A flexible electrode integrated with a feedthrough substrate, a preparation method thereof, and an electrode device

Abstract

The application provides a flexible electrode integrated with a feedthrough substrate, a preparation method of the flexible electrode and an electrode device. The flexible electrode comprises, in sequence, a flexible electrode, a feedthrough substrate, a redistribution layer and an external circuit. The flexible electrode has an electrode conductive layer. The feedthrough substrate is internally provided with an array of conductive micro pillars. The top and bottom surfaces of the feedthrough substrate are both provided with an insulating layer. The outer surface of the insulating layer is provided with a substrate pad. The redistribution layer has a redistribution conductive layer and a redistribution pad connected with the redistribution conductive layer. The electrode conductive layer, the array of conductive micro pillars, the substrate pad and the redistribution conductive layer are electrically connected. The application can realize the integrated MEMS flow processing mode of the device, and has high processing consistency and good biocompatibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible electrodes, in particular, to a flexible electrode integrated with a feedthrough substrate, a preparation method thereof and an electrode device. BACKGROUND

[0002] Brain-computer interface technology provides a way of communication between brain and the outside world, which bypasses peripheral nerves and muscle tissue, and directly transmits brain signals to the outside world or transmits information from the outside world to the brain through stimulation. Based on this way, some patients with limb disability, muscle atrophy or peripheral nerve damage leading to paralysis can read brain electrical signals through brain-computer interface to realize neural connection or connection with external auxiliary devices, and regain motor and sensory functions.

[0003] The electronic devices implanted in animals and humans can be divided into physiological signal acquisition electrodes and signal processing systems from the perspective of signal acquisition. With the development of MEMS technology, many silicon-based electrodes and flexible polymer electrodes have emerged, which have the characteristics of small volume and high-density channels. Among them, flexible polymer electrodes have better long-term stability because they have a Young's modulus closer to biological tissue and can conform to the small movements of the tissue.

[0004] On the other hand, the compatibility of flexible electrodes with IC technology is far inferior to that of silicon-based electrodes, making the packaging and bonding of flexible electrodes with subsequent signal processing systems develop more slowly than silicon-based electrodes. For example, in the paper "Time Multiplexed Active Neural Probe with 1356 Parallel Recording Sites" published by IMEC in 2017, a silicon-based implantable probe and an IC signal processing circuit are integrated on a silicon needle, completing an integrated flow process. In the paper "A Miniaturized 256-Channel Neural Recording Interface With Area-Efficient Hybrid Integration of Flexible Probes and CMOS Integrated Circuits" published by Sung-Yun Park et al. in 2022, flexible electrodes are packaged with ASIC chips through flip-chip bonding and adapter boards, and the diameter of the bonding solder balls is 75 μm. Other bonding processes, such as wire bonding and ball grid array, not only have a large bonding volume, but also require separate manufacturing of adapter boards, which cannot achieve integrated flow with flexible electrodes, increasing the process complexity. SUMMARY

[0005] In view of the defects in the prior art, the present application aims to provide a flexible electrode integrated with a feedthrough substrate, a preparation method thereof and an electrode device.

[0006] According to a first aspect of the present application, a flexible electrode integrated with a feedthrough substrate is provided, which comprises, in sequence:

[0007] a flexible electrode having an electrode conductive layer;

[0008] a feedthrough substrate, an interior of the feedthrough substrate being provided with an array of conductive micro pillars, a top and a bottom surface of the feedthrough substrate each being provided with an insulating layer, an outer surface of the insulating layer being provided with a substrate pad;

[0009] a redistribution layer having a redistribution conductive layer and a redistribution pad connected to the redistribution conductive layer, an external circuit being connected through the redistribution pad, an electrical connection being formed between the electrode conductive layer, the array of conductive micro pillars, the substrate pad and the redistribution conductive layer.

[0010] Further, the feedthrough substrate comprises any one of a ceramic feedthrough substrate, a glass feedthrough substrate and a silicon-based feedthrough substrate.

[0011] Further, the electrode conductive layer has a thickness of 0.01-1 μm.

[0012] Further, the substrate pad has a thickness of 0.5-5 μm, and the insulating layer is made of any one of silicon dioxide, silicon carbide, aluminum oxide and zirconium oxide.

