Component with solder bumps, mounting precursor, and method for manufacturing mounting body

Abstract

Provided is a component with solder bumps comprising: a substrate; and a plurality of electrodes positioned on the substrate and having solder bumps. In at least some of the electrodes, the solder bumps are bumps with protruding parts, having a solder base part formed on the surface of the electrode and at least three solder protruding parts formed on the surface of the solder base part. The top part of the solder protruding parts is higher than the top part of the solder base parts.

Description

Method for manufacturing a member with solder bumps, a mounting precursor, and a mounted body

[0001] The present disclosure relates to a member with solder bumps, a mounting precursor, and a method for manufacturing a mounted body.

[0002] With the development of technologies such as IoT, DX, and AI, the demand for high-end PCs and high-performance servers is increasing. Therefore, further high performance and high integration are required for semiconductors. Along with this, the structure of semiconductor packages has become more complex. For example, it has become common to stack multiple chips, arrange them in parallel, or mix components with different functions. In addition, with the high density of semiconductor chips, the miniaturization of wiring and electrodes is also progressing.

[0003] On the other hand, in some cases, the package may become larger due to an increase in the number of components to be mounted, and various forms are required. In these semiconductor packages, components such as semiconductor chips, capacitors, and memories are mainly mounted on electrodes and wiring on a substrate using solder and electrically connected.

[0004] In semiconductor packaging, connection of electrodes using solder is common. Usually, hemispherical (spherical crown-shaped) solder bumps are formed on the electrodes. This shape is preferred because the top of the solder bump can easily contact the opposing electrode and, when the solder melts, it can create a state where the solder easily spreads and wets the opposing electrode. At the time of mounting, a flux material may be used to remove the oxide films of the solder and the Cu electrode and to promote the spreading of the solder on the Cu electrode. The hemispherical solder bump can surely contact the opposing electrode while pushing aside the flux.

[0005] However, due to the high functionality of semiconductors, the electrode size is miniaturized, and the size of the solder bumps also tends to become smaller. When the solder bumps become smaller, the amount of solder for connecting the opposing electrodes becomes insufficient, making it easier for connection failures to occur. For example, connection failures are likely to occur due to misalignment of the opposing electrodes caused by the movement of the upper and lower members in the reflow process. The reduction in the amount of solder is one of the factors contributing to the degradation of the self-alignment function by the solder.

[0006] Furthermore, with the explosive increase in the amount of information processed, data center packages are becoming larger, with substrate sizes exceeding 50mm x 50mm due to the increase and enlargement of components. When mounting heavy, large substrates, if the upper and lower components become misaligned due to vibrations during reflow soldering, the self-alignment by the solder does not function, making connection failures more likely.

[0007] Thus, the miniaturization of electrodes and the enlargement of substrates are increasingly reducing the self-alignment function provided by solder, leading to a tendency for connection failures to increase.

[0008] Therefore, from the perspective of ensuring a more reliable connection, a method has been considered in which the receiving solder side also has a hemispherical solder bump, making both the upper and lower sides hemispherical solder bumps (for example, Patent Document 1). In addition, a method has been considered in which one of the solder bumps is coined to flatten it, thereby improving the seating of the other hemispherical solder bump (for example, Patent Document 2).

[0009] Japanese Patent Publication No. 10-322007 Japanese Patent Publication No. 2001-203445

[0010] However, when hemispherical solder bumps are placed facing each other, they only make point contact, making them susceptible to misalignment of the upper and lower components due to slight vibrations before reflow soldering. Furthermore, the reduction in solder volume due to the miniaturization of electrodes and the increase in substrate area due to the large size of the substrate are making flattening by coining increasingly difficult.

[0011] This disclosure is made in view of the above circumstances and aims to provide a solder bump member that can suppress connection failures during mounting due to misalignment of upper and lower members. This disclosure also aims to provide a mounting precursor and a method for manufacturing a mounted body using the solder bump member.

[0012] This disclosure provides a solder bump member characterized in that at least three solder protrusions are formed on at least a portion of the solder bump electrode. Even if vibrations occur during mounting, the solder bumps on the opposing electrode fit into the space formed by the at least three solder protrusions, thereby suppressing misalignment of the upper and lower members, and thus enabling stable electrode connection.

[0013] The disclosure outlines the following: [1] A solder bump member comprising a substrate and a plurality of electrodes provided on the substrate and having solder bumps, wherein in at least some of the electrodes, the solder bump is a bump with protrusions having a solder base formed on the electrode surface and at least three solder protrusions formed on the surface of the solder base, and the top of the solder protrusions is higher than the top of the solder base. [2] The solder bump member according to [1], wherein the solder protrusions are fused to the solder base. [3] The solder bump member according to [1] or [2], wherein the height of the solder protrusions is 1.01 times or more and 10 times or less the height of the solder base, with respect to the electrode surface. [4] The solder bump member according to any one of [1] to [3], wherein the solder volume of the bump with protrusions is 1.005 times or more and 10 times or less the solder volume of the solder base. [5] A solder bump member according to any one of [1] to [4], wherein, in a plan view from a direction perpendicular to the main surface of the substrate, the area of ​​the polygon drawn by connecting the vertices of the solder protrusions is 0.0005 times or more and 0.65 times or less the area of ​​the electrode. [6] A solder bump member according to any one of [1] to [5], wherein the solder base and the solder protrusions include tin, a tin alloy, indium, or an indium alloy. [7] A solder bump member according to any one of [1] to [6], wherein the solder protrusions are formed by solder balls. [8] A mounting precursor in which a solder bump member according to any one of [1] to [7] and another solder bump member are arranged opposite each other, wherein the other solder bump member comprises another substrate and a plurality of other electrodes provided on the other substrate and having other solder bumps, and the other solder bumps are fitted into a space formed by the solder protrusions of the solder bumps. [9] A method for manufacturing a mounting body, comprising the steps of: heating the mounting precursor according to [8] to melt the solder bumps and the other solder bumps; and cooling the heated mounting precursor to obtain a mounting body in which the electrodes and the other electrodes are electrically connected via solder.

