Wiring board and method for manufacturing a wiring board

Abstract

To provide a wiring substrate and a method for manufacturing the wiring substrate with high electrical connection reliability against destruction and deformation of pillars consisting of metal posts against stress inside the rewiring layer due to warping and other deformation during heating of semiconductor devices in wiring substrates for FCBGA, which are electrically connected to semiconductor elements.SOLUTION: A wiring substrate according to the present embodiment has a structure in which land pattern 2, solder resist 13 that does not cover the land pattern on the wiring substrate 1 for FCBGA that serves as a connection terminal with semiconductor elements, and metal post 3 are arranged on the land pattern 2, and the connection portion 5A of metal post 3 and land pattern 2 has a gently curved surface shape with an approximate curvature radius and the tip and side of metal post 3 are covered with solder 10.SELECTED DRAWING: Figure 4I

Description

Technical Field

[0001] The present invention relates to a wiring board for FCBGA provided with metal posts and a method for manufacturing the wiring board.

Background Art

[0002] Recently, with the development of the electronics industry, there has been a demand for higher performance, higher functionality, and miniaturization of electronic components. As a result, there has been a rapid increase in the demand for high integration, thinning, and fine circuit patterning in surface-mounted component substrates such as SIP (System in package) and 3D packages. In particular, in the surface mounting technology of electronic components on a substrate, since a semiconductor chip must be connected to a mother board, the flip chip bonding method is often used.

[0003] The flip chip bonding method forms external connection terminals (i.e., posts) of several tens of μm to several hundreds of μm in a semiconductor chip using a material such as gold, solder, or other metals, covers the semiconductor element on which the posts are formed (flip), and mounts it so that the surface faces the substrate side. Furthermore, a method of connecting a semiconductor element to a mother board via a wiring board (wiring board for FCBGA) has been adopted with the miniaturization and large size of semiconductor chips.

[0004] The flip chip bonding method has evolved into a structure using metal posts in order to cope with the narrowing of the pitch of the external connection terminals of semiconductor elements. The use of post-post bonding using metal posts not only ensures the distance between the semiconductor element and the FCBGA substrate, and addresses the narrowing of the pitch by eliminating shorts between adjacent metal posts, but is also attracting attention as an alternative that facilitates the filling of underfill resin and improves heat dissipation performance.

[0005] Conventionally, the connection terminal portion of a wiring board for FCBGAs to semiconductor elements is formed by covering a land pattern made of a conductive material such as copper with an insulating resin solder resist that leaves openings in the areas that will serve as electrical connections, and then forming a metal material such as solder to a height of several tens of micrometers in these openings. In recent years, in order to accommodate the narrow pitch of external connection terminals of 100 μm or less, a structure in which metal posts are formed instead of solder on the connection terminals of FCBGA wiring boards has been disclosed in Patent Documents 1 and 2.

[0006] In the structure for forming metal posts on an FCBGA wiring board, as shown in Figure 3, metal posts with a diameter of several tens of micrometers and a height of several tens of micrometers are formed in the openings of the solder resist, and the semiconductor device is formed by connecting these metal posts to the metal posts on the semiconductor element side via solder posts formed on the metal posts, while maintaining a certain distance between them. Generally, the openings in the solder resist of FCBGA wiring boards are formed in a tapered shape, and the metal posts are electrically connected to the underlying land pattern at the bottom of the solder resist opening, and stand upright by ensuring adhesion between the inclined portion of the solder resist opening and the surface layer. In semiconductor devices integrated with semiconductor elements, thermal deformation such as expansion, contraction, and warping caused by heat generation and thermal processes of the semiconductor elements leads to stress concentration in weaker parts of the connection terminals.

