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 some of the electrodes, the solder bumps are high bumps having a solder base part formed on the electrode surface and a solder protruding part formed on the solder base part surface, and in the remaining electrodes, the solder bumps are small bumps having a solder base part formed on the electrode surface.

Description

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

[0001] The present disclosure relates to a method for manufacturing a member with solder bumps, a mounting precursor, and 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, semiconductors are required to be further enhanced in performance and highly integrated. 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, due to the high density of semiconductor chips, the miniaturization of wiring and electrodes is also progressing.

[0003] On the other hand, 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] However, since the main materials of constituent members such as semiconductor chips, capacitors, and substrates are different, their coefficients of thermal expansion are also different. Therefore, warping or deformation occurs in the package due to temperature changes such as reflow (heating) and reliability evaluation (environmental test) in the mounting process using solder, which causes connection failures in the mounting process.

[0005] Regarding these problems, Patent Document 1 discloses a method of mounting while suppressing the warping of the substrate using a jig. However, when the jig is removed after mounting, there is a concern that the accumulated stress is released and a local force is applied to the solder part, causing damage.

[0006] Furthermore, Patent Document 2 discloses a technique for using partially different solder bumps in an array consisting of multiple solder bumps. According to Patent Document 2, by adding filler to the solder bumps in the area around the chip where stress is easily applied, the elastic modulus can be lowered, thereby reducing connection failures. However, with this method, although it is possible to mount substrates that have suppressed warping as in Patent Document 1, it is difficult to mount substrates that are already warped. In addition, if fillers other than solder are added to the solder, there is a concern that the fillers themselves may cause cracks, and especially given the current progress in miniaturization of electrodes, there is a concern that the amount of solder contributing to solder connections will decrease.

[0007] International Publication No. 2006 / 087769, Japanese Patent Publication No. 2013-105951, Japanese Patent Publication No. 2017-157626

[0008] Incidentally, in recent years, with the explosive increase in the amount of information processed, the functionality of data center packages has advanced remarkably. As a result, the increase and size of mounted components have led to substrate sizes exceeding 50 mm x 50 mm and becoming even larger, and the warping of the substrate is also increasing. In such large packages, the distance in the height direction (Z direction) between opposing electrodes of components widens during mounting, making it difficult for solder to fill the gaps between electrodes, and connection failures are becoming more likely.

[0009] Furthermore, even in packages with large substrate sizes, electrode miniaturization is progressing, resulting in smaller solder bumps or solder balls on the electrodes. Consequently, the amount of solder needed to connect opposing electrodes becomes insufficient, making connection failures more likely.

[0010] By reducing the distance between opposing electrodes during assembly, solder can be sandwiched between electrodes even if they are spread apart due to warping. However, in electrodes located in positions with less warping, i.e., electrodes with a narrow distance between opposing electrodes, solder can be pushed laterally from between the electrodes, bridging to adjacent electrodes and causing short-circuit failures.

[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 warping of the substrate. 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 a solder protrusion is formed on some (at least one) of a plurality of solder bump electrodes. Even if the solder on the electrode does not reach the opposing electrode during mounting due to warping of the member, etc., a stable connection between electrodes can be achieved by increasing the solder height in advance. Furthermore, even for electrodes where the amount of solder becomes insufficient due to localized widening of the space between electrodes due to warping after the electrodes are connected with solder during mounting, a stable connection between electrodes can be maintained by adjusting the amount of solder in advance.

[0013] The disclosure outlines the following: [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 some of the electrodes, the solder bumps are tall bumps having a solder base formed on the electrode surface and a solder protrusion formed on the surface of the solder base, and in the remaining electrodes, the solder bumps are short bumps having a solder base formed on the electrode surface. [2] The solder bump member according to [1], wherein the solder protrusion is fused to the solder base. [3] The solder bump member according to [1] or [2], wherein the solder volume of the tall bump is 1.01 times or more and 15 times or less the solder volume of the solder base. [4] The solder bump member according to any one of [1] to [3], wherein the height of the tall bump is 1.01 times or more and 10 times or less the height of the short bump, with respect to the electrode surface. [5] A solder bump member according to any one of [1] to [4], wherein the solder base and the solder protrusions include tin, a tin alloy, indium, or an indium alloy. [6] A solder bump member according to any one of [1] to [5], wherein the solder protrusions are formed by solder balls. [7] A mounting precursor in which a solder bump member according to any one of [1] to [6] and an electrode member are arranged opposite each other. [8] A mounting precursor in which a solder bump member having a large solder bump formed from the tall bump of a solder bump member according to any one of [1] to [6], where the solder base and the solder protrusions are fused together, and a low bump, and an electrode member are arranged opposite each other. [9] A method for manufacturing a mounting body, comprising the steps of: heating the mounting precursor described in [7] to melt the solder bumps; and cooling the heated mounting precursor to obtain a mounting body in which the electrodes of the solder bump member and the electrodes of the electrode member are electrically connected via solder.

