The present invention relates generally to the field of electronic devices. More specifically, this invention relates to positive temperature coefficient (PTC) devices that are designed for overcurrent protection and can be surface mounted in printed circuit board (PCB) applications.
It is well known that the resistivity of many conductive materials changes with temperature. For example, the resistivity of a PTC material increases as the temperature of the material increases. Examples of such a material are organic polymers, made electrically conductive by dispersing conductive fillers therein. These polymers generally include polyolefins such as polyethylene, polypropylene and ethylene/propylene copolymers. Conductive fillers include carbon black and metal powders.
Typically, a conductive polymer PTC device comprises a layer of conductive polymer PTC material sandwiched between upper and lower metal foil electrodes. The prior art includes single layer devices and multilayer devices, the latter comprising two or more conductive polymer layers separated by one or more internal metal foil electrodes, with external metal foil electrodes on the upper and lower surfaces. Examples of such devices and their methods of manufacture are disclosed in the following US patents, the disclosures of which are incorporated herein by reference: U.S. Pat. No. 6,429,533; U.S. Pat. No. 6,380,839; U.S. Pat. No. 6,377,467, U.S. Pat. No. 6,242,997; U.S. Pat. No. 6,236,302; U.S. Pat. No. 6,223,423; U.S. Pat. No. 6,172,591; U.S. Pat. No. 6,124,781; U.S. Pat. No. 6,020,808; and U.S. Pat. No. 5,802,709.
At temperatures below a certain value, referred to generally as the critical or switching temperature, PTC materials of the type referred to above exhibit a relatively low, constant resistivity. However, as the temperature of the PTC material increases beyond the critical temperature, the resistivity of the material sharply increases with temperature. When the temperature of the material cools down below the critical or switching temperature, the resistivity reverts to its low, constant value. This effect has been used in the production of electronic PTC devices providing overcurrent protection in electrical circuits, where they are generally placed in series with a load.
There is an on-going trend in the electronics industry toward miniaturization, and in particular reduction of the physical size of the components. One way this has been achieved is the introduction of surface mount technology (SMT) components. In SMT components, the devices are soldered directly to the circuit boards, thus doing away with the space requirement for leads on devices and corresponding holes in the circuit boards. Still, as with other electronic applications, in SMT there is an on-going need to minimize the effective surface area or footprint of the devices. However, the operational requirements of PTC devices limit the degree to which the operational surface area of the PTC material can be reduced.
This need for an effective surface area based on the operational requirements of the devices is a major limiting factor in the design of small SMT PTC devices. For example, to maximize the effective surface area for a given footprint, the two electrical terminals for a PTC device may be positioned at opposing ends of the device. While this facilitates the full use of the surface area of the PTC material, the requisite soldering process occupies valuable space on a printed circuit board (PCB), effectively increasing the footprint of the PTC device.
A known solution to this problem is to position the two electrical terminals on the underside of the PTC device. This, however, requires that a connection be provided from the upper foil electrode layer of the PTC device to a terminal on the underside. This connection either significantly reduces the effective area of the PTC material or requires the use of a wrap around connection, which adds cost. For example, in U.S. Pat. No. 6,292,088 a PTC device is disclosed in which an interconnection passes through the device. To prevent the interconnection shorting the two metal layers, a section of one of the metal layers adjacent to the interconnection is removed to provide an isolation barrier. However, the removal of this section significantly reduces the effective surface area of the PTC device, as the area of the metal layer removed to provide isolation equates approximately to the thickness of the PTC material. In addition, the area of metal that has been isolated, and the corresponding region of PTC material, serves no other purpose than to provide an electrical contact. U.S. Pat. No. 6,377,467 discloses a PTC device having a pair of terminals on the underside of device. The terminals are positioned on-top of an insulating layer to isolate them from each other and also from underlying electrodes of the PTC material. Each of the terminals of the pair are connected to a corresponding terminal on the top side of the device by an interconnection. The interconnections also provide electrical connections to the electrodes of the PTC material. However, to prevent the interconnections shorting the two electrodes, a section of one of the metal electrodes adjacent to each interconnection is removed to provide an isolation barrier. Thus the effective area of the PTC device is significantly reduced.
