled, each individual cell (layer) 2 must seal, manage gasses and liquid, produce power and conduct current. Each cell relies on all the other cells for these functions. Additionally, all seals and electrical contacts must be made concurrently at the time of assembly of the stack, see FIGS. 2 and 3.
 The assembly of a traditional PEM cell stack which comprises a plurality of PEM cells each having many separate gaskets which must be fitted to or formed on the various components is labor-intensive, costly and in a manner generally unsuited to high volume manufacture due to the multitude of parts and assembly steps required.
 performance, along with evidence of gas and liquid leakage.
 The traditional method of assembly of Proton Exchange Membrane (PEM) fuel cells requires several parallel mechanical processes that must be accomplished simultaneously for each individual cell, see FIG. 3.
 The traditional construction method does not allow for testing or evaluation of the individual cells before they are assembled into the stack. If there is leakage or a performance problem with a single cell or group of cells in an assembled stack, then the entire stack has to be disassembled to correct the problem. This is very expensive and time consuming.
 Some patents of interest are listed below.
 R. G. Spear et al. in U.S. Pat. No. 5,683,828, assigned to H Power Corporation disclose metal platelet fuel cells production and operation methods.
 R. G. Spear et al. in U.S. Pat. No. 5,858,567, assigned to H Power Corporation discloses fuel cells employing integrated fluid management platelet technology.
 R. G. Spear, et al. in U.S. Pat. No. 5,863,671, assigned to H Power Corporation discloses plastic platelet fuel cells employing integrated fluid management.
 R. G. Spear, et al. in U.S. Pat. No. 6,051,331 assigned to H Power Corporation discloses fuel cell platelet separators having coordinate features.
 These four U.S. patents describe conventional fuel cell assembly.
 W. A. Fuglevand et al. in U.S. Pat. No. 6,030,718, assigned to Avista Corporation describes a proton exchange membrane fuel cell power system. In the figures of this patent, particularly its FIG. 12 and following, component 202 is described as a biasing assembly, as a plurality of metal wave springs which cooperate with the cathode cover and is able to impart force to the adjacent pressure transfer assembly 203 by means of a rigid pressure distribution assembly 204.
 Other art of general interest includes, for example: U.S. Pat. No. 5,338,621; European Patent 446,680; U.S. Pat. No. 5,328,779; U.S. Pat. No. 5,084,364; U.S. Pat. No. 4,445,994; U.S. Pat. No. 5,976,727; U.S. Pat. No. 5,470,671; U.S. Pat. No. 5,176,966; and U.S. Pat. No. 5,945,232;
 All of the references, patents, standards, etc. cited in this application are incorporated by reference in their entirety.
 It is apparent from the above discussion that existing fuel cell technology can be mostly improved with modification in the design and fabrication of components and assembly of the units. The present invention of compliant electrical contacts provides such an improvement for a fuel cell.
 The present invention concerns an array of compliant electrical contacts within a fuel cell electrode which improve fuel cell operation providing substantially and uniform internal load distribution to effect uniform electrical contact across the conductive surface.
 In another aspect the array of compliant electrical contacts are in the form of a plurality of inverted V, Z, S or omega shaped independent metal springs which are electrically, mechanically, metallurgically or combinations theory contacted and connected to a conducting base plate or BSP.
 In another aspect the plurality of metal springs have a regular patterned arrangement having substantially uniform distance between contact points or surfaces.
 In another aspect, the plurality of metal springs have an irregular patterned arrangement and substantially non uniform distance between contact points or surfaces.
 In another aspect, the array of compliant electrical contacts are in the form of a plurality of small metal pins which are electrically and mechanically contacted to a conducting base plate.
 In another aspect, the tips of the small metal pins which are in to contact with the adjacent electrode have a head similar to a nail head.
 In another aspect, in the array the plurality of metal pins form an irregular arrangement or a regular patterned arrangement having a substantially uniform distance between pins.
 In another aspect, the compliant electrical contacts are comprised of alloys of iron, copper, gold, silver, platinum, aluminum, nickel, chromium, and combinations thereof.
FIG. 1 is a schematic representation of the basic conventional fuel cell process. It shows the extracted hydrogen ions which combine with oxygen across a PEM membrane to produce electrical power.
