JP2023179985A - wiring board - Google Patents

Abstract

To improve mounting quality of a wiring board.SOLUTION: A wiring board 1 of an embodiment includes: an insulator layer 22; a first conductor pad 321 that is formed on a surface 22a of the insulator layer 22; a solder mask layer 4 that is formed on the surface 22a and that has a top surface 4a directed in a direction opposite to the insulator layer 22; and a metal bump 5 that is connected to the first conductor pad 321 and that protrudes from the top surface 4a through the solder mask layer 4. In the metal bump 5, an end surface 5a, which is a surface connected to an electrode E1 of a component E mounted on the wiring board 1, is provided on the side of a part protruded from the solder mask layer 4. The wiring board 1 also includes a protrusion 6 that protrudes from the top surface 4a of the solder mask layer 4 and that prevents proximity less than a predetermined interval between the end surface 5a of the metal bump 5 and the electrode E1.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wiring board.

Patent Document 1 discloses a substrate including metal posts used for mounting semiconductor chips. The metal post protrudes above the solder resist layer, and solder bumps are formed on the side and top surfaces of the metal post.

Japanese Patent Application Publication No. 2010-129996

In the substrate disclosed in Patent Document 1, when a semiconductor chip is mounted, the solder bumps melted on the metal post spread around the metal post and come into contact with the solder bumps on the top or side surface of the adjacent metal post, causing a short circuit failure. There is.

The wiring board of the present invention includes an insulating layer, a first conductor pad formed on the surface of the insulating layer, and a solder resist formed on the surface and having an upper surface facing in a direction opposite to the insulating layer. a metal bump connected to the first conductive pad and protruding from the top surface through the solder resist layer. The metal bump has an end surface, which is a connection surface with an electrode of a component mounted on the wiring board, on a protrusion side from the solder resist layer, and the wiring board further includes a The resist layer includes a protrusion that protrudes from the upper surface of the resist layer and prevents the end surface of the metal bump and the electrode from coming closer to each other than a predetermined distance.

According to the embodiments of the present invention, it is thought that short-circuit failures between electrodes of components mounted on a wiring board are suppressed.

FIG. 1 is a cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. The graph which shows an example of the relationship between the space|interval of the electrode of a component and a metal bump, and the thickness of the layer of the connection material. An enlarged view of part III in FIG. 1. FIG. 2 is a plan view of the wiring board shown in FIG. 1; FIG. 3 is a cross-sectional view showing another example of a protrusion on the wiring board according to the embodiment. FIG. 3 is a cross-sectional view showing another example of a protrusion on a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a wiring board according to an embodiment. FIG. 4 is a cross-sectional view showing another example of the manufacturing process of the wiring board according to the embodiment.

A wiring board according to an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 shows a cross-sectional view of a wiring board 1, which is an example of the wiring board of this embodiment. Note that the wiring board 1 is only an example of the wiring board of this embodiment. For example, the laminated structure of the wiring board of this embodiment and the number of conductive layers and insulating layers included in the wiring board of this embodiment are the same as the laminated structure of the wiring board 1 of FIG. The number of conductive layers and insulating layers is not limited. In addition, in the drawings referred to in the following description, certain parts may be enlarged to make it easier to understand the disclosed embodiments, and each component may differ from the other in terms of size and length. may not be drawn to exact proportions.

As shown in FIG. 1, the wiring board 1 is laminated on a core substrate 10 and two main surfaces (a first surface 10a and a second surface 10b) perpendicular to the thickness direction of the core substrate 10. It includes an insulating layer and a conductive layer. Specifically, the wiring board 1 includes an insulating layer 21 laminated on the first surface 10a of the core board 10, a conductor layer 31 formed on the insulating layer 21, and a conductor layer 31 formed on the insulating layer 21 and the conductor layer 31. The conductor layer 32 includes an insulating layer 22 (first insulating layer) stacked on the insulating layer 22 (first insulating layer) and a conductor layer 32 (first conductor layer) formed on the insulating layer 22. The wiring board 1 in FIG. 1 further includes two insulating layers 23 and two conductor layers 33 that are alternately stacked on the second surface 10b of the core board 10. Via conductors 20 are formed in each of the insulating layers 21 to 23 to connect conductor layers sandwiching the insulating layers 21 to 23, respectively.