[10] The method for manufacturing a mounting body according to [9], further comprising a pre-melting step of heating only the solder bump member to melt the solder bumps before the melting step.

[0014] This disclosure provides a solder bump member that can suppress connection failures during mounting due to warping of the substrate. With such a solder bump member, the height of the solder bump can be increased or the amount of solder can be increased at electrodes where there is a possibility of insufficient solder due to warping of the substrate during mounting, thereby enabling stable solder connections. 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 a mounting process using a solder bump member according to the present disclosure. This is a schematic diagram showing a general mounting process using 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 an SEM image of a tall 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, each having solder bumps 5 or 6. In some electrodes 4, the solder bump 5 is a tall bump having a solder base 1 formed on the surface of the electrode 4 and a solder protrusion 2 formed on the surface of the solder base 1, while in the remaining electrodes 4, the solder bump 6 is a short bump having a solder base 1 formed on the surface of the electrode 4.

[0018] A tall solder bump 5 has a solder base 1 and a solder protrusion 2, while a low solder bump 6 has only a solder base 1. A tall solder bump whose height can be adjusted by the size of the solder protrusion 2 may include two or more types of solder bumps with different heights.

[0019] The solder volume of the high bump can be 1.01 to 15 times the solder volume of the solder base 1. If this ratio is above the lower limit, it is easier to make more stable connections between opposing electrodes in areas where the distance between components is large. If this ratio is below the upper limit, compared to the case where it is above the upper limit, solder is less likely to flow outside the electrode 4 during solder melting, and short circuits are less likely to occur. From these viewpoints, the ratio may be 1.2 times or more, 1.5 times or more, or 2 times or more, while the ratio may be 13 times or less, 10 times or less, 7 times or less, or 5 times or less. This ratio can be adjusted by the size and amount of the solder protrusions 2.

[0020] 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.

[0021] Using the electrode surface as a reference, the height of the tall bump can be between 1.01 and 10 times the height of the short bump. If this ratio is above the lower limit, it is easier to make more stable connections between opposing electrodes in areas where the distance between components is large. If this ratio is below the upper limit, solder is less likely to flow outside the electrode during soldering and short circuits are less likely to occur compared to when it is above the upper limit. From these viewpoints, the ratio may be 1.1 times or more, or 2 times or more, while the ratio may be 5 times or less, or 3 times or less. This ratio can be adjusted by the size of the solder protrusion 2. When there are multiple solder protrusions 2 on the solder base 1, the height of the tall bump is the height of the highest point of the solder protrusion 2 (the tallest solder protrusion 2).

[0022] The height of the low bumps is not particularly limited as it varies depending on their 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 high bumps can be appropriately adjusted based on the above height of the low bumps. The heights of the low and high bumps can be measured using a laser microscope, a stylus-type height meter, etc. The height of the low bumps can be said to be the height of the solder base 1.

[0023] (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.

[0024] The base material 3 can be a resin material, an inorganic material, or a composite material thereof.

[0025] 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.

[0026] Inorganic materials such as silicon (Si), glass, and ceramics can be used. Silicon is commonly used as a material for semiconductor chips and memory.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Methods for forming electrode 4 include etching, plating, and sputtering of metal foil. Specifically, these are as follows:

[0034] - Etching - A photosensitive resist is attached to a copper foil substrate, and the desired pattern is exposed and developed to create openings. Then, the copper foil exposed through the openings is dissolved with an etching solution, and the photosensitive resist is removed to form the desired copper pattern (subtra method).

