Patent Abstract:
An implantable device, including a first electrically non-conductive substrate with a plurality of electrically conductive vias. The device also includes a flip-chip multiplexer circuit attached to the electrically non-conductive substrate using conductive bumps, the circuit being electrically connected to at a subset of the plurality of electrically conductive vias. Another a flip-chip driver circuit is attached to the flip-chip multiplexer circuit using conductive bumps while a second electrically non-conductive substrate attached to the flip-chip driver circuit using conductive bumps. Discrete passives are attached to the second electrically non-conductive substrate and a cover is bonded to the first electrically non-conductive substrate. The cover, the first electrically non-conductive substrate and the electrically conductive vias form a hermetic package.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of Application of U.S. patent application Ser. No. 13/783,225, filed Mar. 1, 2013 and issued as U.S. Pat. No. 8,571,672 on Oct. 29, 2013, entitled Package for an Implantable Neural Stimulation Device; which is a divisional application of U.S. patent application Ser. No. 11/924,709, filed Oct. 26, 2007 and issued as U.S. Pat. No. 8,374,698 on Feb. 12, 2013, entitled Package for an Implantable Neural Stimulation Device; which is a divisional application of U.S. patent application Ser. No. 11/893,939, entitled Package for an Implantable Neural Stimulation Device, filed Aug. 18, 2007 and issued as U.S. Pat. No. 8,412,339 on Apr. 2, 2013; which application claims benefit of provisional Application Ser. No. 60/838,714, filed on Aug. 18, 2006, entitled Package for an Implantable Neural Stimulation Device and of provisional Application Ser. No. 60/880,994, filed on Jan. 18, 2007, entitled Package for an Implantable Neural Stimulation Device the disclosures of both are incorporated herein by reference. 
    
    
     GOVERNMENT RIGHTS NOTICE 
     This invention was made with government support under grant No. R24EY12893-01, awarded by the National Institutes of Health. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally directed to neural stimulation and more specifically to an improved hermetic package for an implantable neural stimulation device. 
     BACKGROUND OF THE INVENTION 
     In 1755 LeRoy passed the discharge of a Leyden jar through the orbit of a man who was blind from cataract and the patient saw “flames passing rapidly downwards.” Ever since, there has been a fascination with electrically elicited visual perception. The general concept of electrical stimulation of retinal cells to produce these flashes of light or phosphenes has been known for quite some time. Based on these general principles, some early attempts at devising prostheses for aiding the visually impaired have included attaching electrodes to the head or eyelids of patients. While some of these early attempts met with some limited success, these early prosthetic devices were large, bulky and could not produce adequate simulated vision to truly aid the visually impaired. 
     In the early 1930&#39;s, Foerster investigated the effect of electrically stimulating the exposed occipital pole of one cerebral hemisphere. He found that, when a point at the extreme occipital pole was stimulated, the patient perceived a small spot of light directly in front and motionless (a phosphene). Subsequently, Brindley and Lewin (1968) thoroughly studied electrical stimulation of the human occipital (visual) cortex. By varying the stimulation parameters, these investigators described in detail the location of the phosphenes produced relative to the specific region of the occipital cortex stimulated. These experiments demonstrated: (1) the consistent shape and position of phosphenes; (2) that increased stimulation pulse duration made phosphenes brighter; and (3) that there was no detectable interaction between neighboring electrodes which were as close as 2.4 mm apart. 
     As intraocular surgical techniques have advanced, it has become possible to apply stimulation on small groups and even on individual retinal cells to generate focused phosphenes through devices implanted within the eye itself. This has sparked renewed interest in developing methods and apparati to aid the visually impaired. Specifically, great effort has been expended in the area of intraocular retinal prosthesis devices in an effort to restore vision in cases where blindness is caused by photoreceptor degenerative retinal diseases; such as retinitis pigmentosa and age related macular degeneration which affect millions of people worldwide. 
     Neural tissue can be artificially stimulated and activated by prosthetic devices that pass pulses of electrical current through electrodes on such a device. The passage of current causes changes in electrical potentials across visual neuronal membranes, which can initiate visual neuron action potentials, which are the means of information transfer in the nervous system. 
     Based on this mechanism, it is possible to input information into the nervous system by coding the sensory information as a sequence of electrical pulses which are relayed to the nervous system via the prosthetic device. In this way, it is possible to provide artificial sensations including vision. 
