Solder bump forming apparatus

Abstract

To provide a solder bump formation device capable of securing a certainty of transfer of solder particles to an electrode without making shapes of the solder particles uniform.SOLUTION: A solder bump formation device 11 includes: a stage 12 at which a first execution region R2 is set; a first supply part 13 that has a plurality of concave parts 3 in which solder particles S1 are held, and supplies a solder bump formation member 1 having a deformation part 6 in which a construction part of each concave part 3 can be deformed at a melting point of the solder particle S1; a second supply part 14 that supplies a circuit member 21 so that the solder particle S1 held by the concave part 3 is arranged in a manner to be opposite to an electrode 22; and a heating pressure head 16 that heats the electrode 22 to a temperature of the melting point or higher of the solder particle S1 and presses it against the solder bump formation member 1 in the first execution region R2 to deform the deformation part 6 and thereby brings the solder particle S1 into contact with the electrode 22.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a solder bump forming apparatus.

Background Art

[0002] In recent years, flip chip mounting is known as one of the methods for mounting electronic components with high density. In flip chip mounting, for example, solder bumps are formed in advance on electrodes provided on one circuit member, and the electrodes of one circuit member and the electrodes of the other circuit member are joined by melting the solder bumps. Thereby, a connection structure between circuit members is formed.

[0003] As a technique for forming solder bumps on electrodes, for example, there is a solder bump forming method described in Patent Document 1. In this conventional solder bump forming method, a positioning plate having a plurality of recesses formed corresponding to the mutual intervals of the electrodes of the substrate is prepared, and solder particles are respectively arranged in each recess of the positioning plate. Next, by rolling a transfer roll whose outer peripheral surface is an adhesive surface on the surface of the positioning plate, the solder particles are transferred to the adhesive surface of the transfer roll. Then, by rolling the transfer roll on the electrodes of the substrate provided with the adhesive material, the solder particles are transferred from the transfer roll to the electrodes of the substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a method such as the solder bump formation method described in the above Patent Document 1, from the viewpoint of ensuring the certainty of the transfer of solder particles to the electrodes, it is preferable that the heights of the solder balls protruding from the recesses of the positioning plate are uniform. However, for example, in the case of using minute solder particles such as those used for connection between electrodes at intervals on the order of several μm, it is difficult to make the shapes of the solder particles uniform, and there has been a problem that it is difficult to ensure the certainty of the transfer of the solder particles to the electrodes.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a solder bump forming apparatus capable of ensuring the certainty of the transfer of solder particles to electrodes without making the shapes of the solder particles uniform.

Means for Solving the Problems

[0007] A solder bump forming apparatus according to one aspect of the present disclosure is a solder bump forming apparatus for forming solder bumps on electrodes of a circuit member, including: a stage in which an implementation region for implementing the formation of solder bumps on the electrodes is set; a first supply unit that supplies a solder bump forming member having a plurality of recesses in which solder particles are held, and a deformation part in which a constituent part of the recess is deformable at the melting point of the solder particles; a second supply unit that supplies the circuit member so that the solder particles held in the recesses of the solder bump forming member are disposed opposite to the electrodes; and a heating and pressing unit that heats the electrodes to a temperature equal to or higher than the melting point of the solder particles in the implementation region, presses the electrodes against the solder bump forming member, deforms the deformation part, brings the solder particles held in the recesses into contact with the electrodes, and transfers the solder particles to the electrodes to form solder bumps.

[0008] In this solder bump forming apparatus, solder particles are held in a plurality of recesses of a solder bump forming member, and by applying heat and pressure together with an electrode to be transferred, solder bumps can be formed on the electrode. In the solder bump forming member supplied to this solder bump forming apparatus, the constituent part of the recess has a deformable part that can be deformed at the melting point of the solder particles. Thereby, when heat is applied while pressing the electrode, the deformable part deforms, and the solder particles held in the recess can be exposed to the electrode side. Therefore, in this solder bump forming apparatus, the certainty of the transfer of the solder particles to the electrode can be ensured without aligning the shapes of the solder particles.

[0009] The first supply unit may supply a solder bump forming member in which a deformable part is constituted by a bulk modulus of elasticity at the melting point of the solder particles being 0.1 GPa or more and 5 GPa or less. By setting the bulk modulus of elasticity of the deformable part to 5 GPa or less, when heat is applied while pressing the electrode, the deformable part deforms sufficiently, and the solder particles held in the recess can be more surely exposed to the electrode side. On the other hand, by setting the bulk modulus of elasticity of the deformable part to 0.1 GPa or more, the shape retention of the recess can be maintained, and the holding performance of the solder particles during transfer can be ensured. Thereby, it becomes possible to accurately form the solder particles at the target position on the electrode.

[0010] The heating and pressing unit may heat to a temperature equal to or higher than the melting point of the solder particles while pressing the electrode against the solder bump forming member. In this case, since the melting of the solder particles and the deformation of the deformable part are carried out while the solder particles are sandwiched between the electrode and the solder bump forming member, the displacement of the position of the solder bumps formed on the electrode can be suppressed. Therefore, it becomes possible to more accurately form the solder particles at the target position on the electrode.

[0011] The first supply unit may supply a solder bump forming member in which solder particles are individually arranged in each of the plurality of recesses. In this case, solder particles having a relatively large particle size can be transferred to the electrode with a certain degree of certainty.

[0012] The first supply unit may supply a solder bump forming member in which a plurality of solder particles are arranged in each of the plurality of concave portions. In this case, it becomes easy to adjust the volume of the solder particles held in the concave portion, and it becomes easy to align the size and height of the solder bumps formed on the electrodes within a certain range. In addition, the probability of contact between the electrode and the solder particles can be increased, and the formation of solder bumps on the electrode can be carried out more reliably.

[0013] The C.V. value of the solder particles may be 20% or less. Thereby, in the connection of circuit members using solder bumps, sufficient conduction reliability and insulation reliability can be ensured.