[0007] In conventional FCBGA wiring boards, stress was relieved by the solder joints formed in the solder resist openings. However, in structures where metal posts are formed on FCBGA wiring boards, as the pitch narrows and the diameter of the connection part also decreases, the force due to deformation caused by the total height of the metal posts on the semiconductor element side and the FCBGA wiring board side tends to concentrate as stress on the top and bottom surfaces of the solder resist openings, leading to reliability problems such as electrical disconnection due to metal post failure and increased resistance. Furthermore, the lower adhesion of the seed layer between the inclined portion of the solder resist opening and the surface layer compared to the adhesion between the insulating resin of the inner layer and the seed layer also contributes to the reduced reliability. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 5011329 [Patent Document 2] Japanese Patent Publication No. 2020-188139 [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention was made to solve the above-mentioned problems, and the object of this invention is to provide a wiring board for FCBGA with highly reliable electrical connection of metal posts and a method for manufacturing the same. Another object of the present invention is to provide a wiring board for FCBGA and a method for manufacturing the same that can prevent oxidation and corrosion of metal posts. [Means for solving the problem]

[0010] One embodiment of a wiring board for solving the above problems is as follows: on the mounting surface of the wiring board to be joined to a semiconductor element, a land pattern connected to a connection terminal portion with the semiconductor element is arranged on an insulating resin, the opening pattern of the solder resist covering the insulating resin is arranged so as not to cover the land pattern, a metal post is formed on the land pattern with a diameter smaller than the diameter of the land pattern, the diameter of the metal post is formed to be thicker at the bottom than at the top, the diameter gradually increases towards the connection portion of the metal post with the land pattern, a dome-shaped solder post is formed at the tip of the metal post, the side of the metal post and the connection portion with the land pattern are covered with solder, and an alloy layer of solder is formed on the surface of the metal post.

[0011] Furthermore, the height of the dome-shaped solder posts on the above-mentioned wiring board after reflow soldering may be between 50% and 150% of the height of the metal posts. Furthermore, the wiring board may have a gently curved surface (R-shape) at the connection point between the metal post and the land pattern, with a radius of curvature of 2 μm or more. Furthermore, the thickness of the solder covering the sides of the metal posts and the land patterns on the above-mentioned wiring board may be 5 μm or less. Furthermore, the solder used in the above-mentioned wiring board may be an alloy material consisting of tin, Ag, and Cu. Furthermore, the above-mentioned wiring board may have land patterns and metal posts that are primarily composed of copper.

[0012] Furthermore, one embodiment of a method for forming a wiring substrate to solve the above problems includes the following steps 1) to 7) for a substrate having a land pattern electrically connected to the underlying wiring on an insulating resin, and a solder resist laminated with an aperture diameter wider than the diameter of the land pattern. 1) A step of forming a seed layer by electroless plating or sputtering. 2) A step of covering the seed layer with a photosensitive resin and providing an opening pattern in the photosensitive resin at the position where the metal post will be formed. 3) A step of forming a metal post in the opening of the above photosensitive resin by electrolytic copper plating, 4) A step of filling the openings of the photosensitive resin with solder. 5) A process in which the wiring board having the solder filled in the above-mentioned opening is heat-treated at the melting temperature of the solder paste, melting the solder posts into a dome shape and covering the sides and bottom of the metal posts with solder. 6) Steps to peel off the photosensitive resin and expose the metal post and solder post. 7) A process of heat-treating the wiring board on which the metal posts and solder posts are formed at the melting temperature of the solder, and remelting the solder posts. [Effects of the Invention]

[0013] According to the present invention, in a wiring board for FCBGA on which a semiconductor element is mounted, having a structure of a metal post that is strong against physical forces, it is possible to improve the electrical connection reliability between electrodes by solder bonding and the insulation reliability between adjacent electrodes. Therefore, it becomes possible to provide a wiring board for FCBGA with no disconnection or short circuit and high electrical connection reliability and a method for manufacturing the same.

