JP4761164B2 - Connection structure and component mounting board - Google Patents

Description

The present invention is formed connection structure for electrically connecting the bumps formed a connecting portion provided on the connection terminal and the electronic component by an anisotropic conductive paste provided on the substrate, the contact and anisotropic conductive paste The present invention relates to a component mounting substrate that joins a substrate and an electronic component with the bumps formed.

  For example, the most common technique for mounting an LSI chip on a substrate is to connect a connection terminal on the LSI chip side and a connection terminal on the substrate side via a solder ball. However, since solder is a hard material, if the above technology is applied to a hard substrate such as a substrate with a large surface irregularity, a substrate with poor connection terminal position accuracy, or a ceramic substrate, stress concentration is caused at the connection part. May cause distortion. Moreover, there is a concern that stress cracks may occur in the solder due to residual stress in the long term.

In order to solve such a problem, a connection structure using an anisotropic conductive film (ACF) has been proposed as a technique that can realize stress relaxation at a low cost (for example, Patent Document 1 and Patent Document 1). 2). This anisotropic conductive film is a film made by dispersing conductive material particles in a binder made of a resin material. By compressing by applying a certain load, the conductive material particles come into contact with each other and are compressed. It shows conductivity in the direction. In the connection structure using such an anisotropic conductive film, the resin material, which is a soft material, relieves stress, so that cracks are generated compared to the case where the connection portion is composed only of solder as in the prior art. Hateful.
JP 2002-43363 A JP 2002-261416 A

Problems to be solved by the invention and effects of the invention

  By the way, in the connection structure using an anisotropic conductive film, electroconductive particle will exist also in the intermediate area | region of an adjacent terminal. The conductive particles present in this intermediate region do not contribute to the conduction between the terminals, but also impede insulation between adjacent terminals or cause a short circuit by applying pressure to this intermediate region for some reason. There is a risk that In particular, with the demand for downsizing and high functionality of electronic devices, the distance between terminals tends to be narrowed, so there is a strong demand for the development of a technology that enables reliable connection only at a place where conduction is desired.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a connection structure that can ensure connection reliability between a substrate and an electronic component.

Means for Solving the Problems and Effects of the Invention

  In addition, the code | symbol with the parenthesis attached | subjected to each element shown below is only the illustration of the element, and does not limit each element.

  According to the first aspect of the present invention, there is a connection structure for electrically connecting the connection terminal (14) provided on the substrate (10) and the connection portion (21) provided on the electronic component (20). The first member (16) formed by the first anisotropic conductive paste (P1) containing the conductive material particles (M) and the second member (17) having different conductivity from the first member A connection structure is provided in which the connection terminal and the connection portion are connected via a bump (15) formed by.

  Here, the “anisotropic conductive paste” is a paste formed by dispersing particles made of a conductive material such as a metal in a binder made of a thermosetting resin or the like. The anisotropic conductive paste is compressed by applying a certain load between the connection terminal and the connection portion, whereby the conductive material particles come into contact with each other to form a conductive path, and the conductive in the compression direction Indicates. According to the connection structure of the present invention, the bump is formed by the first member formed of the anisotropic conductive paste and the second member having different conductivity from the first member. For this reason, depending on the arrangement relationship between 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 a portion having high conductivity, conduction between the connection terminal of the substrate and the connection portion of the electronic component can be ensured with a weaker pressure. Therefore, even when the distance between the connection terminal and the connection portion is large and sufficient compressive force is not applied, the electrical connection between the connection terminal and the connection portion is caused by the bumps made of the first member and the second member. Connection can be secured. Moreover, since the first member is formed of an anisotropic conductive paste, the stress applied to the interface between the bump and the connection terminal can be relieved by the thermosetting resin contained in the anisotropic conductive paste. Therefore, connection reliability can be ensured even when a substrate having large surface unevenness and warpage and stress is relatively easily generated at the connection portion. Furthermore, unlike the case where an anisotropic conductive film is used, there is no conductive substance in a region other than the place where the connection terminal and the connection portion are provided. For this reason, a short circuit or the like does not occur, and insulation between adjacent connection terminals and between connection parts is also maintained.

  In the connection structure of the present invention, the second member (17) is made of a conductive material, and is connected to the connection portion (21) from the connection surface (16B) with the connection terminal (14) of the first member (16). It can be formed through to the connection surface (16A). In this case, the second member made of a conductive material can ensure the electrical connection between the connection terminal of the substrate and the connection part of the electronic component, so that the electrical connection between the two is reliable regardless of the strength of the pressure applied to the bump. It can be.

  In the connection structure of the present invention, the bump (31) may include a conductor film (34) formed of a conductive material, and the conductor film is at least the connection terminal (14) in the first member (32). Alternatively, the connection surface (32A or 32C) with the connection portion (21) may be covered and connected to the second member (33). In this case, the conductor film connected to the second member contacts the connection terminal or the connection portion as a surface. Therefore, even when the positional accuracy between the connection terminal of the substrate and the connection part of the electronic component is low, the connection part and the connection terminal are reliably conducted through the second member and the conductor film. The conductive material constituting the particles in the anisotropic conductive paste and the conductive material constituting the second member and the conductor film may be the same or different. Further, the second member and the conductor film may be formed of the same conductive material, or may be formed of different conductive materials.

  In the connection structure of the present invention, the conductor film (34) may cover the entire exposed surface (32A and 32B) of the first member (32). In this case, the durability of the bumps can be improved by covering the entire exposed surface of the first member (the surface that is not in contact with the substrate or the electronic component) with the conductor film.

  In the connection structure of the present invention, the second member (43) is formed from the second anisotropic conductive paste (P2) having a density of the conductive material (M) different from that of the first anisotropic conductive paste (P1). The first member (42) may be formed to penetrate from the connection surface (42B) with the connection terminal (14) to the connection surface (42A) with the connection portion (21). In this case, of the first member and the second member, in the member having higher conductivity, conduction between the connection terminal of the substrate and the connection part of the electronic component can be ensured even with a weaker pressure. Therefore, even when the distance between the connection terminal and the connection portion is large and sufficient compressive force is not applied, the electrical connection between the connection terminal and the connection portion is caused by the bumps made of the first member and the second member. Connection can be secured. Furthermore, since both the first member and the second member are made of an anisotropic conductive paste, the first member and the second member are more flexible than a bump made of only a conductive material, and can relieve stress acting on the bump. Note that “the density of the conductive material is different” means that the weight of the conductive material per unit volume is different. For example, an anisotropic conductive paste having a high density of the conductive material can be prepared by increasing the number of particles of the conductive material to be dispersed per unit volume or using particles having a large average particle diameter.

  In the connection structure of the present invention, a bump group including a plurality of the bumps (41) respectively connecting the plurality of connection terminals (14) and the plurality of connection portions (21) paired with the connection terminals. The bump group may be composed of a plurality of types of bumps having different diameters of the second member (43). Here, the second member is made of an anisotropic conductive paste having a conductive material density different from that of the first member, and has higher flexibility than the case of being made of only the conductive material. Even if the thickness is increased, the flexibility of the entire bump is not impaired. Therefore, the connection reliability can be ensured by adjusting the diameter of the second member in accordance with the distance between the connection terminal and the connection portion in consideration of the warpage of the substrate, the position of the unevenness, and the like.

  In the connection structure of the present invention, the first member (62) may be formed in a disk shape on the connection terminal (14), and the second member (63) is formed from the first anisotropic conductive paste (P1). May be formed of the second anisotropic conductive paste (P2) having a low density of the conductive material (M), and may be formed to cover the upper surface (62A) and the side surface (62B) of the first member. In this case, the bump is formed of a portion where the first member and the second member overlap each other and a portion consisting only of the second member. Here, the first member is made of a first anisotropic conductive paste, and the second member is made of a second anisotropic conductive paste. Since the first anisotropic conductive paste has a higher density of the conductive material than the second anisotropic conductive paste, the first member has higher conductivity than the second member. Therefore, the portion where the first member and the second member overlap is higher in conductivity than the portion consisting only of the second member. Therefore, in the portion where the first member and the second member overlap, it is possible to ensure the continuity between the connection terminal of the substrate and the connection portion of the electronic component even with a weaker pressure than the portion consisting of only the second member. it can. Therefore, even when the distance between the connection terminal and the connection portion is large and sufficient compressive force is not applied, the electrical connection between the connection terminal and the connection portion is caused by the bumps made of the first member and the second member. Connection can be secured. Furthermore, since both the first member and the second member are made of an anisotropic conductive paste, the first member and the second member are more flexible than a bump made of only a conductive material, and can relieve stress acting on the bump.

