JP2006258826A - Bump forming method and bump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and quickly form a bump and a probe card for contacting electrically with an electric component. <P>SOLUTION: This probe card has a plurality of conductors 12 for transmitting an electric signal used for inspection, and the bump 18 formed respectively on the plurality of conductors, and for contacting mechanically with the electric component. The bump 18 has a lower portion fused to the conductors, and an upper portion die-molded into a thin-tip shape reduced in a cross-sectional area along with approach to a tip of the bump. The bump 18 has further an elastomer for pressing the bump onto the electric component. The bump 18 has further a flexible substrate 54 pressed toward a direction of the electric component by the elastomer. Each of the plurality of conductors 12 has a reverse face bonded to the substrate, and a surface provided with the bump. A surface of the bump 18 is plated with a substance of high hardness having hardness higher than that of the upper portion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bump for making electrical contact with an electrical component, a probe card having the bump formed on a conductor, and a method for forming the bump. In particular, the present invention relates to a probe card and a bump formed by fusing a conductive material to a conductor.

  In the Nikkei Microdevice February 1996 issue, an example of a bump shape for making electrical contact with an electrical component is shown. Conventionally, methods such as etching and plating have been used to form such bumps.

  However, in the etching method, the shape of the bump that can be generated is significantly limited. In addition, the dimensional stability of the bumps is poor, the processing time is long, and the manufacturing cost is high. In addition, the bump forming method by plating can produce only bumps having a round outer periphery.

  On the other hand, a method of forming a bump by transferring a solder ball with a suction device is disclosed in the September 1997 issue of M & E (Industry Research Committee) (P168-P169). However, in this method, when solder is fused, the bump shape becomes round, and a desired contact cannot be made with the electrical component.

  Japanese Patent Publication 2691875 (issued December 17, 1997, published on August 30, 1996) by Okubo et al. Discloses a method of generating bumps using a ball formed by melting the tip of a wire. ing. In addition, the process of melting the tip of the wire and generating a ball at the tip of the wire is disclosed in the semiconductor manufacturing equipment terminology of the Japan Semiconductor Manufacturing Equipment Association (4th edition issued on November 20, 1997) (P290). ). However, the method described in this patent publication requires many steps to cut the tip of the wire. Further, when a plurality of bumps are formed, there is a technical problem that the tip height of each bump is not uniform.

  Accordingly, an object of the present invention is to provide a bump, a probe card, and a method of forming the bump that can solve the above-described problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

  That is, the probe card according to the first embodiment of the present invention includes a plurality of conductors that transmit electrical signals used for inspection of characteristics of electrical components, and bumps formed on each of the plurality of conductors. Bumps that are in mechanical contact with the electrical components. The bump has a lower part fused to the conductor and an upper part embossed into a tapered shape whose sectional area decreases as it approaches the tip of the bump. The length of the upper part of the bump is desirably at least 20 μm. Moreover, as a taper shape, it can be set as a cone shape, for example.

  The probe card may further include an elastic body that presses the bump against the electrical component and a flexible substrate that is pressed by the elastic body toward the electrical component. Each of the plurality of conductors has a back surface bonded to the substrate and a surface provided with bumps. As another embodiment, an elastic body made of a conductive metal may be provided independently for each conductor. In this case, each of the plurality of conductors may be a metal integrally formed with the elastic body. A bump is formed on each of the plurality of conductors, and the bumps are embossed with substantially the same height. The surface of the bump is plated with a high-hardness material that is conductive and has a hardness greater than the hardness of the upper portion of the bump. Bumps formed on each of the plurality of conductors are in mechanical contact with the electrical component.

  Further, the method for manufacturing the bump for contacting an electric component includes a fusion step in which the bump is fused on the conductor, and a conductive material fused on the conductor is embossed into a desired shape by a bump molding die. A molding step. As the desired shape, for example, a tapered shape such as a conical shape whose cross-sectional area decreases as it approaches the tip of the bump can be used. In the molding process, it is desirable that the closest distance between the conductor and the peripheral portion of the depression provided in the bump mold is smaller than the depth of the depression. By plating the surface of the formed bump with a high-hardness material such as nickel or palladium nickel having a hardness higher than that of the conductive material, and further performing gold plating, the strength and contact electric resistance of the bump can be lowered.