Brief Description of the Drawings

[0014] [Figure 1A] It is a cross-sectional view showing one form of the structure including the metal post of the wiring board of the present invention. [Figure 1B] It is a cross-sectional view showing one form of the structure including the metal post of the wiring board of the present invention. [Figure 2A] It is a plan view showing one form of the arrangement of the opening of the solder resist of the wiring board and the metal post. [Figure 2B-1] It is a plan view showing one form of the arrangement of the opening of the solder resist of the wiring board and the metal post. [Figure 2B-2] It is a cross-sectional view showing one form of the arrangement of the opening of the solder resist of the wiring board and the metal post. [Figure 2C-1] It is a cross-sectional view showing one form of the curved surface shape of the connection portion between the land pattern of the metal post of the wiring board. [Figure 2C-2] It is a cross-sectional view showing one form of the curved surface shape of the connection portion between the land pattern of the metal post of the wiring board. [Figure 3] It is a cross-sectional view showing a semiconductor device in which a wiring board and a semiconductor element are mounted. [Figure 4A] It is a cross-sectional view showing a state in which a land pattern and a solder resist of the wiring board are formed. [Figure 4B] It is a cross-sectional view showing a state in which a seed layer for forming a metal post is formed on the surface of the wiring board. [Figure 4C-1] It is a cross-sectional view showing a state in which a photosensitive resin for forming a metal post is patterned. [Figure 4C-2]This is a magnified cross-sectional view showing the patterned shape of a photosensitive resin used to form a metal post. [Figure 4D] This is a cross-sectional view showing a metal post formed in the opening of a photosensitive resin. [Figure 4E] This is a cross-sectional view showing the state in which solder has been filled into the opening of the photosensitive resin. [Figure 4F-1] This is a cross-sectional view showing the state after solder has been melted by heat treatment to form a solder post. [Figure 4F-2] This is a cross-sectional view showing an enlarged version of Figure 4F-1. [Figure 4G] This is a cross-sectional view showing the state after the photosensitive resin has been peeled off. [Figure 4H] This is a cross-sectional view showing the state after the seed layer other than the metal post formation location has been dissolved and removed. [Figure 4I] This is a cross-sectional view showing the state after the second heat treatment, where the solder post has been remelted and covered the sides and base of the metal post. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of the thickness of each layer, etc., may differ from reality. Therefore, specific thicknesses and dimensions should be determined by referring to the following description. Furthermore, it should be noted that there are parts in the drawings where the relationships and ratios of dimensions differ from each other.

[0016] Furthermore, the embodiments described below illustrate devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0017] An example of the manufacturing process for a wiring board using a support substrate according to one embodiment of the present invention will be explained using Figures 1 to 4. First, as shown in Figure 1, an insulating resin 11 is formed on an inner layer wiring substrate 1, with an opening in the inner layer wiring pattern 14 of the inner layer substrate 1. Then, a land pattern 2 electrically connected to the inner layer wiring pattern 14, and metal posts 3 and solder posts 5 are laminated on the land pattern 2 to form a wiring substrate. The openings 17 in the solder resist on the insulating resin 11 do not cover the land pattern 2.

[0018] The diameter of the metal post 3 is smaller than the diameter of the land pattern 2, and the diameter d of the bottom of the metal post 3 is smaller than the diameter of the land pattern 2. b The upper diameter d of the metal post 3 t It is thicker than the previous one, and its structure gradually thickens towards the joint with the land pattern 2 mentioned above. The diameter of the bottom of the metal post 3 may be the same as the diameter of the land pattern 2. Furthermore, the solder post 5 at the tip of the metal post 3 is melted by heat treatment and forms a dome shape. Furthermore, the connection portion 5A between the side of the metal post 3 and the land pattern 2 is covered with solder. The solder covering the connection portion 5A between the metal post 3 and the land pattern 2 may also cover the side of the land pattern 2.

[0019] The solder resist 13 formed on the insulating resin 11 has openings so as not to cover the land pattern 2, and the surface of the underlying insulating resin 11 is visible through the openings in the solder resist, as shown in Figure 2. The openings in the solder resist can be positioned as shown in Figure 2-A, leaving the solder resist pattern between the land patterns 2, or as shown in Figure 2-B, opening up the entire solder resist in the area where the semiconductor elements 15 overlap.

[0020] In conventional wiring board structures for FCBGAs, the edges of the land pattern 2 are covered with solder resist, resulting in a structure where the upper surface of the land pattern 2 is lower than the solder resist surface. Although a structure in which metal posts are formed on top of this has been proposed, this causes constriction at the bottom of the metal post due to openings in the solder resist. This leads to stress concentration at this constriction during post-to-post bonding with semiconductor elements, and the low adhesion between the solder resist and the seed layer of the metal post can cause the metal post to break. Therefore, it is desirable that there is no solder resist 13 at the bottom of the metal post 3. Furthermore, the total height of the land pattern 2 and the metal post 3 from the surface of the insulating resin 11 may be higher or lower than the thickness of the solder resist 13 formed on the insulating resin 11.