  According to the present invention, a component mounting board (1) provided with the connection structure of the present invention is provided. In this case, in the component mounting substrate, electrical connection between the connection terminal of the substrate and the connection portion of the electronic component can be ensured without being affected by the warp or unevenness of the substrate.

  According to the second aspect of the present invention, there is provided a connection structure for electrically connecting the connection terminal (14) provided on the substrate (10) and the connection portion (21) provided on the electronic component (20). A plurality of bumps (51A, 51B, 51C, 51D) for connecting between the plurality of connection terminals and a plurality of connection portions that are paired with these connection terminals. A connection structure comprising a plurality of types of bumps formed of a plurality of types of anisotropic conductive pastes (PA, PB, PC, PD) having different densities of the conductive material (M) is provided.

  According to this connection structure, in consideration of the warpage of the substrate, the position of the unevenness, etc., bumps using an anisotropic conductive paste with a high density of the conductive material are provided at locations where the distance between the connection terminal and the connection portion is large. By arranging, connection reliability can be ensured.

  According to the present invention, a component mounting board (1) provided with the connection structure of the present invention is provided. In this case, in the component mounting substrate, electrical connection between the connection terminal of the substrate and the connection portion of the electronic component can be ensured without being affected by the warp or unevenness of the substrate.

  According to the third aspect of the present invention, on the connection terminal (14) provided on the surface of the substrate (10), the connection portion (on the surface of the electronic component (20) mounted on the substrate ( 21) A method of forming a bump (15) for electrically connecting a connection terminal to a connection terminal, wherein an anisotropic conductive paste (P1) containing particles (M) of a conductive material is screened on the connection terminal. There is provided a bump forming method including a printing step (S101) for printing and a curing step (S102) for curing the anisotropic conductive paste after printing. According to such a method, a bump formed of an anisotropic conductive paste can be easily formed.

  In the bump forming method of the present invention, a through hole forming step (S103) for forming a through hole (18) that reaches the connection terminal (14) through the cured anisotropic conductive paste (P1) after curing; There may be further provided a plating step (S104) of forming the conductor portion (17) by filling the through hole with a conductive metal by electroplating using the connection terminal as one electrode. This method is effective when the connection terminal or the connection portion can be used as an electrode for electroplating. When a conductor film is provided on the bump, the conductor film may be formed at the same time in the plating process, or after this plating process, a second plating process for applying a conductor film to the surface of the substrate may be performed. I do not care.

  In the bump forming method of the present invention, a through hole forming step (S103) for forming a through hole (35) that penetrates the cured anisotropic conductive paste (P1) and reaches the connection terminal (14); The electroless plating fills the through hole with a conductive metal to form the conductor portion (33) and the conductive film (34) made of the conductive metal is formed on the surface (32A, 32B) of the anisotropic conductive paste. An electrolytic plating step (S114) may be further included. This method is effective when the connection terminal or the connection portion cannot be used as an electrode necessary for electroplating. When the conductor film is provided on the bump, the conductor film may be formed at the same time in the electroless plating process. After the electroless plating process, a second plating process for further providing a conductor film on the surface of the substrate. You may do.

  In the bump forming method of the present invention, in the printing step (S121), the base body (42) comprising a through hole (44) made of the anisotropic conductive paste (P1) and reaching the connection terminal (14). The second anisotropic conductive paste (P2) having a different density of the conductive material (M) from the anisotropic conductive paste may be formed in the through hole by screen printing to fill the through hole. You may further provide the filling process (S123) which forms (43), and the 2nd hardening process (S124) which hardens the 2nd anisotropic conductive paste after filling. According to such a method, since both the base and the penetrating portion are formed by a simple and inexpensive method called screen printing, the bump can be formed at a low cost.

  In the bump forming method of the present invention, a plurality of connection terminals (14) may be provided on the surface of the substrate (10), and a plurality of connection portions (21) are provided on the surface of the electronic component (20). In the printing step (S131), the density of the conductive material contained in the anisotropic conductive paste (PA, PB, PC, PD) printed on each connection terminal may be different from each other. According to such a method, it is possible to easily form a plurality of types of bumps having different conductivities, so that the manufacturing process can be simplified and the cost can be reduced.

In the bump forming method of the present invention, the second anisotropic conductive paste (P2) having a density of the conductive material (M) different from the anisotropic conductive paste (P1) printed in the printing step (S141). You may further provide the 2nd printing process (S143) which screen-prints, and the 2nd hardening process (S144) which hardens the 2nd anisotropic conductive paste. In this case, bumps can be formed by a simple and inexpensive method of screen printing and curing.

  According to the present invention, there is provided a method for manufacturing a component mounting substrate (1) in which an electronic component (20) is mounted on a substrate (10), comprising the bump (15) formed by the bump forming method of the present invention. A substrate providing step (S101 to S104) for providing a substrate, and an alignment step for aligning the electronic component on the substrate so that the connection terminal (14) and the connection portion (21) face each other with a bump interposed therebetween ( There is provided a method of manufacturing a component mounting board comprising S201) and a joining step (S202) of pressing and joining the electronic component to the board. According to this method, it is possible to manufacture a component mounting substrate in which electrical connection between the connection terminal of the substrate and the connection portion of the electronic component is ensured without being affected by the warp or unevenness of the substrate.

<First Embodiment>
Hereinafter, a first embodiment embodying the present invention will be described in detail with reference to FIGS. FIG. 1 shows a partially enlarged cross-sectional view of the circuit board 1 (component mounting board) of the present embodiment. The circuit board 1 is obtained by mounting an LSI package 20 (electronic component) on a ceramic wiring board 10 (board).

  The ceramic wiring board 10 is a multilayer board having a well-known structure in which insulating layers 11 made of ceramics and conductor layers 12 having a predetermined pattern are alternately laminated, and conductor layers are connected by via holes 13. FIG. 2A shows a top view of the ceramic wiring board 10, and FIG. 2B shows a cross-sectional view of the ceramic wiring board 10. A part of the conductor layer 12 formed on the upper surface (surface on which the LSI package 20 is mounted) of the ceramic wiring board 10 is used as a substrate-side pad 14 (connection terminal). A plurality of substrate side pads 14 are arranged vertically and horizontally corresponding to bump pads 21 of an LSI package 20 (or an LSI chip or a semiconductor device) to be described later.

  On the other hand, a plurality of bump pads 21 (connection portions) arranged vertically and horizontally are formed on the lower surface side of the LSI package 20 mounted on the ceramic wiring board 10. As shown in FIG. 1, the bump pads 21 of the LSI package 20 and the corresponding substrate-side pads 14 of the ceramic wiring board 10 are connected via bumps 15, respectively.

  The bump 15 includes a base body 16 (first member) formed in a substantially disk shape by an anisotropic conductive paste (ACP) P1, and a vertical direction (ceramic wiring board 10 and LSI package 20). And a conductor portion 17 (second member) penetrating in the direction along the stacking direction). The anisotropic conductive paste P1 constituting the substrate 16 is obtained by dispersing particles M of a conductive material such as nickel in a binder made of a thermosetting resin such as a low-temperature curable resin. The anisotropic conductive paste P1 is appropriately compressed between the bump pad 21 and the substrate-side pad 14 so that the conductive material particles M come into contact with each other to form a conductive path in the pressurizing direction. Conductivity is imparted.