U.S. Pat. Nos. 5,907,272 and 5,884,391 show examples of PTC devices in which the connection from the upper foil layer to a terminal on the underside is provided by a wrap-around conductor arrangement. This configuration makes an electrical connection by wrapping a conductive layer around the PTC material rather than wasting surface area of the PTC material in providing an interconnection. It is suggested however that the manufacturing methods of these patents may be inefficient and costly.
Accordingly, there is a need for an improved SMT PTC device, and a method for manufacturing it, in which the usable effective surface area of the PTC material within a given footprint on a PC board is maximized, and in which connections required to connect the upper electrode to the lower electrode use optimum area and at the same time do not reduce the effective area of the PTC material.
In one aspect, the present invention provides a method of manufacturing an electronic device from a structure comprising at least one layer of device material sandwiched between a first layer of metal and a second layer of metal. The method comprises the steps of forming a first aperture through the first layer of metal, the second layer of metal and the device material, applying a first layer of insulating material to the first metal layer, insulating the walls of the first aperture, providing a third metal layer on the first layer of insulating material, forming a second aperture within the region defined by the first aperture, providing a first electrical interconnection between the top and bottom surfaces of the through the second aperture, creating an electrical interconnection between the third metal layer and the first metal layer, selectively removing metal from the third metal layer to define first and second electrode areas, wherein the first terminal includes the electrical interconnection created between the third metal layer and the first metal layer and the second terminal includes the plated second aperture.
By using an insulated conductive channel to provide a path from one side of the device to the other, the effective surface area of the active material may be maximized, since only the area occupied by the channel is required to provide the interconnection between the upper and lower surfaces of the device.
The method may comprise the further steps of applying a second layer of insulating material on the second metal layer, and providing a fourth metal layer on the second layer of insulating material in advance of forming the second aperture.
The step of insulating the walls of the first aperture may be performed at least in part by the step of applying the first layer of insulating material to the first metal layer and/or by the step of applying the second layer of insulating material to the first metal layer,
In advance of the application of the insulating layers, a third aperture may be formed through the first metal layer, second metal layer and the at least one layer of device material subsequent to which a fourth aperture may be formed within the region defined by the third aperture. Whereupon the fourth aperture may be plated to provide a second electrical interconnection between the top and bottom surfaces of the device.
Third and fourth terminals may be defined using an additional step of selectively removing material from the fourth metal layer.
The first and third apertures may be formed at opposing ends of the device.
The method may include the initial step of defining singulation references in the first and second layers of metal.
Advantageously, the steps of applying the first layer of insulating material to the first metal layer and providing a third metal layer on the first layer of insulating material may be performed in a single step by the application of a resin clad metal, optionally copper.
Similarly, the steps of applying the second layer of insulating material to the second metal layer and providing the fourth metal layer on the second layer of insulating material may be performed in a single step by the application of a resin clad metal, optionally copper.
Optionally, the structure comprising at least one layer of device material sandwiched between a first layer of metal and a second layer of metal may be a multi layer structure comprising alternating layers of device material and metal.
The method of manufacturing a device is particularly suitable for the manufacture of PTC devices, and in which case the device material is a PTC material.
The structure comprising at least one layer of device material sandwiched between a first layer of metal and a second layer of metal may be provided as a laminated sheet.
In another aspect of the invention, an electronic device is provided comprising a first metal layer, a second metal layer and at least one layer of device material sandwiched between the first metal layer and the second metal layer which function as electrodes for the device material. A first terminal is provided for a first electrical connection to the device and a second terminal is provided for a second electrical connection to the device, wherein the first terminal is electrically connected to the first metal layer and the second terminal is insulated from the first metal layer and electrically connected to the second metal layer by a conductive channel which passes through and is insulated from the first metal layer and device material. The conductive channel may be a metal plated channel.
The second terminal may be insulated from the first metal layer by a first layer of insulating material. This first layer of insulating material may substantially cover the first layer of metal.
A third layer of metal may be provided on the first layer of insulating material. This third layer may be divided by an isolation area to provide the first terminal and the second terminal.
The device may further comprise a third terminal for providing a third electrical connection to the device and a fourth terminal for providing a fourth electrical connection to the device, wherein the fourth terminal is electrically connected to the second metal layer and the third terminal is insulated from the second metal layer and electrically connected to the first metal layer by a second conductive channel which passes through and is insulated from the second metal layer and device material.
The second conductive channel may be a metal plated channel, which may be located at one end of the device. Moreover, the first conductive channel and the second conductive channel may be located at opposing ends of the device.