The core board 10 includes an insulating layer 11, a conductor layer 12 formed on each of both sides of the insulating layer 11, and a cylindrical through-hole conductor 13 that penetrates the insulating layer 11 and connects the conductor layers 12 on both sides. Contains. The inside of the through-hole conductor 13 is filled with a filler 14 made of epoxy resin or the like.

The wiring board 1 includes first conductor pads 321 formed on the surface 22a of the insulating layer 22. The wiring board 1 in the example of FIG. 1 further includes a second conductor pad 322 formed on the surface 22a of the insulating layer 22. The first conductive pad 321 and the second conductive pad 322 are included in the conductive layer 32. Both the first conductive pad 321 and the second conductive pad 322 are not formed on the surface 22a of the insulating layer 22 as in the example of FIG. It may be embedded within.

Wiring board 1 further includes solder resist layer 4 formed on surface 22 a of insulating layer 22 . The solder resist layer 4 has an upper surface 4a facing in the opposite direction to the insulating layer 22. Solder resist layer 4 covers insulating layer 22 and conductor layer 32. The wiring board 1 in the example of FIG. 1 further includes a solder resist layer 41 that covers the insulating layer 23 and the conductor layer 33.

In the description of the wiring board of the embodiment, the side far from the insulating layer 11 in the thickness direction of the wiring board 1 is also referred to as "upper side", "outer side", or simply "upper" or "outer". . On the other hand, in the thickness direction of the wiring board 1, the side closer to the insulating layer 11 is also referred to as the "lower side", "inside", or simply "lower" or "inner". Further, in each component of the wiring board of the embodiment, the surface facing the opposite side to the insulating layer 11 is also referred to as the "upper surface", and the surface facing the insulating layer 11 side is also referred to as the "lower surface". Note that the thickness direction of the wiring board 1 is also simply referred to as the "Z direction."

Wiring board 1 further includes metal bumps 5. The wiring board 1 in the example of FIG. 1 includes a plurality of metal bumps 5. Each metal bump 5 is formed on the first conductive pad 321 and connected to the first conductive pad 321. The metal bumps 5 penetrate the solder resist layer 4 and protrude from its upper surface 4a. The metal bump 5 has an end surface 5a on the side of the protrusion that protrudes from the solder resist layer 4 as a tip surface on the side of the protrusion. The end surface 5a is a connection surface with the electrode E1 of the component E mounted on the wiring board 1. That is, the component E is mounted on the wiring board 1 in the example of FIG. 1 when the wiring board 1 is used. The metal bump 5 is electrically and mechanically connected to the electrode E1 provided on the component E. The metal bumps 5 have electrical conductivity. Therefore, the first conductor pad 321 and the conductor layer 32 are electrically connected to the electrode E1 of the component E via the metal bump 5. Since the wiring board 1 of the embodiment includes the metal bumps 5, short circuits between the electrodes of mounted components such as the component E are suppressed. In the wiring board 1 of the embodiment, short-circuit failures are further suppressed, as will be described later, compared to conventional wiring boards that simply include conductive bumps.

In the example of FIG. 1, the wiring board 1 further includes a connection layer 7 formed on the end surface 5a of the metal bump 5. By the connection layer 7, the electrode E1 of the component E and the metal bump 5 are electrically connected, and preferably also mechanically connected. The connection layer 7 may be formed of any material capable of at least electrically connecting the electrode E1 and the metal bump 5 in this way. For example, the connection layer 7 connects the electrode E1 and the metal bump 5 by once melting and then solidifying when the component E is mounted on the wiring board 1. The connection layer 7 is formed of, for example, a brazing material made of an arbitrary material such as solder. The solder forming the connection layer 7 contains, for example, tin as a main component, and may also contain silver, copper, bismuth, zinc, and/or indium, or may contain substantially only tin. The connection layer 7 is, for example, an electrolytically plated film containing metals constituting these solders. The connection layer 7 may be a solidified solder obtained by solidifying these solders from a molten state.