  On the other hand, the conductor portion 17 is formed in the shape of an elongated thin line in the vertical direction by using a conductive material such as metal, and is disposed at the center position of the circle as viewed from the upper surface side of the base body 16. One end (upper end) of the base 16 is exposed to the connection surface 16A of the bump pad 21 and contacts the bump pad 21, and the other end (lower end) of the base 16 is exposed to the connection surface 16B of the substrate side pad 14. In contact with the substrate-side pad 14. The conductor portion 17 also electrically connects the bump pad 21 and the substrate side pad 14.

  The conductor portion 17 is preferably made of a conductive material (for example, gold) that is as soft as possible so as not to impair the compressibility of the bump 15 between the bump pad 21 and the substrate-side pad 14. Further, from the same viewpoint, it is preferable that the thickness is as thin as possible within a range where conduction can be ensured. For example, when gold is used as the conductive material, the diameter is preferably 7.5 μm or less.

  Next, a method for forming the bump 15 and a method for connecting the bump pad 21 by the bump 15 and the corresponding substrate-side pad 14 will be described with reference to the flowchart of FIG.

  First, the anisotropic conductive paste P1 is printed on each substrate-side pad 14 of the ceramic wiring board 10 by a screen printing method to form the base 16 of the bump 15 (step S101: printing process). 3A is a top view showing a state where the anisotropic conductive paste P1 is printed on the substrate-side pad 14 by the screen printing method, and FIG. 3B is a sectional view thereof (in FIG. 3A, the screen S Is omitted). When printing is completed, the anisotropic conductive paste P1 is heated and cured (step S102: curing process).

  Next, by performing laser irradiation from the upper surface side of the base body 16 (side connected to the bump pad 21), the through hole 18 reaching the surface of the substrate side pad 14 is formed at the center of the circle as viewed from the upper surface of the base body 16. (Step S103: through-hole forming step; see FIGS. 4A and 4B).

  Next, by performing electroplating using the substrate side pad 14 as one electrode, the through hole 18 is filled with metal to form the conductor portion 17 (step S104: plating step; see FIGS. 5A and 5B). ). In this embodiment, all the board-side pads 14 are conducted to the lower surface side of the ceramic wiring board 10 through the via holes 13 and the inner conductor layer 12 (see FIG. 5B). It can be used as one electrode. The filling amount of the metal is preferably set so that the upper surface thereof is substantially flush with the surface of the substrate 16.

  One end side (lower end side) of the formed conductor portion 17 is in contact with the substrate side pad 14, and the other end side (upper end side) is exposed on the connection surface 16 </ b> A with the bump pad 21. In addition, when using copper as a plating metal, in order to prevent oxidation, it is preferable to attach a protective film such as Ni / Au to the upper end surface of the conductor portion 17 after the filling. Such a protective film can be formed by electroless plating, for example. In this way, bumps 15 are formed on the substrate-side pads 14 of the ceramic wiring board 10 (steps S101 to S104: substrate providing step).

  Next, a procedure for mounting the LSI package 20 on the ceramic wiring board 10 on which the bumps 15 are formed will be described.

  First, the adhesive 19 is applied to the upper surface of the ceramic wiring board 10. Next, the LSI package 20 is placed on the ceramic wiring board 10 while being aligned so that the bumps 15 formed on the substrate-side pad 14 and the corresponding bump pads 21 are aligned (step S201: alignment). Process). Next, the LSI package 20 is heated while being pressed toward the ceramic wiring board 10 by hot pressing or the like, and the adhesive 19 is cured to bond the ceramic wiring board 10 and the LSI package 20 (step S202: bonding step). That is, the LSI package 20 is fixed to the ceramic wiring board 10 at a position when pressed to the ceramic wiring board 10 side. At this time, the anisotropic conductive paste P1 constituting the base 16 of the bump 15 is compressed between the bump pad 21 and the substrate-side pad 14 to impart conductivity in the pressing direction. Thereby, the board | substrate side pad 14 and the bump pad 21 are electrically connected (refer FIG. 1). At the same time, the upper end portion of the conductor portion 17 contacts the bump pad 21, and the substrate side pad 14 and the bump pad 21 are electrically connected also by the conductor portion 17.

  As described above, according to the present embodiment, the board-side pads 14 provided on the ceramic wiring board 10 and the bump pads 21 provided on the LSI package 20 are formed by the bumps 15 formed by the anisotropic conductive paste P1. It is connected. According to such a configuration, the bump 15 formed of the anisotropic conductive paste P1 is superior to the solder bump in flexibility, so that the stress applied to the interface between the bump 15 and the substrate-side pad 14 is relieved. For this reason, even when the ceramic wiring board 10 having large surface unevenness and warpage and causing stress relatively easily at the connection portion between the bump 15 and the substrate-side pad 14, connection reliability can be ensured.

  Unlike the case where an anisotropic conductive film is used, there is no conductive material in a region other than the place where the substrate-side pad 14 and the bump pad 21 are provided. Therefore, a short circuit or the like does not occur, and insulation between the adjacent substrate-side pads 14 and between the bump pads 21 is maintained.

  In addition, when the warp of the ceramic wiring board 10 and the unevenness of the surface are large, the pressure applied to the bumps 15 varies due to the variation in the distance between the substrate-side pad 14 and the bump pad 21. In particular, the bump 15 (see the left bump 15 in FIG. 1) existing at a position where the distance between the substrate-side pad 14 and the bump pad 21 is large is not given a sufficient compressive force, and is sufficiently conductive. There may be situations where it is not ensured. However, in the present embodiment, since the conductor portion 17 is provided on the bump 15, the electrical connection between the substrate-side pad 14 and the bump pad 21 is achieved by this conductor portion 17 regardless of the strength of the pressure applied to the bump 15. Is secured. Thereby, the electrical connection between the board-side pad 14 and the bump pad 21 can be ensured.

  Furthermore, the conductor part 17 is made of a soft conductive material and is made as thin as possible within a range in which conduction can be ensured. According to such a structure, the conduction | electrical_connection defect resulting from preventing the compression of anisotropic conductive paste P1 can be avoided. Furthermore, it is possible to avoid a situation in which the stress relaxation effect is impaired and cracks are likely to occur, and the conductor portion 17 is broken due to compression of the bumps 15 so that conduction cannot be ensured.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. The main difference between this embodiment and the first embodiment is that a bump 31 is provided with a conductor film 34. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  Also in the circuit board 30 of the present embodiment, the bump pads 21 of the LSI package 20 and the corresponding board-side pads 14 of the ceramic wiring board 10 are connected via the bumps 31 (see FIG. 6). . The bump 31 covers the base 32 (first member) formed of the anisotropic conductive paste P1, the conductor portion 33 (second member) penetrating the base 32 in the vertical direction, and the surface of the base 32. And a conductive film 34. The configurations of the base body 32 and the conductor portion 33 are the same as those in the first embodiment.

  The conductor film 34 is formed of a conductive material such as metal, for example, and is formed on the entire upper surface 32A and side surface 32B of the base 32. That is, it is formed in a thin film shape that covers the connection surface 32A to the bump pad 21 and the exposed surface 32B that is not in contact with the ceramic wiring board 10 or the LSI package 20. Further, the conductor film 33 is in contact with the conductor film 34 from the lower surface side, whereby the conductor section 33 and the conductor film 34 are electrically connected. This conductive film 34 is preferably formed thinly using a soft conductive material so as not to impair the compressibility of the bumps 31. However, when the effect of improving the durability of the bump 31 by covering the exposed surface of the base body 32 is also expected, the hardness and thickness of the bump 31 should not be impaired. preferable.

  Next, a method of forming the bump 31 and a method of connecting the bump pad 21 by the bump 31 and the corresponding substrate-side pad 14 will be described with reference to the flowchart of FIG.

  First, the substrate 32 having the through holes 35 is formed on the substrate side pads 14 of the ceramic wiring board 10 by performing a printing process (step S101), a curing process (step S102), and a through hole forming process (step S103). (See FIGS. 7A and 7B). Since the printing process, the curing process, and the through-hole forming process are the same as those in the first embodiment, detailed description thereof is omitted.