  Furthermore, in the semiconductor contact bump forming method of the present invention, the tip portion of the wire having a conductive material is melted by electric discharge machining, and the melted tip portion is brought into contact with the conductor. The wire is stopped for a predetermined time while the tip is in contact with the conductor, and the tip is cut by pulling the wire away from the conductor. A ball-like substance containing a conductive substance may be sucked and conveyed onto a conductor and melted by reflow and then solidified.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  As is apparent from the above description, according to the present invention, bumps and probe cards for making electrical contact with electrical components can be formed accurately and at high speed.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are the solution of the invention. It is not always essential to the means.

  1. Embodiment 1

  FIG. 1 is a cross-sectional view of a flexible substrate type probe card in the present embodiment. The flexible printed circuit board type probe card is a printed circuit board 52, a flexible printed circuit board 54 that is mounted in a state where the central opening of the printed circuit board 52 is covered from one side, and an elastic that presses the flexible printed circuit board 54 within the opening of the printed circuit board 52. The body 50 and the bump 25 provided on the opposite side of the elastic body 50 on the flexible substrate 54 are provided. When the elastic body 50 presses the flexible substrate 54, the bumps 25 are in electrical contact with the electrical component, and the electrical characteristics of the electrical component can be inspected.

  FIG. 2 is a bottom view of the flexible substrate 54 of FIG. The flexible substrate 54 includes a plurality of conductors 12 that transmit or receive electrical signals used for inspection of electrical characteristics to the bumps 25. By melting a wire containing a dielectric material or the like and fusing it on the conductor 12, one bump 25 is formed at the tip of each conductor 12.

  FIG. 3A shows a melting step of melting the tip portion of the wire 13 having a conductive material by electric discharge machining. The wire 13 is gripped by the capillary 16 so that the wire 13 slightly protrudes from the tip of the capillary (bonding machine) 16. The wire 13 has a conductive material such as gold, aluminum, or copper, and generates an electronic spark between the wire 13 and the electric torch 14 to melt the tip of the wire 13. As shown in FIG. 3B, the melted wire is rounded by surface tension, and the ball 10 is formed at the tip of the wire 13. When the ball 10 is formed, the electric torch 14 is pulled away from the ball 10.

  FIG. 4A shows an abutting step in which the ball 10 melted by the melting step abuts on the conductor 12. The capillary 16 descends and the ball 10 comes into contact with the conductor 12. A bump substrate 18 formed by deforming the ball 10 is fused to the conductor 12 while being supported by a recess inside the capillary 16. In order to cool and solidify the bump base material 18, the wire 13 is stopped for a predetermined time while the bump base material 18 is pressed against the conductor 12.

  FIG. 4B shows a cutting process of cutting the bump base material 18 formed at the tip portion of the wire 13. The bump 13 is left on the conductor 12 and is cut from the wire 13 by moving the wire 13 in a direction away from the conductor 12 provided on the flexible substrate 54. In this figure, as an example of the direction of separating from the conductor 12, the wire 13 gripped by the capillary 16 is moved vertically above the conductor 12.

  FIGS. 5A to 5C show a state in which the bump base material 18 fused to the conductor 12 is embossed by a bump molding die 20 having a recess 21. The inner peripheral surface of the recess 21 presses the bump substrate 18 to shape the bump substrate 18. Further, the bump mold 20 has a recess 22 in the peripheral portion of the recess 21 that is shallower than the recess 21 in order to prevent the recess 21 from being too close to the conductor 12. The bump mold 20 is preferably manufactured from an SK material or a material having a hardness equal to or higher than that in order to prevent deformation.