     One typical application of neural tissue stimulation is in the rehabilitation of the blind. Some forms of blindness involve selective loss of the light sensitive transducers of the retina. Other retinal neurons remain viable, however, and may be activated in the manner described above by placement of a prosthetic electrode device on the inner (toward the vitreous) retinal surface (epiretinal). This placement must be mechanically stable, minimize the distance between the device electrodes and the visual neurons, control the electronic field distribution and avoid undue compression of the visual neurons. 
     In 1986, Bullara (U.S. Pat. No. 4,573,481) patented an electrode assembly for surgical implantation on a nerve. The matrix was silicone with embedded iridium electrodes. The assembly fit around a nerve to stimulate it. 
     Dawson and Radtke stimulated cat&#39;s retina by direct electrical stimulation of the retinal ganglion cell layer. These experimenters placed nine and then fourteen electrodes upon the inner retinal layer (i.e., primarily the ganglion cell layer) of two cats. Their experiments suggested that electrical stimulation of the retina with 30 to 100 μA current resulted in visual cortical responses. These experiments were carried out with needle-shaped electrodes that penetrated the surface of the retina (see also U.S. Pat. No. 4,628,933 to Michelson). 
     The Michelson &#39;933 apparatus includes an array of photosensitive devices on its surface that are connected to a plurality of electrodes positioned on the opposite surface of the device to stimulate the retina. These electrodes are disposed to form an array similar to a “bed of nails” having conductors which impinge directly on the retina to stimulate the retinal cells. U.S. Pat. No. 4,837,049 to Byers describes spike electrodes for neural stimulation. Each spike electrode pierces neural tissue for better electrical contact. U.S. Pat. No. 5,215,088 to Norman describes an array of spike electrodes for cortical stimulation. Each spike pierces cortical tissue for better electrical contact. 
     The art of implanting an intraocular prosthetic device to electrically stimulate the retina was advanced with the introduction of retinal tacks in retinal surgery. De Juan, et al. at Duke University Eye Center inserted retinal tacks into retinas in an effort to reattach retinas that had detached from the underlying choroid, which is the source of blood supply for the outer retina and thus the photoreceptors. See, e.g., E. de Juan, et al., 99 Am. J. Ophthalmol. 272 (1985). These retinal tacks have proved to be biocompatible and remain embedded in the retina, and choroid/sclera, effectively pinning the retina against the choroid and the posterior aspects of the globe. Retinal tacks are one way to attach a retinal electrode array to the retina. U.S. Pat. No. 5,109,844 to de Juan describes a flat electrode array placed against the retina for visual stimulation. U.S. Pat. No. 5,935,155 to Humayun describes a retinal prosthesis for use with the flat retinal array described in de Juan. 
     US Patent Application 2003/0109903 to Peter G. Berrang describes a Low profile subcutaneous enclosure, in particular and metal over ceramic hermetic package for implantation under the skin. 
     U.S. Pat. No. 6,718,209, US Patent Applications Nos. 2002/0095193 and 2002/0139556 and US Patent Applications Nos. 2003/0233133 and 2003/0233134 describe inter alia package for an implantable neural stimulation device. Further descriptions of package for an implantable neural stimulation device can be found inter alia in U.S. Pat. No. 7,228,181; and US Patent Applications Nos. 20050288733 and 20060247754, all of which are assigned to a common assignee and incorporated herein by reference. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an improved hermetic package for implantation in the human body. The implantable device of the present invention includes an electrically non-conductive substrate including electrically conductive vias through the substrate. A circuit is flip-chip bonded to a subset of the vias. A second circuit is wire bonded to another subset of the vias. Finally, a cover is bonded to the substrate such that the cover, substrate and vias form a hermetic package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the implanted portion of the preferred retinal prosthesis. 
         FIG. 2  is a side view of the implanted portion of the preferred retinal prosthesis showing the strap fan tail in more detail. 
         FIG. 3  is a perspective view of a partially built package showing the substrate, chip and the package wall. 
         FIG. 4  is a perspective view of the hybrid stack placed on top of the chip. 
         FIG. 5  is a perspective view of the partially built package showing the hybrid stack placed inside. 
         FIG. 6  is a perspective view of the lid to be welded to the top of the package. 
         FIG. 7  is a view of the completed package attached to an electrode array. 
         FIG. 8  is a cross-section of the package. 