  Next, by filling the through hole 35 with metal by electroless plating to form the conductor portion 33, the conductor film 34 is formed on the entire upper surface and side surface of the base 32 (step S114: electroless plating step; FIG. 8A). FIG. 8B). In the present embodiment, unlike the first embodiment, not all the board-side pads 14 are conducted to the via holes 13 and the lower surface side of the inner ceramic wiring board 10 (see FIG. 8B). Since it is not easy to use 14 as one electrode, electroless plating is suitable as a method of forming the conductor portion 33 and the conductor film 34.

  When the bumps 31 are thus formed on the substrate-side pads 14, the LSI package 20 is mounted on the ceramic wiring board 10 in the same manner as in the first embodiment (step S201: alignment process, step S202: bonding process). . At this time, similarly to the first embodiment, the anisotropic conductive paste P1 constituting the base 32 of the bump 31 is compressed between the bump pad 21 and the substrate side pad 14 to impart conductivity in the pressurizing direction. The Thereby, the board | substrate side pad 14 and the bump pad 21 are electrically connected. At the same time, the upper end portion of the conductor portion 33 contacts the bump pad 21 via the conductor film 34, and the substrate side pad 14 and the bump pad 21 are electrically connected also by the conductor portion 33 and the conductor film 34.

  Here, when the bump 31 is formed on the substrate side pad 14 and the LSI package 20 is mounted after that as in the present embodiment, the substrate side pad 14 of the ceramic wiring board 10 and the bump pad 21 of the LSI package 20 are mounted. If the positional accuracy is not so high, there is a concern that the conductor portion 33 is detached from the bump pad 21 and electrical connection between the board-side pad 14 and the bump pad 21 cannot be ensured. However, since the conductor film 34 is provided on the bump 31 in this embodiment, the conductor film 34 comes into surface contact with the bump pad 21. As a result, the bump pad 21 and the conductor portion 33 are electrically connected via the conductor film 34, and as a result, the electrical connection between the substrate-side pad 14 and the bump pad 21 is ensured.

  Furthermore, the conductor film 34 covers not only the connection surface 32A to the bump pad 21 but also the entire exposed surface 32B in the base 32. Thus, by covering and protecting the exposed surface 32B of the base body 32 with the conductor film 34, it is possible to impart wear resistance to the bumps 31 and improve durability.

  As described above, also in this embodiment, the substrate side pad 14 and the bump pad 21 are connected by the bump 31 formed by the anisotropic conductive paste P1, and the bump 31 is provided with the conductor portion 33. The same effects as the first embodiment are achieved. Furthermore, since the conductor film 34 is provided on the bump 31 and the conductor film 34 comes into surface contact with the bump pad 21, even when the positional accuracy of the substrate side pad 14 and the bump pad 21 is not high. The conduction between the two can be ensured.

<Third reference example >
Hereinafter, a third reference example of the present invention will be described with reference to FIGS. The main difference between this reference example and the first embodiment is that the bump 41 is formed of a base 42 (first member) formed of the first anisotropic conductive paste P1 and the first anisotropic conductive paste. It is in the point comprised by the high density part 43 (2nd member, penetration part) formed with the 2nd anisotropic conductive paste P2 whose density of an electroconductive material is higher than P1. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

Also in the circuit board 40 of this reference example , the bump pads 21 of the LSI package 20 and the corresponding board-side pads 14 of the ceramic wiring board 10 are connected via the bumps 41 (see FIG. 9). .

  The bump 41 includes a base body 42 (first member) and a high-density portion 43 (second member) penetrating the base body 42 in the vertical direction (the stacking direction of the ceramic wiring board 10 and the LSI package 20). Yes. The base 42 is formed in a substantially annular shape by the first anisotropic conductive paste P1.

  On the other hand, the high-density portion 43 is formed into a disk shape having a diameter equal to the inner diameter of the ring in the base 42 by the second anisotropic conductive paste P2, and is accommodated inside the ring of the base 42. One end (upper end) of the base 42 is exposed on the connection surface 42A of the bump pad 21 and contacts the bump pad 21, and the other end (lower end) of the base 42 is exposed on the connection surface 42B of the substrate side pad 14. In contact with the substrate-side pad 14.

  The second anisotropic conductive paste P2 that forms the high-density portion 43 has a higher density of conductive material than the first anisotropic conductive paste P1 that forms the base 42. Here, “the density of the conductive material is high” means that the weight of the conductive material per unit volume is large. In order to adjust the anisotropic conductive paste having a high density of the conductive material, for example, the number of particles M of the conductive material dispersed in the resin per unit volume is increased, or the particles M having a large average particle diameter Can be considered. The resin and the conductive material constituting the two types of anisotropic conductive pastes P1 and P2 may be the same or different from each other.

  Both the base body 42 and the high-density portion 43 are appropriately compressed between the bump pad 21 and the substrate-side pad 14 to impart conductivity in the pressurizing direction, whereby the bump pad 21 and the substrate-side pad are provided. 14 is electrically connected. In addition, since the high density part 43 is comprised by the anisotropic conductive paste P2 with a high density of an electroconductive material compared with the base | substrate 42, conduction | electrical_connection is ensured with a weaker applied pressure.

  Next, a method of forming the bump 41 and a method of connecting the bump pad 21 by the bump 41 and the corresponding substrate-side pad 14 will be described with reference to the flowchart of FIG.

First, the first anisotropic conductive paste P1 is printed on the substrate-side pad 14 of the ceramic wiring board 10 by a screen printing method to form the base 42 (step S121: printing step; see FIGS. 10A and 10B). . At this time, a base 42 having a through hole 44 penetrating in the vertical direction is formed on a part of the substrate-side pads 14. In this reference example , an anisotropic conductive paste P1 is printed in a disc shape on a part of the substrate-side pads 14 located at the peripheral edge when viewed from the upper surface of the ceramic wiring board 10 (the mounting surface of the LSI package 20). A base 42 having no through hole 44 is formed. On the other hand, an anisotropic conductive paste P1 is printed in an annular shape on another substrate-side pad 14 located on the inner side of them, thereby forming a base 42 having a through hole 44. In addition, the diameter of the through-hole 44 is made larger in the base 42 formed on the substrate-side pad 14 located closer to the center. When printing is completed, the anisotropic conductive paste P1 is heated and cured (step S122: curing process).

  Next, the through hole 44 is filled with the second anisotropic conductive paste P2 by screen printing to form the high density portion 43 (through portion) (step S123: filling step; see FIGS. 11A and 11B). . When the filling is completed, the second anisotropic conductive paste P2 is cured by heating. (Step S124: second curing step).

  When the bumps 41 are thus formed on the substrate-side pads 14, the LSI package 20 is mounted on the ceramic wiring board 10 in the same manner as in the first embodiment (step S201: alignment process, step S202: bonding process). . At this time, the first anisotropic conductive paste P1 constituting the base 42 of the bump 41 and the second anisotropic conductive paste P2 constituting the high-density portion 43 are both the bump pad 21 and the substrate-side pad 14. And conductivity is imparted in the pressurizing direction. Thereby, the board | substrate side pad 14 and the bump pad 21 are electrically connected.

Here, when the warp of the ceramic wiring board 10 or the unevenness of the surface is large, the pressure applied to the bumps 41 varies depending on the distance between the substrate-side pad 14 and the bump pad 21. In particular, the bump 41 (see the left bump 41 in FIG. 9) located at a position where the separation distance between the substrate side pad 14 and the bump pad 21 is large is not given a sufficient compressive force, and is sufficiently conductive. There is a possibility that the situation will not be secured. However, in the present reference example , the bump 41 is provided with the high density portion 43. And in this high density part 43, since it is comprised by the 2nd anisotropic conductive paste P2 with a relatively high density of an electroconductive material, conduction | electrical_connection is ensured even with a weaker applied pressure. Thereby, the electrical connection between the board-side pad 14 and the bump pad 21 can be ensured.