  As shown in FIG. 5B, the surplus portion of the bump base material 18 protrudes into the recess 22 at the time of stamping. If the protruding portion of the bump protrudes further outward than the concave portion 22, there is a possibility that it will contact an adjacent bump or conductor 12. In order to prevent this, it is desirable that the closest distance between the conductor 12 and the peripheral portion of the recess 21 is somewhat large. Therefore, the concave portion 22 is set so that the closest distance between the conductor 12 and the peripheral portion of the depression 21 is larger than ½ of the depth of the depression 21, that is, larger than ３ of the height of the bump base material 18. Determine the depth of the. More preferably, the depth of the recess 22 is determined so that the closest distance between the conductor 12 and the peripheral portion of the recess 21 is 40% or more of the height of the bump base 18. In this embodiment, the height of the bump substrate 18 is 40 micrometers, and the closest distance between the conductor 12 and the peripheral portion of the recess 21 is 20 micrometers (μm), that is, 1 / of the height of the bump substrate. 2. In order for the bump mold 20 to mold the bump substrate 18, the bump mold 20 is pressed against the bump substrate 18 for several tens of milliseconds and stopped.

  FIG. 5C shows an embossed bump substrate 18. The shaped bump substrate 18 has a lower portion 27 fused to the conductor 12 and a tapered shape whose cross-sectional area decreases as it approaches the tip of the bump 25, for example, an upper portion 29 formed into a conical shape. Have. In order to increase the hardness, the surface of the formed bump base material 18 is plated with a high hardness material 15 having a hardness higher than that of the bump base material 18. As the high hardness substance 15, for example, nickel or palladium nickel can be used. In order to improve electrical contact with the electrical parts, a gold plating 23 is further applied to the surface of the plating with the high hardness material 15. Thus, the length of the plated upper portion 29 is at least 20 μm or more.

  FIG. 6 shows another form of the concave portion 22 of the bump mold 20 shown in FIG. By providing the support 24 on the bump mold 20, a predetermined distance is secured between the peripheral portion of the recess 21 and the conductor 12. This support 24 may be provided for each depression 21 or one for the plurality of depressions 21. The support 24 secures the recess 22 around the recess 21 and prevents the bump base 18 protruding from the recess 21 from contacting the adjacent bump base 18 or the conductor 12.

  FIG. 7 shows an embossing process when the bumps 25 are formed on the flexible substrate 54 in a grid pattern. First, the conductors 12 are provided in a grid pattern on the flexible substrate 54, and the bump base material 18 is fused on each conductor 12. Next, the bump base 18 is shaped into a desired shape by pressing the bump forming die 20 provided with the depressions 21 in a lattice shape against the bump base 18.

  FIG. 8 shows a grid-like bump 25 formed by the forming step shown in FIG. A conical bump 25 is formed by a recess 21 provided in the bump mold 20. According to the present embodiment, the bump base material 18 arranged in a lattice shape is embossed at once by the single bump forming die 20, so that the bump height can be made uniform.

  2. Embodiment 2

  In the first embodiment, the tip of the wire 13 is fused to form the bump base material 18. In this embodiment, a ball-shaped substance containing a conductive substance is manufactured in advance, and the bump base material 18 is formed by fusing it on the conductor 12. 9A and 9B are perspective views of the container 34 in which the ball-shaped material 30 containing the conductive material is stored, and the adsorption device 32. The ball-shaped substance 30 is manufactured from a conductive material that can be plastically processed, such as copper (Cu) or gold (Au). The ball-shaped substance 30 is sucked by the suction device 32 and sucked and conveyed onto the table 56. A guide rod 48 for positioning is provided on the table 56, and a flexible substrate 54 having a guide hole corresponding to the guide rod 48 is positioned by the guide rod 48 and installed on the table 56. The suction device 32 is similarly provided with a guide hole 46, and the guide device 48 is inserted into the guide hole 46, whereby the suction device 32 is positioned with respect to the table 56.