[0021] When the total height of the land pattern 2 and the metal post 3 is higher, the occurrence of defects such as voids can be suppressed when connecting the metal post 20 formed on the semiconductor element 15 via solder and filling with underfill 16. Furthermore, if the total height of the land pattern 2 and the metal post 3 is lower, the land pattern 2 and the solder resist 13 do not overlap, and therefore, especially in the structure shown in Figure 2-B, the solder resist 13 does not obstruct the proximity of the semiconductor element 15 to the metal post 20, allowing for mounting.

[0022] The solder post 5 on the metal post 3 can be formed by solder printing or electroplating, and a dome shape can be obtained by reflow processing at the temperature at which the solder melts. As a solder material, Sn-Ag-Cu alloy can be melted at a low temperature of around 240°C, and can easily form an alloy with the copper of the metal post 3. Other alloys can also be used as solder, and alloys such as Sn-Pb, Pb-Sn-Sb, Sn-Sb, Sn-Pb-Bi, Bi-Sn, Sn-Cu, Sn-Pb-Cu, Sn-In, Sn-Ag, and Sn-Pb-Ag can be used as appropriate. The height of the dome-shaped solder post described above should preferably be 50 to 150% of the height of the metal post 3 described above. The height of the metal post 3 varies depending on the arrangement and density of the pattern, resulting in variations in the electroplating height. In this embodiment, the height of the metal post can be determined from the design value or the average value of multiple points.

[0023] In this embodiment, the wiring board 22 is formed with warping of the wiring board itself and variations in the height of the metal posts. As shown in Figure 3, the solder posts 5 are crushed to ensure electrical connection in order to avoid connection failures when mounting with the metal posts 20 on the semiconductor element 15 side. If the height of the solder posts 3 is less than 50%, it cannot absorb the warping of the wiring board itself and the variations in the height of the metal posts 3, resulting in many connection failures with the metal posts 20 on the semiconductor element 15 side. Furthermore, if the amount exceeds 150%, the solder that is crushed and protrudes laterally between the semiconductor element 15 and the metal post 20 will connect with nearby metal posts, resulting in a high incidence of short-circuit failures.

[0024] Height can be measured using methods such as laser microscopy, focused microscopy, and image analysis of cross-sections. Figures 2C-1 and 2C-2 show that the connection portion 5A of the metal post with the land pattern has a gently curved shape (R shape). The metal post 3 is covered with solder from the solder post 5 to the solder side 6 and solder base 7, and the figures describe a structure in which the base of the metal post 3 and the solder base 7 have a gently curved shape, and a structure in which only the solder base 7 has a gently curved shape.

[0025] Furthermore, the diameter of the seed layer 12 is not specifically defined. Although Figure 2C shows a structure equivalent to that of the metal post 3, it may also be a structure with a larger diameter than the base of the metal post 3, or a structure equivalent to that of the solder base 7. In a structure where a semiconductor element 15 is mounted on a metal post 20 and the gap between it and the wiring board of this embodiment is filled with underfill 16, an external force is applied due to thermal deformation to a weak point between the semiconductor element and the wiring board of this embodiment. In the post-post connection of this embodiment, stress concentrates at the connection point 5A between the land pattern 2 and the metal post 3. By making this stress-concentrating area a gently curved shape, it is possible to avoid the force concentrating at a single point and causing structural fracture.

[0026] If we represent the value of the radius of curvature R that approximates the value formed by the curve of this curved structure, then this fracture prevention effect can be obtained if the curved shape is greater than R = 2 μm. Furthermore, it is desirable that the thickness of the solder on the solder side surface 6 and the solder base 7 be 5 μm or less. By covering the metal post 3 with solder and forming an alloy layer with the solder, it is possible to prevent the solder on the upper solder post from melting and excessively flowing down during subsequent heating processes.

[0027] By forming an alloy layer with the solder as described above, for example, a Cu3Sn alloy is more brittle than a Cu6Sn5 alloy, and by forming multiple types of alloys with different hardnesses in a granular form, it is possible to prevent the brittle parts within the solder alloy layer from being continuously exposed on the outermost surface of the alloy layer, and the alloy layer covers the surface of the metal post 3, thereby improving the reliability of the joint. The land patterns 2 and metal posts 3 of the wiring board 22 are formed from a copper-based metal commonly used in wiring boards for FCBGA. Here, "copper-based metal" means that copper is the primary component in terms of quantity.

