Method of making high accuracy surface mount inductors

• US 5,398,400 A
• Filed: 04/15/1993
• Issued: 03/21/1995
• Est. Priority Date: 12/27/1991
• Status: Expired due to Fees

• Current Assignee: AVX Corporation (Kyocera Corporation)
• Original Assignee: AVX Corporation (Kyocera Corporation)
• Inventors: Breen, Barry N.
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US08/047,789
• Time in Patent Office: 705 Days
• Field of Search: 336/200, 29/602.1, 29/605, 29/854-856, 427/116
• US Class Current: 29/602.1
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

A high accuracy surface mount inductor device is comprised of first and second parallel planar spiral conductive patterns mounted over a rectangular substrate. The outermost conductive traces of the respective patterns extend to opposite edges of the device and are contacted by terminations extending over the ends of the device. The terminations are U-shaped and include legs extending over parts of the upper and lower surfaces adjacent the ends. The legs overlie the outermost traces and preferably terminate at a position coincident with or not extending inwardly beyond the innermost portions of the outermost traces.

Claims

1. A method of manufacturing a high accuracy surface mount inductor comprising the steps of:

(1) providing an insulating substrate having upper and lower planar surfaces;

(2) depositing a first insulating layer on the upper surface of the substrate;

(3) photolithographically defining and removing selected portions of the first insulating layer to form a channel in the first insulating layer, said channel defining a first spiral coil pattern having an outermost portion and an inner terminus;

(4) depositing metal in the channel formed in the first insulating layer to a predetermined depth to form a first planar conductive coil conforming to the first coil pattern, the first conductive coil having an outermost portion and an inner terminus;

(5) depositing a second insulating layer over the first insulating layer and first conductive coil;

(6) photolithographically defining and removing a selected portion of the second insulating layer to form a via in said second layer in registration with the inner terminus of the first conductive coil;

(7) filling the via in said second insulating layer with metal in contact with the inner terminus of the first conductive coil;

(8) depositing a third insulating layer over the second insulating layer and metal filling the via;

(9) photolithographically defining and removing selected portions of the third insulating layer to form a channel in the third insulating layer, said channel defining a second spiral coil pattern having an outermost portion and an inner terminus, the inner terminus of the second coil pattern being in registration with the metal filling the via;

(10) depositing metal in the channel formed in the third insulating layer to a predetermined depth to form a second planar conductive coil conforming to the second coil pattern, the second conductive coil having an inner terminus in contact with the metal in the via, and an outermost portion;

(11) covering the surface of the third insulating layer and the second conductive coil with an insulating cover layer; and

(12) applying first and second conductive terminations in contact with the outermost portions of the first and second conductive coils, respectively.

2. A method of manufacturing a high accuracy surface mount inductor as defined in claim 1 wherein the first, second and third insulating layers comprise photoimagable polyimide.

3. A method of manufacturing a high accuracy surface mount inductor as defined in claim 1 wherein the metal is deposited in the channels of the first and third insulating layers by electroplating to a thickness of about 28 microns.

4. A method of manufacturing a high accuracy surface mount inductor as defined in claim 3 wherein the metal is copper, aluminum, gold or silver.

5. A method of manufacturing a high accuracy surface mount inductor as defined in claim 3 wherein the second insulating layer has a thickness of about 50 microns.

6. A method of manufacturing a high accuracy surface mount inductor, comprising the steps of:

(1) depositing a first layer of metal on a surface of an insulating substrate, said substrate having opposed end edges;

(2) photolithographically defining and removing selected portions of the metal layer to define a first conductive spiral coil pattern, said first pattern including an outermost edge coincident with one of said end edges of the substrate, and an inner terminus;

(3) depositing a first photoimagable polyimide layer over the surface of the substrate and first coil pattern;

(4) photolithographically defining and removing selected portions of the first polyimide layer to define a channel in the first polyimide layer in registration with the first coil pattern, said first pattern being thereby exposed;

(5) electroplating the exposed first coil pattern to a predetermined depth within the channel in the first polyimide layer to form a first planar conductive coil having an outermost edge and an inner terminus, the outermost edge of the first conductive coil being in registration with said one edge of said substrate;

(6) depositing a second photoimagable polyimide layer over the first polyimide layer and the first planar conductive coil;

(7) photolithographically defining and removing a selected portion of the second polyimide layer to form a via in registration with the inner terminus of the first conductive coil;

(8) electroplating said inner terminus to fill the via;

(9) depositing a second layer of metal on the surface of the second polyimide layer and metal filling the via;

(10) photolithographically defining and removing selected portions of the second metal layer to define a second conductive spiral coil pattern, said second pattern including an outermost edge coincident with the other of the end edges of the substrate, and an inner terminus in registration with and connected to the metal filling the via;

(11) depositing a third photoimagable polyimide layer over the second polyimide layer and second coil pattern;

(12) photolithographically defining and removing selected portions of the third polyimide layer to define a channel in the third polyimide layer in registration with the second coil pattern, said second coil pattern being thereby exposed;

(13) electroplating the exposed second coil pattern to a predetermined depth within the channel in the third polyimide layer to form a second planar conductive coil having an outmost edge in registration with the other of said end edges of the substrate, and an inner terminus;

(14) covering the third polyimide layer and second conductive coil with an insulating cover layer; and

(15) depositing a conductive termination in contact with each of the outermost edges of the first and second conductive coils.

7. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

said substrate comprises alumina and said first and second layers of metal comprise chromium or titanium tungsten alloy.

8. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, including the step of:

sputter depositing a second layer of metal over the first and second layers of metal.

9. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 8, in which:

the layer of metal sputter deposited over the first and second layers of metal comprises aluminum, copper or silver.

10. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

said first and second conductive spiral patterns have square sides.

11. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

said first and third polyimide layers each have a thickness of about 30 microns.

12. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

said exposed first and second coil patterns are electroplated with copper, aluminum, gold or silver.

13. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 12, in which:

the exposed first and second patterns are each electroplated to a depth of about 28 microns.

14. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

the second polyimide layer is deposited to a thickness of about 50 microns.

15. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

the insulating cover layer is made of thermal polyimide.

16. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which:

the insulating cover layer is a thin glass plate bonded in place by an epoxy.

17. A method of manufacturing a high accuracy surface mount inductor as set forth in claim 6, in which the terminations are formed by:

sputtering a layer of chromium on the end faces of the inductor assembly;

electroplating the copper layer with nickel; and

depositing a layer of solder over the layer of nickel.