In particular, in the present reference example , the high density portion 43 is provided on the bump 41 located on the center side when viewed from the upper surface of the ceramic wiring board 10, and the bump 41 disposed closer to the center is located closer to the center of the bump 41. The diameter is made larger. This is because, in general, the ceramic wiring board 10 tends to warp so that the upper surface is concave, and the distance between the substrate-side pad 14 and the bump pad 21 tends to increase in a region closer to the center of the ceramic wiring board 10. Is taken into account.

  That is, the high-density portion 43 is made of the anisotropic conductive paste P2 and has high flexibility as compared with the case where it is made only of the conductive material. There is no loss of sex. By utilizing this fact, in the bump 41 formed at a position where the separation distance between the substrate side pad 14 and the bump pad 21 is large, the diameter of the high-density portion 43 is increased, so that the connection reliability is further ensured. It can be.

Also in this reference example, as described above, since the substrate side pads 14 and the bump pads 21 are connected by the bumps 41 formed by the anisotropic conductive paste P1, P2, the same effects as the first embodiment Play. Further, since the bump 41 is provided with a high density portion 43 formed of the second anisotropic conductive paste P2 having a relatively high density of the conductive material, the pressure applied to the bump 41 can be reduced. Regardless, the electrical connection between the substrate-side pad 14 and the bump pad 21 can be ensured.

<Fourth Reference Example >
Hereinafter, a fourth reference example of the present invention will be described with reference to FIGS. The main difference of this reference example from the first embodiment is that a plurality of types of bumps 51 formed of a plurality of types of anisotropic conductive pastes PA, PB, PC, PD having different conductive material densities are provided. There is in point. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

Also in the circuit board 50 of the present reference example , the bump pads 21 of the LSI package 20 and the corresponding board-side pads 14 of the ceramic wiring board 10 are connected via the bumps 51 (see FIG. 12). .

The bumps 51 of this reference example are formed in a substantially disc shape by anisotropic conductive pastes PA, PB, PC, PD. The plurality of bumps 51 respectively connecting the plurality of pairs of substrate-side pads 14 and the bump pads 21 are a plurality of types of bumps formed by anisotropic conductive pastes PA, PB, PC, PD having different conductive material densities. 51A, 51B, 51C, 51D are included. In the following, when distinguishing a plurality of types of bumps, a suffix is added to the reference numeral, such as “Bumps 51A, 51B, 51C, 51D”, and when referring to them without distinction, “Bump 51” Thus, the code shall be written without adding a subscript.

  “Different densities of the conductive material” means that the weight of the conductive material per unit volume is different. In order to adjust the anisotropic conductive paste having a different density of the conductive material, for example, the number of particles M of the conductive material dispersed in the resin per unit volume is varied, or the average particle diameter of the particles M is varied. It can be considered. The materials of the resin and the conductive material constituting the plurality of types of anisotropic conductive pastes may be the same or different.

  The bump 51 is appropriately compressed between the bump pad 21 and the substrate-side pad 14 to impart conductivity in the pressurizing direction, whereby the bump pad 21 and the substrate-side pad 14 are electrically connected. Is done. Note that the bump 51 formed of an anisotropic conductive paste having a high density of the conductive material ensures connection with a weaker pressure.

  Next, a method of forming the bump 51 and a method of connecting the bump pad 21 by the bump 51 and the corresponding substrate-side pad 14 will be described with reference to the flowchart of FIG.

First, the anisotropic conductive pastes PA, PB, PC, PD are printed on the substrate side pads 14 of the ceramic wiring board 10 by screen printing to form bumps 51 (step S131: printing step). At this time, a plurality of types of anisotropic conductive pastes PA, PB, PC, PD having different conductive material densities are sequentially screen-printed on the substrate-side pad 14. In this reference example , first, the anisotropic conductive paste PA having the lowest density of the conductive material is printed on the group of substrate-side pads 14 located near the periphery of the ceramic wiring board 10 to form the bumps 51A. (FIG. 13A, FIG. 13B). Next, an anisotropic conductive paste PB having a higher density of conductive material than that used for the first printing is printed on a group of substrate-side pads 14 located on the center side to form bumps 51B. To do. Further, the anisotropic conductive pastes PC and PD having a higher density of the conductive material are sequentially printed on the group of substrate-side pads 14 positioned on the center side to form bumps 51C and 51D. In this way, a plurality of types of anisotropic conductive pastes PA, PB, PC, and PD are sequentially printed, and closer to the center as viewed from the upper surface of the ceramic wiring board 10 (the mounting surface of the LSI package 20). The bumps 51 formed on the substrate-side pads 14 are arranged such that the density of the conductive material is higher (see also FIGS. 14A and 14B).

  When printing is completed, the anisotropic conductive pastes PA, PB, PC, PD are heated and cured (step S132: curing process).

  When the bumps 51 are thus formed on the board-side pads 14, the LSI package 20 is mounted on the ceramic wiring board 10 in the same manner as in the first embodiment (step S201: alignment process, step S202: bonding process). . At this time, the anisotropic conductive pastes PA, PB, PC, and PD constituting the bump 51 are compressed between the bump pad 21 and the substrate-side pad 14 to impart conductivity in the pressing direction. Thereby, the board | substrate side pad 14 and the bump pad 21 are electrically connected.

Here, when the warp of the ceramic wiring board 10 and the unevenness of the surface are large, the pressure applied to the bumps 51 varies depending on the distance between the substrate-side pad 14 and the bump pad 21. In particular, the bump 51 (see the left bump 51 in FIG. 12) existing at a position where the distance between the substrate-side pad 14 and the bump pad 21 is large is not given a sufficient compressive force, and is sufficiently conductive. There may be situations where it is not ensured. However, in this reference example , the bumps 51 are provided with a plurality of types formed by anisotropic conductive pastes PA, PB, PC, PD having different conductive material densities. Therefore, by providing the bump 51 using the anisotropic conductive paste having a higher density of the conductive material at a location where the separation distance between the substrate side pad 14 and the bump pad 21 is larger, connection reliability is improved. Can be secured. In general, the ceramic wiring board 10 tends to warp so that the upper surface is concave, and the distance between the substrate-side pad 14 and the bump pad 21 tends to increase as the distance from the center of the ceramic wiring board 10 increases. In the present reference example , bumps 51 formed of an anisotropic conductive paste having a higher density of conductive material are arranged closer to the center to ensure connection reliability.

Also in this reference example, as described above, the anisotropic conductive paste PA, PB, PC, from the substrate side pads 14 and the bump pads 21 are connected by the bumps 51 formed by the PD, as in the first embodiment Has the effect of. Furthermore, since bumps 51 are provided with a plurality of types of anisotropic conductive pastes PA, PB, PC, and PD having different conductive material densities, the warpage of the ceramic wiring board 10, the position of the unevenness, etc. In consideration of the above, by providing the bump 51 using the anisotropic conductive paste having a higher density of the conductive material in the region where the separation distance between the substrate side pad 14 and the bump pad 21 is larger, the connection reliability Sex can be secured.

<Fifth Reference Example >
Hereinafter, a fifth reference example of the present invention will be described with reference to FIGS. 15A to 15E. The main difference between this reference example and the first embodiment is that the bumps 61 are composed of a high-density portion 62 (first member) formed of the first anisotropic conductive paste P1 and the first anisotropic conductive material. It is in the point comprised with the base | substrate 63 (2nd member) formed with the 2nd anisotropic conductive paste P2 whose density of an electroconductive material is lower than a paste. Further, the high-density portion 62 is not formed so as to penetrate the bump 61, that is, the high-density portion 62 is covered with the base 63 and is not in contact with the bump pad 21 of the LSI package 20. . In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

Also in the circuit board 60 of this reference example , the bump pads 21 of the LSI package 20 and the corresponding board-side pads 14 of the ceramic wiring board 10 are connected via the bumps 61 (see FIG. 15A). .

  The bump 61 includes a high-density portion 62 (first member) formed of the first anisotropic conductive paste P1 and a second conductive material having a density lower than that of the first anisotropic conductive paste P1. And a base 63 (second member) formed of the anisotropic conductive paste P2. The high density portion 62 is formed in a disk shape on the substrate side pad 14.