[0014] The average particle diameter of the solder particles may be 1 μm to 35 μm. When using fine solder particles in such a range, it is generally difficult to align the shapes of the solder particles. However, by applying the above method, the certainty of transferring the solder particles to the electrode can be ensured without aligning the shapes of the solder particles.

Advantages of the Invention

[0015] According to the present disclosure, the certainty of transferring the solder particles to the electrode can be ensured without aligning the shapes of the solder particles.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0017] Hereinafter, with reference to the drawings, a preferred embodiment of a solder bump forming apparatus according to one aspect of the present disclosure will be described in detail.

[0018] In this specification, a numerical range indicated using "~" includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively. The upper limit value or the lower limit value of a numerical range described stepwise in this specification may be replaced with the upper limit value or the lower limit value of a numerical range in other steps.

[0019] [Configuration of Solder Bump Forming Member] FIG. 1 is a schematic cross-sectional view showing the configuration of a solder bump forming member according to an embodiment of the present disclosure. The solder bump forming member 1 shown in FIG. 1 is a member used, for example, when forming solder bumps on electrodes of a circuit member. As shown in FIG. 1, the solder bump forming member 1 includes a main body portion 2. The main body portion 2 has, for example, a rectangular shape in plan view, and has a first surface 2a and a second surface 2b opposite to the first surface 2a.

[0020] On the side of the first surface 2a of the main body portion 2, a plurality of recesses 3 for holding solder particles S1 are provided. These recesses 3 can be formed using known methods such as, for example, the imprint method, photolithography, machining, and laser processing. In particular, when using the nanoimprint method, the recesses 3 can be accurately formed in a relatively short process by pressing a desired mold.

[0021] The size (width, volume, depth, etc.) of the recess 3 is appropriately set according to the size of the solder particles S1. The planar shape of the recess 3 is, for example, circular. The planar shape of the recess 3 may be various shapes such as elliptical, triangular, quadrangular, polygonal, etc. in addition to the circular shape. In the example of FIG. 1, the cross-sectional shape of the recess 3 is rectangular. The cross-sectional shape of the recess 3 may be tapered such that the opening area expands from the bottom surface 3b side toward the opening surface side (the first surface 2a side). The bottom surface 3b of the recess 3 is not limited to a flat surface and may be, for example, a concave curved surface.

[0022] Also, an alignment mark 4 may be provided on the side of the first surface 2a of the main body portion 2. The alignment mark 4 is formed, for example, by an uneven shape provided on the first surface 2a of the main body portion 2, printing with ink or pigment, printing of an inorganic substance by plating or sputtering, or burning by a laser. The alignment mark 4 forms, in plan view, for example, a circular shape, a double circular shape, a multiple circular shape, a triangular shape, a rectangular shape, a polygonal shape, a multiple polygon thereof, etc. The alignment mark 4 may be composed of a magnetic material or a material that involves absorption, reflection, and diffraction of electromagnetic waves, and the shape in this case is not particularly limited.

[0023] By detecting the alignment mark 4 with imaging devices 15A and 15B such as cameras, during solder bump formation, the alignment between the electrode to be formed and the solder particles S1 in the recess 3 becomes easier. As a result, the transfer of the solder particles S1 to the electrode can be accurately performed. The alignment mark 4 may be provided at one or more locations on the first surface 2a side, but providing a plurality of them can further improve the alignment accuracy. Also, for example, when the main body 2 is transparent, the alignment mark 4 may be further provided on the second surface 2b side of the main body 2.

[0024] The main body 2 includes a deformed portion 6 configured to include the first surface 2a, and a base portion 7 configured on the second surface 2b side of the deformed portion 6. The deformed portion 6 is a portion that constitutes at least the first surface 2a side of the recess 3. In the depth direction of the recess 3 from the first surface 2a, it may be provided with a thickness of 1 / 3 or more of the depth D of the recess 3, may be provided with a thickness of 1 / 2 or more, or may be provided with a thickness of 2 / 3 or more. In the example of FIG. 1, the thickness T of the deformed portion 6 is equal to the depth D of the recess 3. As a result, the entire partition portion 8 separating the adjacent recesses 3, 3 becomes the deformed portion 6, the inner wall surface 3a of the recess 3 is constituted by the deformed portion 6, while the bottom surface 3b of the recess 3 is constituted by the base portion 7.

[0025] There is no particular limitation on the width of the partition portion 8 (the separation distance between the adjacent recesses 3, 3), but for example, it can be 0.1 times or more the average particle diameter of the solder particles held in the recess 3. The width of the partition portion 8 may be 0.2 times or more the average particle diameter of the solder particles held in the recess 3, or may be 0.3 times or more. The separation distance between the recesses 3, 3 is defined, for example, as the shortest distance between the opening edge of one recess 3 and the opening edge of the other recess 3.

[0026] The deformable portion 6 is formed of an elastic body 9 that can be deformed at the melting point of the solder particles S1 held in the recess 3, for example. Therefore, when forming the solder bump, the deformable portion 6 can be elastically deformed in the compression direction when the electrode to be formed is pressed against it. From the viewpoint of improving the transferability of the solder particles S1, the bulk modulus of elasticity of the elastic body 9 at the melting point of the solder particles S1 may be, for example, 0.1 GPa or more and 5 GPa or less. The bulk modulus of elasticity of the elastic body 9 at the melting point of the solder particles S1 may be, for example, 0.5 GPa or more and 3 GPa or less, or 0.8 GPa or more and 2 GPa or less.

[0027] Examples of the elastic body 9 constituting the deformable portion 6 include photocurable materials, thermosetting materials, and thermoplastic materials. Examples of the elastic body 9 constituting the deformable portion 6 also include resins, polymers, rubbers, elastomers, and mixtures thereof. When the constituent material of the solder particles S1 is SnBi (melting point: 139°C), for example, polyethylene terephthalate (bulk modulus of elasticity at the melting point: 0.6 GPa), acrylic (bulk modulus of elasticity at the melting point: 1 GPa), or PMMA (bulk modulus of elasticity at the melting point: 1 GPa) can be used as the elastic body 9 constituting the deformable portion 6. When the constituent material of the solder particles S1 is SnAgCu (melting point: 217°C), for example, polyimide (bulk modulus of elasticity at the melting point: 1 GPa) can be used as the elastic body 9 constituting the deformable portion 6.