FIG. 2 is a schematic representation of the conventional PEM fuel cell stack of electrodes compressed together with heavy end plates and tie rod bolts.
FIG. 3 is a schematic representation of an exploded view of a conventional PEM single cell of a fuel cell assembly.
FIG. 4 is a schematic representation of an exploded view of a conventional PEM fuel cell stack of electrodes showing the arrangement of the internal and external parts.
FIG. 5 is a schematic representation of the compliant electrical contacts with the array of cantilevered inverted V-shaped thin metal spring.
FIG. 5A is a schematic representation of the obverse integrated and modular bipolar separator plate (BSP), membrane electrode assembly (MEA) and manifold.
FIG. 6 is a schematic crossectional representation of the compliant electrical contacts with the array of cantilevered inverted V-shaped springs shown contacting the adjacent MEA.
FIG. 7 is a photographic representation of the compliant electrical contacts and array of inverted V-shaped cantilevered springs.
FIG. 8 is a photographic representation of an end view of the compliant electrical contacts of FIG. 7.
FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J, 9K, 9L, 9M, 9N and 9P are each schematic or isometric or cross sectional representations of various types of compliant electrical contacts.
FIG. 9A is an inverted V-shape.
FIG. 9B is a circular portion of an arc.
FIG. 9C is a right angle contact.
FIG. 9D is a rounded inverted V-shape.
FIG. 9E is an omega shape, with multiple deflection areas and multiple contact areas.
FIG. 9F is an array of the omega shape in strip form.
FIG. 9G is a “S” shape with a right angle contact.
FIG. 9H is in an S shape in strip form.
FIG. 9I is in an S shape with a radiused contact point and interlocking and alignment/locating features.
FIG. 9J is a S with interlocking and locating features, in strip form.
FIG. 9K is a Z form with right angle contact area.
FIG. 9L is a Z in strip form.
FIG. 9M is a modified omega shape similar to FIG. 9E showing two versions.
FIG. 9N has the support feet pointing inward FIG. 9M has the support feet pointing outward.
FIG. 9P is a modified omega design, similar to FIG. 9E, without the crown or point in the top arch.
 In all cases, regardless of spring shape, the contact areas of the springs maximize the physical contact to the MEA and facilitate electrical conduction, and reduce electrical resistance.
FIG. 10 is a schematic cross sectional representation of the “bed of nails” as the compliant electrical contacts. The array of contact points (48) contact the adjacent MEA.
FIG. 11 is a photograph of the current embodiment showing the array of the modified omega design of FIG. 9P attached to the bipolar separator plate and with the multi manifold arrangement.
FIG. 12 is an edge view of the spring/plate/manifold configuration shown in FIG. 11. This shows the array of springs attached to the bipolar separator plate.
FIG. 13 shows an uncompressed stack of bipolar separator plates, manifolds and springs.
FIG. 14 shows the same parts as in FIG. 13 in the compressed state with the springs making contact with the adjacent cell.
 As described herein:
 “Bed of nails” refers to a configuration of compliant electrode contacts of vertical thin metal rods which accommodate forces and loads in an operating fuel cell usualy the top (exposed) end of the rod is larger than the shaft (for better electrical contact).
 “BSP” refers to bipolar separator plates.
 “Compliant electrode contact” refers to a spring-like adjusting electrical contact which create the loads and pressures of an operating fuel cell which maintain constant electrical contact.
 “MEA” refers to the membrane electrode assembly.
 “PEM” refers to proton exchange membrane—a component of a fuel cell.
 In one embodiment, the compliant contacts are an array of individual metal strips which have been folded to produce an inverted V configuration. This is shown in FIGS. 5-8 and 9D. One side of the inverted V-shape is connected mechanically and electrically to a conducting base. The points of the inverted V configuration provide electrical and mechanical contact to the electrode. As each individual folded strip contacts the electrode, it adjusts to the variation in cell spacing and maintains uniform electrical contact with the MEA.
 Compliant Electrical Contacts
 As stated above, traditional fuel cell design has relied on the “filter press” type of fabrication and assembly, see FIG. 2, i.e., end-plates and tie-rods, to create suitable electrical contact between the MEA and adjacent BSP. These designs have not made use of other, more standardized forms of electrical contact such as (1) metallurgical, by methods such as welding, soldering or brazing, (2) mechanically such as fastened with bolts, screws, cams, etc., and (3) spring contacts such as battery clips or wall plugs. As a method of decoupling the electrical contacts, spring loaded electrical contacts of the present invention are a novel solution and add mechanical compliance.