[0035] -Plating- A photosensitive resist is applied to a copper foil substrate, and the desired pattern is exposed and developed to create openings. Next, copper is deposited on the copper foil in the openings by electroplating to form a pattern. After that, the photosensitive resist is peeled off, and the excess copper foil is etched to form the desired copper pattern.

[0036] -Sputtering- A metal sputtered layer is placed on a substrate, a photosensitive resist is attached to the surface of the sputtered layer, and the desired pattern is exposed and developed to create openings. Next, copper is deposited in the openings by electrolytic copper plating, the photosensitive resist is removed, and the excess copper is etched to obtain the desired copper pattern.

[0037] The surface of the portion of the resulting copper pattern used as an electrode can be formed with a multilayer metal film such as nickel, nickel-gold, or nickel-palladium-gold. For example, placing a gold layer on the outermost surface improves solder wetting and spreading. Additionally, by adding a nickel layer, the nickel layer acts as a barrier layer after soldering, preventing the solder material from diffusing into other metal layers and resulting in a stable connection.

[0038] These metal multilayer films can be formed by methods such as sputtering, electroplating, and electroless plating. Electroless plating, in particular, allows for the layering of metal films onto copper electrodes after pattern formation without the need for lead wires. Furthermore, electroless plating allows for highly precise control of film thickness.

[0039] (Solder base) A general soldering 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.

[0040] Indium or an indium alloy can also be used for the solder base 1. Examples of indium alloys include In-Bi alloy and In-Ag alloy.

[0041] 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 viewpoint 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 viewpoint of reducing the thermal influence on surrounding components due to 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 lower. In recent years, considering the impact on the environment, a lead-free composition that does not contain lead (Pb) is preferred.

[0042] The ratios of these materials contained in the solder base 1 can be arbitrarily adjusted according to the requirements in use. Typical 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.

[0043] The solder base 1 is formed on the surface of the electrode 4. By forming the solder base 1 continuously with the surface of the electrode 4, the resistance of the electrical connection becomes low. By forming the solder base 1 on the upper surface side of the electrode 4, the electrodes facing each other during mounting can be effectively connected via the solder. If the solder base 1 is present on the side surface of the electrode 4, there is a concern that a solder bridge may occur between adjacent electrodes during mounting, causing a short circuit defect. Therefore, it is preferable that the solder base 1 is present on the upper surface side of the electrode 4.

[0044] By covering the entire upper surface of the electrode 4 with the solder base 1, the fixing force between components after mounting can be maximized to obtain stable connection characteristics, and the variation in electrical characteristics for each electrode is reduced. When the surface of the base material 3 including a part of the surface of the electrode 4 is covered with an insulating material, the solder base 1 may be formed on the remaining part of the surface of the electrode 4 that is not covered with the insulating material. As the insulating material, a resin coating material called solder resist is common.

[0045] Examples of the shape of the solder base 1 include a layered shape, a columnar shape, a spherical shape, a hemispherical shape (spherical crown shape), a concavo-convex shape, etc. In particular, a spherical or hemispherical shape is easy to contact the electrode facing it during mounting. At the time of mounting, an organic material may be provided in advance between the member with the solder bump 10 and the opposing member, and then the electrode 4 and the opposing electrode may be connected via solder. In this case, when the solder base 1 is spherical or hemispherical, it is easy to penetrate the organic material provided between the members and easy to contact the opposing electrode, so that a stable connection is easily obtained. As the organic material, an underfill material or a flux material can be used. These organic materials include a film type and a liquid type.

[0046] As methods for forming the solder base 1, various methods such as a method using solder balls, a method using solder paste, plating, sputtering, etc. can be used.

[0047] - Solder ball - Prepare a mask with openings formed in the same pattern as the arrangement pattern of the electrodes 4, and align the openings of the mask with the electrodes 4. Apply flux on the electrodes 4, put solder balls in the openings of the mask, and remove the mask. Then, reflow (heat) the base material 3 to melt the solder balls, spread the solder on the surface of the electrodes 4, and round it into a hemispherical shape by the surface tension of the solder. After cooling, wash and remove the flux to form a hemispherical solder base 1 on the electrodes 4.