[0028] The base portion 7 is a portion that constitutes the second surface 2b side of the main body portion 2. The base portion 7 is formed of a material having a bulk modulus of elasticity higher than that of the deformable portion 6 at the melting point of the solder particles S1. Therefore, the base portion 7 contributes to the shape retention of the solder bump forming member 1 during solder bump formation. The bulk modulus of elasticity of the base portion 7 at the melting point of the solder particles S1 is, for example, 1 GPa or more. The bulk modulus of elasticity of the base portion 7 at the melting point of the solder particles S1 may be, for example, 3 GPa or more, or 5 GPa or more.

[0029] Examples of the constituent material of the base portion 7 include inorganic materials such as silicon, various ceramics, glass, and stainless steel, and organic materials such as various resins. Further, the constituent material of the base portion 7 may be a material having high light transmittance. Examples of such materials include polyethylene terephthalate, transparent (colorless) polyimide, and polyamide. The constituent material of the base portion 7 may be a material having heat resistance that does not deteriorate at the melting point of the solder particles S1. The constituent material of the base portion 7 may be a material that does not change by alloying or reacting with the material constituting the solder particles S1.

[0030] As the constituent material of the base portion 7, for example, if it is in the form of a flexible film, polyethylene terephthalate, polyethylene naphthalate, vinyl chloride resin, polystyrene, polyethylene polyphenylene sulfide, polycarbonate, etc. can be used. Further, from the viewpoint of improving the handleability of the base portion 7, deformation can be suppressed by increasing the thickness of the materials listed above. Further, from the viewpoint of improving the positional accuracy when transferring the solder particles S1 onto the electrode, engineering plastics, super engineering plastics, materials in which fillers or fibers are compounded with the general-purpose plastics listed above, and inorganic materials can be used. For example, polyamide, polyacetal, polycarbonate, polyphenylene sulfide, polyimide, polyetherimide, polyamideimide, polysulfone, polyetheretherketone, etc. can be used.

[0031] When the constituent material of the solder particles S1 is SnBi (melting point: 139 ° C), for example, glass (bulk modulus of elasticity at the melting point: 40 GPa), silicon wafer (bulk modulus of elasticity at the melting point: 40 GPa), stainless steel (bulk modulus of elasticity at the melting point: 165 GPa) can be used as the constituent material of the base portion 7. When the constituent material of the solder particles S1 is SnAgCu (melting point: 217 ° C), for example, glass (bulk modulus of elasticity at the melting point: 40 GPa), silicon wafer (bulk modulus of elasticity at the melting point: 40 GPa), stainless steel (bulk modulus of elasticity at the melting point: 165 GPa), aluminum (bulk modulus of elasticity at the melting point: 75 GPa) can be used as the constituent material of the base portion 7.

[0032] If the matrix part 7 has a higher bulk modulus of elasticity than the deformed part 6, the deformed part 6 and the matrix part 7 may be made of the same material system. For example, in the case of a resin material, the bulk modulus of elasticity can be adjusted by differences in the degree of crosslinking, addition of reinforcing materials such as fillers and fibers, or kneading of other materials. For example, the deformed part 6 may be made of a thermosetting epoxy resin, and the matrix part 7 may be made of the thermosetting epoxy resin with glass fibers added to reinforce the bulk modulus of elasticity.

[0033] The deformed part 6 may be made of a photocurable acrylic resin, and the matrix part 7 may be made of polyethylene terephthalate. In this case, uncured photocurable acrylic resin is applied to a stamper having a convex shape, irradiated with light while pressing polyethylene terephthalate, and then the stamper is peeled off to form the concave part 3 in the photocurable acrylic resin. By this method, the main body part 2 having continuously rolled concave parts 3 can be obtained. Also, by adjusting the illuminance of light, the curing time, and the amount of the starting material of the photocurable acrylic resin, the degree of crosslinking can be adjusted, and the bulk modulus of elasticity can be adjusted.

[0034] The matrix part 7 may be an inorganic material. For example, the deformed part 6 may be made of a photocurable acrylic resin (bulk modulus of elasticity: 0.1 GPa), and the matrix part 7 may be made of glass (bulk modulus of elasticity: 40 GPa). In this case, the bulk modulus of elasticity at the melting point of the matrix part 7 can be sufficiently ensured, and the positional accuracy when transferring the solder particles S1 to the electrodes using the alignment marks 4 can be improved. Also, even if the solder particles S1 are heated above their melting point when transferring them to the electrodes, since the matrix part 7 is difficult to deform, distortion and elongation of the entire main body part 2 can be suppressed. Also, the main body part 2 can be repeatedly used.

[0035] If the matrix part 7 is made of a silicon wafer and a photosensitive material is used to form the deformed part 6, formation of the concave part 3 becomes easy. In this case, as the photosensitive material, for example, acrylic-based, epoxy-based, polyimide-based, or mixtures thereof can be used.

[0036] The bulk modulus K of the deformable portion 6 and the base portion 7 can be obtained by K = E / 3(1 - 2ν), where E is the Young's modulus of the material and ν is the Poisson's ratio. The bulk modulus K of the deformable portion 6 and the base portion 7 can be measured, for example, by a mechanical test method, a resonance method, or an ultrasonic pulse method. For the measurement, for example, a nanoindenter, a surface hardness tester is used. For example, a heating stage is attached to a surface hardness tester (manufactured by Fischer Instruments), the deformable portion 6 and the base portion 7 are placed on the heating stage, the stage is heated, and the deformable portion 6 and the base portion 7 are heated to a predetermined temperature. Thereafter, a indenter is brought into contact with the surface of the measurement target, and the bulk modulus can be calculated by obtaining a load-displacement (Stress-Strain) curve.