  On the other hand, the base 63 is formed so as to cover the upper surface 62A and the side surface 62B of the high-density portion 62. The base 63 is in contact with the bump pad 21 on the upper surface 63A, and is in contact with the substrate-side pad 14 on the lower surface 63B.

  The second anisotropic conductive paste P2 forming the base 63 has a lower density of the conductive material than the first anisotropic conductive paste P1 constituting the high-density portion 62. Here, “the density of the conductive material is low” means that the weight of the conductive material per unit volume is small. In order to adjust the anisotropic conductive paste having a low density of the conductive material, for example, the number of particles M of the conductive material dispersed in the resin per unit volume is reduced, or the particles M having a small average particle diameter Can be considered. The resin and the conductive material constituting the two types of anisotropic conductive pastes P1 and P2 may be the same or different from each other.

  Both the high-density portion 62 and the base 63 are imparted with conductivity in the pressurizing direction by being appropriately compressed between the bump pad 21 and the substrate-side pad 14, whereby the bump pad 21 and the substrate-side pad are provided. 14 is electrically connected. In the bump 61, the portion where the high-density portion 62 and the base 63 overlap in the stacking direction of the LSI package 20 and the ceramic wiring board 10 is compared with the portion consisting only of the base 63 of the bump 61 due to the presence of the high-density portion 62. Thus, conduction is ensured with a weaker pressure.

  Next, a method for forming the bump 61 and a method for connecting the bump pad 21 by the bump 61 and the corresponding substrate-side pad 14 will be described with reference to the flowchart of FIG.

  First, the first anisotropic conductive paste P1 is printed on the substrate-side pad 14 of the ceramic wiring board 10 by a screen printing method to form a disk-shaped high-density portion 62 (step S141: printing process; FIG. 15B). FIG. 15C). When printing is completed, the anisotropic conductive paste P1 is heated and cured (step S142: curing process).

  Next, the second anisotropic conductive paste P2 is printed by screen printing so as to cover the high-density portion 62, thereby forming the base 63 (step S143: second printing step; see FIGS. 15E and 15D). When printing is completed, the second anisotropic conductive paste P2 is cured by heating. (Step S144: Second curing step).

  When the bumps 61 are thus formed on the substrate-side pads 14, the LSI package 20 is mounted on the ceramic wiring board 10 in the same manner as in the first embodiment (step S201: alignment process, step S202: bonding process). . At this time, the first anisotropic conductive paste P1 constituting the high-density portion 62 of the bump 61 and the second anisotropic conductive paste P2 constituting the base 63 are both the bump pad 21 and the substrate-side pad 14. And conductivity is imparted in the pressurizing direction. Thereby, the board | substrate side pad 14 and the bump pad 21 are electrically connected.

Here, when the warp of the ceramic wiring board 10 and the unevenness of the surface are large, the pressure applied to the bumps 61 varies depending on the distance between the substrate-side pad 14 and the bump pad 21. In particular, the bump 61 (see the left bump 41 in FIG. 15A) that exists at a position where the separation distance between the substrate-side pad 14 and the bump pad 21 is large is not given a sufficient compressive force and is sufficiently conductive. There is a possibility that the situation will not be secured. However, in the present reference example , the bump 61 is provided with the high density portion 62. In the bump 61, in the portion where the high density portion 62 and the base 63 overlap, there is a high density portion 62 composed of the first anisotropic conductive paste P1 having a relatively high density of the conductive material. Thus, conduction is ensured even with a weaker pressure. Thereby, the electrical connection between the board-side pad 14 and the bump pad 21 can be ensured.

Also in this reference example, as described above, since the substrate side pads 14 and the bump pads 21 by the bumps 61 formed by the anisotropic conductive paste P1, P2 are connected, the same effects as the first embodiment Play. Further, since the bump 61 is provided with a high density portion 62 formed of the first anisotropic conductive paste P1 having a relatively high density of the conductive material, the pressure applied to the bump 61 is increased or decreased. Regardless, the electrical connection between the substrate-side pad 14 and the bump pad 21 can be ensured. Further, since the through hole forming step is not necessary, the forming step of the bump 61 can be simplified.

Also in this reference example , as described in the third reference example , the bumps 61 located on the center side when viewed from the upper surface of the ceramic wiring board 10 are provided with the high-density portion 62 and at a position closer to the center. You may make it the diameter of the high-density part 62 become large, as the bump 61 arrange | positioned. This is because the ceramic wiring board 10 generally has a tendency to warp so that the upper surface is concave, and the distance between the substrate-side pad 14 and the bump pad 21 tends to increase as the area is closer to the center of the ceramic wiring board 10. Because there is.

  That is, the high-density portion 62 is made of the anisotropic conductive paste P2 and has high flexibility as compared with the case where the high-density portion 62 is made of only the conductive material. There is no loss of sex. Therefore, in the bump 61 formed at a position where the separation distance between the substrate-side pad 14 and the bump pad 21 is large, the connection reliability is further ensured by increasing the diameter of the high-density portion 62. Can do.

  Hereinafter, the present invention will be described in more detail with reference to examples. As materials, a ceramic wiring board and an anisotropic conductive paste were used.

1. Material (1) Ceramic wiring board As a ceramic wiring board, a multilayer ceramic wiring board having a known structure in which a plurality of insulating layers made of ceramics and a conductor layer having a predetermined pattern are alternately laminated and the layers are connected by via holes. It was used. A plurality of substrate-side pads are formed on the surface of the ceramic wiring board, and each substrate-side pad is conducted to the back surface side of the ceramic wiring board through a via hole and an inner conductive layer.

(2) Anisotropic conductive paste The following six types of anisotropic conductive paste were prepared.

The AC series of Mitsui Chemicals, Inc. was used as a base. This is obtained by adding an acrylic / silicon-based stress relaxation agent to a low-temperature curing type epoxy resin. What mixed nickel particle | grains with an average particle diameter of 5 micrometers as an electroconductive filler to this base was further added. The particle density of the conductive filler was set to 2500 pcs / mm ³ by measuring using a laser scattering type particle size measuring device while adjusting the added weight. By such a method, an anisotropic conductive paste A having a conductive filler particle density of 2500 pcs / mm ³ was prepared.

Nickel particles having an average particle diameter of 10 μm were used as the conductive filler, and an anisotropic conductive paste B having a conductive filler particle density of 2500 pcs / mm ³ was prepared in the same manner as the anisotropic conductive paste A. .

Nickel particles having an average particle diameter of 13 μm were used as the conductive filler, and an anisotropic conductive paste C having a conductive filler particle density of 4400 pcs / mm ³ was prepared in the same manner as the anisotropic conductive paste A. .

Nickel particles having an average particle diameter of 10 μm were used as the conductive filler, and an anisotropic conductive paste D having a conductive filler particle density of 3300 pcs / mm ³ was prepared in the same manner as the anisotropic conductive paste A. .

Nickel particles having an average particle diameter of 10 μm were used as the conductive filler, and an anisotropic conductive paste E having a particle density of the conductive filler of 4400 pcs / mm ³ was prepared in the same manner as the anisotropic conductive paste A. .

Nickel particles having an average particle size of 10 μm were used as the conductive filler, and an anisotropic conductive paste F having a particle density of the conductive filler of 6400 pcs / mm ³ was prepared in the same manner as the anisotropic conductive paste A. .

2. Method <Preliminary experiment>
The surface of the ceramic wiring board was subjected to surface treatment such as polishing and cleaning. On the substrate-side pad of this ceramic wiring board, anisotropic conductive paste A was printed at 40 ° C. by screen printing to form a disk-shaped pattern having a diameter of 40 to 650 μm. The height of the pattern was 30 μm. This pattern was 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.

The contact resistance was measured using a tensile and compression tester while changing the load on the bumps from 0 to 400 g / mm ² . The tensile / compression tester is provided with a table on which the object to be measured is set and a measurement terminal that contacts the object to be measured while applying a desired load. A contact resistance value is calculated by applying a predetermined current to an object and measuring a voltage value at that time. In this example, a ceramic wiring board on which bumps were formed was set on a table, and a contact resistance value was measured by bringing a measurement terminal into contact with the bumps while applying a desired load.