Note that the wiring board 1 does not necessarily include the connection layer 7. Instead, a connection layer similar to the connection layer 7 (for example, a connection layer having a cross-sectional shape obtained by vertically inverting the connection layer 7 illustrated in FIG. 1) may be provided on the electrode E1 of the component E. Alternatively, when mounting the component E on the wiring board 1, a bonding material such as the solder described above as the material for the connection layer 7 may be supplied onto the end surface 5a of the metal bump 5.

The wiring board 1 of this embodiment further includes a protrusion 6 protruding from the upper surface 4a of the solder resist layer 4. The protrusion 6 prevents the end surface 5a of the metal bump 5 and the electrode E1 of the component E from coming close to each other below a predetermined distance when the component E is mounted on the wiring board 1. The protrusion 6 is formed to prevent the component E and the metal bump 5 from coming close to each other such that the end surface 5a and the electrode E1 come closer to each other at a distance smaller than a predetermined distance. For example, the protrusion 6 comes into contact with the component E, thereby preventing the end surface 5a of the metal bump 5 and the electrode E1 of the component E from coming close to each other below a predetermined distance. Therefore, the height of the protrusion 6 from the upper surface 4a of the solder resist layer 4 is set such that the closer the end face 5a and the electrode E1 are than the predetermined distance, the more the protrusion 6 comes into contact with the component E that is closer to the metal bump 5. may have.

The "predetermined interval" between the end surface 5a of the metal bump 5 and the electrode E1 of the component E is determined by the volume (V) of the connecting material between the metal bump 5 and the electrode E1, such as the connection layer 7, and the area (S) of the end surface 5a. can be arbitrarily selected depending on. For example, the "predetermined interval" may be (0.5 x V/S) or more, (1.5 x V/S), (0.8 x V/S) or more, (1.2 x V /S). Hereinafter, the "proximity of the end surface 5a and the electrode E1 that is less than a predetermined distance" will also be simply referred to as "excessive proximity".

The protrusion 6, which prevents the end surface 5a of the metal bump 5 from coming too close to the electrode E1 of the component E, supports the component E by leaving at least a gap between the top surface 4a of the solder resist layer 4 and the component E. That is, the protrusion 6 may be a support that supports the component E at a predetermined position in the Z direction further above the upper surface 4a of the solder resist layer 4 on the wiring board 1. Further, the protrusion 6 may also be a spacer that secures a predetermined gap between the component E and the upper surface 4a of the solder resist layer 4 on the wiring board 1.

In this way, in the wiring board 1 including the protrusion 6 that prevents the electrode E1 of the component E from coming too close to the end surface 5a of the metal bump 5, the electrode E1 is prevented from coming too close to the end surface 5a, and the electrode E1 and the end surface 5a An appropriately sized gap can be secured between the two. Therefore, the connecting material between the electrode E1 and the metal bump 5, such as the connecting layer 7, is prevented from remaining in the area sandwiched between the electrode E1 and the end surface 5a of the component E, and from protruding excessively around the area. be able to. That is, it is possible to suppress excessive spread of the conductive connecting material such as the connecting layer 7 from the region sandwiched between the electrode E1 and the end surface 5a in the direction intersecting the Z direction. Therefore, it is possible to prevent short circuits between adjacent electrodes E1 and/or short circuits between adjacent metal bumps 5 and, by extension, between adjacent first conductor pads 321.