[0013] Further, the redistribution conductive layer has a thickness of 1-10 μm.

[0014] According to a second aspect of the present application, a preparation method of the above flexible electrode integrated with a feedthrough substrate is provided, which comprises:

[0015] forming a substrate having an array of micro holes;

[0016] filling the array of micro holes with a conductive material, and planarizing the surface of the substrate to form a feedthrough substrate;

[0017] forming an insulating layer on a first surface of the feedthrough substrate and a second surface opposite to the first surface, and forming a substrate pad on the insulating layer;

[0018] placing the feedthrough substrate with the first surface on the second surface, spin-coating a flexible polymer on the first surface to form a flexible electrode base layer; and patterning the flexible electrode base layer to expose the substrate pad;

[0019] Sputtering to form an electrode metal layer on the flexible electrode substrate layer; and spin-coating a photoresist mask on the electrode metal layer, and after exposure and development, patterning to obtain an electrode conductive layer;

[0020] Spin-coating a flexible polymer on the electrode conductive layer to form a flexible electrode encapsulation layer;

[0021] Turning the feedthrough substrate so that the second surface is above the first surface, spin-coating a flexible polymer on the second surface to form a redistribution substrate layer;

[0022] According to the redistribution layer lead layout, sequentially performing patterning, sputtering a metal layer, spin-coating a mask on the redistribution substrate layer, and after exposure and development, patterning to form a redistribution lead layer;

[0023] Spin-coating a flexible polymer on the redistribution lead layer to form a redistribution encapsulation layer; and patterning the redistribution encapsulation layer to expose the redistribution pads.

[0024] Further, the single-layer thickness of the flexible electrode substrate layer and the flexible electrode encapsulation layer is 0.2-20 μm.

[0025] Further, the spin-coating of the flexible polymer on the second surface to form a redistribution substrate layer, wherein: the flexible polymer used in the redistribution layer is doped with thermally conductive particles to improve thermal conductivity.

[0026] Further, the single-layer thickness of the redistribution layer substrate layer and the redistribution layer encapsulation layer is 5-10 μm; and the total thickness of the redistribution layer is 10-50 μm.

[0027] According to a third aspect of the present application, there is provided an electrode device, comprising an ASIC chip and the flexible electrode of the integrated feedthrough substrate as described above, wherein the ASIC chip is connected to the redistribution pads.

[0028] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0029] 1. The biocompatible flexible electrode used in the present application not only has the advantages of small size and high channel number of a silicon-based probe, but also has a Young's modulus closer to biological tissues, can conform to the micro-motion of biological tissues, reduce implantation damage, and realize long-term physiological signal acquisition function.

[0030] 2. In the integrated preparation method described above, the bonding and packaging of the flexible electrode and the adapter plate (i.e. the electrical interconnection feedthrough substrate) are completed under MEMS technology, which simplifies the bonding process flow and bonding difficulty, and the integrated wafer process can realize high controllability and high repeatability.

[0031] 3. In the above-mentioned integrated fabrication method of the present invention, the electrical connection between the flexible electrode and the feedthrough substrate is achieved through metal pads. Compared with the conventional solder ball connection method, the pad size is greatly reduced. In practice, the bonding feature length can be within 10μm, which improves the sealing feedthrough density and integration.

[0032] 4. The feedthrough substrate of the present invention has a redistribution layer deposited on the back, which can adapt to the pin distribution of different ASIC chips and expand the applicability and application scenarios of integrated feedthrough and flexible electrode devices. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1 This is a bottom view schematic diagram of the flexible electrode of an integrated feedthrough substrate according to an embodiment of the present invention;

[0035] Figure 2 This is a top view schematic diagram of the flexible electrode of an integrated feedthrough substrate according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the electrical interconnection between an ASIC chip and a flexible electrode according to an embodiment of the present invention;

[0037] Figure 4 This is a schematic flowchart illustrating a method for fabricating a flexible electrode on an integrated feedthrough substrate according to an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the structure corresponding to each step of the fabrication method of the flexible electrode of the integrated feedthrough substrate according to an embodiment of the present invention.