[0037] In the example of FIG. 1, solder particles S1 are held individually in each of the plurality of recesses 3. The solder particles S1 in the recess 3 are in a state of being in contact with at least the bottom surface 3b of the recess 3. The solder particles S1 in the recess 3 may be in contact with the inner wall surface 3a of the recess 3. Further, in the example of FIG. 1, all the solder particles S1 are located within the recess 3, and the top of the solder particle S1 does not protrude outside the opening surface of the recess 3. That is, when the depth of the recess 3 is D and the height of the solder particle S1 (height from the bottom surface 3b) is H, D > H is satisfied.

[0038] The ratio of the height of the solder particle S1 to the depth D of the recess 3 is not particularly limited, but considering the amount of deformation in the compression direction of the deformable portion 6, it may be, for example, 0.3 to 1.5. By setting the ratio to 0.3 or more, the electrode and the solder particle S1 can be more reliably brought into contact with each other when the electrodes are pressed against each other. By setting the ratio to 1.5 or less, it is possible to preferably suppress the solder particles S1 from falling out of the recess 3. Further, it is possible to suppress the solder particles S1 from protruding from the recess 3 during transfer, and it is possible to suppress the solder particles S1 from bonding to each other between adjacent recesses 3, 3. The ratio of the height of the solder particle S1 to the depth D of the recess 3 may be 0.5 to 1.2, or may be 0.6 to 1.

[0039] The solder particles S1 are composed of, for example, tin or a tin alloy. Examples of the tin alloy include In-Sn alloy, In-Sn-Ag alloy, Sn-Au alloy, Sn-Bi alloy, Sn-Bi-Ag alloy, Sn-Ag alloy, Sn-Ag-Cu alloy, Sn-Cu alloy, and the like. The solder particles S1 may contain indium or an indium alloy. Examples of the indium alloy include In-Bi alloy, In-Ag alloy, and the like.

[0040] The solder particles S1 may contain one or more elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, Sb, Ge, Mn, Co, Si, Al, P, and B. From the viewpoint of obtaining good conduction reliability, the solder particles S1 may contain Ag or Cu among the aforementioned elements. By the solder particles S1 containing Ag or Cu, the melting point of the solder particles S1 can be reduced to about 220°C, and the bonding strength with the electrode can be improved.

[0041] The average particle diameter of the solder particles S1 is, for example, 35 μm or less. The average particle diameter of the solder particles S1 may be 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less. The average particle diameter of the solder particles S1 is, for example, 1 μm or more. The average particle diameter of the solder particles S1 may be 2 μm or more, 3 μm or more, 5 μm or more.

[0042] The average particle diameter of the solder particles S1 can be measured using various methods according to the size. Examples of the measurement methods include the dynamic light scattering method, laser diffraction method, centrifugal sedimentation method, electrical sensing zone method, resonant mass measurement method, etc. Other measurement methods include a method of measuring the particle size based on an image obtained by an optical microscope or an electron microscope, etc. Specific devices include a flow-type particle image analyzer, Microtrac, Coulter counter, etc. The average particle diameter of the solder particles S1 can be calculated based on the equivalent diameter of the projected area circle (the diameter of a circle having an area equal to the projected area of the particle) when observing the solder particles S1 from a direction perpendicular to the first surface 2a of the solder bump forming member 1. When the solder particles S1 are arranged individually in each of the plurality of recesses 3, the sizes (average particle diameters) of the solder particles S1 may be uniform.

[0043] The C.V. value of the solder particles S1 is a value calculated by multiplying the value obtained by dividing the standard deviation of the particle diameter measured by the above-described method by the average particle diameter by 100. When a plurality of solder particles S1 are arranged in each of the plurality of recesses 3, the C.V. value of the solder particles S1 may be 20% or less from the viewpoint of realizing more excellent conductive reliability and insulating reliability. The C.V. value of the solder particles S1 may be 10% or less, or may be 7% or less. The lower limit of the C.V. value of the solder particles S1 is not particularly limited. For example, the C.V. value of the solder particles S1 may be 1% or more, or may be 2% or more.

[0044] As described above, one embodiment of the solder bump forming member has been described, but the solder bump forming member of the present disclosure is not limited to the above embodiment.

[0045] [Solder Bump Forming Apparatus] Figs. 2(a) and 2(b) are schematic diagrams showing an example of the configuration of a solder bump forming apparatus. Fig. 2(a) is a side view, and Fig. 2(b) is a plan view. The solder bump forming apparatus 11 shown in the figure forms a circuit member 21A with solder bumps (see Fig. 9) by transferring solder particles S1 held in the recess 3 of the solder bump forming member 1 described above to the electrode 22 of the circuit member 21.

[0046] As shown in Figs. 2(a) and 2(b), the solder bump forming apparatus 11 includes a stage 12 displaceable in the horizontal direction, a first supply unit 13 for supplying the solder bump forming member 1, a second supply unit 14 for supplying the circuit member 21, imaging devices 15A and 15B, and a heating and pressing head (heating and pressing unit) 16. In the present embodiment, the solder bump forming apparatus 11 has a function of electrically connecting the circuit member 21 on which the solder bumps S2 (see Fig. 9) are formed to another circuit member 31 as a post-process of the process of forming the solder bumps S2 to form a connection structure 41 (see Fig. 3). The solder bump forming apparatus 11 further includes a third supply unit 17 for supplying another circuit member 31. The operation of the solder bump forming apparatus 11 is controlled by a control unit (not shown). The function of forming the connection structure 41 does not necessarily have to be integrated with the solder bump forming apparatus 11 and may be configured as an independent apparatus.