When components are mounted on a wiring board that includes conductive bumps for connection to components, such as wiring board 1, if the amount of connection material such as connection layer 7 is less than the appropriate range, the electrodes of the components may An open failure occurs in which the electrical conductor in the wiring board is not electrically connected. The appropriate range of the amount of the connecting material easily changes depending on the warpage of the wiring board, variations in the extent to which the molten connecting material wraps around the side surfaces of the conductive bumps, and the like. Further, when a plurality of conductive bumps are formed, the appropriate range of the amount of the connecting material varies for each conductive bump due to variations in height between the conductive bumps. Therefore, in order to prevent open defects, it may be preferable to supply a larger amount of the connecting material than the median value of the appropriate range. However, if the distance between the conductor in the wiring board and the electrode of the component becomes too close due to various conditions when mounting the component, the amount of connecting material will exceed the relative appropriate range. Short-circuit defects may occur between adjacent electrodes of components.

Regarding this point, in this embodiment, since the protrusion 6 is provided to prevent the electrode E1 of the component E and the end surface 5a of the metal bump 5 from coming too close to each other, the electrode E1, the metal bump 5, and/or the first conductor Short circuits at the pads 321 can be suppressed. Since short-circuit failures are suppressed in this way, the amount of connecting material between electrode E1 and metal bump 5 can be increased with a low risk of short-circuit failures. Therefore, in the wiring board 1, short-circuit defects related to the electrode E1 and the like can be suppressed, and open defects between the electrode E1 and the metal bumps 5 can also be suppressed.

FIG. 2 shows the thickness t of a layer made of a connecting material between the metal bump 5 such as the connection layer 7 in FIG. 1 and the electrode E1 of the component E, and the connection between the end surface 5a of the metal bump 5 and the electrode E1. An example of the relationship between the distance g between the connecting parts of the parts and the wiring board that are connected to each other by the material is shown. In FIG. 2, the straight line L1 indicates the lower limit of the interval g at which short-circuit defects are unlikely to occur for each thickness t shown on the X-axis, and the straight line L2 indicates the lower limit of the interval g at which short-circuit defects are unlikely to occur for each thickness t shown on the X-axis. This shows the upper limit of the distance g that is difficult to maintain. That is, the range from the straight line L1 to the straight line L2 in each X-axis coordinate indicates the appropriate range of the interval g in which short-circuit defects and open defects are unlikely to occur at the thickness t indicated by the X-axis coordinate. In other words, the range from the straight line L2 to the straight line L1 in each Y-axis coordinate indicates the appropriate range of the thickness t of the connecting material layer in which open defects and short-circuit defects are unlikely to occur at the interval g indicated by the Y-axis coordinate. There is. As shown in FIG. 2, the appropriate range of the distance g becomes wider as the thickness t of the connecting material layer increases, that is, as the amount of the connecting material increases.

As described above, in this embodiment, the protrusion 6 suppresses short circuit failures, so the amount of connecting material between the metal bump 5 and the electrode E1 of the component E can be increased. As illustrated in FIG. 2, when the amount of the connecting material is large, the appropriate range of the distance between the connecting parts connected by the connecting material may be widened. Therefore, in this embodiment, for example, by increasing the thickness of the connection layer 7 and increasing the amount of connection material between the metal bump 5 and the electrode E1 of the component E, the distance between the end surface 5a of the metal bump 5 and the electrode E1 is increased. It is thought that it is possible to expand the appropriate range of That is, although the distance between the end surface 5a of the metal bump 5 and the electrode E1 may vary depending on the mounting of the component E, the allowable range of the variation may be widened. Therefore, short-circuit defects related to the electrode E1, metal bumps 5, etc., and open defects between the electrode E1 and the metal bumps 5 can be reduced.

Furthermore, in this embodiment, as described above, the protrusion 6 prevents the electrode E1 of the component E from coming too close to the end surface 5a of the metal bump 5, so that the process capability regarding the thickness of the connection layer 7 can be improved. Sometimes. This point will be explained with continued reference to FIG. As an example, when there is no protrusion 6, the distance g between the electrode E1 of the component E and the end surface 5a of the metal bump 5 varies with a width of Δg0 shown in FIG. 2, and the thickness T0 shown in the figure is set to the target value ( A situation is assumed in which the connection layer 7 is formed as a design value). In that case, the thickness t of the connection layer 7 is changed from the thickness T01 so that an open failure will not occur even if the interval g varies toward a large side, and a short circuit failure will not occur even if the interval g varies toward a small side. It needs to be managed within the range of T02.