[0039] In the figure: 1 is the feedthrough substrate, 101 is the conductive micropillar, 2 is the flexible electrode, 201 is the flexible electrode pad, 3 is the redistribution layer, 301 is the physiological signal input pad, 302 is the ASIC redistribution pad, and 4 is the ASIC chip. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0041] This invention provides a flexible electrode with an integrated feedthrough substrate, referring to... Figures 1-2The flexible electrode comprises a flexible electrode 2, a feedthrough substrate 1 and a redistribution layer 3 (RDL) arranged in sequence, the flexible electrode 2 has an electrode conductive layer; the feedthrough substrate 1 is internally provided with a conductive microcolumn array formed by conductive microcolumns 101, the top and bottom surfaces of the feedthrough substrate 1 are each provided with an insulating layer, and the outer surface of the insulating layer is provided with a substrate pad; the redistribution layer 3 has a redistribution conductive layer and a redistribution pad connected with the redistribution conductive layer, and an external circuit is connected through the redistribution pad, and an electrical connection is formed between the electrode conductive layer, the conductive microcolumn array, the substrate pad and the redistribution conductive layer, so as to realize electrical interconnection feedthrough.

[0042] In some embodiments, the feedthrough substrate 1 comprises any one of a ceramic feedthrough substrate, a glass feedthrough substrate and a silicon-based feedthrough substrate. The conductive microcolumns 101 are formed by filling a conductive material, wherein the filling of the conductive material includes electroplating or sintering and hot pressing.

[0043] A layer of insulating layer is deposited on the upper and lower surfaces of the feedthrough substrate 1, which can solve the device failure problem caused by the gap between the feedthrough substrate 1 and the conductive microcolumns 101. In some embodiments, the material of the insulating layer is any one of silicon dioxide, silicon carbide, aluminum oxide and zirconium oxide. The diameter of the insulating layer via 3 is 1-20 um smaller than the diameter of the conductive microcolumn 101. The insulating layer has a small hole at the conductive microcolumn 101, so that the insulating layer can cover the gap between the feedthrough substrate 1 and the conductive microcolumn 101, and also maintain the electrical connection between the conductive microcolumn 101 and the flexible electrode 2 or the redistribution layer 3.

[0044] The feedthrough substrate 1 in the above embodiment is formed by a MEMS process, which can realize micron-level processing line width, thereby having a high-density feedthrough number; the insulating layer via covers the gap between the conductive microcolumn 101 and the substrate, strengthens the cracks that may exist in the contact surface of different materials, and has the characteristics of high sealing performance; the insulating layer via can be formed by a reverse mold process, and the smoothness and uniformity of the mold are improved by high-precision processing, thereby improving the uniformity of the morphology of the ceramic via. The above-mentioned feedthrough substrate 1 has the advantages of high-density feedthrough number, high sealing performance, uniform via morphology, etc.

[0045] In some embodiments, the substrate pad is too small, the welding is not firm, and the effect is poor; and if the substrate pad is too large, the impedance will be increased, preferably, the thickness of the substrate pad is 0.5-5 um, and the material of the substrate pad includes but is not limited to titanium, platinum, chromium, gold or an alloy therebetween.

[0046] In some embodiments, the flexible electrode 2 and the redistribution layer 3 each comprise a polymer substrate layer, a metal layer (conductive layer), and a polymer encapsulation layer. The thickness of the electrode conductive layer is 0.01-1 μm, the electrode conductive layer of the flexible electrode 2 comprises a flexible electrode pad 201, one end of the electrode conductive layer is an electrode collection point, and the other end is the flexible electrode pad 201. The material of the conductive layer includes but is not limited to titanium, platinum, chromium, gold, or an alloy thereof. The material of the polymer encapsulation layer of the flexible electrode 2 includes but is not limited to PDMS, PI, SU-8, Parylene, etc.

[0047] In some embodiments, the thickness of the redistribution conductive layer is 1-10 μm. One end of the redistribution conductive layer is connected to the substrate pad, and the other end is exposed as a redistribution pad. The redistribution layer pad includes a physiological signal input pad 301 and an ASIC redistribution pad 302. The material of the polymer encapsulation layer of the redistribution layer 3 includes but is not limited to PDMS, PI, SU-8, Parylene, etc. In view of the problem of heat accumulation of the ASIC chip and the difficulty of heat dissipation of the conventional polymer, the flexible polymer of the redistribution layer 3 is doped with heat-conducting particles to improve the heat conductivity. The heat-conducting particles include but are not limited to aluminum nitride, silver nanowires, carbon nanotubes, etc.