  FIG. 10A is a cross-sectional view of the container 34 and the suction device 32 shown in FIG. 9A as viewed from the side. Suction holes 31 are provided on the lower surface of the suction device 32, and when the suction device 32 descends in the direction of the arrow, one ball-like substance 30 is sucked into each suction hole 31 one by one. FIG. 10B shows a state in which the ball-shaped substance 30 is adsorbed in the adsorption hole 31 of the adsorption device 32. The suction hole 31 is provided in advance at a position corresponding to the bump formation position on the conductor 12.

  FIG. 10C shows a process in which the ball-shaped substance 30 is adsorbed in the adsorption hole 31 of the adsorption device 32 and conveyed to a position facing the flexible substrate 54. The position of the positioning guide hole 46 is aligned with the guide rod 48. The conductor 12 is provided on the upper surface of the flexible substrate 54. In order to obtain good electrical conductivity and mechanical strength when the ball-shaped material 30 is fused to the conductor 12, a conductive adhesive 36 such as solder paste or flux is spread on the upper surface of the conductor 12 in advance. Keep it.

  FIG. 10D shows a process of installing the ball-shaped substance 30 on the conductor 12. After the ball-shaped substance 30 is placed on the conductor 12, the ball-shaped substance 30 is melted by reflow, solidified, and fused to the upper surface of the conductor 12. The fused bump base material is embossed with a bump forming die 20 in the same manner as in the first embodiment to form a tapered bump. Since the stamping process is the same as that of the first embodiment, the description thereof is omitted.

  According to the present embodiment, since a large number of ball-shaped substances 30 can be disposed on the conductor 12 at a time, when a large number of bumps are formed, the bumps are formed earlier than in the first embodiment. Can do.

  3. Embodiment 3

  FIG. 11 shows a metal probe type probe card. In the first and second embodiments, the conductor 12 is provided on the flexible substrate 54, but in the present embodiment, the conductor 12 is directly attached on the printed circuit board 52. The conductor 12 is thicker than the conductor 12 of Embodiment 1 or 2, and has a large spring coefficient against bending. For this reason, the bump 25 can be pressed against the electrical component by the elasticity of the conductor 12 itself. Even when the conductor 12 in the first or second embodiment is directly attached to the printed circuit board 52 as in the present embodiment, the bumps 25 can be formed on the conductor 12 by the same method as in the first or second embodiment.

  According to this embodiment, it is possible to accurately and rapidly form bumps and probe cards for making electrical contact with electrical components. As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the appended claims that the embodiments added with such changes or improvements are also included in the technical scope of the present invention.

It is a longitudinal cross-sectional view of the probe card using the flexible substrate in Embodiment 1. It is a bottom view of the flexible substrate 54 shown in FIG. The melting step of melting the tip portion of the wire 13 having a conductive material by electric discharge machining will be shown. An abutting process in which the bump base material 18 melted in the melting process is brought into contact with the conductor 12 and a cutting process in which the bump base material 18 is left on the conductor 12 by separating the wire 13 from the conductor 12 are shown. A state in which the bump base 18 fused to the upper surface of the conductor 12 is embossed by a bump mold 20 is shown. A bump 25 formed by stamping and plating is shown. The bump base material 18 embossed and shaped by the bump mold 20 of another form is shown. The process of shape | molding the bump base material 18 arrange | positioned at the grid | lattice form is shown. The bumps 25 are formed in a lattice shape by the molding process shown in FIG. A step of sucking and conveying the ball-like substance 30 containing the conductive substance by the adsorption device 32 is shown. It is sectional drawing which looked at the process of attracting | sucking the ball-shaped substance 30 from the side. A metal probe type probe card is shown.

Explanation of symbols

10 ball 12 conductor 13 wire 14 electric torch 15 high hardness substance 16 capillary (bonding machine)
18 Bump substrate 20 Bump mold 21 Dimple 22 Recess 23 Gold plating 24 Support body 25 Bump 27 Lower part 29 Upper part 30 Ball-shaped material 31 Suction hole 32 Suction tool 34 Container 36 Conductive adhesive 46 Guide hole 48 Guide bar 50 Elastic body 52 Printed circuit board 54 Flexible circuit board 56 units

Claims (25)