[0048] - Solder paste - Prepare a mask with openings formed in the same pattern as the arrangement pattern of the electrodes 4, and align the openings of the mask with the electrodes 4. Print the solder paste to form a solder paste layer on the electrodes 4. Then, reflow (heat) the base material 3 to melt the solder paste, spread the solder on the surface of the electrodes 4, and round it into a hemispherical shape by the surface tension of the solder. After cooling, wash and remove the flux to form a hemispherical solder base 1 on the electrodes 4.

[0049] -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.

[0050] -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.

[0051] (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.

[0052] 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.

[0053] 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.

[0054] 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 height of the solder bump from the surface of the substrate 3 and the surface of the electrode 4 becomes higher than that of a bump (low bump) with only the solder base 1. This makes it easier to connect electrodes located in positions where the substrate warps significantly, such as the edges of the substrate.

[0055] The solder protrusion 2 may be provided as a single unit on the solder base 1, or it may be provided as a multiple unit. For example, if the solder protrusion 2 is formed by a solder ball, the surface of the solder base 1 will have one or more spherical (spherical crown-shaped) solder protrusions 2.

[0056] 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.

[0057] If the solder protrusion 2 is formed on the upper surface of the solder base 1, that is, if it is formed so that the solder protrusion 2 is contained within the solder base 1 in a plan view from a direction perpendicular to the main surface of the substrate, bridging between adjacent electrodes can be reduced.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] When transferring solder balls, temperatures ranging from below the melting point of the solder to above the melting point can be used.

[0063] When the solder base 1 or solder ball is Sn 42% by mass - Bi 58% by mass (melting point 138°C), the temperature during transfer is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 130°C or higher, and particularly preferably 138°C or higher.

[0064] 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, particularly preferably 190°C or higher, and most preferably 217°C or higher.

[0065] When the solder base 1 or solder ball is Sn97% by mass - Ag3% by mass (melting point 221°C), the transfer temperature is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, particularly preferably 190°C or higher, and most preferably 221°C or higher.

[0066] 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.

[0067] 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.

[0068] (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.

[0069] Figure 8 schematically shows the shape of solder bumps that can occur depending on the combination of mounting temperature and solder melting point. Examples are shown for cases using large and small solder balls. 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 fuse the two together, there may not always be a clear boundary between the solder protrusion 2 and the solder base 1.

[0070] In both shapes A and B, the height from the surface of the substrate 3 to the top of the solder bump is higher than the height to the top of a solder bump without the solder protrusion 2, allowing for stable connection between opposing electrodes.

[0071] In shape A, solder balls that substantially maintain their ball shape form solder protrusions 2 on the solder base 1. Shape A makes it easier to increase the height from the surface of the substrate 3 to the top of the solder bump compared to shape B, thus facilitating connection between opposing electrodes when mounting substrates with significant warping. Furthermore, if the mounting temperature is above the melting point of the solder base 1, the solder balls sink into the solder base 1. Although this reduces the height of the solder bump, it strengthens the adhesion between the solder protrusions 2 and the solder base 1, making it easier to prevent the solder protrusions 2 from falling off.

[0072] In shape B, multiple solder balls melt and fuse together, or are partially connected, to form the 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.

[0073] 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.

[0074] 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.

[0075] Even when the solder protrusion 2 and the solder base 1 are not fused together, as in shape A, reducing and heating at a temperature higher than the melting point of both solder materials can cause the solder protrusion 2 and the solder base 1 to fuse together, forming a solder bump with a larger volume compared to the solder base 1 alone.

[0076] The above describes an example of forming solder protrusions 2 using solder balls, but the shape and formation method of solder protrusions 2 are not limited to this. For example, there is also a method of supplying solder for solder protrusions 2 using a mask that has openings corresponding to the arrangement of electrodes 4 and is thicker than the combined height of electrodes 4 and solder base 1. The thickness of the mask should be set according to the volume of solder protrusions 2 to be formed. After placing the mask on the substrate 3 so that electrodes 4 fit into the openings of the mask, a desired amount of solder is supplied. Methods of supply include paste printing, sputtering, and plating. When solder is supplied by paste printing, a heating process is then performed to melt and fuse the paste portion and obtain solder protrusions 2. When solder is supplied by sputtering or plating, a heating process is then performed to improve the adhesion between solder base 1 and solder protrusions 2, or to change the shape of solder protrusions 2 to a desired shape.