[0014] This disclosure provides a solder bump member that can suppress connection failures during mounting due to misalignment of upper and lower members. Such a solder bump member can be used particularly suitably in the current semiconductor packaging environment where electrode miniaturization and substrate enlargement are progressing. Furthermore, this disclosure provides a mounting precursor and a method for manufacturing a mounting body using the solder bump member.

[0015] This is a schematic diagram showing one embodiment of a solder bump member according to the present disclosure. This is a schematic diagram showing one embodiment of a solder bump electrode according to the present disclosure. This is a schematic diagram showing another embodiment of a solder bump member. This is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. This is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. This is a schematic diagram showing a mounting process using a general solder bump member. This is the result of optical microscope observation of a protruding bump according to this embodiment. This schematically shows the shape of a solder bump that can be produced depending on the combination of mounting temperature and solder melting point.

[0016] <Solder bump member> Figure 1 is a schematic diagram showing one embodiment of a solder bump member according to the present disclosure.

[0017] The solder bump member 10 comprises a base material 3 and a plurality of electrodes 4 provided on the base material 3 and having solder bumps 5. In at least some of the electrodes 4, the solder bump 5 has a solder base 1 formed on the surface of the electrode 4 and at least three solder protrusions 2 formed on the surface of the solder base 1. In the remaining electrodes 4, the solder bump 6 may have only a solder base 1 formed on the surface of the electrode 4.

[0018] Solder bump 5 can be described as a bump with a protrusion having a solder base 1 and a solder protrusion 2, while solder bump 6 can be described as a general bump having only a solder base 1. A bump with a protrusion in which the size and number of solder protrusions 2 can be adjusted may include two or more different types of solder bumps.

[0019] In a bump with a protrusion, the solder protrusion 2 is formed such that its top is higher than the top of the solder base 1. The term "top" refers to the point or region where the height from the electrode surface is locally maximum. For example, in a hemispherical solder base, its highest point is the top, and in a flat, layered solder base, the entire top surface of the layer is the top. In a shape with multiple peaks, such as the connected solder protrusions described later, the highest point of each peak is the top.

[0020] The solder volume of the protruding bump can be 1.005 times or more and 10 times or less the solder volume of the solder base 1. If this ratio is above the lower limit, the fitability of the solder bump on the opposing electrode is improved, and connections between opposing electrodes can be made more stably at locations where the distance between components is large. If this ratio is below the upper limit, solder bridging between adjacent electrodes due to excessive solder volume is less likely to occur, and connections between opposing electrodes can be made more stably. From these viewpoints, the ratio may be 1.01 times or more, or 1.015 times or more, while the ratio may be 8 times or less, or 5 times or less. This ratio can be adjusted by the size or amount of the solder protrusion 2.

[0021] The volume of the solder base 1 is not particularly limited as it varies depending on its shape, the size of the electrode 4, etc., but for example, it is 30 to 600,000 μm. ３ This can be done, with a range of 200 to 250,000 μm. ３ This is also acceptable. The volume of the solder protrusion 2 can be appropriately adjusted based on the above volume of the solder base 1. The volumes of the solder base 1 and the solder protrusion 2 can be calculated by measuring the particle size using an optical microscope or a scanning electron microscope.

[0022] With respect to the electrode surface, the height of the solder protrusion 2 can be between 1.01 and 10 times the height of the solder base 1. If this ratio is above the lower limit, the fitability of the solder bump on the opposing electrode is improved, and connections between opposing electrodes become more stable in areas where the distance between components is large. If this ratio is below the upper limit, solder bridging between adjacent electrodes due to excessive solder is less likely to occur, and connections between opposing electrodes become more stable. From these viewpoints, the ratio may be 1.02 or more, or 1.03 or more, while the ratio may be 8 or less, or 6 or less. This ratio can be adjusted by the size of the solder protrusion 2. The height of the solder protrusion 2 is the average value of the heights of individual solder protrusions 2. The height of the solder protrusion 2 can be said to be the height of the bump with a protrusion.

[0023] The height of the solder base 1 is not particularly limited as it varies depending on its shape, the size of the electrode 4, etc., but it can be, for example, 2 to 80 μm, or 5 to 40 μm, relative to the electrode surface. The height of the solder protrusion 2 can be appropriately adjusted based on the above height of the solder base 1. The heights of the solder base 1 and the solder protrusion 2 can be measured using a laser microscope, a stylus-type height meter, etc. The height of the solder base 1 can be called the height of a general bump.

[0024] Figure 2 is a schematic diagram showing one embodiment of a solder bump electrode according to the present disclosure. Figures (a) and (b) are side and top views of the solder bump electrode, respectively. In the bump with protrusions, at least three solder protrusions 2 are arranged so that the solder bump on the opposing electrode fits into the space formed by these solder protrusions 2. That is, as shown in the figure, in a plan view from a direction perpendicular to the main surface of the substrate 3, the top (center) 1a of the solder base 1 is inside the polygon (triangle) drawn by connecting the tops 2a of the solder protrusions 2. This relationship is the same even when the solder protrusions 2 are melted and partially connected to each other, as shown in shape B of Figure 8 described later. Note that the top 1a of the solder base 1 may be the center of the electrode 4.