< Reference Example 1-1>
The surface of the ceramic wiring board was subjected to surface treatment such as polishing and cleaning. On the substrate-side pad of this ceramic wiring board, anisotropic conductive paste A was printed at 40 ° C. by screen printing to form a disk-shaped pattern having a diameter of 300 μm and a height of 30 μm. This pattern was heated at 150 ° C. for 40 seconds and then heated at 180 ° C. for 15 seconds to be cured to form bumps.

About the formed bump, the contact resistance was measured using a tensile and compression tester while changing the load on the bump from 0 to 400 g / mm ² .

< Reference Example 1-2>
Using anisotropic conductive paste B, bumps were formed in the same manner as in Reference Example 1-1, and contact resistance was measured.

<Example 2-1>
The surface of the ceramic wiring board was subjected to surface treatment such as polishing and cleaning. On the substrate-side pad of this ceramic wiring board, anisotropic conductive paste A was printed at 40 ° C. by screen printing to form a disk-shaped pattern having a diameter of 300 μm and a height of 30 μm. This pattern was heated at 150 ° C. for 40 seconds and then heated at 180 ° C. for 15 seconds to be cured to form a bump substrate. Next, laser irradiation was performed from the upper surface side of the substrate to form a through hole having a diameter of 5 μm. Next, by performing electroplating using the substrate side pad as one electrode, the through hole was filled with copper to form a conductor portion. Further, a Ni / Au protective film was attached to the upper end surface of the conductor portion by electroless plating. The contact resistance of the formed bump was measured in the same manner as in Reference Example 1-1.

<Example 2-2>
Bumps were formed using the anisotropic conductive paste B in the same manner as in Example 2-1, and the contact resistance was measured.

< Reference Example 3>
The surface of the ceramic wiring board was subjected to surface treatment such as polishing and cleaning. On the substrate side pad of this ceramic wiring board, anisotropic conductive paste B is printed at 40 ° C. by screen printing to form a plurality of ring-shaped patterns having an outer diameter of 300 μm, a height of 30 μm and different inner diameters. did. The formed pattern was heated at 150 ° C. for 40 seconds and then heated at 180 ° C. for 15 seconds to be cured to form a bump substrate. Next, the anisotropic conductive paste C was filled in the through holes by screen printing. The paste after filling was heated at 150 ° C. for 40 seconds and then heated at 180 ° C. for 15 seconds to be cured to form a high-density portion. The contact resistance of the formed bump was measured in the same manner as in Reference Example 1-1.

< Reference Example 4>
The surface of the ceramic wiring board was subjected to surface treatment such as polishing and cleaning. On the substrate side pad of this ceramic wiring board, anisotropic conductive pastes B, D, E, and F were respectively printed at 40 ° C. by screen printing to form a disk-shaped pattern having an outer diameter of 300 μm, an inner diameter of 30 μm, and a height of 30 μm. Formed. This pattern was heated at 150 ° C. for 40 seconds and then heated at 180 ° C. for 15 seconds to be cured to form bumps. The contact resistance of each formed bump was measured in the same manner as in Reference Example 1-1.

3. Results and Discussion (1) Preliminary Experiment FIG. 16 is a graph showing the relationship between the bump load and the contact resistance value in the preliminary experiment. The relative value is the ratio of the measured value to the saturation value of the contact resistance. The contact resistance value was saturated at a load of 400 g / mm ² and showed stable electrical connectivity. FIG. 17 is a graph showing the relationship between the bump size and the saturation value of the contact resistance in the preliminary experiment. The bump size on the horizontal axis is indicated by the reciprocal of the cross-sectional area of the bump. It can be seen that the saturation value of the contact resistance increases as the bump cross-sectional area decreases. From this, it can be said that the smaller the bumps, the more the contact resistance due to the load variation must be suppressed.

(2) Reference example 1
FIG. 18 is a graph showing the relationship between the bump load and the contact resistance value in Reference Example 1-1 (Paste A) and Reference Example 1-2 (Paste B). It can be seen that the bump using the paste B in which the density of the conductive material is high (the particle diameter of the conductive material used is large) has a smaller contact resistance and better conductivity.

(3) Example 2
FIG. 19 shows a graph showing the relationship between the bump load and the contact resistance value in Example 2-1 (Paste A) and Example 2-2 (Paste B). When the allowable value of the contact resistance is 200 mΩ, it is sufficient to apply a load of about 2.9 g / mm ^{2 in} Example 2-1 and about 2.6 g / mm ² or more in Example 2-2. From the comparison with FIG. 18, it can be seen that the provision of the conductor portion greatly reduces the contact resistance and can significantly improve the conductivity.

(4) Reference example 3
FIG. 20 is a graph showing the relationship between the load of each bump and the contact resistance value when the diameter of the high density portion is 50 μm, 100 μm, 150 μm, and 200 μm in Reference Example 3. For comparison, experimental results for bumps not provided with a high density portion are also shown. It can be seen that the contact resistance value under the same load is lower in the bump provided with the high density portion than in the bump not provided with the high density portion, and the conductivity is improved. It can also be seen that the contact resistance value decreases as the diameter of the high density portion increases.

Here, assuming that the variation in the load on the bump due to the warpage of the substrate and the unevenness is about 100 to 250 g / mm ² , the variation in the contact resistance value is about 130 mΩ when the high density portion is not provided. Become. On the other hand, variation in contact resistance can be reduced if the bumps are appropriately arranged so that bumps having a large diameter in the high density portion are arranged in the region where the load on the bumps is small. For example, bumps having a high-density portion with a diameter of 200 μm are arranged in a region where the load is 100 g / mm ^2, and bumps without a high-density portion are arranged in a region where the load is 250 g / mm ² , which is the maximum. By doing so, the variation in contact resistance can be reduced to about 30 mΩ.

(5) Reference example 4
FIG. 21 is a graph showing the relationship between the load of each bump and the contact resistance value for the bump formed using anisotropic conductive pastes B, D, E, and F in Reference Example 4. It can be seen that the bumps using the paste having a higher density of the conductive material have a lower contact resistance.

Here, assuming that the variation in the load on the bump due to the warpage of the substrate and the unevenness is about 100 to 250 g / mm ² , the large variation in the contact resistance value when one type of bump is used alone. For example, the bump using the anisotropic conductive paste B becomes about 130 mΩ. On the other hand, if the bumps are appropriately arranged so that the anisotropic conductive paste having a high density of the conductive material is disposed in the region where the load on the bumps is small, the variation in contact resistance can be reduced. . For example, bumps using the anisotropic conductive paste F are arranged in a region where the load is 100 g / mm ^2, and the anisotropic conductive paste B is used in a region where the load is 250 g / mm ² . If bumps are provided, the variation in contact resistance can be reduced to 30 mΩ.

<Other embodiments>
The technical scope of the present invention is not limited by the above-described embodiments, and, for example, those described below are also included in the technical scope of the present invention.

(1) In the above embodiment, the LSI package 20 is shown as an example of the electronic component. However, the type of the electronic component is not limited to the above embodiment, and can be applied as long as it is connected to the substrate via the bump. is there.

(2) In the first embodiment and the second embodiment, copper is used as the plating metal for forming the conductor portions 17, 33 or the conductor film 34. For example, tin, silver, solder, copper / tin, copper / Any metal that can be plated, such as silver, can be used.

(3) In the second embodiment, the conductor film 34 covers the connection surface 32A, which is a region corresponding to the bump pad 21 in the base 32, and the exposed surface 32B that is not in contact with the ceramic wiring board 10 or the LSI package 20. Although formed in a thin film shape, the conductor film may be formed only on the connection surface with the connection portion.

(4) In the second embodiment, the conductor part 33 and the conductor film 34 are formed by one plating process. However, for example, the plating process may be performed in two stages, and the conductor part and the conductor film may be formed of different conductive materials. I do not care.