[0077] <Packaging Precursor> The packaging precursor (semiconductor packaging precursor) consists of the solder bump member and the electrode member described above, arranged facing each other. Specifically, the electrodes of the solder bump member and the electrodes of the electrode member are arranged facing each other.

[0078] Examples of components with solder bumps include semiconductor chips such as HBMs, GPUs, and CPUs, where the substrate 3 is made of Si or ceramics and wiring and electrodes are formed on its surface, and chip modules that integrate these into one unit. On the other hand, examples of components with electrodes include interposers and substrates, where wiring and electrodes are formed on a substrate made of resin or glass.

[0079] The following explanation of the implementation precursor will be given using the case where the tall bump has the shape A described above as an example.

[0080] Figure 2 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. The figure shows how a mounting precursor is obtained in which the solder bump member and the electrode member described above are arranged opposite each other. As shown in the upper part of Figure 2, the electrode member 20 comprises a base material 30 and a plurality of electrodes 40 provided on the base material 30. The electrode member 20 is warped, with the central part of the base material 30 lifted and the ends lowered. On the other hand, the solder bump member 10, which is arranged opposite the electrode member 20, not only has low-profile solder bumps but also high-profile solder bumps corresponding to the ends of the electrode member 20 which are warped. In this state, by bringing the two members closer together as shown in the lower part of Figure 2, the solder bumps of the solder bump member 10 can be brought into contact with the electrodes 40 of the electrode member 20 at the central and end parts of the members. With such a mounting precursor 100, stable solder connections between opposing electrodes can be made during mounting.

[0081] On the other hand, Figure 3 is a schematic diagram showing a mounting process using a typical solder bump member. This figure also shows how to obtain a mounting precursor in which a typical solder bump member and an electrode member are positioned opposite each other. As shown in the upper part of Figure 3, the typical solder bump member 11 has solder bumps of substantially uniform height, corresponding to the low-profile bumps mentioned above. As a result, even if the two members are brought close together as shown in the lower part of Figure 3, the solder bumps of the solder bump member 11 cannot be brought into contact with the electrodes 40 of the electrode member 20 at the ends of the members. With such a mounting precursor 110, stable solder connections between opposing electrodes cannot be made during mounting.

[0082] Figure 4 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. This figure shows how a mounting precursor is obtained using a solder bump member 12 having a large solder bump 7, which is obtained by reflowing (heating) only the solder bump member to melt and cool the solder bumps before bringing the two members together in Figure 2. In other words, Figure 4 can also be described as a schematic diagram showing a mounting precursor in which a solder bump member having a large solder bump formed from the tall bump of the solder bump member described above, where the solder base and solder protrusion are melted and merged, and a solder bump member having a low-profile bump, and an electrode member are arranged opposite each other. At the tall bump at the end of the member, the solder base 1 and the solder protrusion 2 melt and merge to form a large solder bump 7. Since a single large solder bump has the same function as a tall bump, the mounting precursor 120 shown in Figure 4 can also stably make solder connections between opposing electrodes during mounting.

[0083] The solder volume of the large solder bump 7 can be 1.01 to 15 times the solder volume of the solder base 1, similar to the tall bump. The height of the large solder bump 7, relative to the electrode surface, can be 1.01 to 10 times the height of the low bump, similar to the tall bump.

[0084] Figure 5 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. As shown in the figure, a solder layer 50 may be provided on the electrode 40 of the electrode member 21 as a receiving solder. When a receiving solder is formed on the electrode 40, it is easier to make a more stable solder connection during mounting.

[0085] Figure 6 is a schematic diagram showing a mounting process using a solder bump member according to the present disclosure. In this figure, an electrode member 22 is used, which has a solder protrusion 2 on the receiving solder side of the electrode member 21 shown in Figure 5. Since the solder layer 50, which is the receiving solder, corresponds to the solder base 1, the electrode member 22 can also be said to be a solder bump member according to the present disclosure. In this case, a general solder bump member 13 can be used facing the electrode member 22. As shown in Figure 6, the solder bump member itself may be warped.