[0025] Furthermore, even if the number of solder protrusions 2 is increased to four or five, the solder protrusions 2 should be arranged so that the top 1a of the solder base 1 lies inside the square or pentagon drawn by connecting the tops of the solder protrusions 2.

[0026] In a plan view from a direction perpendicular to the main surface of the substrate 3, the area of ​​the polygon drawn by connecting the vertices 2a of the solder protrusions 2 can be between 0.0005 and 0.65 times the area of ​​the electrode 4. If this ratio is above the lower limit, the fitability of the solder bumps on the opposing electrode is improved, making it easier to make a more stable connection between the opposing electrodes. If this ratio is below the upper limit, solder bridging between adjacent electrodes due to excess solder is less likely to occur, making it easier to make a more stable connection between the opposing electrodes. From these viewpoints, the ratio may be 0.001 times or more, 0.003 times or more, or 0.005 times or more, while the ratio may be 0.5 times or less, 0.4 times or less, or 0.3 times or less. This ratio can be adjusted by the distance or number of solder protrusions 2.

[0027] (Substrate) Substrate 3 is a component that makes up a semiconductor package, and specifically includes semiconductor chips, mounting substrates, motherboards, etc. Electrical wiring is provided on the surface or inside of substrate 3, and metals with high electrical conductivity such as copper, gold, and aluminum are used for this. In addition, semiconductor elements may be incorporated into substrate 3.

[0028] The base material 3 can be a resin material, an inorganic material, or a composite material thereof.

[0029] Examples of resin materials include thermoplastic materials, thermosetting materials, photocurable materials, and composites thereof. From the viewpoint of dimensional stability and reliability, thermosetting materials or photocurable materials are particularly preferred. Specifically, examples include substrates made of thermosetting resin containing glass cloth, and substrates (mounting substrates) with copper wiring on their surface and inside. These resin materials may contain fillers to improve their properties. As fillers, organic fillers, inorganic fillers, or mixtures thereof can be used.

[0030] Inorganic materials such as silicon (Si), glass, and ceramics can be used. Silicon is commonly used as a material for semiconductor chips and memory.

[0031] Furthermore, the base material 3 may have multiple layers. For example, it may be a form in which a resin base material containing glass cloth with copper wiring on its surface is laminated, or it may be composed of resin without glass cloth and copper wiring. The copper wiring in each layer may be electrically connected by through-holes that penetrate between the layers.

[0032] These are manufactured by a build-up method, in which resin layers and copper wiring are formed sequentially to create a multilayer structure. The base material 3 may also be a multilayer structure combining a resin base material containing glass cloth with copper wiring, and a resin layer and copper wiring layer formed by the build-up method.

[0033] Furthermore, the substrate 3 may be a component in which semiconductor chips, memory, power supply semiconductors, sensors, capacitors, etc. are mounted on the aforementioned multilayer structure. Alternatively, the substrate 3 may be a structure in which components such as memory, capacitors, and sensors are mounted when the layer structure is formed sequentially, and then sealed or laminated with a resin layer, thereby incorporating the components.

[0034] The electrode 4 is formed on the surface of the substrate 3 and is electrically connected to the wiring of the substrate 3 to form part of the circuit. The shape of the electrode 4 can be selected as any shape depending on the purpose. Specifically, examples include a pad shape, a pillar shape, a slit shape, etc.

[0035] The material of electrode 4 is preferably an electrically conductive metal. Specifically, electrode 4 can be a layer containing at least one element from among Cu, Au, Ag, Ni, Pd, Pt, Ti, and Sn. Electrode 4 can also be a layer containing composites, mixtures, alloys, etc., of these elements.

[0036] The area of ​​electrode 4 is not particularly limited as it varies depending on its shape, size, etc., but in a plan view from a direction perpendicular to the main surface of the substrate, for example, it is 15 to 40,000 μm. ２ This can be done, with a range of 100 to 8,000 μm. ２ That's fine.

[0037] As methods for forming the electrode 4, metal foil etching, plating, sputtering, etc. can be used. Specifically, it is as follows.

[0038] - Etching - Stick a photosensitive resist on a substrate with a copper foil, expose and develop it to a desired pattern to create an opening. Then, dissolve the copper foil exposed from the opening with an etching solution, and remove the photosensitive resist to form a desired copper pattern (subtractive method).

[0039] - Plating - Stick a photosensitive resist on a substrate with a copper foil, expose and develop it to a desired pattern to create an opening. Next, deposit copper on the copper foil in the opening by electroplating copper to form a pattern. Then, peel off the photosensitive resist and etch the excess copper foil portion to form a desired copper pattern.

[0040] - Sputtering - Provide a metal sputtering layer on a substrate, stick a photosensitive resist on the surface of the sputtering layer, expose and develop it to a desired pattern to create an opening. Next, deposit copper in the opening by electrolytic copper plating, then remove the photosensitive resist, and etch the excess copper to obtain a desired copper pattern.

[0041] On the surface of the portion used as the electrode of the obtained copper pattern, a metal film with a multilayer structure such as nickel, nickel - gold, or nickel - palladium - gold can be formed. For example, by providing a gold layer on the outermost surface, the wetting spread of solder is improved. Also, by providing a nickel layer, the nickel layer functions as a barrier layer after solder mounting, preventing the solder material from diffusing into other metal layers and obtaining a stable connection.