  A bump forming method for forming a bump on an electric conductor for making electrical contact with an electric component, wherein a conductive material having substantially the same material as the bump is fused on the electric conductor. A bump forming method comprising: a step, and a molding step of embossing the conductive material fused onto the conductor into a desired shape by a bump molding die having a recess of a predetermined shape .   2. The bump forming method according to claim 1, wherein the desired shape is a tapered shape in which an area of a cross-section decreases as approaching a tip of the bump.   The bump forming method according to claim 2, wherein the tapered shape is a conical shape.   The said formation process WHEREIN: The closest distance of the said conductor and the peripheral part of the said hollow provided in the said bump shaping | molding die is larger than 1/2 of the depth of the said hollow. Bump formation method.   2. The bump forming die used in the forming step has a concave portion shallower than the depth of the recess in a peripheral portion of the recess, which suppresses the remaining widening of the conductive material. Bump forming method.   The bump forming method according to claim 1, further comprising a plating step of plating the surface of the bump formed in the forming step with a high-hardness material having a hardness higher than that of the conductive material.   The bump forming method according to claim 6, wherein the high-hardness substance is any one of nickel and palladium nickel.   The bump forming method according to claim 6, wherein the surface of the bump plated by the plating step is further gold-plated.   The fusion step includes a melting step of melting a tip portion of the wire having the conductive material by electric discharge machining, a contact step of bringing the tip portion melted by the melting step into contact with the conductor, and the tip portion Stopping the wire for a predetermined time in contact with the conductor, and fusing the tip portion to the conductor, and pulling the wire away from the conductor to place the tip portion in the conductor The bump forming method according to claim 1, further comprising: a cutting step of cutting the remaining portion.   The fusing step includes a conveying step of sucking and conveying the ball-shaped material containing the conductive material onto the conductor, a melting step of melting the ball-shaped material conveyed by the conveying step by reflow, The method of forming a bump according to claim 1, further comprising a step of cooling and solidifying the ball-shaped material melted in the melting step.   A bump formed on a conductor to make electrical contact with an electrical component, a lower portion fused to the conductor, and a tapered area that decreases in cross-sectional area as it approaches the tip of the bump A bump characterized by comprising an upper part embossed into a shape.   The bump according to claim 11, wherein the tapered shape is a conical shape.   The bump according to claim 11, wherein a length of the upper portion formed by the embossing is at least 20 μm or more.   The bump according to claim 11, wherein the surface is plated with a high hardness material having a hardness greater than that of the upper portion.   The bump according to claim 14, wherein the high-hardness substance is any one of nickel and palladium nickel.   The bump according to claim 14, wherein the surface of the plating with the high-hardness material is further gold-plated.   A probe card for making electrical contact with an electrical component and inspecting electrical characteristics of the electrical component, the plurality of conductors transmitting an electrical signal used for the inspection, and the plurality of electrical conductors Bumps formed on each of the electrical components, wherein the bumps are in mechanical contact with the electrical component, the bumps being in close contact with the lower portion fused to the conductor and the tip of the bumps. A probe card comprising: an upper portion formed by press-molding into a tapered shape having a reduced cross-sectional area.   The probe card according to claim 17, further comprising an elastic body that presses the bump against the electrical component.   A flexible board pressed in the direction of the electrical component by the elastic body; and each of the plurality of conductors has a back surface bonded to the board and a surface provided with the bumps. The probe card according to claim 18, characterized in that:   The probe card according to claim 18, wherein the elastic body is a conductive metal and is provided independently for each of the plurality of conductors.   21. The probe card according to claim 20, wherein each of the plurality of conductors is a metal formed integrally with the elastic body provided corresponding to the conductor.   The probe card according to claim 17, wherein the tapered shape is a conical shape.   18. The probe card according to claim 17, wherein the bumps formed on each of the plurality of conductors are formed by substantially the same height.   18. The probe card according to claim 17, wherein the length of the upper portion of the bump is at least 20 [mu] m or more. The probe card according to claim 17, wherein a surface of the bump is plated with a high hardness material having a hardness larger than that of the upper portion.

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