         FIG. 9  is a perspective view of the implanted portion of the preferred retinal prosthesis. 
         FIG. 10  is a cross-section of the three stack package. 
         FIG. 11  is a cross-section of the three stack package. 
         FIG. 12  is a cross-section of the two stack package. 
         FIG. 13  is a cross-section of the two stack package. 
         FIG. 14  is a cross-section of the two stack package. 
         FIG. 15  is a cross-section of the one stack package. 
         FIG. 16  is a cross-section of the folded stack package. 
         FIG. 17  is a cross-section of the package. 
         FIG. 18  is a cross-section of the package. 
         FIG. 19  is a cross-section of the lid shaping package. 
         FIG. 20  is a cross-section of the lid shaping package. 
         FIGS. 21 and 22  are cross-sections the package showing interconnects in detail. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. 
     The present invention is an improved hermetic package for implanting electronics within a body. Electronics are commonly implanted in the body for neural stimulation and other purposes. The improved package allows for miniaturization of the package which is particularly useful in a retinal or other visual prosthesis for electrical stimulation of the retina. 
       FIG. 1  shows a perspective view of the implanted portion of the preferred retinal prosthesis. A flexible circuit includes a flexible circuit electrode array  10  which is mounted by a retinal tack (not shown) or similar means to the epiretinal surface. The flexible circuit electrode array  10  is electrically coupled by a flexible circuit cable  12 , which pierces the sclera in the pars plana region, and is electrically coupled to an electronics package  14 , external to the sclera. Further an electrode array fan tail  15  is formed of molded silicone and attaches the electrode array cable  12  to a molded body  18  to reduce possible damage from any stresses applied during implantation. 
     The electronics package  14  is electrically coupled to a secondary inductive coil  16 . Preferably the secondary inductive coil  16  is made from wound wire. Alternatively, the secondary inductive coil  16  may be made from a flexible circuit polymer sandwich with wire traces deposited between layers of flexible circuit polymer. The electronics package  14  and secondary inductive coil  16  are held together by the molded body  18 . The molded body  18  holds the electronics package  14  and secondary inductive coil  16  end to end. This is beneficial as it reduces the height the entire device rises above the sclera. The design of the electronic package (described below) along with a molded body  18  which holds the secondary inductive coil  16  and electronics package  14  in the end to end orientation minimizes the thickness or height above the sclera of the entire device. This is important to minimize any obstruction of natural eye movement. 
     The molded body  18  may also include suture tabs  20 . The molded body  18  narrows to form a strap  22  which surrounds the sclera and holds the molded body  18 , secondary inductive coil  16 , and electronics package  14  in place. The molded body  18 , suture tabs  20  and strap  22  are preferably an integrated unit made of silicone elastomer. Silicone elastomer can be formed in a pre-curved shape to match the curvature of a typical sclera. However, silicone remains flexible enough to accommodate implantation and to adapt to variations in the curvature of an individual sclera. The secondary inductive coil  16  and molded body  18  are preferably oval shaped. A strap  22  can better support an oval shaped secondary inductive coil  16 . 
     Further it is advantageous to provide a sleeve or coating  50  that promotes healing of the scleratomy. Polymers such as polyimide, which may be used to form the flexible circuit cable  12  and flexible circuit electrode array  10 , are generally very smooth and do not promote a good bond between the flexible circuit cable  12  and scleral tissue. A sleeve or coating of polyester, collagen, silicon, GORETEX®, or similar material would bond with scleral tissue and promote healing. In particular, a porous material will allow scleral tissue to grow into the pores promoting a good bond. 
     It should be noted that the entire implant is attached to and supported by the sclera. An eye moves constantly. The eye moves to scan a scene and also has a jitter motion to improve acuity. Even though such motion is useless in the blind, it often continues long after a person has lost their sight. By placing the device under the rectus muscles with the electronics package in an area of fatty tissue between the rectus muscles, eye motion does not cause any flexing which might fatigue, and eventually damage, the device. 
       FIG. 2  shows side view of the implanted portion of the retinal prosthesis, in particular, emphasizing the strap fan tail  24 . When implanting the retinal prosthesis, it is necessary to pass the strap  22  under the eye muscles to surround the sclera. The secondary inductive coil  16  and molded body  18  must also follow the strap  22  under the lateral rectus muscle on the side of the sclera. The implanted portion of the retinal prosthesis is very delicate. It is easy to tear the molded body  18  or break wires in the secondary inductive coil  16  or electrode array cable  12 . In order to allow the molded body  18  to slide smoothly under the lateral rectus muscle, the molded body  18  is shaped in the form of a strap fan tail  24  on the end opposite the electronics package  14 . 
