Source: http://www.google.com/patents/US7687906?dq=6,547,249
Timestamp: 2016-05-28 13:00:23
Document Index: 625544024

Matched Legal Cases: ['Application No. 2006', 'art 43', 'art 43', 'art 43', 'art 62', 'art 62', 'art 62', 'art 62']

Patent US7687906 - Connecting structure, method for forming bump, and method for producing ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA connecting terminal provided on a substrate and a connector provided on an electronic device are connected via a bump formed of a first member, which is formed of an anisotropic conductive paste including particles of a conductive material, and a second member which is different in conductivity from...http://www.google.com/patents/US7687906?utm_source=gb-gplus-sharePatent US7687906 - Connecting structure, method for forming bump, and method for producing device-mounting substrateAdvanced Patent SearchPublication numberUS7687906 B2Publication typeGrantApplication numberUS 11/729,115Publication dateMar 30, 2010Filing dateMar 28, 2007Priority dateMar 31, 2006Fee statusPaidAlso published asUS20070228559Publication number11729115, 729115, US 7687906 B2, US 7687906B2, US-B2-7687906, US7687906 B2, US7687906B2InventorsMasanori TsurukoOriginal AssigneeBrother Kogyo Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (7), Referenced by (2), Classifications (29), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetConnecting structure, method for forming bump, and method for producing device-mounting substrate
US 7687906 B2Abstract
A connecting terminal provided on a substrate and a connector provided on an electronic device are connected via a bump formed of a first member, which is formed of an anisotropic conductive paste including particles of a conductive material, and a second member which is different in conductivity from the first member. According to such a structure, since the anisotropic conductive paste which is softer as compared to a solder bump is used, stress applied to an interface between the bump and the connecting terminal is relaxed. Accordingly, reliability of connection can be assured even when using a substrate with large surface irregularities and/or bending, in which stress occurs relatively easily in a connection part of the bump and the connecting terminal.
a bump formed of a first conductive member, which is formed of a first anisotropic conductive paste including particles of a conductive material, and a second conductive member which is different in conductivity from the first conductive member,
wherein the connecting terminal and the connector are connected via the bump.
2. The connecting structure according to claim 1,
wherein the second conductive member is formed of a conductive material and formed in the first conductive member to penetrate the first conductive member from a connecting surface for the connecting terminal to another connecting surface for the connector.
3. The connecting structure according to claim 1,
wherein the bump has a conductive film formed of a conductive material; the conductive film is formed between the first conductive member and at least one of the connecting terminal and the connector, and is connected to the second conductive member.
4. The connecting structure according to claim 3,
wherein the conductive film entirely covers an exposed surface of the first conductive member.
5. The connecting structure according to claim 1,
wherein the second conductive member is formed of a second anisotropic conductive paste which is different in density of the conductive material from that of the first anisotropic conductive paste, and is formed in the first conductive member to penetrate the first conductive member from a connecting surface for the connecting terminal to another connecting surface for the connector.
6. The connecting structure according to claim 5,
wherein the connecting terminal is provided as a plurality of connecting terminals, the connector is provided as a plurality of connectors paired with the connecting terminals respectively, the bump is provided as a plurality of bumps which form a bump group and which connect the connecting terminals and the connectors respectively, and the bumps are mutually different in a diameter of the second conductive member.
7. The connecting structure according to claim 1,
wherein the first conductive member is formed in a disc shape on the connecting terminal, and the second conductive member is formed of a second anisotropic conductive paste which is lower in density of conductive material than the first anisotropic conductive paste and formed to cover an upper surface and a side surface of the first conductive member.
8. The connecting structure according to claim 1,
wherein the second conductive member has higher conductivity than the first conductive member.
10. A device-mounting substrate which is formed by the connecting structure as defined in claim 1. Description
The present application claims priority from Japanese Patent Application No. 2006-099088, filed on Mar. 31, 2006, the disclosure of which is incorporated herein by reference in its entirety.
Incidentally, in the connecting structure using the anisotropic conductive film, conductive particles also exist in an intermediate region between adjacent terminals. The conductive particles existing in this intermediate region do not contribute to conduction between the terminals, and moreover, there is possible that insulation between the adjacent terminals is disturbed and/or a short circuit is generated due to application of pressurizing force to this intermediate region by some kind of cause. In particular, along with demands for reduction in size and increasing performance of electronic equipment, the distance between terminals tend to be narrow, and therefore there is a strong demand for development of a technique that enables secure connection only in a portion where conduction is needed.