[0086] The above explanation of the mounting precursor was based on the example of the case where the tall bump has the shape A described above, but the shape of the tall bump is not limited to this and may also be shape B.

[0087] <Method for manufacturing a mounting body> The method for manufacturing a mounting body (semiconductor mounting body) comprises the steps of: melting solder bumps by heating the above-mentioned mounting precursor; and obtaining a mounting body in which the electrodes of the solder bump-attached member and the electrodes of the electrode-attached member are electrically connected via solder by cooling the heated mounting precursor.

[0088] The resulting mounting structure exhibits excellent connection reliability, as the solder connections between opposing electrodes are properly maintained even in areas where the distance between opposing electrodes is widened due to the effects of material warping or other factors.

[0089] As explained in Figure 4, the manufacturing method of the mounted assembly may further include a pre-melting step in which only the component with solder bumps is heated to melt the solder bumps before the melting step. The pre-melting step melts the solder base 1 and the solder protrusion 2 together to form a single large solder bump in advance.

[0090] From the viewpoint of achieving more precise electrical connections, the manufacturing method of the mounted assembly may further include a step of applying flux to the surface of the solder bump-equipped member and / or electrode-equipped member before the melting step. Examples of methods for applying flux include spray coating, spin coating, and application by printing press. Depending on the structure of the surface to be coated, the type of flux and the application method can be appropriately combined.

[0091] From the viewpoint of achieving more precise electrical connections, the method for manufacturing the mounting assembly may further include a step of heating the mounting precursor in a reducing atmosphere before the melting step.

[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 was a 10mm x 10mm Si substrate with wiring formed to allow for electrical resistance measurement when the evaluation Si chip was mounted. The evaluation substrate was warped, with the center of the substrate raised and the edges lowered.

[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 20 μm was prepared. The spherical protrusions were arranged in the same configuration as the solder bumps in the peripheral area of ​​the evaluation Si chip prepared in Step 0. 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 recesses with an aperture diameter of 20 μmΦ (Form 1) at the desired positions.

[0097] Using a squeegee, SnAgCu solder microparticles (manufactured by Mitsui Mining & Smelting Co., Ltd., melting point 217°C, ST-5) 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 150°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 230°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 SnAgCu solder balls in the recesses. The solder ball mounting component can also be called a solder protrusion forming component.

[0099] Furthermore, solder ball mounting members for forms 2 and 3 were obtained using the same method as in steps 1 and 2, except that the opening diameter of the base body was adjusted.

[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 220°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 is an SEM image of the tall bump according to this embodiment, specifically an external view of the tall bump (solder bump with solder ball) obtained in Embodiment 3. From this figure, a hemispherical (spherical crown-shaped) solder base provided on the electrode and a spherical solder protrusion provided on the solder base can be seen. Because the mounting machine was set to a temperature of 220°C, the actual temperature of the surface of the solder ball mounting member was lower than the melting point of SnAgCu solder (217°C), and the solder protrusion 2 maintained its ball shape (Figure 8: Shape A).

[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 tall bumps 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 tall bumps using a laser microscope (LEXT OLS5000-SAF, manufactured by Olympus Corporation). Similarly, the height from the electrode surface of the evaluation Si chip to the top of the solder base was measured, and the height of the solder ball was calculated by taking the difference before and after solder ball mounting. An evaluation Si chip without solder balls was designated as Comparative Example 1. The results are shown in Table 1.

[0104]

[0105] <Implementation Evaluation> The evaluation Si chips are mounted on the evaluation substrate to form daisy-chain circuits in both the full area and peripheral areas. The evaluation Si chips with solder balls already mounted, 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 forms 1 to 3 obtained in steps 1 to 3 and the Cu electrodes 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 in 100 full-area circuits and 100 peripheral circuits to investigate the probability of connection failures 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 connection failures, particularly in the peripheral area, were improved.

[0107]

[0108] (Example 2) <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.

[0109] The evaluation substrate is a 100mm x 100mm resin substrate (FR-4) with wiring formed to allow for electrical resistance measurement when an evaluation Si chip is mounted on it.