The second terminal may be insulated from the second metal layer by a second layer of insulating material, which may substantially cover the second layer of metal.
The fourth terminal may be electrically connected to the second metal layer by an interconnect formed through said second layer of insulating material.
The terminals of the device may be plated, optionally with nickel, copper and/or gold. The insulating material may comprise a cured resin. The at least one layer of device material may comprise alternating layers of device material and metal.
The device may be a PTC device and in which case the device material is a PTC material.
In another aspect of the invention a PTC device is provided comprising: a first metal layer, a second metal layer and at least one layer of PTC material sandwiched
In a further aspect of the invention, a method of manufacturing a matrix of electronic devices from a structure comprising at least one layer of device material sandwiched between a first layer of metal and a second layer of metal is provided. The method comprising the steps of forming a first array of apertures through the first layer of metal, the second layer of metal and the device material, applying a first layer of insulating material to the first metal layer, insulating the walls of the first array of apertures, providing a third metal layer on the first layer of insulating material, forming a second array of apertures such that each aperture of the second array is positioned within the region defined by an aperture from the first array of apertures, providing electrical interconnections between the top and bottom surfaces of the matrix through the second array of apertures to create electrical interconnections between the third metal layer and the first metal layer, selectively removing metal from the third metal layer to define first and second terminals for each device of the matrix, wherein each first terminal includes an electrical interconnection between the third metal layer and the first metal layer and each second terminal includes an insulated electrical interconnection between the top and bottom surfaces of the device.
The step of insulating the walls of the first array of apertures may be performed at least in part by the step of applying the first layer of insulating material to the first metal layer,
The method may comprise the further steps of: applying a second layer of insulating material on the second metal layer, and providing a fourth metal layer on the second layer of insulating material in advance of forming the second array of apertures.
Advantageously, the step of insulating the walls of the first array of apertures may be performed at least in part by the step of applying the second layer of insulating material to the first metal layer.
The method may comprise the further steps of forming a third array of apertures, in advance of the application of the insulating layers, through the first metal layer, second metal layer and the at least one layer of device material, forming a fourth array of apertures within the region defined by the third array of apertures, and providing electrical interconnections between the top and bottom surfaces of the device through the fourth array of apertures.
The method may comprise the additional step of selectively removing material from the fourth metal layer to define third and fourth terminals for individual devices in the matrix.
Each of the first array of apertures and each corresponding aperture of the third array of apertures may be formed on opposing ends of the individual devices within the matrix.
As an initial step singulation references may be defined in the first and second layers of metal.
Advantageously, the steps of applying a first layer of insulating material to the first metal layer and providing a third metal layer on the first layer of insulating material may be performed in a single step by the application of a resin clad metal, optionally copper.
Similarly, the steps of applying a second layer of insulating material to the second metal layer and providing a fourth metal layer on the second layer of insulating material may be performed in a single step by the application of a resin clad metal, optionally copper.
Optionally, the structure comprising at least one layer of device material sandwiched between a first layer of metal and a second layer of metal may be a multi layer structure comprising alternating layers of device material and layers of metal.
Where the device is a PTC device, the device material is a PTC material.
The method may comprise the additional step of joining a second matching matrix of electronic devices to the matrix such that terminals of adjoining faces of each matrix are aligned and electrically connected. As a final step, the devices may be singulated from the matrix.
As part of the singulation process, groups of two or more devices may be singulated together as individual devices. In this case, they may be configured as SIP or DIP packages.
The device material may be a dielectric material.
In a further aspect of the invention, a matrix of electronic devices is provided comprising a first metal layer, a second metal layer and at least one layer of device material sandwiched between the first metal layer and the second metal layer which function as electrodes for the device material. First and second arrays of terminals provide electrical connections to individual devices of the matrix, wherein the first array of terminals are electrically connected to the first metal layer and the second array of terminals are insulated from the first metal layer and electrically connected to the second metal layer by conductive channels which pass through and are insulated from the first metal layer and device material. The conductive channels may be metal plated channels. The second array of terminals may be insulated from the first metal layer by a first layer of insulating material, which may substantially cover the first layer of metal.
A third layer of metal may be disposed on the first layer of insulating material, here said third layer is divided by an array of isolation areas to provide the first array of terminals and the second array of terminals.