[0048] In some embodiments, the thinner the flexible polymer substrate layer and the encapsulation layer, the softer the flexible polymer substrate layer and the encapsulation layer, the smaller the damage to the tissue when implanted in the animal body. However, the flexible polymer substrate layer and the encapsulation layer are too soft to be inconvenient for manual operation. According to the different polymer materials used, the thickness of the flexible polymer substrate layer and the encapsulation layer is between 0.2-20 μm, and more preferably between 1-20 μm. The redistribution layer substrate layer and the encapsulation layer are too thick to be conducive to heat dissipation, and too thin to be conducive to the subsequent connection of the ASIC chip. According to the different polymer materials used, the thickness of the redistribution layer substrate layer and the encapsulation layer is between 5-10 μm, and according to the number of redistribution layer conductive layers, the total thickness of the redistribution layer is between 10-50 μm.

[0049] In the embodiments of the present application, the polymer layers of the feedthrough substrate 1, the insulating layer, the flexible electrode 2, and the redistribution layer 3 are all made of inert materials with good biocompatibility. The metal pads and conductive layers deposited by titanium, chromium, gold, etc. cover the conductive micro-pillars 101, further isolating their biological toxicity. Thus, the biological tissue safety and long-term stability of the integrated feedthrough substrate 1 and the flexible electrode device can be ensured.

[0050] The flexible electrode in the above embodiment can be formed by a MEMS process, and a soft polymer is used to form an encapsulation layer, so that the flexible electrode has the advantages of a small size, a high number of channels, a Young's modulus close to that of a biological tissue, and the like, can conform to the micro-motion of the biological tissue, reduces the implantation damage, and realizes the long-term physiological signal acquisition function. In the prior art, the minimum size of the ball welding process is about 50 um, and in the embodiment of the present application, the electrical connection between the flexible electrode 2 and the feedthrough substrate 1 is realized through the flexible electrode pad 201 and the substrate pad, and the thicknesses of the two are within 10 um. Compared with the conventional ball connection mode, the size of the pad is greatly reduced, the bonding feature length in practice can be within 10 um, and the sealing feedthrough density and the integration degree are improved. The redistribution layer 3 is deposited on the back of the feedthrough substrate 1, and can adapt to the pin distribution of different ASIC chips, so that the application range and application scenarios of the integrated feedthrough and flexible electrode device are expanded.

[0051] Another embodiment of the present application provides a preparation method of the flexible electrode of the integrated feedthrough substrate. Figure 4 The method comprises the following steps:

[0052] Step 1, forming a substrate with a micro-hole array;

[0053] Step 2, filling the micro-holes in the micro-hole array with a conductive material, and planarizing the surface of the substrate to form a feedthrough substrate;

[0054] Step 3, forming an insulating layer on the first surface and the second surface opposite to the first surface of the feedthrough substrate, and forming a substrate pad on the insulating layer;

[0055] Step 4, placing the feedthrough substrate so that the first surface is above the second surface, spin-coating a flexible polymer on the first surface to form a flexible electrode base layer, and patterning the flexible electrode base layer to expose the substrate pad;

[0056] Step 5, sputtering an electrode metal layer on the flexible electrode base layer, spin-coating a photoresist mask on the electrode metal layer, and patterning the electrode conductive layer after exposure and development, and the step simultaneously forms a flexible electrode pad;

[0057] Step 6, spin-coating a flexible polymer on the electrode conductive layer to form a flexible electrode encapsulation layer;

[0058] Step 7, turning over the feedthrough substrate so that the second surface is above the first surface, spin-coating a flexible polymer on the second surface to form a redistribution base layer;

[0059] Step 8, patterning, sputtering a metal layer, spin-coating a mask, and patterning after exposure and development on the redistribution base layer according to the lead layout of the redistribution layer to form a redistribution lead layer; the step simultaneously forms a redistribution pad;

[0060] Step 9, spin-coat a flexible polymer on the redistribution wire layer to form a redistribution encapsulation layer; and pattern the redistribution encapsulation layer to expose the redistribution pads.