(5) In the first embodiment, the conductor portion 17 is formed by electroplating, but it may be formed by electroless plating. Also, when the conductor part and the conductor film are formed in the plating process as in the second embodiment, for example, the substrate side pad extends to the lower surface of the substrate through the via hole (the surface opposite to the substrate side pad side). When conducting, the conductor portion and the conductor film may be formed by electroplating.

(9) In the above embodiments, the physical bonding between the LSI package 20 and the ceramic wiring board 10 is performed using the adhesive 19, but other bonding means may be used. Examples of other joining means include a mechanical joining mechanism using a tray on which the LSI package 20 and the ceramic wiring board 10 are mounted and a load blade. Hereinafter, this joining mechanism will be briefly described. The tray is formed with a recess for positioning the LSI package 20, a recess for positioning the ceramic wiring board 10, and a bolt through-hole used for fastening the load blade. Further, the load blade includes a through hole of a bolt and a connection terminal (on the substrate side via the conductor layer 12) formed on the lower surface of the ceramic wiring board 10 (the surface opposite to the side on which the substrate-side pad 14 is formed). An opening exposing a terminal connected to the pad 14 is formed. Next, the joining process will be described. First, the LSI package 20 is placed on the tray with the bump pad 21 facing upward. Next, the ceramic wiring board 10 is placed on the LSI package 20 with the substrate side pads 14 facing downward. At this time, the LSI package 20 and the ceramic wiring board 10 are positioned by the recesses, whereby the bump pads 21 and the corresponding substrate-side pads 14 come into contact with each other. Further, a load blade is set on the tray. Thereby, the LSI package 20 and the ceramic wiring board 10 are sandwiched between the tray and the load blade. Finally, a bolt is inserted into the through hole and fastened so that a desired load is applied. According to the above joining mechanism, the circuit board is handled as a module including a tray and a load blade. With such a configuration, the LSI package 20 and the ceramic wiring board 10 are joined so as to be re-separable from each other. Therefore, when there is a defect in the LSI package 20, the replacement is easy.

(10) In the above embodiment, the shape, structure, and material of the bump have been described by taking specific examples as examples. However, the present invention is not limited thereto, and any bumps can be used as long as they produce the effects of the present invention. it can. The embodiment described above is an example in which the present invention is applied to the connection between the LSI package 20 and the ceramic wiring board 10, but the present invention can be applied to the connection between an arbitrary electronic component and a substrate.

It is a partial expanded sectional view of the circuit board of a 1st embodiment. It is a top view of a ceramic wiring board. It is the IIB-IIB sectional view taken on the line of FIG. 2A. It is a top view which shows a mode that the anisotropic conductive paste was printed on the board | substrate side pad of the ceramic wiring board by the screen printing method. It is the IIIB-IIIB sectional view taken on the line of FIG. 3A. It is a top view which shows a mode that the through-hole from the upper surface side of a base | substrate to the surface of a board | substrate side pad was formed. It is the IVB-IVB sectional view taken on the line of FIG. 4A. It is a top view which shows a mode that the metal part was filled in the through-hole and the conductor part was formed. It is the VB-VB sectional view taken on the line of FIG. 5A. It is a partial expanded sectional view of the circuit board of a 2nd embodiment. It is a top view which shows a mode that the anisotropic conductive paste was printed on the board | substrate side pad of the ceramic wiring board by the screen printing method, and the through-hole from the upper surface side of a base | substrate to the surface of a board | substrate side pad was formed. It is the VIIB-VIIB sectional view taken on the line of FIG. 7A. It is a top view which shows a mode that the conductor part was formed by filling a metal in a through-hole, and the conductor film was formed on the surface of a base | substrate. It is the VIIIB-VIIIB sectional view taken on the line of FIG. 8A. It is a partial expanded sectional view of the circuit board of the 3rd reference example . It is a top view which shows a mode that the 1st anisotropic conductive paste was printed on the board | substrate side pad of the ceramic wiring board by the screen printing method, and the base | substrate was formed. It is the XB-XB sectional view taken on the line of FIG. 10A. It is a top view which shows a mode that the 2nd anisotropic conductive paste was filled into the through-hole by the screen printing method, and the high-density part was formed. It is the XIB-XIB sectional view taken on the line of FIG. 11A. It is a partial expanded sectional view of the circuit board of the 4th reference example . It is a top view which shows a mode that the anisotropic conductive paste was printed on the board | substrate side pad of a part of ceramic wiring board by the screen printing method, and the bump was formed. It is the XIIIB-XIIIB sectional view taken on the line of FIG. 13A. It is a top view which shows a mode that the anisotropic conductive paste was printed by the screen printing method on the other board | substrate side pad of a ceramic wiring board, and the bump was formed. It is the XIVB-XIVB sectional view taken on the line of FIG. 14A. It is a partial expanded sectional view of the circuit board of the 5th reference example . It is a top view which shows a mode that the 1st anisotropic conductive paste was printed on the board | substrate side pad of the ceramic wiring board by the screen printing method. It is the XVC-XVC sectional view taken on the line of FIG. 15B. It is a top view which shows a mode that the 2nd anisotropic conductive paste was further printed on the 1st anisotropic conductive paste by the screen printing method. It is the XVE-XVE sectional view taken on the line of FIG. 15D. It is a graph showing the relationship between the bump load in a preliminary experiment, and the relative value of contact resistance. It is a graph showing the relationship between the bump size and the saturation value of contact resistance in a preliminary experiment. It is a graph showing the relationship between the bump load and the contact resistance value in Reference Example 1-1 and Reference Example 1-2. It is a graph showing the relationship between the bump load and the contact resistance value in Example 2-1 and Example 2-2. In the reference example 3 , it is a graph showing the relationship between the bump load and the contact resistance value when the diameter of the high density portion is 50 μm, 100 μm, 150 μm, and 200 μm and when the high density portion is not provided. In the reference example 4 , it is a graph showing the relationship between the load of each bump | vamp, and the contact resistance value about the bump formed using anisotropic conductive paste B, C, D, E. It is a flowchart which shows the procedure of the formation method of the bump in 1st Embodiment, and the connection method of a LSI package and a ceramic wiring board. It is a flowchart which shows the procedure of the formation method of the bump in 2nd Embodiment, and the connection method of a LSI package and a ceramic wiring board. It is a flowchart which shows the procedure of the formation method of the bump in a 3rd reference example , and the connection method of a LSI package and a ceramic wiring board. It is a flowchart which shows the procedure of the formation method of the bump in a 4th reference example , and the connection method of a LSI package and a ceramic wiring board. It is a flowchart which shows the procedure of the formation method of the bump in a 5th reference example , and the connection method of a LSI package and a ceramic wiring board.

1, 30, 40, 50 ... Circuit board (component mounting board)
10 ... Ceramic wiring board (substrate)
14 ... Pad board side (connection terminal)
15, 31, 41, 51 ... bumps 16, 32, 42 ... base portions 16A, 32A, 42A ... connection surfaces 16B, 42B ... connection surfaces 17, 33 ... conductor portions 18, 35 44 ... through hole 20 ... LSI package (electronic component)
21 ... Bump pad (connection part)
34 ... conductor film 32B ... exposed surface 43 ... high density part (penetrating part)

Claims (4)

A connection structure for electrically connecting a connection terminal provided on a substrate and a connection portion provided on an electronic component,
A first member formed by the first anisotropic conductive paste containing particles of conductive material, between the connecting portion and the connecting terminal wherein the first member by a second member conductivity is different The connection terminal and the connection portion are connected through the formed bump ,
The second member is made of a conductive material;
The second member is disposed at a position corresponding to a center position of the connection terminal and the connection portion when viewed from the stacking direction of the substrate and the electronic component, and the first member surrounds the second member;
The connection structure , wherein the second member penetrates the first member in a stacking direction of the substrate and the electronic component . Which the bump is provided with a conductive film formed of a conductive material, it covers the connection surface of at least the connection terminal or the connecting portion the conductor film in said first member, and is connected to the second member The connection structure according to claim 1, wherein The conductive film is one that covers the entire exposed surface of the first member, the connection structure according to claim 2. The component mounting board provided with the connection structure of any one of Claims 1-3.

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