[0042] These metal multilayer films can be formed by methods such as sputtering, electroplating, electroless plating, etc. In particular, electroless plating can laminate a metal film on the copper electrode after pattern formation without a lead wire. Also, electroless plating can control the film thickness with high precision.

[0043] (Solder Base) A general solder material can be used for the solder base 1. Specifically, tin or a tin alloy can be used as the main material. Examples of tin alloys 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, etc.

[0044] Indium or an indium alloy can also be used for the solder base 1. Examples of indium alloys include In-Bi alloy, In-Ag alloy, etc.

[0045] The solder base 1 may contain one or more elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, Sb, Ge, Mn, Co, Si, Al, In, P, and B. From the perspective of obtaining good conduction reliability, the solder base 1 can contain Ag or Cu. By including Ag or Cu in the solder base 1, the melting point of the solder base 1 can be reduced to about 220°C, and the bonding strength with the electrode can be improved. Also, from the perspective of reducing the thermal influence on surrounding components due to the heating in the mounting process, the solder base 1 can contain Bi or In. By including Bi or In in the solder base 1, it is also possible to reduce the melting point of the solder base 1 to 200°C or less. In recent years, considering the impact on the environment, a lead-free composition without lead (Pb) is preferred.

[0046] The ratios of these materials contained in the solder base 1 can be arbitrarily adjusted according to the requirements in use. Representative solder materials include Sn 42 mass% - Bi 58 mass% (melting point 138°C), Sn 96.5 mass% - Ag 3.0 mass% - Cu 0.5 mass% (melting point 217°C), Sn 97 mass% - Ag 3 mass% (melting point 221°C), etc.

[0047] The solder base 1 is formed on the surface of the electrode 4. The continuous formation of the solder base 1 with the surface of the electrode 4 reduces the electrical connection resistance. The formation of the solder base 1 on the upper side of the electrode 4 allows for effective connection of opposing electrodes via solder during mounting. If the solder base 1 is present on the side of the electrode 4, there is a concern that solder bridging may occur between adjacent electrodes during mounting, leading to short-circuit failures. Therefore, it is preferable that the solder base 1 be located on the upper side of the electrode 4.

[0048] By covering the entire upper surface of the electrode 4 with the solder base 1, the fixing force between components after mounting is maximized, resulting in stable connection characteristics and reduced variations in electrical characteristics between electrodes. If the surface of the substrate 3, including a portion of the surface of the electrode 4, is covered with an insulating material, the solder base 1 may also be formed on the remaining portion of the electrode 4 surface that is not covered with the insulating material. A resin coating material called solder resist is commonly used as the insulating material.

[0049] The solder base 1 can take various shapes, including layered, columnar, spherical, hemispherical (spherical crown), and uneven shapes. Spherical or hemispherical shapes, in particular, facilitate contact with opposing electrodes during mounting. During mounting, an organic material may be pre-placed between the solder bump member 10 and the opposing member before connecting the electrode 4 and the opposing electrode via solder. In this case, if the solder base 1 is spherical or hemispherical, it is easier for it to penetrate the organic material placed between the members and make contact with the opposing electrode, thus making it easier to obtain a stable connection. Underfill material or flux material can be used as the organic material. These organic materials come in film type and liquid type.

[0050] Various methods can be used to form the solder base 1, including using solder balls, using solder paste, plating, and sputtering.

[0051] -Solder Ball- A mask is prepared with openings formed in the same pattern as the arrangement pattern of electrode 4, and the openings of the mask are aligned with electrode 4. Flux is applied to electrode 4, and solder balls are placed in the openings of the mask and the mask is removed. Then, the substrate 3 is reflowed (heated) to melt the solder balls, wetting and spreading the solder on the surface of electrode 4, and the surface tension of the solder causes it to roll into a hemispherical shape. After cooling, the flux is washed and removed to form a hemispherical solder base 1 on electrode 4.

[0052] -Solder Paste- A mask is prepared with openings formed in the same pattern as the arrangement pattern of electrode 4, and the openings of the mask are aligned with electrode 4. Solder paste is printed to form a solder paste layer on electrode 4. Then, the substrate 3 is reflowed (heated) to melt the solder paste, wetting and spreading the solder on the surface of electrode 4, and the surface tension of the solder causes it to roll into a hemispherical shape. After cooling, the flux is washed and removed to form a hemispherical solder base 1 on electrode 4.

[0053] -Plating / Sputtering- A photosensitive resist is formed on the substrate 3, and openings are created in the photosensitive resist in the arrangement pattern of the electrodes 4 by exposure and development processing. A solder base 1 is formed on the electrodes 4 by electroplating using the electrodes 4 as a seed, and then the photosensitive resist is removed. Alternatively, the solder base 1 may be formed on the electrodes 4 by sputtering instead of plating.

[0054] -Other- As a method for forming electrode 4, copper plating is performed on the openings of the photosensitive resist using the method described above to form Cu pillars. Then, solder plating is performed to deposit solder on the Cu pillars (electrodes 4). When this method is used, the solder base 1 is formed only on the upper surface of electrode 4 (Cu pillar), and there is no solder on the sides of the Cu pillar, thus reducing the possibility of solder bridging between adjacent electrodes. Alternatively, solder paste or sputtering may be used instead of plating to place the solder base 1 on electrode 4 (Cu pillar). In this case as well, since the photosensitive resist covers the sides of electrode 4 (Cu pillar), short-circuit defects between adjacent electrodes can be reduced.