[0047] On the stage 12, there are provided a placement area R1 on which the circuit member 21 supplied from the second supply unit 14 is placed, a first implementation area (implementation area) R2 where the formation of solder bumps S2 is carried out, and a second implementation area R3 where the formation of the connection structure 41 is carried out. The imaging devices 15A and 15B are parts for reading the alignment marks 4 of the solder bump forming member 1 and the alignment marks (not shown) of the circuit members 21 and 31. The imaging device 15A is disposed on the front surface side of the stage 12 (the setting surface side of the first implementation area R2 and the second implementation area R3), and the imaging device 15B is disposed on the back surface side of the stage 12. The imaging device 15B may be incorporated in the stage 12. The stage 12 is displaced according to the reading results of the alignment marks by the imaging devices 15A and 15B, and performs alignment between the solder bump forming member 1 and the circuit member 21, and alignment between the circuit member 21A with solder bumps and the circuit member 31.

[0048] The heating and pressing head 16 is a part for performing heating and pressing in the first implementation area R2 and the second implementation area R3. The heating and pressing head 16 has a suction function, and transfers the circuit member 21 from the placement area R1 to the first implementation area R2, transfers the circuit member 21A with solder bumps from the first implementation area R2 to the second implementation area R3, and transfers the obtained connection structure 41. The heating and pressing head 16 is configured to be movable up and down with respect to the stage 12, and by descending toward the stage 12, performs heating and pressing when forming the solder bumps S2 and heating and pressing when forming the connection structure 41.

[0049] As described above, one embodiment of the solder bump forming apparatus has been explained, but the solder bump forming apparatus of the present disclosure is not limited to the above embodiment.

[0050] [Connection structure] FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the connection structure. As shown in FIG. 3, the connection structure 41 is configured by electrically connecting the electrode 22 of one circuit member 21 and the electrode 32 of the other circuit member 31 via solder bumps S2. In the present embodiment, the space between one circuit member 21 and the other circuit member 21 is filled with an underfill material 42 mainly composed of, for example, an epoxy resin. The underfill material 42 is formed so as to cover, for example, the electrodes 22, 32 and the solder bumps S2 between the electrodes 22, 32.

[0051] Specific examples of the connection structure 41 include connection parts such as semiconductor memories and semiconductor logic chips, connection parts for primary and secondary mounting of semiconductor packages, bonded bodies such as CMOS image sensor elements, laser elements, and LED light-emitting elements, and devices such as cameras, sensors, liquid crystal displays, personal computers, mobile phones, smartphones, and tablets using these.

[0052] Specific examples of the circuit members 21 and 31 include chip components such as IC chips (semiconductor chips), resistor chips, capacitor chips, and driver ICs, and rigid package substrates. These circuit members are provided with circuit electrodes, and those having a large number of circuit electrodes are common. Other examples of substrates having a plurality of electrodes on the surface include wiring substrates such as flexible tape substrates having metal wiring, flexible printed wiring boards, and glass substrates on which indium tin oxide (ITO) is deposited.

[0053] Specific examples of the electrodes 22 and 32 include electrodes such as copper, copper / nickel, copper / nickel / gold, copper / nickel / palladium, copper / nickel / palladium / gold, copper / nickel / gold, copper / palladium, copper / palladium / gold, copper / tin, copper / silver, and indium tin oxide. The electrodes 22 and 32 can be formed using, for example, methods such as electroless plating, electrolytic plating, sputtering, and etching of metal foils.

[0054] Although one embodiment of the connection structure has been described above, the connection structure of the present disclosure is not limited to the above embodiment.

[0055] [Solder bump forming method] FIG. 4 is a flowchart showing an example of a solder bump forming method. The flowchart shown in the figure shows the steps for forming the solder bump S2 using the above-described solder bump forming apparatus 11, and also includes the step of forming the connection structure 41 following the formation of the solder bump S2. Details of each step will be described with appropriate reference to FIGS. 5 to 9.

[0056] In this solder bump forming method, first, one circuit member 21 and the solder bump forming member 1 are supplied toward the first implementation region R2 (step S01). In step S01, the solder bump forming member 1 is supplied from the first supply unit 13 to the first implementation region R2 so that the recess 3 faces upward. Also, the circuit member 21 is supplied from the second supply unit 14 to the placement region R1 so that the electrode 22 faces downward.

[0057] Next, in the first implementation region R2, the solder particles S1 held in the recess 3 and the electrode 22 of the circuit member 21 are arranged to face each other (step S02). In step S02, the stage 12 is displaced while the circuit member 21 is adsorbed by the heating and pressing head 16, and as shown in FIG. 5, the circuit member 21 is transferred from the placement region R1 onto the first implementation region R2. At this time, for example, the position of the alignment mark 4 on the solder bump forming member 1 side is confirmed by the imaging device 15A, and the position of the alignment mark on the circuit member 21 side is confirmed by the imaging device 15B, thereby performing alignment between the solder particles S1 held in the recess 3 and the electrode 22 of the circuit member 21.

[0058] Subsequently, the electrode 22 is pressed against and heated to the solder particles S1 (step S03). In step S03, as shown in FIG. 6, the circuit member 21 adsorbed to the heating and pressurizing head 16 is lowered toward the solder bump forming member 1 on the stage 12, and the electrode 22 is pressed against and heated to the solder particles S1. Here, after the electrode 22 of the circuit member 21 is brought into contact with the first surface 2a of the solder bump forming member 1, the heating and pressurizing head 16 may be heated to a temperature equal to or higher than the melting point of the solder particles S1 (for example, about 130°C to 260°C) while the electrode 22 is pressed against the solder bump forming member 1 side. Alternatively, the electrode 22 may be pressed against the solder bump forming member 1 side after the heating and pressurizing head 16 is heated to a temperature equal to or higher than the melting point of the solder particles S1 (for example, about 130°C to 260°C). By bringing the electrode 22 into close contact with the first surface 2a of the solder bump forming member 1, the solder bump S2 can be formed only on the electrode 22, and the formation of a bridge due to the solder between the adjacent electrodes 22, 22 can be suppressed. The pressing force of the electrode 22 against the solder bump forming member 1 by the heating and pressurizing head 16 is, for example, 0.1 MPa to 600 MPa. This pressing force may be 1 MPa to 300 MPa, or may be 10 MPa to 100 MPa.