       FIG. 3  shows the hermetic electronics package  14  is composed of a ceramic substrate  60  brazed to a metal case wall  62  which is enclosed by a laser welded metal lid  84 . The metal of the wall  62  and metal lid  84  may be any biocompatible metal such as Titanium, niobium, platinum, iridium, palladium or combinations of such metals. The ceramic substrate is preferably alumina but may include other ceramics such as zirconia. The ceramic substrate  60  includes vias (not shown) made from biocompatible metal and a ceramic binder using thick-film techniques. The biocompatible metal and ceramic binder is preferably platinum flakes in a ceramic paste or frit which is the ceramic used to make the substrate. After the vias have been filled, the substrate  60  is fired and lapped to thickness. The firing process causes the ceramic to vitrify biding the ceramic of the substrate with the ceramic of the paste forming a hermetic bond. Thin-film metallization  66  is applied to both the inside and outside surfaces of the ceramic substrate  60  and an ASIC (Application Specific Integrated Circuit) integrated circuit chip  64  is bonded to the thin film metallization on the inside of the ceramic substrate  60 . 
     The inside thin film metallization  66  includes a gold layer to allow electrical connection using wire bonding. The inside film metallization includes preferably two to three layers with a preferred gold top layer. The next layer to the ceramic is a titanium or tantalum or mixture or alloy thereof. The next layer is preferably palladium or platinum layer or an alloy thereof. All these metals are biocompatible. The preferred metallization includes a titanium, palladium and gold layer. Gold is a preferred top layer because it is corrosion resistant and can be cold bonded with gold wire. 
     The outside thin film metallization includes a titanium adhesion layer and a platinum layer for connection to platinum electrode array traces. Platinum can be substituted by palladium or palladium/platinum alloy. If gold-gold wire bonding is desired a gold top layer is applied. 
     The package wall  62  is brazed to the ceramic substrate  60  in a vacuum furnace using a biocompatible braze material in the braze joint. Preferably, the braze material is a nickel titanium alloy. The braze temperature is approximately 1000° Celsius. Therefore the vias and thin film metallization  66  must be selected to withstand this temperature. Also, the electronics must be installed after brazing. The chip  64  is installed inside the package using thermocompression flip-chip technology. The chip is underfilled with epoxy to avoid connection failures due to thermal mismatch or vibration. 
       FIGS. 4 and 5  show off-chip electrical components  70 , which may include capacitors, diodes, resistors or inductors (passives), are installed on a stack substrate  72  attached to the back of the chip  64 , and connections between the stack substrate  72  and ceramic substrate  60  are made using gold wire bonds  82 . The stack substrate  72  is attached to the chip  64  with non-conductive epoxy, and the passives  70  are attached to the stack substrate  72  with conductive epoxy. 
       FIG. 6  shows the electronics package  14  is enclosed by a metal lid  84  that, after a vacuum bake-out to remove volatiles and moisture, is attached using laser welding. A getter (moisture absorbent material) may be added after vacuum bake-out and before laser welding of the metal lid  84 . The metal lid  84  further has a metal lip  86  to protect components from the welding process and further insure a good hermetic seal. The entire package is hermetically encased. Hermeticity of the vias, braze, and the entire package is verified throughout the manufacturing process. The cylindrical package was designed to have a low profile to minimize its impact on the eye when implanted. 
     The implant secondary inductive coil  16 , which provides a means of establishing the inductive link between the external video processor (not shown) and the implanted device, preferably consists of gold wire. The wire is insulated with a layer of silicone. The secondary inductive coil  16  is oval shaped. The conductive wires are wound in defined pitches and curvature shape to satisfy both the electrical functional requirements and the surgical constraints. The secondary inductive coil  16 , together with the tuning capacitors in the chip  64 , forms a parallel resonant tank that is tuned at the carrier frequency to receive both power and data. 