Third and fourth arrays of terminals may also provide electrical connections to individual devices. Moreover, the fourth array of terminals may be electrically connected to the second metal layer, and the third array of terminals may be insulated from the second metal layer and electrically connected to the first metal layer by a second array of conductive channels which pass through and are insulated from the second metal layer and material.
The second array of conductive channels may comprise metal plated channels. The second array of terminals may be insulated from the second metal layer by a second layer of insulating material which may substantially cover the second layer of metal.
The fourth array of terminals are electrically connected to the second metal layer by interconnects formed from through said second layer of insulating material.
Each of the array of second conductive channels is provided at an end of each device of the matrix moreover each of the array of first conductive channels and second conductive channels may located at opposing ends of each device of the matrix.
The terminals of the matrix may be plated, optionally with nickel, copper and/or gold.
The insulating material may comprise a cured resin.
The at least one layer of device material may comprise alternating layers of device material and layers of metal. Where the devices of the matrix are PTC devices the device material is a PTC material.
The invention extends to a stacked matrix comprising at least two matrices of the type described which are stacked on top of each other and in which corresponding terminals are electrically connected.
The above mentioned advantages of the present invention, as well as others, will be more readily appreciated from the detailed description that follows.
The invention will now be described with reference to the drawings in which:
Referring now to the drawings,
The layer of conductive polymer PTC material 16 may comprise any suitable PTC material, including for example any suitable conductive polymer composition. An example of a suitable conductive polymer composition would be high density polyethylene (HDPE) into which is mixed an amount of carbon black that results in the desired electrical operating characteristics. An example of such a mixture is disclosed in WO97/06660, the disclosure of which is incorporated herein by reference. The metal layers 12, 14 may comprise any suitable metal, typically provided as a thin foil, with copper being preferred, although other metals, such as nickel and aluminum along with a number of alloys are also acceptable.
The laminated sheet 10 may be formed by any of several suitable processes that are well known in the art, as exemplified by the above referenced publication WO97/06660.
The present invention, in one aspect, is a manufacturing method or process comprising a series of processing steps performed upon the laminated sheet 10 to produce a matrix comprising a plurality of electronic devices. These steps will now be explained with reference to
An advantageous first step in the exemplary process is the definition, in the sheet 10, of an array of singulation lines (not shown), that define a matrix of sheet sections 23, 24, 25 (
After the formation of the singulation lines, the next step in the process, illustrated in
The remaining steps of the process will be described with reference to this single section 24 defining an individual unit or device. It will be appreciated, however, that the subsequent process steps are intended to produce a matrix of devices from the laminated sheet 10 as a whole, and that the individual unit is only shown for clarity. In practice the individual unit is not singulated from the matrix until substantially all of the process steps have been completed.
As illustrated in
The insulating material may be any suitable material, including plastic (e.g. epoxy resin). Fibers (e.g. glass) may be included within the insulating material to provide mechanical strength. In particular, the material referred to generally in the PCB industry as pre-preg, is an ideal insulating material. A preferred specific type of pre-preg for this application comprises a 1080 glass fabric (fiber glass) filled with a 62% resin content.
A third metal layer 48 is formed on or applied to the first layer of insulating material 40. Similarly, a fourth metal layer 50 is formed on or applied to the second layer of insulating material 42, resulting in the structure shown in
Advantageously, the steps of applying the layers of insulating material and metal may be combined into a single step through the use of resin clad metal materials, for example resin clad copper (RCC). The use of RCC allows the metal and insulating layers to be applied concurrently. A suitable RCC material would be a 1080 glass fabric impregnated with a 62% resin content and clad with copper. The adherence of the first and second insulating layers 40, 42 to the first and second metal layers 12, 14 respectively may be achieved by conventional PCB techniques, familiar to those skilled in the art.