[0059] In the present embodiment, the solder particles S1 held in each of the plurality of recesses 3 of the solder bump forming member 1 are in a state of not protruding outside the opening surface of the recess 3. Therefore, when the electrode 22 is brought into contact with the first surface 2a of the solder bump forming member 1, the electrode 22 and the solder particles S1 in the recess 3 do not come into contact. When the heating and pressurizing head 16 is heated to a temperature equal to or higher than the melting point of the solder particles S1 in this state, as shown in FIG. 6, among the main body portions 2 of the solder bump forming member 1, the deformed portion 6 (the partition portion 8 between the recesses 3, 3) is deformed in the compression direction. As a result, the electrode 22 enters the recess 3 and comes into contact with the solder particles S1, and the solder bump S2 is transferred onto the electrode 22 by the melting of the solder particles S1.

[0060] In addition, when the bulk modulus of elasticity of the elastic body 9 is small, or when the total area of the electrodes 22 is small and the pushing pressure becomes high with respect to the thrust of the heating and pressing head 16, the elastic body 9 may be deformed even when the heating and pressing head 16 is not heated, and the solder particles S1 can be brought into contact with the electrodes 22. After the electrodes 22 and the solder particles S1 are brought into contact with each other, by heating the heating and pressing head 16 to a temperature equal to or higher than the melting point of the solder particles S1, the solder bumps S2 are transferred onto the electrodes 22 by melting of the solder particles S1.

[0061] After the solder bumps S2 are transferred onto the electrodes 22, the heating and pressing by the heating and pressing head 16 are stopped. Then, as shown in FIG. 7, the heating and pressing head 16 is lifted together with the circuit member 21, and the electrodes 22 of the circuit member 21 and the solder bumps S2 on the electrodes 22 are cooled in a state where the circuit member 21 is separated from the solder bump forming member 1. Thereby, the electrodes 22 and the solder bumps S2 formed by melting the solder particles S1 are fixed, and both are electrically connected. By the electrical connection between the electrodes 22 and the solder bumps S2, the circuit member 21A with solder bumps is obtained.

[0062] It is considered that the solder particles S1 rapidly oxidize by heating in the atmosphere, and the wetting spread onto the electrodes 22 may be inhibited. Therefore, the atmosphere during heating and pressing in step S03 may be a deoxidized atmosphere. The deoxidized atmosphere may be, for example, an inert gas atmosphere using nitrogen, argon, etc., or a vacuum atmosphere. As the furnace, a reflow furnace (under a nitrogen atmosphere) and a vacuum reflow furnace generally used in the solder bonding process can be used. Also, a conveyor type reflow furnace, a batch type (chamber type) reflow furnace, etc. under a nitrogen atmosphere can be used. When using these reflow furnaces, if a process of evacuating after the solder melts is carried out, the bubbles (voids) in the solder bumps S2 can be removed.

[0063] In addition, the solder particles S1 may not melt even when heated at a temperature equal to or higher than the melting point due to the influence of the oxide film, or wetting spread may not occur. Therefore, a step of exposing at least one of the solder particles S1 and the electrode 22 to a reducing atmosphere may be further provided before step S02 or between step S02 and step S03. By reducing the oxide film on the surface of the solder particles S1 or the oxide film on the surface of the electrode 22, melting and wetting spread of the solder particles S1 on the electrode 22 can be efficiently advanced. The step of step S03 may be implemented in a reducing atmosphere. For forming a reducing atmosphere, for example, hydrogen gas, hydrogen radicals, formic acid gas, etc. can be used. As the furnace, a hydrogen reduction furnace, a hydrogen reflow furnace, a hydrogen radical furnace, a formic acid furnace, these vacuum furnaces, continuous furnaces, conveyor furnaces, etc. can be used.

[0064] After forming the circuit member 21A with solder bumps, the connection structure 41 is formed. First, the other circuit member 31 is supplied toward the second implementation region R3 (step S04). In step S04, the circuit member 31 is supplied from the third supply unit 17 to the second implementation region R3 so that the electrode 32 faces upward. An underfill material 42 may be disposed on the circuit member 31 supplied to the second implementation region R3 so as to cover the electrode 32.

[0065] Next, in the second implementation region R3, the circuit member 21A with solder bumps and the circuit member 31 are arranged to face each other (step S05). In step S05, as shown in FIG. 8, the stage 12 is displaced with the circuit member 21A with solder bumps adsorbed to the heating and pressing head 16, and the circuit member 21A with solder bumps is disposed on the second implementation region R3. At this time, for example, the position of the alignment mark on the circuit member 31 side is confirmed by the imaging device 15A, and the position of the alignment mark on the circuit member 21A with solder bumps side is confirmed by the imaging device 15B, thereby performing alignment between the electrode 22 of the circuit member 21A with solder bumps and the electrode 32 of the circuit member 31.

[0066] Subsequently, heating and pressing are performed on circuit member 21 and circuit member 31 via solder bump S2 (step S06). In step S06, as shown in FIG. 9, the circuit member 21A with solder bump adsorbed to the heating and pressing head 16 is lowered toward the circuit member 31 on the stage 12, and the solder bump S2 is sandwiched between the electrode 22 of the circuit member 21A with solder bump and the electrode 32 of the circuit member 31. By heating the heating and pressing head 16 to a temperature equal to or higher than the melting point of the solder particles S1 (for example, about 130°C to 260°C), the solder bump S2 may be melted between the electrodes 22 and 32. Also, after heating the heating and pressing head 16 to a temperature equal to or higher than the melting point of the solder particles S1 (for example, about 130°C to 260°C), the solder bump S2 may be melted between the electrodes 22 and 32 by sandwiching the solder bump S2 between the electrode 22 of the circuit member 21A with solder bump and the electrode 32 of the circuit member 31. The pressing force applied to the circuit member 21 and the circuit member 31 by the heating and pressing head 16 can be made equivalent to the pressing force used in step S03.