       FIG. 7  shows the flexible circuit, includes platinum conductors  94  insulated from each other and the external environment by a biocompatible dielectric polymer  96 , preferably polyimide. One end of the array contains exposed electrode sites that are placed in close proximity to the retinal surface  10 . The other end contains bond pads  92  that permit electrical connection to the electronics package  14 . The electronic package  14  is attached to the flexible circuit using a flip-chip bumping process, and epoxy underfilled. In the flip-chip bumping process, bumps containing conductive adhesive placed on bond pads  92  and bumps containing conductive adhesive placed on the electronic package  14  are aligned and melted to build a conductive connection between the bond pads  92  and the electronic package  14 . Leads  76  for the secondary inductive coil  16  are attached to gold pads  78  on the ceramic substrate  60  using thermal compression bonding, and are then covered in epoxy. The electrode array cable  12  is laser welded to the assembly junction and underfilled with epoxy. The junction of the secondary inductive coil  16 , array  1 , and electronic package  14  are encapsulated with a silicone overmold  90  that connects them together mechanically. When assembled, the hermetic electronics package  14  sits about 3 mm away from the end of the secondary inductive coil. 
     Since the implant device is implanted just under the conjunctiva it is possible to irritate or even erode through the conjunctiva. Eroding through the conjunctiva leaves the body open to infection. We can do several things to lessen the likelihood of conjunctiva irritation or erosion. First, it is important to keep the over all thickness of the implant to a minimum. Even though it is advantageous to mount both the electronics package  14  and the secondary inductive coil  16  on the lateral side of the sclera, the electronics package  14  is mounted higher than, but not covering, the secondary inductive coil  16 . In other words the thickness of the secondary inductive coil  16  and electronics package should not be cumulative. 
     It is also advantageous to place protective material between the implant device and the conjunctiva. This is particularly important at the scleratomy, where the thin film electrode cable  12  penetrates the sclera. The thin film electrode array cable  12  must penetrate the sclera through the pars plana, not the retina. The scleratomy is, therefore, the point where the device comes closest to the conjunctiva. The protective material can be provided as a flap attached to the implant device or a separate piece placed by the surgeon at the time of implantation. Further material over the scleratomy will promote healing and sealing of the scleratomy. Suitable materials include DACRON®, TEFLON®, GORETEX® (ePTFE), TUTOPLAST® (sterilized sclera), MERSILENE® (polyester) or silicone. 
       FIG. 8  shows the package  14  containing a ceramic substrate  60 , with metallized vias  65  and thin-film metallization  66 . The package  14  contains a metal case wall  62  which is connected to the ceramic substrate  60  by braze joint  61 . On the ceramic substrate  60  an underfill  69  is applied. On the underfill  69  an integrated circuit chip  64  is positioned. On the integrated circuit chip  64  a ceramic hybrid substrate  68  is positioned. On the ceramic hybrid substrate  68  passives  70  are placed. Wirebonds  67  are leading from the ceramic substrate  60  to the ceramic hybrid substrate  68 . A metal lid  84  is connected to the metal case wall  62  by laser welded joint  63  whereby the package  14  is sealed. 
       FIG. 9  shows a perspective view of the implanted portion of the preferred retinal prosthesis which is an alternative to the retinal prosthesis shown in  FIG. 1 . 
     The electronics package  14  is electrically coupled to a secondary inductive coil  16 . Preferably the secondary inductive coil  16  is made from wound wire. Alternatively, the secondary inductive coil  16  may be made from a flexible circuit polymer sandwich with wire traces deposited between layers of flexible circuit polymer. The electronics package  14  and secondary inductive coil  16  are held together by the molded body  18 . The molded body  18  holds the electronics package  14  and secondary inductive coil  16  end to end. The secondary inductive coil  16  is placed around the electronics package  14  in the molded body  18 . The molded body  18  holds the secondary inductive coil  16  and electronics package  14  in the end to end orientation and minimizes the thickness or height above the sclera of the entire device. 
     Lid  84  and case wall  62  may also contain titanium or titanium alloy or other metals and metal alloys including platinum, palladium, gold, silver, ruthenium, or ruthenium oxide. Lid  84  and case wall  62  may also contain a polymer, copolymer or block copolymer or polymer mixtures or polymer multilayer containing parylene, polyimide, silicone, epoxy, or PEEK™ polymer. Via substrate may be preferably contain alumina or zirconia with platinum vias. 
       FIG. 15  shows one stack assembly. One stack means that all of the parts including discretes  102  and chip  112  are on the ceramic substrate  60 , with our without a separate demux  108 . A via substrate  60  is placed on the bottom below a flip IC which includes RF Transceiver, power recovery, drivers, and an optional demux  108 . 