[0061] In some embodiments, in step 1, a substrate with a micro-hole array is formed, and the substrate includes any one of a ceramic substrate, a glass substrate, and a silicon substrate. The ceramic substrate can be prepared by a ceramic sintering process using ceramic powder and a mold with a micro-pillar array, and the ceramic sintering process includes hot-press sintering, hot isostatic pressing sintering, microwave sintering, plasma activated sintering, and other sintering methods. The micro-hole array formed by a plurality of micro-holes is formed in the ceramic substrate by sintering demolding. The sintering demolding method has batch production capability, low process cost, and good pore morphology, and the internal stress of the formed micro-holes is uniformly distributed. The glass substrate can be formed by using molten glass instead of ceramic powder and then being cooled and solidified by a mold with a micro-pillar array. The silicon substrate can form a through-silicon via array by using TSV technology under etching mask and Bosch process.

[0062] In some embodiments, the single-layer thickness of the flexible electrode base layer and the flexible electrode encapsulation layer is 1-20 μm.

[0063] In some embodiments, a flexible polymer is spin-coated on the second surface to form a redistribution base layer, wherein: the flexible polymer used in the redistribution layer is doped with thermally conductive particles to improve thermal conductivity.

[0064] In some embodiments, the single-layer thickness of the redistribution layer base layer and the redistribution layer encapsulation layer is 5-10 μm; and the total thickness of the redistribution layer is 10-50 μm.

[0065] The above method for preparing a flexible electrode includes the following steps: sintering a ceramic feedthrough substrate and forming an electrically interconnected conductive micro-pillar array in the substrate; depositing metal pads on the surface and back of the feedthrough substrate, and the pads correspond one-to-one to the micro-pillar array of the substrate; spin-coating a polymer base layer on the surface and back of the feedthrough substrate and patterning the polymer base layer to expose the micro-pillar holes of the substrate; depositing a metal layer on the surface and back of the substrate and patterning the metal layer; spin-coating a polymer encapsulation layer on the surface and back of the substrate and patterning the polymer encapsulation layer to complete the construction of the flexible electrode and the redistribution layer. The redistribution layer can be further connected to an application-specific integrated circuit (ASIC), and the pads of the redistribution layer are matched with the pins of the ASIC chip to meet special and diversified pin layouts, so that the integrated MEMS flow sheet method can be used to form a device, and the processing consistency is high and the biocompatibility is good. Subsequent steps such as metal pad deposition, flexible polymer film deposition, conductive layer deposition, and flexible polymer encapsulation layer deposition in the MEMS process can be performed on the ceramic substrate to form a flexible electrode and a redistribution layer.

[0066] In one embodiment, the method for manufacturing the flexible electrode integrated with the feedthrough substrate comprises the following steps:

[0067] 1) Forming a ceramic substrate with a micro-hole array by a ceramic sintering process;

[0068] 2) Electroplating conductive vias in the micro-hole array and further planarizing to form a ceramic feedthrough substrate;

[0069] 3) Depositing a biocompatible insulating layer on the outer surface of the ceramic and metal pads on the top and back of the feedthrough;

[0070] 4) Spin-coating a biocompatible flexible polymer on the top of the feedthrough substrate to form a flexible electrode base layer;

[0071] 5) Patterning the flexible electrode base layer to expose the metal pads;

[0072] 6) Sputtering a conductive layer on the flexible electrode base layer;

[0073] 7) Spin-coating a photoresist mask on the conductive layer, and after exposure and development, patterning the conductive metal layer;

[0074] 8) Spin-coating a biocompatible flexible polymer on the top of the substrate to form a flexible electrode encapsulation layer;

[0075] 9) Inverting the ceramic substrate, spin-coating a flexible polymer doped with biocompatible particles such as AlN on the back of the ceramic substrate to form a redistribution base layer;

[0076] 10) According to the lead layout of the redistribution layer, performing steps 5) to 7) on the back of the ceramic substrate;

[0077] 11) Spin-coating a flexible polymer doped with particles such as AlN on the back of the substrate to form a redistribution encapsulation layer;

[0078] 12) Patterning the redistribution encapsulation layer to expose the redistribution pads.