After the insulating layers 40, 42 and additional metal layers 48, 50 have been applied/formed, a second array of apertures 60, 62 is defined/formed in the laminated sheet 10. Any suitable process including conventional drilling or laser drilling techniques may form these apertures. Each aperture 60, 62 of this second array is suitably formed within the boundary defined by a corresponding aperture 30, 32 of the first array of apertures, as illustrated in
The next step in the process, illustrated in
After forming the external conductive interconnections 66, 68, a first array of internal interconnections is formed between the fourth metal layer 50 and the second metal layer 14. Similarly, a second array of internal interconnections is provided between the third metal layer 48 and the first metal layer 12. These internal interconnections will provide conductive paths between the first metal layer 12 and the third metal layer 48, and between the second metal layer 14 and the fourth metal layer 50. As shown in
Once the micro-vias 70, 72 have been formed, the internal electrical interconnections may be established through the micro-vias by disposing conductive material within them. The preferred method of providing the conductive material is a conventional plating process, such as electroplating or electroless plating. The electrical connections may also be provided by inserting a conductive material, for example conductive epoxy or solder paste, into the micro-vias 70, 72. Assuming a suitable plating process is used,
At this point it is necessary to form two separate, electrically isolated conductive paths so as to provide a first terminal that electrically connects the first metal layer 12 to the upper plating layer 82, and a second terminal, electrically isolated from the first terminal, that electrically connects the second metal layer 14 to the lower plating layer 12. The formation of the first and second terminals for subsequent use as connection points for the PTC devices is shown in
The two lower terminal pads 90, 92 are suitably positioned in regions adjacent the opposite ends of the device or unit 24, and they are respectively connected to the corresponding upper terminal pads 94, 96 by the respective insulated conductive channels that respectively form the external interconnections 66, 68. Furthermore, the first metal layer 12 is electrically connected to the first lower terminal pad 90 by the lower internal interconnection 84, while second metal layer 14 is electrically connected to the second upper terminal pad by the upper internal interconnection 86. Thus, a first terminal is formed, comprising the first lower terminal pad 90, the first external interconnection 66, and the first upper terminal pad 94, which terminal provides electrical connection to the first metal layer 12, which thereby forms a first electrode. Likewise, a second terminal is formed, comprising the second lower terminal pad 92, the second external interconnection 68, and the second upper terminal pad 96, which terminal provides electrical connection to the second metal layer 14, which thereby forms a second electrode. This results in a symmetrical PTC device 24 which, when singulated from the sheet 10 (i.e., the overall matrix of devices), may used directly as an SMT PTC device. Suitable techniques for singulation are well known in the art and include routing, guillotining, dicing, punching, laser cutting and scouring.
In particular, the process described above produces a matrix comprising a plurality of laminar PTC devices which may be singulated from the original matrix. Each of the PTC devices comprises a first or lower electrode 12 formed from the first metal layer 12, and a second or upper electrode 14 formed from the second metal layer 14. A layer of PTC material 16 is sandwiched between these first and second electrodes 12, 14. The first electrode 12 is substantially covered by a first layer 40 of insulating material. Similarly, the second electrode 14 is substantially covered by a second layer of insulating material 42. A third metal layer 48 is provided on the first insulating layer 40. The third metal layer 48 is divided to form first and second lower terminal pads 90, 92 on the underside of the device. The two lower terminal pads are positioned in regions adjoining opposing ends of the PTC device. The first lower terminal pad 90 is connected to the first electrode 12 by the first internal interconnection 84 that passes through the first layer of insulating material 40. The second lower terminal pad 92 is separated from the first lower terminal pad 90 by the lower isolation area 97 where the third metal layer 48 has been selectively removed, and it is insulated from the first electrode 12 by the first layer of insulating material 40.
Likewise, the fourth metal layer 50 is divided by the upper isolation area 99, where metal has been selectively removed, to provide the first and second upper terminal pads 94, 96. The first and second upper terminal pads 94, 96 are positioned in regions adjoining opposing ends of the PTC devices. Suitably, the positioning of the first and second upper terminal pads 94, 96 corresponds directly to positioning of the first and second lower terminals 90, 92, respectively. In other words, the first upper terminal pad 94 is formed on the opposing side of the PTC device to the first lower terminal pad 90, and the second upper terminal pad 96 is formed on the opposing side of the PTC device to the second lower terminal pad 92.
The second upper terminal pad 96 is connected to the second electrode 14 by the second or upper internal interconnection 86 that passes through the second layer of insulating material 42. The first upper terminal pad 94 is separated from the second upper terminal pad 96 by the upper isolation area 99 where metal has been selectively removed, and it is insulated from the second electrode 14 by the second layer of insulating material 42.