       FIG. 12 ,  FIG. 13  and  FIG. 14  show two stack assemblies.  FIG. 16  shows a folded stack assembly.  FIG. 12  shows a ceramic substrate  104  next to RF transceiver/power recovery chip  114  and both placed on a flipchip driver/demux  108 .  FIG. 13  shows ceramic substrate  104  on a flipchip driver/demux  108 . RF transceiver/power recovery chip  1144  is provided on the ceramic substrate  104 .  FIG. 14  shows ceramic substrate  104  on a flipchip driver/demux  108 . RF transceiver/power recovery chip  114  is provided not directly on the ceramic substrate  60 . The difference between  FIG. 13  and  FIG. 14  is that in  FIG. 13  the ceramic substrate  104  is in direct contact with RF transceiver/power recovery chip  114  but not in  FIG. 14 . The substrate  104  can be ceramic but also any kind of polymer or glass.  FIG. 16  shows a folded flex substrate  116  and a flipchip demux  108  on the bottom and an IC  106  placed on the flip chip demux  108 . The substrate  116  is folded twice. 
       FIG. 10  and  FIG. 11  show a three stack assembly. A three stack demux flip-chip  108  bonded to substrate  104  with chip  106  and hybrid with discrete passives  102  wire-bonded above is preferred.  FIG. 10  shows a ceramic substrate  104  on a IC  106  including a RF transceiver/power recovery drivers and the IC is placed on a flipchip driver/demux  108 .  FIG. 11  shows a similar assembly as  FIG. 10  however the ceramic substrate  104  is placed on pedestal  110  which is placed between the substrate  104  and the IC  106 . 
       FIG. 17  and  FIG. 18  show additional flip chip configurations. Both figures have a similar assembly. However, in  FIG. 17  the IC  106  is bonded to flipchip demux by a bump bond. In  FIG. 18 , a double-sided multilayer ceramic substrate  104  is bonded to the IC by a bump bond. 
     They can be two stack or folded stack and could be one or two-sided. It may be passive on the substrate next to IC. A pedestal is useful but optional to make room for wire bonds. A through via means that via goes through the IC. A bump bond to IC and then bump bond to IC to passive substrate or demux is possible. Bond pads on IC to line up with vias to eliminate the inside metallization can be provided. Driver IC flipchip can be bonded to substrate with passives. Demux flip-chip can be bonded to via substrate and the two substrates can be wire-bonded or flex circuit bonded together. Driver portion can be moved to demux chip and everything else to a separate chip to reduce interconnect lines. Two stack chip can be provided with smaller chip (RF and demux) and hybrid above. It may include wire-bonds directly from the Hybrid to the chip. Chip may include a demux driver on the same wafer. 
       FIG. 19  and  FIG. 20  show different variations of the lid shape. Possible is a concave lid to conform to eye. 
       FIG. 21  and  FIG. 22  are cross-sections the package showing redistribution routing and interconnect traces  66  in detail. Both figures show redistribution routings and interconnect traces  66  on the top and the bottom of via substrate  60 . Redistribution routing on top of the via substrate and the braze stop on top of the via substrate contain preferably metals like Ti, Zr, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, mixtures, layers or alloys thereof. The top layer of the top redistribution routing is gold or gold alloy. Redistribution routing on bottom of the via substrate and the braze stop on top of the via substrate contain preferably metals like Ti, Zr, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, mixtures, layers or alloys thereof. The top layer of the top redistribution routing is platinum or platinum alloy. Interconnect and redistribution routing is the connection the bond between flexible circuit and via substrate on the bottom of the substrate and a connection between the flip chip circuit  64  and the substrate on top of the substrate. Additional braze stop traces  102  surround the redistribution and interconnect traces  66  to prevent the braze metal  104  from running into the redistribution and interconnect traces  66 . The walls in  FIG. 22  show the same braze metal  104  as mentioned before as a flange. 
     Accordingly, what has been shown is an improved method making a hermetic package for implantation in a body. While the invention has been described by means of specific embodiments and applications thereof, it is understood that numerous modifications and variations could be made thereto by those skilled in the art without departing from the spirit and scope of the invention. It is therefore to be understood that within the scope of the claims, the invention may be practiced otherwise than as specifically described herein.

Technology Classification (CPC): 7