Ceramic substrate for implantable medical devices

• US 5,855,995 A
• Filed: 04/28/1997
• Issued: 01/05/1999
• Est. Priority Date: 02/21/1997
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Haq, Samuel F., Malone, Patrick F., Varner, Donald P., Fortney, John H.
• Primary Examiner(s): Krynski, William
• Assistant Examiner(s): LAM, CATHY FONG FONG
• Application Number:
  US08/847,856
• Time in Patent Office: 617 Days
• Field of Search: 428/209, 428/210, 428/901, 174/256, 174/257, 607/5, 607/9, 607/119
• US Class Current: 428/210
• CPC Class Codes: A61N 1/02 Details
• CPC Class Codes: A61N 1/375 Constructional arrangements, e.g. casings
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: H01L 21/4857 Multilayer substrates multilayer metallisation on monolayer substrate H01L21/4846
• CPC Class Codes: H01L 21/4867 Applying pastes or inks, e.g. screen printing H01L21/486 takes precedence
• CPC Class Codes: H01L 23/49883 the conductive materials containing organic materials or pastes, e.g. for thick films for printed circuits H05K1/092
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 1/092 Dispersed materials, e.g. conductive pastes or inks
• CPC Class Codes: H05K 2201/035 Paste overlayer, i.e. conductive paste or solder paste over conductive layer
• CPC Class Codes: H05K 3/248 fired compositions for inorganic substrates
• CPC Class Codes: H05K 3/4061 for via connections in inorganic insulating substrates
• CPC Class Codes: H05K 3/4611 by laminating two or more circuit boards H05K3/4652 takes precedence
• CPC Class Codes: H05K 3/4629 laminating inorganic sheets comprising printed circuits, e.g. green ceramic sheets
• CPC Class Codes: H05K 3/4676 Single layer compositions
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24917 : including metal layer
• CPC Class Codes: Y10T 428/24926 : including ceramic, glass, porcelain or quartz layer

Abstract

The present invention relates to multi-layer ceramic packaging of hybrid micro-electronic devices, including those for implantable medical devices. The invention permits size reduction and design simplification in such packaging by eliminating the need for electrolytic or electroless plating, and by eliminating or substantially eliminating the shrinkage variation typically associated with surface metallization techniques.

Claims

1. A substrate for use in implantable medical device applications, comprising:

(a) at least three stacked, laminated and trimmed ceramic layers formed from green tape, wherein at least one of the at least three ceramic layers is an internal layer, and wherein two of the at least three ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) at least one internal via formed in the at least one internal layer, the internal via being formed from an internal via paste, the internal via paste comprising tungsten, molybdenum, ruthenium, rhodium, osmium, iridium, palladium, titanium, platinum, an alloy, or mixture or combination thereof, a pre-milled ceramic powder and a paste medium containing a binder;

(c) at least one external via formed in at least one of the external layers, the external via being formed from an external via paste, the external via paste having no tungsten, molybdenum or silver therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof;

(d) at least one internal metallization circuitry pattern disposed on at least one of an upper surface and a lower surface of at least one internal layer and formed from an internal paste;

wherein the unfired stacked, laminated and trimmed ceramic layers are fired in the ordered steps of;

(i) firing at high temperatures in a reducing atmosphere;

(ii) firing at low temperatures in an inert atmosphere, and (iii) firing at low temperatures in an air atmosphere, to form the substrate.

2. The substrate of claim 1, wherein at least one of the upper external surface and the lower external surface has disposed thereon at least one thick film external surface metallization circuitry pattern.

3. The substrate of claim 1, wherein the binder is ethyl cellulose.

4. The substrate of claim 1, wherein the internal via paste from which the at least one internal via is formed comprises at least about 70% by weight tungsten or molybdenum refractory powder, or alloys, mixtures, or combinations thereof, and about 30% by weight or less pre-milled, ceramic powder comprising alumina, talc, and clay.

5. The substrate of claim 1, wherein the internal paste from which the at least one internal metallization circuitry pattern is formed comprises at least one metal selected from the group consisting of iridium, molybdenum, osmium, palladium, platinum, rhenium, rhodium, ruthenium, technetium, tungsten, and alloys, mixtures or combinations thereof, and about 30% by weight or less pre-milled, ceramic powder comprising alumina, talc, and clay.

6. The substrate of claim 1, wherein the external via paste from which the at least one external via is formed comprises at least about 70% by weight ruthenium refractory powder and about 30% by weight or less pre-milled, ceramic powder comprising alumina, talc, and clay.

7. The substrate of claim 1, wherein the substrate is disposed in, and forms an operative electronic component in the circuitry of, one of a pacemaker, a defibrillator, a pacer cardio defibrillator, implantable cardio defibrillator, a neurological stimulator and a gastro-intestinal stimulator.