The first lower terminal pad 90 is electrically connected to the first upper terminal pad 94 by the first conductive external interconnection 66, which passes through and is insulated from the first and second electrodes 12, 14 and the layer of PTC material 16. Similarly, the second lower terminal pad 92 is connected to the second upper terminal pad 96 by the second conductive external interconnection 68, which passes through and is insulated from the first and second electrodes 12, 14 and the layer of PTC material 16. It will be appreciated that the resulting PTC device comprises two paired arrangements of terminal pads on opposing sides of the PTC device. The effective resistance between the terminal pads in each pair is that of the PTC material (as contact and interconnect resistances are small in comparison, particularly when the PTC material is in a tripped state).
By using insulated conductive channels to provide the external interconnections 66, 68 from one side of the PTC device to the other, the effective surface area of the PTC material utilized by the device may be maximized.
The above described process results in a symmetrical PTC device that facilitates easy placement without the need for correct orientation of the device beforehand.
Of particular advantage is that the PTC devices are manufactured using techniques that are commonplace in the reasonably low cost manufacturing environment of the PCB industry. The above described process has been described with reference to the production of a symmetrical PTC device having a single layer of PTC material. It will be appreciated that further embodiments are possible. For example, a non-symmetrical device, i.e. where the device will only function correctly when placed with the underside down, may be provided by the omission of a number of the steps in the above described process and correspondingly the omission of a number of the features in the above described PTC device. In particular, the requirement for a second external interconnection provided by an insulated channel, a fourth metal layer and a second layer of insulating material may be obviated as illustrated in the exemplary structure of
The second terminal pad 92 is electrically connected to the second electrode 14 by a conductive channel that forms an external interconnection 68, formed as described above (with modifications to account for the absence of the second insulating layer and fourth metal layers), which passes through and is insulated from the first and second electrodes 12, 14 and the layer of PTC material 16.
A further exemplary embodiment, as illustrated in
This further embodiment in effect provides two PTC devices in series, with the middle electrode acting as a common electrode to the first device, comprising the top electrode and top layer of PTC material, and the second device comprising the bottom electrode and bottom layer of PTC material. It is believed that this multilayer structure provides a series combined PTC device having a higher breakdown voltage than would be achievable with a single PTC device.
An exemplary multi device package configuration is illustrated in
The resulting IC type device may be readily modified for use as a dual in-line package (DIP) by appropriate fixing of a lead frame.
Although DIP packages are popular, in circumstances where board space is at a premium, single in-line packages (SIP) are preferred. The present invention may be readily adapted for use as a SIP package by providing paired terminals for connecting to each PTC device along one side of the package rather than on opposing sides of the device, for example as shown in the embodiment of
Depending on the application, the individual characteristics of the devices may be equivalent or different. Different characteristics may be achieved by having differently sized electrodes, which may be effected at the previously described stage of defining singulation references.
As the PTC devices described herein are manufactured using conventional PCB techniques, the resulting devices may be used as miniature printed circuit boards onto which further circuit protection devices, for example a battery charge controller or an over-voltage protection device, such as a gas discharge tube, a thyristor or a metal oxide varistor (MOV) may be fixed, for example by direct soldering to the terminals, to provide a circuit protection module. An exemplary input protection circuit is shown in
The circuit of
A drawback of existing PTC devices is that the effective area of the PTC material limits the trip currents of the devices. However, as circuit board space is generally at a premium, designers are reluctant to use devices having large device footprints. One solution to this problem is to provide PTC devices in a parallel configuration using a multilayer device construction. There has been a constant effort in the art to reduce the costs and to increase the efficiencies of manufacturing such multilayer devices.
The matrix construction of the present invention facilitates a simple and efficient method of providing two or more devices in parallel in a quasi-multilayer construction. A side view of a section of a matrix of devices (of the symmetrical type shown in
Although the present invention has been described with reference primarily to an active material of the PTC type, it will be appreciated that the manufacturing process of the present invention may be advantageously applied to other active polymer materials and PTC materials and also to other materials including dielectrics, resistive, magnetic and semiconductor materials.
Although the present invention has been described with reference to commencement of manufacture from a laminated sheet of electronically active (e.g. PTC) material sandwiched between a first layer of metal and a second layer of metal, the method may commence with a layer of electronically active (e.g. PTC) material upon which metal foils may be placed, or metal layers deposited (e.g. by plating) as part of the manufacturing process described herein.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US03/07875 | 3/14/2003 | WO | 6/9/2005 |
Number | Date | Country | |
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60432492 | Dec 2002 | US |