 The present fuel cell uses thin metal plate BSPs in which the reactant gas flow patterns are integrated. Each BSP is independently held in intimate contact with the MEA via independent acting compliant spring electrical contacts and do not require the heavy end plates, tie rods and the massive compressive forces required of traditional fuel cell stacks to achieve contact and conductance.
 Conventional fuel cell design is followed up to a certain point. See U.S. Pat. No. 6,030,718 and the other U.S. patents listed on pages 2 and 3 above. One of skill in the art with these incorporated-by-reference U.S. patents will have the basic design to fabricate a conventional fuel cell. With the text and figures provided herein, one of skill in the art is enabled to fabricate the present invention. In the creation of the compliant electrical contacts of the present invention within the cell, the following additional methodology is followed.
 With reference to FIG. 5A the present fuel cell design 50 uses a single thin metal plate BSP onto which the MEA and reactant manifolds 51A, 51B and 51D are assembled into modular units prior to being incorporated into a complete fuel cell unit (stack). These fuel cell modules are comprised of a single BSP, which may contain a reactant flow pattern, the MEA with or without an incorporated diffusion layer, separate diffusion layers if needed, an adhesive or an adhesive backed gasket, the reactant manifolds 51A and 51B and the manifold seals or adhesives. Other features in FIG. 5A include on the obverse adhesive or gasket by the hole 52, reactant passageway 53, 53A and 53B, edge seal 54, inactive border 55 and active membrane 56.
 Compliant electrical contact is achieved in the subject fuel cell design by use of springs and contact points. In the spring design a large array of individual springs are attached to each BSP each of which makes intimate contact with the MEA attached to the adjacent BSP, see FIG. 5 and SA. When these springs are compressed, continuous electrical contact is assured between the adjacent BSPs through the MEAS, FIG. 6. FIGS. 7 and 8 are photographs of one array of inverted V-shaped compliant electrical contacts.
 The compliant electrical contacts can take a number of forms. All units are flexible. For example, FIGS. 7 and 8 to 9 show a rounded contact point which is in an inverted V-shape. Other shapes include the following:
FIG. 9A which shows a sharp inverted V-shape 10 having a cantilevered portion 11 which is mechanically contacted at area 12 to a base plate 13.
FIG. 9B shows a round metal arc 14 as contact having a cantilevered portion 15 which is contacted at area 12 to a base plate 13.
FIG. 9C shows a flat surface 16 as the contact having a cantilevered portion 15 which is contacted at area 12 to base plate 13.
FIG. 9D shows a rounded, inverted “V” form 17 having a cantilevered portion 15 which is contacted at area 12 to base plate 13.
FIG. 9E shows a modified omega shape 21, with multiple deflection areas and multiple contact areas. One or both flat portions 22A and 22B are connected to a base plate.
FIG. 9F is an array 23 of the modified omega shape in strip form 18 which are connected to the base plate 24A and 24B.
FIG. 9G is a “S” shape 25 with right angle contact 26 having a flat area 27 to connect to a base plate.
FIG. 9H is an array of “S”-shape 26 of FIG. 9G, wherein the array of S-shape contacts are connected to a base plate 28.
FIG. 9I is a “S” shape 29 with radiused contact point 30 and interlocking and alignment/locating features. The “S” shape is connected to base 31.
 Figure J is an array of the S-shape 32 in strip form connected to base 33.
FIG. 9K is a “Z” form 34 with right angle contact area 35. The Z-shape is connected to a base 36.
FIG. 9L is an array 37 of the Z-shape of FIG. 9K which is connected to base 38.
 The compliant electrical contact approach (springs) is not limited by size or shape of the application. The springs are usually between 0.020″ and 2″ high. The forces (e.g. tension) in the spring portion, within the cell that are accommodated by the compliant electrical contacts is usually between about 0.10 lb and 10 lb per spring leaf depending on the configuration as described herein. The plates are as small as ¼″×¼″ (for very small, light, portable devices such as video cameras, movie cameras, etc.) to the large sizes required for homes, businesses, large buildings, or even small cities.