[0079] In the above integrated manufacturing method, the bonding of the flexible electrode and the adapter plate (i.e. the electrically interconnected feedthrough substrate) is completed under the MEMS process, simplifying the bonding process flow and bonding difficulty, and the integrated flow process can achieve high controllability and high repeatability.

[0080] Another embodiment of the present application also provides an electrode device, which comprises an ASIC chip and the flexible electrode integrated with the feedthrough substrate as described above, and the electrode device is described in detail with reference to Figure 3The ASIC chip 4 is connected with the redistribution pads to realize signal communication between the flexible electrode and the ASIC chip 4 and redistribution of pins such as power supply pins and output pins of the ASIC chip 4. The ASIC chip is not limited in the embodiment, and any chip meeting the functional requirement can be used, and the chip pad structure and the layout of the feedthrough array in the feedthrough substrate are correspondingly coordinated, so that the signal communication can be realized.

[0081] The electrode device is connected with the ASIC chip through the redistribution pads of the redistribution layer, and the connection method includes any one of welding, anisotropic conductive film (ACF) connection and conductive epoxy resin connection.

[0082] The integrated feedthrough substrate flexible electrode, the preparation method and the electrode device of the present application are further described below through specific embodiments.

[0083] Embodiment 1

[0084] The preparation method of the integrated feedthrough substrate flexible electrode of the embodiment (integrated flow process) is described with reference to Figure 5 The preparation method specifically includes the following steps:

[0085] As shown in S1 of Figure 5 , the electrically fused mullite, the capacitive white corundum, the sintered α-Al2O3 micropowder and the SiO2 micropowder are ground and mixed, and a water-soluble resin binder is added and poured into a ceramic mold with a microcolumn array.

[0086] As shown in S2 of Figure 5 , after drying at 110°C for 24 hours under a pressure atmosphere of 120 MPa, the mold and the ceramic powder are put into a high-temperature gas kiln for hot-press sintering at 1750°C for 6 hours.

[0087] As shown in S3 of Figure 5 , the sintered ceramic is separated from the mold to obtain a ceramic substrate with a microhole array.

[0088] As shown in S4 of Figure 5 , a 10 nm chromium barrier layer and a 30 nm copper seed layer are sputtered at the microholes, and the microhole array is filled by a copper electroplating process to form a conductive microcolumn array. As shown in S4 of Figure 5 , on the top and back of the ceramic substrate, the ceramic sintering process and the electroplating process cause unevenness of the surface of the entire ceramic substrate.

[0089] As shown in S5 of Figure 5 , the surface of the ceramic substrate is planarized by chemical mechanical polishing to obtain a conductive feedthrough structure connected between the top and the bottom;

[0090] As shown in S6 of Figure 5As shown in S6, a layer of SiC about 1 μm thick is deposited by plasma enhanced chemical vapor deposition. A mask is applied to the surface of the ceramic substrate prior to the deposition of SiC to prevent the SiC from blocking the micro-pillar holes.

[0091] As shown in S3, a layer of SiC about 1 μm thick is deposited by plasma enhanced chemical vapor deposition. A mask is applied to the surface of the ceramic substrate prior to the deposition of SiC to prevent the SiC from blocking the micro-pillar holes. Figure 5 As shown in S7, a 30 nm thick layer of Cr and a 1 μm thick layer of Au are sputter deposited on the SiC insulating layer in the openings of the SiC insulating layer, i.e. the micro-pillar holes.

[0092] As shown in S3, a layer of SiC about 1 μm thick is deposited by plasma enhanced chemical vapor deposition. A mask is applied to the surface of the ceramic substrate prior to the deposition of SiC to prevent the SiC from blocking the micro-pillar holes. Figure 5 As shown in S8, a layer of photo-sensitive polyimide Durimide 7505 is spin-coated on the SiC insulating layer (1000 rpm for 7 seconds, 1500 rpm for 30 seconds). After 6 seconds of exposure, 35 seconds of development and 350 °C curing, a 5 μm thick layer of polyimide is obtained. A 30 nm thick layer of Cr and a 200 nm thick layer of Au are sputter deposited between the polyimide substrate layer (base layer) and the encapsulation layer. The polyimide layer and the conductive layer constitute the flexible electrode.