[0067] Thereafter, the heating and pressing by the heating and pressing head 16 are stopped, and the heating and pressing head 16 is raised without adsorbing the circuit member 21. In this state, the electrode 22 of the circuit member 21, the electrode 32 of the circuit member 31, and the solder bump S2 between the electrodes 22 and 32 are cooled. Thereby, the electrodes 22 and 32 and the solder bump S2 are fixed, and the circuit members 21 and 31 are electrically connected to each other. By the electrical connection between the circuit members 21 and 31, the connection structure 41 shown in FIG. 3 is obtained. Finally, the obtained connection structure 41 is adsorbed to the heating and pressing head 16 and transferred to a predetermined placement area to complete the process (step S07).

[0068] In step S06 as well, a step of exposing at least one of the solder bump S2 and the electrodes 22 and 32 to a reducing atmosphere may be further provided. For forming the reducing atmosphere, similar to step S03, for example, hydrogen gas, hydrogen radicals, formic acid gas, etc. can be used. As the furnace, similar to step S03, a hydrogen reduction furnace, a hydrogen reflow furnace, a hydrogen radical furnace, a formic acid furnace, these vacuum furnaces, continuous furnaces, conveyor furnaces, etc. can be used.

[0069] As a method for forming a reducing atmosphere, a material having a reducing action can also be used. For example, a flux material or a material containing a flux component can be disposed in the vicinity of the solder bump S2 and the electrodes 22 and 32. As the material containing the flux material and the flux component, a paste, a film, or the like containing these materials can be used. The paste and the film containing the flux component may contain a thermosetting material. Thereby, the thermosetting component is cured simultaneously with the melting of the solder bump S2, and the circuit members 21 and 31 can be fixed to each other. The curing of the thermosetting material may be performed by heating again in a subsequent process separately from the melting heating of the solder bump S2.

[0070] As described above, one embodiment of the solder bump forming method has been described, but the solder bump forming method of the present disclosure is not limited to the above embodiment.

[0071] [Advantages and effects of the present disclosure] As described above, in the solder bump forming apparatus 11, the solder particles S1 are held in the plurality of recesses 3 of the solder bump forming member 1, and the solder bump S2 can be formed on the electrode 22 by applying heat and pressure together with the electrode 22 to be transferred. In the solder bump forming member 1 supplied to the solder bump forming apparatus 11, the constituent part of the recess 3 is formed by the deformable portion 6 that can be deformed at the melting point of the solder particles S1. Thereby, when the electrode 22 is pressed and heat is applied, the deformable portion 6 is deformed, and the solder particles S1 held in the recess 3 can be exposed to the electrode 22 side. Therefore, in the solder bump forming apparatus 11, the certainty of the transfer of the solder particles S1 to the electrode 22 can be ensured without aligning the shapes of the solder particles S1.

[0072] In this embodiment, the first supply unit 13 supplies the solder bump forming member 1 in which the deformation part 6 is constituted by the elastic body 9 having a bulk modulus of 0.1 GPa or more and 5 GPa or less at the melting point of the solder particles S1. By setting the bulk modulus of the deformation part 6 to 5 GPa or less, when heat is applied by pressing the electrode 22, the deformation part 6 is sufficiently deformed, and the solder particles S1 held in the recess 3 can be more reliably exposed to the electrode 22 side. On the other hand, by setting the bulk modulus of the deformation part 6 to 0.1 GPa or more, the shape retention of the recess 3 can be maintained, and the holding performance of the solder particles S1 during transfer can be ensured. As a result, it becomes possible to accurately form the solder particles S1 at the target position on the electrode 22. Further, when the deformation part 6 is constituted by the elastic body 9, after the transfer of the solder particles S1 to the electrode 22, the deformation part 6 can be returned to its original shape. Thereby, the solder bump forming member 1 can be reused.

[0073] In this embodiment, the heating and pressing head 16 heats the electrode 22 to a temperature equal to or higher than the melting point of the solder particles S1 while pressing the electrode 22 against the first surface 2a of the solder bump forming member 1. As a result, the melting of the solder particles S1 and the deformation of the deformation part 6 are carried out while the solder particles S1 are sandwiched between the electrode 22 and the solder bump forming member 1, so that the displacement of the solder bump S2 formed on the electrode 22 can be suppressed. Therefore, it becomes possible to more accurately form the solder particles S1 at the target position on the electrode 22.

[0074] In this embodiment, the first supply unit 13 supplies the solder bump forming member 1 in which the solder particles S1 are individually arranged in each of the plurality of recesses 3. Thereby, the solder particles S1 having a relatively large particle diameter can be transferred to the electrode 22 with a certain degree of certainty.

[0075] In this embodiment, the average particle diameter of the solder particles S1 is 1 μm to 35 μm. When using such fine solder particles S1 in this range, generally, it is difficult to align the shapes of the solder particles S1. However, by applying the above method, the certainty of the transfer of the solder particles S1 to the electrode 22 can be ensured without aligning the shapes of the solder particles S1. [Modification Example]

[0076] The present disclosure is not limited to the above-described embodiments. For example, in the example of FIG. 1, the deformed portion 6 is provided with a thickness corresponding to the depth of the recess 3 from the first surface 2a toward the second surface 2b side, but the thickness of the deformed portion 6 is not limited thereto. For example, like the solder bump forming member 1A shown in FIG. 10(a), the thickness T of the deformed portion 6 may be smaller than the depth D of the recess 3. In this case, only the first surface 2a side of the partition portion 8 separating the adjacent recesses 3, 3 is constituted by the deformed portion 6. Therefore, while the first surface 2a side of the inner wall surface 3a of the recess 3 is constituted by the deformed portion 6, the second surface 2b side of the inner wall surface 3a of the recess 3 and the bottom surface 3b of the recess 3 are constituted by the base portion 7.

[0077] As in the example of FIG. 10(a), when the thickness T of the deformed portion 6 is made smaller than the depth D of the recess 3, the solder particles S1 held in the recess 3 may protrude to the first surface 2a side rather than the interface between the deformed portion 6 and the base portion 7. That is, the height H of the solder particles S1 may satisfy H > D - T with respect to the depth D of the recess 3 and the thickness T of the deformed portion 6. By doing so, reliable contact between the solder particles S1 and the electrode 22 during deformation of the deformed portion 6 can be ensured.