[0055] (Solder protrusions) Various materials as exemplified in the solder base 1 described above can be used for the solder protrusions 2. Specifically, tin or tin alloys can be used as the main material. Examples of tin alloys 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, etc.

[0056] Indium or an indium alloy can also be used for the solder protrusion 2. Examples of indium alloys include In-Bi alloy and In-Ag alloy.

[0057] The solder protrusion 2 may contain one or more elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, Sb, Ge, Mn, Co, Si, Al, In, P, and B.

[0058] The shape of the solder protrusion 2 can be spherical, hemispherical (spherical crown), layered, pseudosphere, cube, pseudocube, rectangular prism, pseudorectangular prism, polygon, pseudopolygon, pillar-shaped, conical, ellipsoidal, or a variation thereof. By providing the solder protrusion 2, the solder bump on the opposing electrode can be fitted. In addition, the height of the solder bump from the surface of the substrate 3 and the surface of the electrode 4 is higher than that of a bump consisting only of the solder base 1 (general bump). This makes it easier to connect electrodes located in positions where the curvature of the substrate is large, such as the edges of the substrate.

[0059] At least three solder protrusions 2 are provided on the solder base 1. For example, when the solder protrusions 2 are formed by solder balls, the surface of the solder base 1 will have a shape in which three or more spherical (spherical crown-shaped) solder protrusions 2 are provided.

[0060] The number of solder protrusions 2 is not particularly limited, but from the viewpoint of suppressing misalignment of the upper and lower members by having the solder protrusions 2 contact the solder bumps on the opposing electrode and effectively engage them, the number can be set to a maximum of 30.

[0061] By providing multiple solder protrusions 2 of the same size, it is possible to increase the amount of solder only on specific electrodes while suppressing the solder bump height from the surface of the substrate 3 and the surface of the electrode 4. Furthermore, if the substrate warps towards the edge of the substrate, causing the distance between opposing electrodes to change continuously depending on the electrode position, the amount of solder can be adjusted by changing the number of solder protrusions 2 for each electrode in accordance with the distance between electrodes.

[0062] As described above, the solder protrusions 2, of which there are at least three, are arranged so that the solder bumps on the opposing electrodes fit into the space formed by these solder protrusions 2. In this case, if the solder protrusions 2 are formed on the upper surface of the solder base 1, that is, if they are formed so that the solder protrusions 2 are contained within the solder base 1 in a plan view from a direction perpendicular to the main surface of the substrate 3, bridging between adjacent electrodes can be reduced.

[0063] The solder protrusion 2 is adhered to the surface of the solder base 1. In this case, adhesion means that the solder protrusion 2 is held to the surface of the solder base 1 even without external force.

[0064] Specific examples of adhesion include adhesion by electrostatic force, intermolecular force, frictional force, etc. acting between the solder protrusion 2 and the solder base 1, fusion of the constituent materials of the solder protrusion 2 and the solder base 1 (metal bonding), and adhesion of the solder protrusion 2 and the solder base 1 by organic materials. Examples of organic materials include flux materials containing organic acids such as citric acid and malic acid, long-chain alkanes such as decane and dodecane, and high-boiling point solvents such as ethylene glycol.

[0065] The solder protrusion 2 can be formed in the same manner as the solder base 1. Below, we will illustrate a method for forming the solder protrusion 2 using solder balls.

[0066] For example, a mask with openings in the electrode arrangement pattern is placed on the surface of a substrate 3 on which the solder base 1 is formed, and flux is applied to the solder base 1 by flux printing. Subsequently, another mask with openings in the electrode arrangement pattern is placed, and solder balls are introduced through the openings in the mask and placed on the solder base 1 via the flux. In this method, the member described in Japanese Patent Application Publication No. 2017-157626 can be used. Specifically, a member can be used which consists of a base material, a recess formed on the surface of the base material, and solder balls (solder particles) arranged in the recess, with a portion of the solder balls exposed higher than the surface of the base material. The solder ball side of this member is placed opposite the surface of the solder base 1, the solder balls are brought into contact with the surface of the solder base 1, and the solder balls are adhered to the surface of the solder base 1 by heating and pressurizing. Then, by removing the base material, a solder protrusion 2 can be formed on the surface of the solder base 1. In this method, an organic material can also be pre-applied to the surface of the solder base 1. The adhesive properties of the organic material allow solder balls in the recesses of the base material to be transferred to the surface of the solder base 1 and bonded. If the organic material contains flux components, heating causes parts of the solder base 1 and solder protrusions 2 to melt and fuse together, resulting in a strong bond.

[0067] The temperature used when transferring the solder ball can range from a temperature below the melting point of the solder to a temperature above the melting point. The transfer temperature may be set to match the solder material with the lower melting point among the solder base 1 and the solder ball.

[0068] When the solder base 1 or solder ball is Sn 42% by mass - Bi 58% by mass (melting point 138°C), the transfer temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher.

[0069] When the solder base 1 or solder ball is Sn 96.5 mass% - Ag 3.0 mass% - Cu 0.5 mass% (melting point 217°C), the transfer temperature is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and particularly preferably 190°C or higher.

[0070] When the solder base 1 or solder ball is Sn97% by mass - Ag3% by mass (melting point 221°C), the temperature during transfer is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and particularly preferably 190°C or higher.

[0071] The solder material constituting the solder base 1 and the solder protrusion 2 may be the same or have different compositions and ratios. Specifically, the composition of the solder protrusion 2 may be the same as that of the solder base 1 with trace amounts of metal added. By using a solder protrusion 2 with trace amounts of metal added at electrodes in positions where stress is easily applied due to warping of the substrate, the ductility of the solder and the growth of the alloy layer can be altered, thereby ensuring reliability.