Here, the “anisotropic conductive paste” is one made in a paste form by dispersing particles of a conductive material such as metal in a binder formed of thermoset resin or the like. The anisotropic conductive paste has a conductivity in a compressive direction by being compressed between the connecting terminal and the connector with a constant load, thereby causing the particles of the conductive material to contact each other and form a conductive path. According to the connecting structure of the present invention, the bump is formed of the first member formed of the anisotropic conductive paste and the second member which is different in conductivity from the first member. Accordingly, depending on an arrangement relationship of the first member and the second member in the bump, a portion having higher conductivity and a portion having lower conductivity can be formed. In this case, in the portion having higher conductivity, conduction of the connecting terminal on the substrate and the electronic device can be assured by a weaker pressurizing force. Therefore, even when a distance between the connecting terminal and the connector is large and a sufficient compressive force cannot be applied, the bump formed of the first member and the second member can assure electrical connection of the connecting terminal and the connector. Further, since the first member is formed of the anisotropic conductive paste, the thermoset resin included in the anisotropic conductive paste can relax a stress applied to an interface between the bump and the connecting terminal. Therefore, reliability of connection can be assured even when using a substrate with large surface irregularities and/or bending, in which stress occurs relatively easily in a connector. Further, being different from the case of using an anisotropic conductive film, the conductive material does not exist in a region except positions where the connecting terminal and the connector are provided. Accordingly, short-circuit or the like does not occur, and insulating characteristics between adjacent connecting terminals and connectors can be maintained.
In the connecting structure of the present invention, the second member (17) may be formed of a conductive material and formed in the first member (16) to penetrate the first member from a connecting surface (16B) for the connecting terminal (14) to another connecting surface (16A) for the connector (21). In this case, since conduction of the connecting terminal on the substrate and the connector on the electronic device can be assured by the second member formed of a conductive material, electrical connection of the both can be assured independent of the pressurizing force to the bump. Note that, the “connecting surface” means not only a surface which makes direct contact with the connecting terminal or the connector, but also a surface which is electrically connected with the connecting terminal or the connector through any conductive material (See the second embodiment).
In the connecting structure of the present invention, the second member (43) may be formed of a second anisotropic conductive paste (P2) which is different in density of the conductive material (M) from that of the first anisotropic conductive paste (P1), and may be formed in the first member (42) to penetrate the first member from a connecting surface (42B) for the connecting terminal (14) to another connecting surface (42A) for the connector (21). In this case, a member having higher conductivity, out of the first member and the second member, can assure conduction between the connecting terminal on the substrate and the connector on the electronic device even when a weaker pressurizing force is applied. Therefore, even when a distance between the connecting terminal and the connector is large and a sufficient compressive force cannot be applied, the bump formed of the first member and the second member can assure electrical connection of the connecting terminal and the connector. Further, since both the first member and the second member are formed of anisotropic conductive pastes, the first member and the second member have more flexibility as compared to the bump formed only of the conductive material, and a stress applied to the bump can be relaxed. Note that “different in density of conductive material” means that the weight of conductive material per unit volume is different. For example, by increasing the number of dispersed particles of a conductive material per unit volume, or by using particles having a larger average particle diameter, an anisotropic conductive paste having a higher density of conductive material can be prepared.
FIG. 1 is a partially enlarged cross-sectional view of a circuit substrate of a first embodiment;
Hereinafter, a first embodiment embodying the present invention will be explained in detail with reference to FIG. 1 to FIG. 5B. FIG. 1 shows a partially enlarged cross-sectional view of a circuit substrate 1 (device-mounting substrate) of this embodiment. The circuit substrate 1 is a substrate on which an LSI package 20 (electronic device) is mounted on a ceramic wiring board 10 (substrate).
Hereinafter, a second embodiment of the present invention will be explained with reference to FIG. 6 to FIG. 8B. The main difference of this embodiment from the first embodiment is that each of bumps 31 is provided with a conductive film 34. Note that the same structures as in the first embodiment are designated the same reference numerals, and explanations of which are omitted.
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. 9 to FIG. 11B. The main difference of this embodiment from the first embodiment is that each of bumps 41 is formed of a base 42 (first member) formed of a first anisotropic conductive paste P1 and a high density part 43 (second member, through part) formed of a second anisotropic conductive paste P2 which is higher in density of conductive material than the first anisotropic conductive paste P1. In other words, the high density part 43 has higher conductivity than the base 42. Note that the same structures as in the first embodiment are designated the same reference numerals, and explanations thereof are omitted.