[0028] The metal post can be formed by electroplating. As shown in Figure 4D, an opening is made in the photosensitive resin 8 to form the metal post 3, and the metal post 3 is formed by electroplating. In this case, the shape of the base of the metal post 3 can be controlled by the cross-sectional shape of the opening 9 in the photosensitive resin 8. As shown in Figure 4C-2, by forming the bottom of the opening 9 in contact with the land pattern 2 of the photosensitive resin 8 to be gently wider than the top of the opening 9 in the photosensitive resin 8, it is possible to make the bottom of the metal post 3 formed in this opening 9 a gently curved shape.

[0029] Since copper-based metals are prone to forming oxide films on their surfaces due to exposure to air, heat treatment, or chemical treatment, coating them with the solder posts 5, solder sides 6, and solder bases 7 described in this embodiment and forming an alloy layer with the solder can prevent deterioration due to oxidation of the land pattern 2 and the surface of the metal posts 3.

[0030] The manufacturing method of the wiring board of this embodiment will be described with reference to Figures 4A to 4I. Note that the explanatory diagrams show one embodiment of the invention and are not limited to the structures shown in the figures. As shown in Figure 4A, the substrate has land patterns 2 electrically connected to the wiring of the lower layer on an insulating resin 11, and solder resist 13 is placed away from the land patterns 3. If the solder resist 13 is placed excluding all areas where the semiconductor elements 15 overlap, as shown in Figure 2-B, the solder resist 13 will not be shown in the enlarged view of a portion of the wiring board, as shown in Figure 1A.

[0031] Next, as shown in Figure 4B, a seed layer 12 is formed using an electroless plating film or a sputtered film. The seed layer 12 acts as a power supply layer for the electrolytic plating of the metal post 3. For the electroless plating film, metals such as Cu, Pd, Al, Sn, Ni, and Cr can be used. Sputtered films can be made from materials such as Cu, Ni, Al, Ti, Cr, Mo, W, Ta, Au, Ir, Ru, Pd, Pt, AlSi, AlSiCu, AiCu, NIFe, ITO, IZO, AZO, ZnO, PZT, TiN, Cu3N4, Cu alloys, or combinations of these materials. In this embodiment, electroless copper plating is used, taking into consideration electrical properties, ease of manufacturing, and cost. The thickness of the electroless copper plating is preferably 1 μm or less as the power supply layer for electroplating. In one embodiment of the present invention, Cu:300 nm is formed.

[0032] Next, as shown in Figure 4C, the seed layer 12 is covered with a photosensitive resin 8, and an opening 9 is formed in the photosensitive resin 8 at the position where the metal post is to be formed. The photosensitive resin 8 can be a liquid resist or a dry film formed into a form. The photosensitive resin 8 needs to be several tens of micrometers thick in order to form metal posts and solder posts in the openings 9. In one embodiment of the present invention, a dry film is used. Furthermore, while both negative and positive resists can be used, in one embodiment of the present invention, an acrylic-based negative dry film resist is used because positive resists are photocurable resins and offer stability during the process and are ultimately peelable.

[0033] Next, as shown in Figure 4D, a metal post 3 is formed in the opening 9 of the photosensitive resin 8 by electrolytic copper plating. The metal post 3 is made of a metal mainly composed of copper, and its height and diameter can be selected according to the product design and are not specifically defined. However, for stable height control, it is desirable to form the metal post 3 to be lower than the photosensitive resin 8. At this time, it is also possible to form a surface treatment layer 4 on the metal post 3 at the opening 9 of the photosensitive resin 8. Whether or not to form the surface treatment layer 4 can be selected depending on the product design, and the top surface or side surface of the metal post 3 can be selected for formation.

[0034] The opening 9 of the photosensitive resin 8 can be formed in a tapered shape, widening towards the top in cross-sectional view. The electroplating grows along the wall surface of the opening 9 of the photosensitive resin 8, but it does not completely adhere to the wall surface of the opening 9 of the photosensitive resin 8. Inside the opening 9, a gap of 1 to 5 μm in width is created between the metal post 3 and the insulating resin 12. If this gap is wide enough, the surface treatment layer 4 can be formed not only on the top surface of the metal post 3 but also on the sides. The surface treatment layer 4 can be a single or multiple layer structure of nickel, palladium, gold, or tin, and the material can be selected from the materials listed.