FIG. 9M is a modified omega configuration similar to FIG. 9E has two versions, FIG. 9M with the support feet pointing inward and FIG. 9N with the support feet pointing outward. The modified omega has a slight break in the curve at the top 42. One or both flat portions 43A and 43B are mechanically (e.g. soldered) and electrically attached to a conducting base plate and can point either inward or outward.
FIG. 9P is a modified omega configuration shown in an array 45 similar to FIGS. 9E and 9F. The modified omega has no break in the curve at the top 46. One or both flat portions 47A and 47B are mechanically and electrically attached to a conducting base plate.
 The compliant electrical contact approach (springs) is not limited by size or shape of the application. The springs are usually between 0.020″ and 2″ high. The forces (e.g. tension) in the spring portion, within the cell that are accommodated by the compliant electrical contacts is usually between about 0.10 lb and 50 lb per spring leaf depending on the configuration as described herein. For example, when the spring strip has a thickness of 0.004 inches, and is deflected (compressed 0.040 inches, 0.84 pounds force is created. The plates are as small as ¼″×¼″ (for very small, light, portable devices such as video cameras, movie cameras, etc.) to the large sizes required for homes, businesses, large buildings, or even small cities.
 In the contact points design, very thin, very flexible metal BSPs (0.001-0.500 inch thick) with numerous metal contact pins (48) with heads (49) which are optionally larger than the diameter of the pins are used to effect the contact, FIG. 10. Each pin is attached to the metal BSP. The head of the pin is the electrical contact surface and mechanical support for the adjacent MEA. The individual BSPs do not have springs. The springs are located on each end of the stack or in the center of the stack, pushing the thin flexible metal BSPs to create compliant electrical contacts.
 These methods does not rely on perfectly flat BSPs and the heavy and bulky endplates and tie-rods of the conventional fuel cell art.
 A variety of materials are used for such contacts. Gold plate is the obvious choice due to its resistance to the high humidity atmosphere associated with fuel cell operation and its corrosion resistance. Spring-loaded contacts fabricated from stainless steel (without gold plating) were used to demonstrate the technology with significant performance improvement over expected results.
 In the preferred embodiment, FIG. 9N, a modified omega configuration compliant electrical contacts, in strip or array form 45, without crown or break at top 46, are orientated vertically on the thin metal conductive plate and bipolar separator plate. The contact portion of the 0.004 in. thick compliant contact (springs) has essentially flat surfaces that are approximately 0.100 in. by 0.400 in. Each compliant contact is separated from the other by 0.050 in. The strip or individual springs are approximately 0.200 in. high. Each individual contact exerts approximately 2.5 pounds of spring force, when compressed .0.030 to 0.040 inches in the fuel cell stack.
 The one preferred embodiment, FIGS. 11 and 12, shows the array of FIG. 9N attached to the bipolar separator plate along with the attached manifolds. In the relaxed condition, the crowns of the spring contacts extend above the level of the manifolds. FIG. 13 shows a stack of the plates in the relaxed spring condition. When compressed, in FIG. 14, the spring arrays are compressed and the individual springs contact the neighboring cell with the result of a positive electrical contact with its neighbor. Each spring acts independently from the adjacent spring of the arrays and therefore compensates for any variation in fabrication or assembly.
 The preferred method of fabrication is to stamp or coin the metal conducting plates, stamp the spring or compliant contact blank and form the compliant contact to shape by stamping. The compliant contact(s) are then attached to the conducting plate via pre-applied solder paste and soldered using conventional electronic circuit board manufacturing equipment and techniques. This embodiment provides a uniform thermal gradient, especially when the compliant electrical contacts are oriented vertically in the fuel cell stack. This configuration creates a chimney effect and increasing the amount of air (oxygen) to the membrane. The heated air, due to the chimney effect, carries the excess heat away. This is an usually desirable feature.
 While only a few embodiments of the invention have been shown and described herein, it will become apparent to those skilled in the art that various modifications and changes can be made in the compliant electrical contacts and applications to provide long-term substantially uniform or nonuniform spacing between electrodes and consistent electrical contact of electrodes in a fully functioning fuel cell device without departing from the spirit and scope of the present invention. All such modifications and changes coming within the scope of the appended claims are intended to be carried out thereby.