The second anisotropic conductive paste P2 forming the high density part 43 is higher in density of conductive material than the first anisotropic conductive paste P1 forming the base 42. Namely, the second anisotropic conductive paste P2 has higher conductivity than the first anisotropic conductive paste P1. Here, “higher in density of conductive material” means that the weight of the conductive material per unit volume is larger. To prepare the anisotropic conductive paste having a higher density of conductive material, it is conceivable, for example, to increase the number of particles of a conductive material M dispersed in resin per unit volume, or use particles having a large mean particle diameter. Materials of the resin and the conductive material forming the two kinds of anisotropic conductive pastes P1, P2 may be the same as or different from each other.
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. 12 to FIG. 14B. The main difference of this embodiment from the first embodiment is that a plurality of kinds of bumps 51 formed of a plurality of kinds of anisotropic conductive pastes PA, PB, PC, PD which are different in density of conductive material from each other are provided. Note that the same structures as in the first embodiment are designated the same reference numerals, and explanations of which are omitted.
Each of the bumps 51 of this embodiment is formed in a substantially disc shape by anisotropic conductive pastes PA, PB, PC, PD. The plurality of bumps 51 connecting a plurality of pairs of substrate-side pads 14 and bump pads 21 include a plurality of kinds of bumps 51A, 51B, 51C, 51D formed respectively by the anisotropic conductive pastes PA, PB, PC, PD which are different in density of conductive material from each other. Note that in the following, when the plurality of kinds of bumps are to be distinguished, indices are given to the reference numerals such as “bumps 51A, 51B, 51C, 51D”, while when the plurality of kinds of bumps are not to be distinguished but are referred generally, indices are not given to the reference numeral such as “bumps 51.”
Here, “different in density of conductive material” means that the weight of conductive material per unit volume is different. To prepare anisotropic conductive pastes which are different in density of conductive material from each other, it is conceivable that, for example, the number of particles M of a conductive material per unit volume dispersed in resin is differentiated or mean particle diameters of particles M are differentiated. Materials of the resin and the conductive material forming the plurality of kinds of anisotropic conductive pastes may be the same as or different from each other.
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG. 15A to FIG. 15E. The main difference of this embodiment from the first embodiment is that each of bumps 61 is formed of a high density part 62 (first member) formed of a first anisotropic conductive paste P1 and a base 63 (second member) formed of a second anisotropic conductive paste P2 which is lower in density of conductive material than the first anisotropic conductive paste. Furthermore, this embodiment is different in that the high density part 62 is formed not to penetrate through the bump 61, in order words, the high density part 62 is covered by the base 63, and is not in contact with a bump pad 21 of the LSI package 20. Note that the same structures as in the first embodiment are designated the same reference numerals, and explanations thereof are omitted.
The second anisotropic conductive paste P2 forming the base 63 is lower in density of conductive material than the first anisotropic conductive paste P1 forming the high density part 62. Here, “lower in density of conductive material” means that the weight of the conductive material per unit volume is smaller. To prepare the anisotropic conductive paste having a lower density of conductive material, it is conceivable, for example, to decrease the number of particles M of a conductive material dispersed in resin per unit volume, or to use particles M having a small mean particle diameter. Materials of the resin and the conductive material forming the two kinds of anisotropic conductive pastes P1, P2 may be the same as or different from each other.
Hereinafter, the present invention will be described in more detail with examples. As materials, a ceramic wiring board and anisotropic conductive pastes are used.
On a surface of the ceramic wiring board, surface processing such as polishing, cleansing, and the like are performed. On substrate-side pads of this ceramic wiring board, the anisotropic conductive paste A is printed at 40� C. by a screen printing method, thereby forming a pattern of disc shapes each having a diameter of 40 μm to 650 μm. Note that the pattern is given a height of 30 μm, and this pattern is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to cure the anisotropic conductive paste, thereby forming bumps.
On a surface of the ceramic wiring board, surface processing such as polishing, cleansing, and the like are performed. On substrate-side pads of this ceramic wiring board, the anisotropic conductive paste A is printed at 40� C. by a screen printing method, thereby forming a pattern of disc shapes each having a diameter of 300 μm and a height of 30 μm. This pattern is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to be cured, thereby forming bumps. Contact resistance of the formed bumps is measured using the tension and compression testing machine while varying the load applied to the bumps from 0 g/mm2 to 400 g/mm2.
Using the anisotropic conductive paste B, bumps are formed similarly to the example 1-1 and contact resistance thereof is measured.