[0035] Electrolytic plating and electroless plating methods can be used to form the surface treatment layer 4. Next, as shown in Figure 4E, solder 10 is laminated onto the metal post 3 at the opening 9 of the photosensitive resin 8. The solder 10 can be laminated using either a method of filling the opening 9 with solder paste using a squeegee, or by electroplating to deposit the solder 10.

[0036] In the method of filling with solder paste, the opening 9 of the photosensitive resin 8 is used as a mask pattern, and the solder paste placed on the photosensitive resin 8 is scraped with a squeegee and pushed into the opening 9 to fill it. In the electroplating method, it is possible to deposit solder 10 by supplying power from the seed layer 12 used when forming the metal post 3. In either construction method, by forming the solder layer height lower than the height of the opening 9 in the photosensitive resin 8, it becomes possible to control the combined height of the metal post 3 and the solder post 5.

[0037] Next, as shown in Figure 4F-1, the wiring board having solder 10 filled in the opening 9 of the photosensitive resin 8 is heat-treated at the melting temperature of the solder 10, so that the molten solder 10 can form dome-shaped solder posts 5 due to surface tension. The melting temperature of solder varies depending on its material composition. In one embodiment of the invention, an alloy material of SnAgCu was used, and the melting temperature was controlled to 250°C.

[0038] As shown in Figure 4F-2, the photosensitive resin 8 shrinks and deforms when heated at the melting temperature of the solder material, so that the gap between the photosensitive resin 8 and the metal post 3 becomes wider than when the solder 10 is laminated. In the process of melting the solder 10, the molten solder 10 enters the gap between the photopolymer resin 12 and the metal post 3, making it possible to form a solder surface 6 on the side surface of the metal post.

[0039] Next, as shown in Figure 4G, the photosensitive resin 8 is peeled off with a stripping solution to obtain a structure that exposes the metal post and the solder post. While there are no specific requirements for the stripping solution, any solution that can strip the photosensitive resin 8 and causes minimal damage to the metal post or solder material should be selected. For example, an alkaline amine-based aqueous solution can be used. Next, as shown in Figure 4H, the seed layer 12 is dissolved and removed with an etching solution to obtain a structure in which the metal post 3 and the land pattern 2 are formed in isolation from those in close proximity. There are no specific requirements for the etching solution, but you should choose one that causes minimal damage to the solder material.

[0040] Next, as shown in Figure 4I, the wiring board on which the metal posts and solder posts are formed is heat-treated again at the melting temperature of the solder material, the solder material is melted again, and the grain boundaries on the surface of the solder posts 5, which have been roughened by the peeling of the photosensitive resin 8 and etching of the seed layer 12, can be smoothed out. Furthermore, as shown in Figure 4I, the side etched portion of the interface between the metal post 3 and the land pattern 2, which is formed by etching away the seed layer 12, can be covered with the solder base 7. This allows for the formation of a continuous curved shape without constrictions at the base between the metal post 3 and the land pattern 2, thereby improving the strength against stress. By controlling the dimensions and temperature of the base of the land pattern 2 and the metal post 3, the remelted solder material may be wetted and spread to the sides of the land pattern 2.

[0041] Furthermore, by performing the etching removal of the seed layer 12 as shown in Figure 4I after remelting the solder, the location of the twisting caused by side etching of the seed layer at the interface between the metal post and the land pattern can be shifted to the solder base 7 position, thereby mitigating the concentration of stress on the constricted portion of the metal post 3. Furthermore, when coining the solder post 5 above the metal post 3 to adjust the combined height of the metal post and the solder post, the gently curved shape of the bottom of the metal post can prevent it from tipping over. The wiring board 22 obtained in this way is mounted with the semiconductor element 15, and the underfill 16 is filled to complete the semiconductor device 23 shown in Figure 3. [Examples]

[0042] To verify the effect in this embodiment, in the structure shown in Figure 2B-2, metal posts 3 made of copper plating are formed at a 100 μm pitch in the process shown in Figures 4A to 4J, with a height / upper diameter of metal post 3 = 20 μmt / Φ40 μm, a land pattern diameter of copper plating Φ60 μm, and a radius of curvature R = 5 μm that approximates the curved shape of the joint between the metal post 3 and the land pattern 2. On top of the above metal post 3, a structure was obtained in which SnAgCu solder was applied to a height of 20 μmt and the solder from the side to the base of the solder to a thickness of 3 μmt.