[0072] The appropriate pressure for transferring solder balls to the solder base 1 can be set according to the number of electrodes or the electrode area (total area). The appropriate pressure during transfer should be set so that the solder balls make sure to make contact with the solder base 1.

[0073] (Shape of solder bumps) The shape of the solder base 1 and the solder bump 2, the contact area between them, etc. can be appropriately adjusted by the temperature when the solder ball is mounted on the solder base 1 (when the solder protrusion 2 is formed), and the temperature applied after the solder protrusion 2 is mounted on the solder base 1.

[0074] Figure 8 schematically shows the shape of solder bumps that can occur depending on the combination of mounting temperature and solder melting point. In Figure 8, a boundary is depicted between the solder protrusion 2 and the solder base 1, but since the solder may melt or diffuse and the two may fuse together, there may not always be a clear boundary between the solder protrusion 2 and the solder base 1.

[0075] In both shapes A and B, three solder protrusions 2 are formed on the surface of the solder base 1, allowing the solder bumps on the opposing electrodes to be fitted. This ensures a stable connection between the opposing electrodes. Furthermore, both shapes have the advantage of easily maintaining a high height from the surface of the substrate 3 to the top of the solder bump, making it easier to connect opposing electrodes when mounting substrates with significant warping.

[0076] In shape A, a solder ball that substantially maintains its ball shape forms a solder protrusion 2 on the solder base 1.

[0077] In shape B, multiple solder balls melt and connect (unify) to form a solder protrusion 2. In shape B, the adhesion between the solder protrusion 2 and the solder base 1 is strong, making it easier to prevent the solder protrusion 2 from falling off.

[0078] The mounting temperature T in Figure 8 can also be interpreted as the heating temperature when the solder protrusion 2 is mounted onto the surface of the solder base 1 and then heated.

[0079] If the melting point of the solder protrusion 2 is lower than that of the solder base 1, the mounting temperature can be set to a temperature close to the melting point of the solder protrusion 2, thus allowing the mounting process to be performed at a lower temperature.

[0080] The above describes an example of forming solder protrusions 2 using solder balls, but the shape and formation method of the solder protrusions 2 are not limited to these. For example, a mask can be prepared with openings corresponding to the arrangement of the solder protrusions 2. The protrusions 2 can be formed by precisely aligning the openings of the mask so that they are positioned on the solder base 1 and supplying solder to the openings. One example of a method for supplying solder is solder paste printing.

[0081] (Other embodiments of the solder bump member) Figure 3 is a schematic diagram showing another embodiment of the solder bump member. The solder bump member 60 comprises a base material 63 and a plurality of electrodes 64 provided on the base material 63 and having solder bumps 65. The solder bump 65 is composed of at least three solder protrusions 62 formed on the surface of the electrode 64.

[0082] Even if vibrations occur during mounting, the solder bumps on the opposing electrode of the solder bump member 60 will fit into the space formed by the at least three solder protrusions, thereby suppressing misalignment of the upper and lower members and enabling stable electrode connection.

[0083] <Packaging Precursor> The packaging precursor (semiconductor packaging precursor) is a configuration in which the aforementioned solder bump member and another solder bump member are arranged facing each other. Specifically, the two are arranged so that the electrodes of the aforementioned solder bump member and the electrodes of the other solder bump member face each other. In this packaging precursor, the other solder bump member comprises another substrate and a plurality of other electrodes provided on the other substrate and having other solder bumps, and the other solder bumps are fitted into the space formed by the solder protrusions of the solder bumps of the aforementioned solder bump member. Note that "fitting" means, as shown in Figure 5, that the other solder bump 50 is located in a space surrounded by three or more solder protrusions 2, and as a result when horizontal vibration or shock is applied to the packaging precursor, the side surface of the other solder bump 50 comes into contact with the solder protrusions 2, and any further relative displacement is physically restricted. This state includes not only the state in which other solder bumps 50 are in constant contact with the solder protrusions 2, but also the state in which they are facing each other with a small gap in between.

[0084] Examples of solder bump members include interposers and substrates, which have wiring and electrodes formed on a substrate made of resin or glass. Other solder bump members include semiconductor chips such as HBMs, GPUs, and CPUs, where the base material 3 is made of Si or ceramics and wiring and electrodes are formed on the surface, and chip modules that integrate these into one. The shape of the solder bumps in other solder bump members is not particularly limited as long as it fits into the space formed by the solder protrusions of the solder bumps of the solder bump members described above, and examples include spherical, hemispherical (spherical crown), layered, pseudosphere, cube, pseudocube, rectangular parallelepiped, pseudorectangular parallelepiped, polygonal, pseudopolygonal, pillar-shaped, conical, ellipsoidal, and deformed forms thereof. However, solder bump members may be any of the examples given as other solder bump members, and conversely, other solder bump members may be any of the examples given as solder bump members.

[0085] The following explanation of the mounting precursor will be based on the example where the protruding bump of the solder bump-equipped member described above has the shape A described above, and the solder bumps of other bump-equipped members are hemispherical.