[0093] Figure 5 As shown in S9, the ceramic substrate is flipped over and a SiC insulating layer is deposited on the flipped surface. A mask is applied to the surface of the ceramic substrate prior to the deposition of SiC to prevent the SiC from blocking the micro-pillar holes. A 30 nm thick layer of Cr and a 1 μm thick layer of Au are sputter deposited on the SiC insulating layer in the openings of the SiC insulating layer, i.e. the micro-pillar holes.

[0094] Figure 5 As shown in S10, a layer of photo-sensitive polyimide Durimide 7505 is spin-coated on the ceramic substrate. The polyimide polymer is doped with AlN particles to improve its thermal conductivity, as the redistribution layer is connected to the ASIC chip and heat is easily accumulated. The thickness of the polyimide polymer substrate layer and the encapsulation layer is 6 μm. The thickness of the conductive layer is 3 μm and a single layer of wiring is used. The thickness of the Au pads at the opening of the encapsulation layer is 1 μm. The total thickness of the redistribution layer is 16 μm.

[0095] Example 2

[0096] The difference between this example and the previous examples is that Parylene C is used as the flexible electrode substrate layer. The steps of the preparation method are as follows:

[0097] S1 : The electrically fused mullite, the capacitive white corundum, the sintered α-Al2O3 micropowder and the SiO2 micropowder are ground and mixed, and a water-soluble resin binder is added. The mixture is poured into a ceramic mold with a micro-pillar array. After drying at 110 °C for 24 hours under a pressure of 120 MPa, the mold and the ceramic powder are placed in a high-temperature gas kiln and sintered at 1750 °C for 6 hours.

[0098] S2: The sintered ceramic is separated from the mold to obtain a ceramic substrate with a micro-hole array. A 10 nm chromium barrier layer and a 30 nm copper seed layer are sputtered at the micro-holes, and the micro-hole array is filled by a copper electroplating process to form a conductive micro-column array.

[0099] S3: The ceramic substrate surface is planarized by chemical mechanical polishing to obtain an electrically interconnected feedthrough structure that is connected from top to bottom.

[0100] S4: A layer of about 1 μm of silicon carbide (SiC) is deposited by plasma-enhanced chemical vapor deposition. A mask layer is pre-coated near the micro-column holes before the deposition of SiC to prevent the SiC from blocking the silicon column holes.

[0101] S5: A 30 nm chromium and 1 μm gold metal pad is sputtered and deposited at the opening of the SiC insulating layer, i.e., the micro-column hole.

[0102] S6: A 5 μm Parylene C is deposited on the SiC insulating layer as a polymer substrate layer in the flexible electrode structure by a chemical vapor deposition system (CVD).

[0103] S7: A 12 μm thick positive photoresist AZ4620 is spin-coated on the 5 μm Parylene C, and after pre-baking, photoetching, developing and post-baking, a patterned photoresist mask is obtained. The Parylene C substrate layer with the photoresist mask is etched using an oxygen plasma device to obtain a patterned Parylene C film.

[0104] S8: The ceramic substrate with the Parylene C film is placed in an acetone solution and gently shaken to remove the photoresist AZ4620. The acetone soaking and degumming time is about 10 min.

[0105] S9: A 30 nm thick chromium and 200 nm thick gold conductive layer is sputtered and deposited on the Parylene C substrate layer, and the above-mentioned positive photoresist is used as a patterned mask. The metal layer is patterned using ion beam etching, and the same method is used to remove the residual positive photoresist.

[0106] S10: A 5 μm thick Parylene C top encapsulation layer is deposited by the same processing method as S6-S8. The substrate layer, metal layer and top encapsulation layer of Parylene C constitute a flexible electrode.

[0107] S11: The ceramic substrate is turned over, and the SiC insulating layer and the metal pad deposition process are performed on the turned over surface. The relevant parameters are consistent with the foregoing.