[0043] The wiring board 22 and semiconductor element 15 obtained in this embodiment were post-post bonded to form a semiconductor device 23, and the connection reliability of the post structure was evaluated. The evaluation method involved checking for fracture at the post-post joints during a temperature cycling test (JESD22-A104: -55℃⇔125℃, 15℃ / min, 1000 cycles). The wiring board 22 obtained in this embodiment has a structure in which metal posts 3 are covered with solder 10, and by forming a solder alloy layer, oxidative degradation of the copper metal posts during the process is avoided, and solder joints are formed between the semiconductor element 15 and the posts, making it possible to obtain a semiconductor device 23.

[0044] Furthermore, with the semiconductor device 23 obtained in this embodiment, the height of the solder 10 compensates for the waviness of the wiring board 22 and the height variations of the metal posts 3, and it was possible to obtain the semiconductor device 23 without any problems such as disconnections in the solder joints between all posts inside one of the semiconductor devices 23 or joints between adjacent posts.

[0045] Furthermore, after the above temperature cycling test, slight cracks were observed within the solder at the interface between land pattern 2 and inner layer wiring pattern 14, and at the interface between metal post 3 and metal post 20 on the semiconductor element side. Thus, this embodiment makes it possible to control the height variation of post-post connections between the wiring board 22 and the semiconductor element 15, thereby avoiding stress-induced failure and obtaining a semiconductor device 23 with high electrical connection reliability.

[0046] (Comparative example) The materials, methods, and configuration used are the same as in the example. A land pattern 2 with a diameter of Φ60 μm made of copper plating is covered with solder resist 13, and a Φ30 μm opening is formed for bonding with the metal posts. Metal posts 3 are then formed on top of this at a 100 μm pitch with a height / top diameter of 20 μm / Φ40 μm. The photosensitive resin 8 is peeled off, and the seed layer 12 is etched to form a wiring board having the metal posts 3.

[0047] On the metal post 3 of the above-mentioned wiring board, flux was printed using a metal mask, and SnAgCu solder balls were sprinkled in and heat-melted to form a solder post with a height of 20 μmt. By forming it in the process of sprinkling in solder balls and heat-melting it, a structure in which the sides of the metal post 3 are not covered with solder 10 will be explained as a comparative example. The resulting wiring board 22 and semiconductor element 15 were post-post bonded to form a semiconductor device 23, and the connection reliability of the post structure was evaluated.

[0048] The evaluation method involved checking for fracture at the post-post joints during a temperature cycling test (JESD22-A104: -55℃⇔125℃, 15℃ / min, 1000 cycles). In the comparative example, flux printing and solder ball placement were performed using a metal mask on top of the metal post 3. However, due to expansion and contraction caused by the wiring board manufacturing process and deviations in the dimensional accuracy of the metal mask, alignment was difficult, resulting in variations in the height of the solder post 5 due to variations in the number of solder balls placed.

[0049] The wiring board 22 has a structure in which the metal posts 3 are covered only on the top with solder posts 10. During the mounting process, an oxide film is formed on the sides of the copper metal posts, resulting in a state where the post portion of the semiconductor device 23 has parts that are prone to deterioration over time. Furthermore, in the comparative example semiconductor device 23, numerous defects were observed, such as disconnections in solder joints between posts of the semiconductor device 23 and joints between adjacent posts, due to variations in the height of the solder posts 5, caused by the waviness of the wiring board 22 and variations in the height of the metal posts 3.

[0050] Furthermore, after the temperature cycling test described above, numerous cracks were observed in the metal post 3 at the point where the solder resist 13 was twisted near the connection point 5A between the land pattern 2 and the metal post 3, as well as cracks at the interface between the solder resist 13 and the metal post 3. Analysis revealed that the constricted portion of the solder resist 13 is a location where stress tends to concentrate, due to the structural concentration of external forces associated with the thermal deformation of the semiconductor device 23. Furthermore, the adhesion force between the solder resist 13 and the seed layer 12 was weak, at 100 mN, as measured by a Char test of the metal post 3 formed on the solder resist 13, and delamination occurred at the interface between the solder resist 13 and the seed layer 12.