On a surface of the ceramic wiring board, surface processing such as polishing, cleansing, and the like are performed. On substrate-side pads of this ceramic wiring board, the anisotropic conductive paste A is printed at 40� C. by a screen printing method, thereby forming a pattern of disc shapes each having a diameter of 300 μm and a height of 30 μm. This pattern is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to be cured, thereby forming bases of bumps. Next, laser is irradiated from upper surface sides of the bases to thereby form through holes each having a diameter of 5 μm. Then, by performing electroplating with the substrate-side pads being one of electrodes, copper is filled in the through holes, thereby forming conductive parts. Furthermore, Ni/Au protective films are formed on upper end surfaces of the conductive parts by electroless plating. Contact resistance of the formed bumps is measured similarly to the example 1-1.
Using the anisotropic conductive paste B, bumps are formed similarly to the example 2-1 and contact resistance thereof is measured.
On the surface of the ceramic wiring board, surface processing such as polishing, cleansing, and the like are performed. On substrate-side pads of this ceramic wiring board, the anisotropic conductive paste B is printed at 40� C. by a screen printing method, thereby forming a pattern of a plurality of kinds of ring shapes each having an outside diameter of 300 μm, a height of 30 μm and a different inner diameter. The formed pattern is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to be cured, thereby forming bases of bumps. Then, the anisotropic conductive paste C is filled in the through holes by a screen printing method. The paste after filling is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to be cured, thereby forming high density parts. Contact resistance of the formed bumps is measured similarly to the example 1-1.
On the surface of the ceramic wiring board, surface processing such as polishing, cleansing, and the like are performed. On substrate-side pads of this ceramic wiring board, anisotropic conductive pastes B, D, E, F are printed respectively at 40� C. by a screen printing method, thereby forming a pattern of disc shapes each having a diameter of 300 μm, an inner diameter of 30 μm, and a height of 30 μm. This pattern is heated at 150� C. for 40 seconds and then heated at 180� C. for 15 seconds to be cured, thereby forming bumps. Contact resistance of the formed bumps is measured similarly to the example 1-1.
The scope of the present invention is not limited to the above-described embodiments, and for example, embodiments as described below are also included in the scope of the present invention.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5891366 *Jun 16, 1995Apr 6, 1999Robert Bosch GmbhAnisotropically conducting adhesive, and process for producing an anisotropically conducting adhesiveUS6101708 *May 20, 1997Aug 15, 2000Citizen Watch Co., Ltd.Method for electrically connecting terminals to each otherUS20040028893 *Dec 5, 2001Feb 12, 2004Kazuo InoueAnisotropic conductive sheet and wafer inspection deviceUS20040257516 *Jun 4, 2004Dec 23, 2004Mitsuhiro SugimotoAnisotropic conductive material body, display apparatus, method for producing the display apparatus, and conductive memberUS20060211280 *Mar 23, 2004Sep 21, 2006Jsr CorporationAnisotropic conductive connector, conductive paste composition, probe member, wafer inspection device and wafer inspection methodJP2002043363A Title not availableJP2002261416A Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS8124885 *Mar 30, 2007Feb 28, 2012Jsr CorporationAnisotropically conductive connector and anisotropically conductive connector deviceUS20090159325 *Mar 30, 2007Jun 25, 2009Jsr CorporationAnisotropically conductive connector and anisotropically conductive connector device* Cited by examinerClassifications U.S. Classification257/737, 257/E23.07, 257/338, 257/E23.069, 257/337, 438/254International ClassificationH01L23/52, H01L29/40, H01L23/48Cooperative ClassificationH01L2224/0401, H05K2201/035, H05K2201/0367, H01L21/4867, H05K2201/0391, H05K3/321, H05K2201/10674, H05K3/4007, H05K2201/0347, H01L23/49816, H01L23/49838, H05K3/246, H05K2201/094, H01L2224/06102, H01L2224/1403European ClassificationH01L21/48C4S, H05K3/32B, H01L23/498G, H01L23/498C4, H05K3/40BLegal EventsDateCodeEventDescriptionApr 30, 2007ASAssignmentOwner name: BROTHER KOGYO KABUSHIKI KAISHA, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TSURUKO, MASANORI;REEL/FRAME:019242/0172Effective date: 20070328Owner name: BROTHER KOGYO KABUSHIKI KAISHA,JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TSURUKO, MASANORI;REEL/FRAME:019242/0172Effective date: 20070328Aug 26, 2013FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services