[0086] Figure 4 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. Figures (a) and (b) show how a mounting precursor is obtained in which the aforementioned solder bump member and another solder bump member are arranged facing each other. As shown in Figure (a), the other solder bump member 20 comprises a base material 30, a plurality of electrodes 40 provided on the base material 30, and solder bumps 50 provided on the electrodes 40. In this state, as shown in Figure (b), when the two members are brought closer together and the solder bumps of the solder bump member 10 are brought into contact with the solder bumps 50 of the other solder bump member 20, the solder bumps 50 of the other solder bump member 20 can be fitted into the space formed by the solder protrusions of the solder bump member 10. With the mounting precursor 100 in this state, misalignment of the upper and lower members during mounting is suppressed, so that a mounted body 101 with properly soldered connections between opposing electrodes can be obtained, as shown in Figure (c).

[0087] Figure 5 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. Specifically, the figure shows a state in the mounting precursor 100 shown in Figure 4(b) in which the solder bump on the opposing electrode is fitted into a space formed by three solder protrusions. As shown in the figure, this state satisfies the following relationship, with respect to the height 4h of the electrode 4 surface of the solder bump member 10 according to the present disclosure: height 1h of the top of the solder base 1 ≤ height 50h of the top of the solder bump 50 of another solder bump member < height 2h of the top of the solder protrusion 2.

[0088] On the other hand, Figure 6 is a schematic diagram showing a mounting process using a general solder bump member. This figure shows how a mounting precursor is obtained in which a general solder bump member and another solder bump member are positioned opposite each other. As shown in Figure (a), the general solder bump member 11 has general bumps that are not the raised bumps mentioned above. As shown in Figure (b), when the two members are brought close together and the solder bumps come into contact with each other, the solder bumps come into contact at a single point. In this state, the mounting precursor 110 is prone to misalignment of the upper and lower members during mounting, and there is a risk that a mounting body 111 will be obtained in which the opposing electrodes are not properly soldered together, as shown in Figure (c).

[0089] The above explanation of the mounting precursor was based on the example of the bump with a protrusion having shape A as described above. However, the shape of the bump with a protrusion is not limited to this, and it may also be shape B.

[0090] <Method for Manufacturing a Packaging Assembly> The method for manufacturing a packaging assembly (semiconductor packaging assembly) comprises the steps of: heating the above-mentioned packaging precursor to melt the solder bumps and other solder bumps; and cooling the heated packaging precursor to obtain a packaging assembly in which electrodes are electrically connected to other electrodes via solder.

[0091] The resulting mounting structure exhibits excellent connection reliability because the misalignment of the upper and lower components during mounting is suppressed, resulting in proper solder connections between opposing electrodes.

[0092] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0093] (Example 1) <Fabrication of components for solder ball mounting> Step 0: Preparation of evaluation substrate and chip An evaluation substrate and evaluation Si chip were prepared, with a circuit capable of daisy-chain evaluation assembled on it.

[0094] The evaluation substrate is a 10mm x 10mm Si substrate with wiring formed to allow for electrical resistance measurement when the evaluation Si chip is mounted on it.

[0095] The evaluation Si chip is 8 mm x 8 mm in size and consists of two electrode pattern areas called the full area and the peripheral area. In the full area, solder bump electrodes are arranged in a square grid at a 300 μm pitch in a 5.7 mm x 5.7 mm central area of ​​the evaluation Si chip. In the peripheral area, solder bump electrodes are aligned at an 80 μm pitch, bordering a 7.8 mm x 7.8 mm square in the center of the evaluation Si chip. In both solder bump electrodes, SnAg solder bumps with a height of 15 μm are formed by a plating method on Cu electrodes with an electrode size of Φ40 μm.

[0096] Step 1: Preparation of a substrate with solder microparticles A convex imprint mold having spherical protrusions with a diameter of 8 μm was prepared. Three spherical protrusions were placed for each solder bump of the evaluation Si chip prepared in Step 0 (Form 1). The three spherical protrusions were positioned so that the center point of the solder bump, when viewed from above the solder bump in a plan view, falls inside the triangle drawn by connecting the vertices of the three spherical protrusions. Next, a photocurable resin was applied to a transparent film substrate, and the convex imprint mold was placed on the resin side. While pressing the imprint mold, 366 nm light was shone from the transparent film surface to cure the photocurable resin. After that, the imprint mold was peeled off to create a substrate having a recess with an aperture diameter of 8 μmΦ at the desired position.

[0097] Using a squeegee, SnBi solder microparticles (manufactured by Mitsui Mining & Smelting Co., Ltd., melting point 139°C, ST-2) were filled into the recesses of the substrate. Excess solder microparticles were then removed by rubbing the side of the substrate where the recesses were formed with a micro-adhesive roller, resulting in a substrate in which solder microparticles were arranged only within the recesses.

[0098] Step 2: Forming solder balls The substrate obtained in Step 1 (a substrate with solder microparticles placed in the recesses) was placed in a formic acid reflow oven (manufactured by Shinko Seiki Co., Ltd., batch-type vacuum soldering device). After vacuuming, nitrogen gas bubbled through a formic acid solution was introduced into the oven to fill it with a reducing gas. The oven was then maintained at 130°C for 5 minutes while the reducing gas flowed. After stopping the supply of the reducing gas, the oven was evacuated and the temperature was raised to 200°C and maintained for 5 minutes. Solder particles were then formed by lowering the temperature inside the oven to room temperature while nitrogen flowed. This produced a solder ball mounting component for Form 1, which had SnBi solder balls in the recesses. The solder ball mounting component can also be called a solder protrusion forming component.

[0099] Furthermore, a solder ball mounting component for Form 2 was obtained using the same method as in steps 1 and 2, except that an imprint mold was used in which four spherical protrusions were arranged for each solder bump of the evaluation Si chip.