[0051] Thus, depending on the configuration of the comparative example, it is difficult to control the height variation of the post-post connection between the wiring board 22 and the semiconductor element 15, and stress-induced fracture occurs due to the post structure, resulting in a semiconductor device 23 with low electrical connection reliability. The above embodiment is merely an example, and of course, other specific structural details can be modified as appropriate. The present invention relates to a wiring board equipped with metal posts for connecting to semiconductor elements, and can be used in semiconductor devices by mounting the wiring board and semiconductor elements on it. [Explanation of symbols]

[0052] 1. Inner layer wiring board 2. Land pattern (FCBGA wiring board) 3. Metal posts (FCBGA wiring board) 4. Surface treatment layer 5 solder posts 5A Connection 6. Solder side 7 Handa Foothills 8 Photosensitive resin 9 Opening (photosensitive resin) 10 Solder 11 Insulating resin 12 Seed layer (for metal posts) 13 Solder Resist 14. Inner layer wiring pattern 15 Semiconductor devices 16 Underfill 17. Opening (solder resist) 18. Seed Layer 2 (Land Pattern) 19. Land Pattern (Semiconductor Device) 20 Metal posts (semiconductor devices) 21 Solder resist (semiconductor device) 22 Wiring board 23 Semiconductor equipment

Claims

1. On the mounting surface of the wiring substrate that is joined to the semiconductor element, A land pattern is arranged on the insulating resin that connects to the connection terminal portion with the semiconductor element, The opening pattern of the solder resist coated with the insulating resin is arranged so as not to come into contact with the land pattern. A metal post is formed on the land pattern with a diameter smaller than the diameter of the land pattern, and the diameter of the metal post is wider at the bottom than at the top, and the diameter gradually increases towards the connection point between the metal post and the land pattern. The metal post has a dome-shaped solder post formed at its tip, the solder post covers the connection between the side of the metal post and the land pattern, and an alloy layer of solder is formed on the surface of the metal post. A wiring board characterized in that the thickness of the solder covering the side surface of the metal post and the land pattern is 5 μm or less.

2. The wiring board according to claim 1, characterized in that the height of the dome-shaped solder post after reflow is 50% to 150% of the height of the metal post.

3. The wiring board according to claim 1 or 2, characterized in that the connection portion of the metal post with the land pattern has a gently curved shape with a radius of curvature of 2 μm or more.

4. The wiring board according to any one of claims 1 to 3, characterized in that the solder is made of an alloy material of tin, Ag, and Cu.

5. The wiring board according to any one of claims 1 to 4, characterized in that the land pattern and the metal post are made of a metal mainly composed of copper.

6. On the mounting surface of the wiring substrate that is joined to the semiconductor element, A land pattern is arranged on the insulating resin that connects to the connection terminal portion with the semiconductor element, The opening pattern of the solder resist coated with the insulating resin is arranged so as not to cover the land pattern. A metal post is formed on the land pattern with a diameter smaller than the diameter of the land pattern, and the diameter of the metal post is wider at the bottom than at the top, and the diameter gradually increases towards the connection point between the metal post and the land pattern. The metal post has a dome-shaped solder post formed at its tip, the solder post covers the connection between the side of the metal post and the land pattern, and an alloy layer of solder is formed on the surface of the metal post. A wiring board characterized in that the thickness of the solder covering the side surface of the metal post and the land pattern is 5 μm or less.

7. A method for manufacturing a wiring board according to any one of claims 1 to 6, A method for manufacturing a wiring substrate, characterized by having the following steps 1) to 7) for a substrate having a land pattern electrically connected to the underlying wiring on an insulating resin, and a solder resist laminated on the substrate with an aperture diameter wider than the diameter of the land pattern. 1) Steps to form a seed layer by electroless plating or sputtering. 2) A step of covering the seed layer with a photosensitive resin and providing an opening pattern in the photosensitive resin at the position where the metal post will be formed. 3) A step of forming a metal post in the opening of the photosensitive resin by electrolytic copper plating. 4) A step of filling the opening of the photosensitive resin with solder. 5) A process of heat-treating the wiring board having solder filled in the openings at the melting temperature of the solder paste, melting the solder posts into a dome shape, and covering the sides of the metal posts with solder. 6) Steps to peel off the photosensitive resin and expose the metal post and the solder post. 7) A step of heat-treating the wiring board on which the metal posts and solder posts are formed at the melting temperature of the solder, and remelting the solder posts.

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