[0110] The evaluation Si chip measures 50 mm x 50 mm, with solder bump electrodes measuring Φ80 μm arranged in a square grid at 150 μm intervals in a central 45 mm x 45 mm area. The solder bump electrodes consist of 30 μm high SnAg solder bumps formed on 30 μm high Cu electrodes. The evaluation circuit consists of an outer circuit formed by dividing the outer edge of the chip into eight areas and an inner circuit formed by dividing the inside of the outer circuit into eight areas and forming the wiring. Two 15 mm x 15 mm dummy chips are mounted in parallel on the back side of the evaluation Si chip, and the space between the evaluation Si chip and the dummy chips is sealed with a liquid sealant. Due to the presence of these dummy chips, the edges of the evaluation Si chip are curved upwards toward the back side.

[0111] Step 1: Preparation of a substrate with solder microparticles A substrate having recesses was obtained in the same manner as in Step 1 of Example 1. The arrangement of the recesses was the same as the electrode arrangement corresponding to the outer periphery circuit on the evaluation Si chip. A substrate with solder microparticles was obtained by filling the recesses with SnAgCu solder microparticles using a squeegee in the same manner as in Step 1 of Example 1.

[0112] Step 2: Formation of solder balls Similar to Step 2 of Example 1, the substrate obtained in Step 1 was heated in a formic acid reflow oven to obtain a solder ball mounting member for Form 4, which had SnAgCu solder balls in the recesses.

[0113] <Mounting of solder balls onto solder bumps> Step 3: Mounting solder balls The solder balls were transferred from the solder ball mounting member onto the solder bumps on the surface of the evaluation Si chip in the same manner as in Step 3 of Example 1, except that the thermocompression conditions for mounting solder balls were set to a set temperature of 220°C and a set load of 20N for 60 seconds.

[0114] <Evaluation of Solder Bumps> The same evaluation as in Example 1 was performed. A Si chip without solder balls was used as Comparative Example 2. The results are shown in Table 3.

[0115]

[0116] <Implementation Evaluation> The evaluation Si chip is mounted on the evaluation substrate to form a daisy-chain circuit in both the inner and outer circuit.

[0117] After applying flux to the evaluation Si chip with solder balls of form 4 obtained in steps 1 to 3 and the Cu electrode on the evaluation substrate, the chip was mounted onto the evaluation substrate using a mounting machine by thermocompression at a set temperature of 260°C and a set load of 50N for 10 seconds. Twenty mounted units were prepared, and continuity tests were performed on 160 inner circuits and 160 outer 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 2. The evaluation results are shown in Table 4. In Example 2, it was confirmed that connection failures in the outer circuits, where the effect of chip warping was significant, were improved.

[0118]

[0119] 1...Solder base, 2...Solder protrusion, 3...Base material, 4...Electrode, 5...Solder bump (high bump), 6...Solder bump (low bump), 7...Large solder bump, 10...Member with solder bumps, 11...General member with solder bumps, 12...Member with solder bumps having large solder bumps, 13...General member with solder bumps, 20, 21...Member with electrodes, 22...Member with electrodes (member with solder bumps), 30...Base material, 40...Electrode, 50...Solder layer (receiving solder), 100, 110, 120...Mounting precursor.

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 some of the electrodes, the solder bumps are tall bumps having a solder base formed on the electrode surface and a solder protrusion formed on the surface of the solder base, and in the remaining electrodes, the solder bumps are short bumps having a solder base formed on the electrode surface.

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 solder volume of the tall bump is 1.01 times or more and 15 times or less the solder volume of the solder base.

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

5. 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.

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

7. A mounting precursor comprising a solder bump member according to any one of claims 1 to 6 and an electrode member arranged opposite each other.

8. A mounting precursor comprising a solder bump member having low bumps and an electrode member, wherein the solder base and the solder protrusion are fused together, and the solder bump member having low bumps is oriented opposite each other.

9. A method for manufacturing a mounting body, comprising the steps of: heating the mounting precursor described in claim 7 to melt the solder bumps; and cooling the heated mounting precursor to obtain a mounting body in which the electrodes of the solder bump member and the electrodes of the electrode member are electrically connected via solder.

10. The manufacturing method according to claim 9, further comprising a pre-melting step of heating only the member with solder bumps to melt the solder bumps before the melting step.

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