[0100] <Mounting Solder Balls onto Solder Bumps> Step 3: Mounting Solder Balls A mounting machine (FC3000-WS, manufactured by Toray Engineering Co., Ltd.) was used to mount the solder balls. The design information for each type of solder ball mounting component and the evaluation Si chip was input into the machine in advance, and the machine was set so that when the components were heat-pressed, the desired position of the solder balls on the solder ball mounting component would come into contact with the solder bumps on the surface of the evaluation Si chip.

[0101] In the solder ball mounting process, flux (NS-334, manufactured by Nippon Superior Co., Ltd.) was applied to the solder bumps on the surface of the evaluation Si chip. A solder ball mounting component was placed on the stage of the mounting machine, and the evaluation Si chip was placed on the chip tray of the mounting machine. The evaluation Si chip on the chip tray was picked up with the crimping tool of the mounting machine and heat-pressed onto the solder ball mounting component on the stage at a set temperature of 140°C and a set load of 3N for 30 seconds. After crimping, the evaluation Si chip was peeled off, transferring the solder balls from the solder ball mounting component onto the solder bumps (solder bases) on the surface of the evaluation Si chip. The solder balls were fused onto the solder bumps.

[0102] Figure 7 shows the results of optical microscope observation of the bump with protrusions according to this embodiment, specifically the external appearance of the bump with protrusions obtained in embodiments 1 and 2. Figures (a) and (b) show the bump with protrusions observed from above, and three (a) or four (b) solder protrusions provided on the solder base can be seen in each.

[0103] <Evaluation of Solder Bumps> The evaluation Si chips obtained through steps 1 to 3 were fixed to the surface of the SEM observation base, and platinum sputtering was applied to the surface. The diameter of the solder balls was measured for 100 bumps with protrusions using an SEM, and the average diameter was calculated. In addition, the height from the electrode surface of the evaluation Si chip to the top of the solder ball was measured for 100 bumps with protrusions using a laser microscope (LEXT OLS5000-SAF, manufactured by Olympus Corporation). Furthermore, the area of ​​the polygon drawn by connecting the tops of the solder balls in a plan view from a direction perpendicular to the main surface of the evaluation Si chip (polygon area) was measured for 100 bumps with protrusions. An evaluation Si chip without solder balls was used as Comparative Example 1. The results are shown in Table 1.

[0104]

[0105] <Implementation Evaluation> The evaluation Si chip is mounted on the evaluation substrate to form multiple daisy-chain circuits within the mounted body. The evaluation Si chips with solder balls of form 1 and 2, obtained through steps 1 to 3, are mounted, and the frequency of connection failures within the circuit is investigated to evaluate the improvement in connectivity due to the mounting of solder balls.

[0106] After applying flux to the evaluation Si chips with solder balls of form 1 and 2 obtained in steps 1 to 3 and the Cu electrode on the evaluation substrate, the chips were mounted onto the evaluation substrate using a mounting machine by thermocompression at a set temperature of 260°C and a set load of 5N for 10 seconds. Twenty-five mounted units were prepared, and continuity tests were performed on a total of 200 circuits to investigate the probability of connection failure in each. A mounted unit with evaluation Si chips without solder balls was designated as Comparative Example 1. The evaluation results are shown in Table 2. In Example 1, it was confirmed that the probability of connection failure was significantly reduced.

[0107]

[0108] 1...Solder base, 1a...Top of solder base, 2...Solder protrusion, 2a...Top of solder protrusion, 3...Base material, 4...Electrode, 5...Solder bump (bump with protrusion), 6...Solder bump (general bump), 10...Member with solder bump, 11...General member with solder bump, 20...Other member with solder bump, 30...Base material, 40...Electrode, 50...Solder bump, 60...Member with solder bump, 62...Solder protrusion, 63...Base material, 64...Electrode, 65...Solder bump, 100, 110...Plating precursor, 101, 111...Plating body.

Claims

1. A solder bump member comprising a base material and a plurality of electrodes provided on the base material and having solder bumps, wherein in at least some of the electrodes, the solder bump is a bump with protrusions having a solder base formed on the electrode surface and at least three solder protrusions formed on the surface of the solder base, and the top of the solder protrusions is higher than the top of the solder base.

2. The solder bump member according to claim 1, wherein the solder protrusion is fused to the solder base.

3. The solder bump member according to claim 1, wherein the height of the solder protrusion is 1.01 times or more and 10 times or less the height of the solder base, with respect to the electrode surface.

4. The solder bump member according to claim 1, wherein the solder volume of the protruding bump is 1.005 times or more and 10 times or less the solder volume of the solder base.

5. The solder bump member according to claim 1, wherein, in a plan view from a direction perpendicular to the main surface of the substrate, the area of ​​the polygon drawn by connecting the vertices of the solder protrusions is 0.0005 times or more and 0.65 times or less the area of ​​the electrode.

6. The solder bump member according to claim 1, wherein the solder base and the solder protrusion include tin, a tin alloy, indium, or an indium alloy.

7. The solder bump member according to claim 1, wherein the solder protrusion is formed by a solder ball.

8. A mounting precursor comprising a solder bump member according to any one of claims 1 to 7 and another solder bump member arranged opposite each other, wherein the other solder bump member comprises another substrate and a plurality of other electrodes provided on the other substrate and having other solder bumps, and the other solder bumps are fitted into the space formed by the solder protrusions of the solder bumps.

9. A method for manufacturing a mounting body, comprising the steps of: heating the mounting precursor described in claim 8 to melt the solder bumps and the other solder bumps; and cooling the heated mounting precursor to obtain a mounting body in which the electrode and the other electrode are electrically connected via solder.

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