[0078] Also, from the viewpoint of ensuring a sufficient amount of deformation of the deformed portion 6, even when the thickness T of the deformed portion 6 is made smaller than the depth D of the recess 3, the deformed portion 6 may be provided with a thickness of 1 / 2 or more of the depth D of the recess 3 in the depth direction of the recess 3 from the first surface 2a. In this case, the deformed portion 6 may be provided with a thickness of 3 / 5 or more of the depth D of the recess 3 in the depth direction of the recess 3 from the first surface 2a, or may be provided with a thickness of 4 / 5 or more.

[0079] Further, for example, as in the solder bump forming member 1B shown in FIG. 10(b), the thickness T of the deformed portion 6 may be greater than the depth D of the concave portion 3. In this case, the entire partition wall portion 8 separating the adjacent concave portions 3, 3 becomes the deformed portion 6, and both the inner wall surface 3a and the bottom surface 3b of the concave portion 3 are constituted by the deformed portion 6. The interface between the deformed portion 6 and the base portion 7 can be set at an arbitrary position between the bottom surface 3b of the concave portion 3 and the second surface 2b. For example, as in the solder bump forming member 1C shown in FIG. 10(c), the base portion 7 may not be provided, and the entire main body portion 2 may be constituted by the deformed portion 6.

[0080] In the above embodiment, all the solder particles S1 do not protrude outside the opening surface of the concave portion 3. However, in the present disclosure, since the certainty of the transfer of the solder particles S1 to the electrode 22 can be demonstrated even without aligning the heights of the solder particles S1 in the concave portion 3, some or all of the solder particles S1 may protrude outside the opening surface of the concave portion 3. That is, as shown in FIG. 11(a), the height H of some or all of the solder particles S1 may satisfy H > D with respect to the depth D of the concave portion 3.

[0081] In the above embodiment, a configuration in which the solder particles S1 are arranged individually in each of the plurality of concave portions 3 is illustrated. However, a plurality of solder particles S1 may be arranged in each of the plurality of concave portions 3. In this case, for example, as shown in FIG. 11(b), a plurality of solder particles S1 having a smaller average particle diameter than the example of FIG. 1 may be arranged in the concave portion 3. In this case, it becomes easier to adjust the volume of the solder particles S1 held in the concave portion 3, and it becomes easier to align the size and height of the solder bumps S2 formed on the electrode 22 within a certain range. Further, the probability of contact between the electrode 22 and the solder particles S1 can be increased, and the formation of the solder bumps S2 on the electrode 22 can be carried out more reliably. When a plurality of solder particles S1 are arranged in the concave portion 3, as described above, the C.V. value of the solder particles S1 may be 20% or less. Thereby, in the connection of the circuit members 21, 31 using the solder bumps S2, sufficient electrical connection reliability and insulation reliability can be ensured.

[0082] Even when a plurality of solder particles S1 are arranged in the recess 3, the force (e.g., intermolecular force such as van der Waals force) acting between the solder particle S1 and the partition wall portion 8 is considered to be greater than the gravitational force acting on the solder particle S1. Therefore, even when the recess 3 is in a downward-facing posture, the solder particle S1 can remain within the recess 3. When there is a flat portion on the outer surface of the solder particle S1 and the flat portion is in contact with the inner wall surface 3a or the bottom surface 3b of the recess 3, the dropout of the solder particle S1 from the recess 3 can be more preferably prevented.

Explanation of Signs

[0083] 1, 1A to 1C... solder bump forming members, 3... recess, 6... deformed portion, 9... elastic body, 11... solder bump forming apparatus, 12... stage, 13... first supply unit, 14... second supply unit, 16... heating and pressing head (heating and pressing unit), 21... circuit member, 22... electrode, S1... solder particle, S2... solder bump, R2... first implementation region (implementation region).

Claims

1. A solder bump forming apparatus for forming solder bumps on electrodes of a circuit member, comprising: a stage in which an implementation region for forming the solder bumps on the electrodes is set; a first supply unit that supplies a solder bump forming member having a plurality of recesses in which solder particles are held, the solder particles being accommodated in the recesses such that the top surfaces of the solder particles are positioned within the recesses, and a deforming portion of a constituent part of the recess being deformable at the melting point of the solder particles; a second supply unit that supplies the circuit member such that the solder particles held in the recesses of the solder bump forming member are disposed opposite to the electrodes; a heating and pressing unit that, in the implementation region, heats the electrodes to a temperature equal to or higher than the melting point of the solder particles, presses the electrodes against the solder bump forming member, compresses and deforms the deforming portion in its height direction, brings the solder particles held in the recesses into contact with the electrodes, and transfers the solder particles to the electrodes to form solder bumps.

2. The solder bump forming apparatus according to claim 1, wherein the first supply unit supplies the solder bump forming member in which the deforming portion is constituted by an elastic body having a bulk modulus at the melting point of the solder particles of 0.1 GPa or more and 5 GPa or less.

3. The solder bump forming apparatus according to claim 1 or 2, wherein the heating and pressing unit heats the electrodes to a temperature equal to or higher than the melting point of the solder particles while pressing the electrodes against the solder bump forming member.

4. The solder bump forming apparatus according to any one of claims 1 to 3, wherein the first supply unit supplies the solder bump forming member in which the solder particles are disposed individually in each of the plurality of recesses.

5. The solder bump forming apparatus according to any one of claims 1 to 3, wherein the first supply unit supplies the solder bump forming member in which a plurality of the solder particles are disposed in each of the plurality of recesses.

6. The solder bump forming apparatus according to claim 5, wherein the C.V. value of the solder particles is 20% or less.

7. The solder bump forming apparatus according to any one of claims 1 to 6, wherein the average particle diameter of the solder particles is 1 μm to 35 μm.

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