[0108] The process of building redistribution layer on ceramic substrate with photosensitive polyimide Durimide 7505, considering the connection between redistribution layer and ASIC chip, is easy to cause heat accumulation. Therefore, AlN particles are doped in the polyimide polymer of redistribution layer to improve its heat conduction capacity. The single layer thickness of polyimide polymer substrate layer and packaging layer is 6 μm. The thickness of conductive layer is 3 μm, and single layer wiring mode is adopted. The thickness of pad at the opening soldering point of packaging layer is 1 μm thick Au pad. The total thickness of redistribution layer is 16 μm.

[0109] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the above specific embodiments, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The above preferred features can be used in combination as long as they are not in conflict with each other.

Claims

1. A flexible electrode integrated with a feedthrough substrate, characterized by, The flexible electrode comprises, in sequence: a flexible electrode having an electrode conductive layer; a feedthrough substrate, the inside of the feedthrough substrate being provided with an array of conductive micro pillars, the top and bottom surfaces of the feedthrough substrate being provided with an insulating layer, the outer surface of the insulating layer being provided with a substrate pad; a redistribution layer having a redistribution conductive layer and a redistribution pad connected to the redistribution conductive layer, the external circuit being connected through the redistribution pad, and the electrode conductive layer, the array of conductive micro pillars, the substrate pad and the redistribution conductive layer being electrically connected.

2. The integrated feedthrough-substrate flexible electrode of claim 1, wherein, The feedthrough substrate comprises any one of a ceramic feedthrough substrate, a glass feedthrough substrate and a silicon-based feedthrough substrate.

3. The integrated feedthrough-substrate flexible electrode of claim 1, wherein, The thickness of the electrode conductive layer is 0.01-1 μm.

4. The integrated feedthrough-substrate flexible electrode of claim 1, wherein, The thickness of the substrate pad is 0.5-5 μm, and the material of the insulating layer is any one of silicon dioxide, silicon carbide, aluminum oxide and zirconium oxide.

5. The integrated feedthrough-substrate flexible electrode of claim 1, wherein, The thickness of the redistribution conductive layer is 1-10 μm.

6. A method of producing the integrated feedthrough substrate flexible electrode according to any one of claims 1 to 5, characterized by, The method comprises: forming a substrate having an array of micropores; filling the micropores of the array of micropores with a conductive material, and planarizing the surface of the substrate to form a feedthrough substrate; forming an insulating layer on the first surface of the feedthrough substrate and the second surface opposite to the first surface, and forming a substrate pad on the insulating layer; placing the feedthrough substrate with the first surface above the second surface, spin-coating a flexible polymer on the first surface to form a flexible electrode base layer, and patterning the flexible electrode base layer to expose the substrate pad; sputtering an electrode metal layer on the flexible electrode base layer, and spin-coating a photoresist mask on the electrode metal layer, and patterning after exposure and development to obtain an electrode conductive layer; spin-coating a flexible polymer on the electrode conductive layer to form a flexible electrode encapsulation layer; turning over the feedthrough substrate with the second surface above the first surface, spin-coating a flexible polymer on the second surface to form a redistribution base layer; patterning, sputtering a metal layer, spin-coating a mask and patterning after exposure and development on the redistribution base layer according to the lead layout of the redistribution layer to form a redistribution lead layer; spin-coating a flexible polymer on the redistribution lead layer to form a redistribution encapsulation layer, and patterning the redistribution encapsulation layer to expose the redistribution pad.

7. The method of claim 6, wherein the method further comprises: The single-layer thickness of the flexible electrode base layer and the flexible electrode encapsulation layer is 0.2-20 μm.

8. The method of claim 6, wherein the flexible electrode is integrated with the feedthrough substrate. The spin-coating of the flexible polymer on the second surface to form a redistribution base layer, wherein the flexible polymer used by the redistribution layer is doped with heat-conducting particles to improve heat conductivity.

9. The method of claim 6, wherein the flexible electrode is integrated with the feedthrough substrate. The single-layer thickness of the redistribution layer base layer and the redistribution layer encapsulation layer is 5-10 μm, and the total thickness of the redistribution layer is 10-50 μm.

10. An electrode device, characterized by The flexible electrode comprises an ASIC chip and an integrated feedthrough substrate according to any one of claims 1-5, the ASIC chip being connected to the redistribution pad.

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