When this embodiment including the protrusion 6 is applied to such a situation, first, short circuit failures are suppressed, so that the thickness of the connection layer 7 can be increased. As an example, the connection layer 7 may be formed to have a thickness T1. In that case, the appropriate range of the interval g (distance in the Y-axis direction from the straight line L1 to the straight line L2) in which short-circuit defects and open defects are unlikely to occur is from the appropriate range for the thickness T0 to the appropriate range for the thickness T1 (the interval G11 to The interval G12) is expanded. In this case, for example, a protrusion 6 having a height that can prevent the electrode E1 and the end surface 5a from coming close to each other, which is less than the distance G13, is provided. Note that the interval G13 may be an interval that has an appropriate margin in a larger direction than the interval G11, which is the lower limit of the appropriate range.

On the other hand, it is considered that variations in the distance g between the electrode E1 and the end surface 5a are reduced because variations in the smaller direction are prevented by the protrusions 6. Therefore, if the variation width is Δg1, the thickness t of the connection layer 7 is within a range in which open defects do not occur even if the distance g varies toward a large value, and short circuit defects do not occur even at the distance G13. The thickness can be controlled within the range of T11 to T12. That is, according to the present embodiment, it is possible to widen the control range required for the thickness of the connection layer 7, thereby improving the process capability regarding the thickness of the connection layer 7.

Subsequently, the overall structure and the structure of each part of the wiring board 1 will be explained with reference to FIG. 1 and FIGS. 3 and 4. 3 shows an enlarged view of part III of the wiring board 1 shown in FIG. 1, and FIG. 4 shows a plan view of the wiring board 1. FIG. 1, to which reference will be continued, is a cross-sectional view of the wiring board 1 taken along the line II shown in FIG. Note that in FIG. 3, the component E is depicted at an exemplary fixed position of the component E to the wiring board 1. For example, after the connection layer 7 is melted and re-hardened, the component E is fixed to the wiring board 1 at the position shown in FIG.

The insulating layer 11 and the insulating layers 21 to 23 constituting the wiring board 1 may each be formed using a thermosetting insulating resin such as epoxy resin, bismaleimide triazine resin (BT resin), or phenol resin. The insulating layer 11 and the insulating layers 21 to 23 are made of thermoplastic insulation such as fluororesin, liquid crystal polymer (LCP), fluorinated ethylene (PTFE) resin, polyester (PE) resin, and modified polyimide (MPI) resin, respectively. It may be formed using a synthetic resin. In the example of FIG. 1, the insulating layer 11 includes a reinforcing material (core material) 11a made of, for example, glass fiber or aramid fiber. The insulating layers 21 to 23 may also include a reinforcing material like the reinforcing material 11a included in the insulating layer 11. Each insulating layer may further contain an inorganic filler such as silica or alumina.

The solder resist layers 4 and 41 are each made of, for example, photosensitive epoxy resin or polyimide resin (PI resin). Note that the resins shown here as materials for the insulating layers 11, 21 to 23 and the solder resist layers 4, 41 are merely examples of materials that can form each insulating layer and each solder resist layer. Each insulating layer and each solder resist layer may be formed of any material that can provide insulation between conductor layers included in wiring board 1 and insulation between each conductor layer and an external conductor.

The conductor layer 12, the conductor layers 31 to 33, the through-hole conductor 13, and the via conductor 20 are formed using any metal such as copper or nickel. The conductor layer 12, the conductor layers 31 to 33, the through-hole conductor 13, and the via conductor 20 may be formed of, for example, metal foil such as copper foil, and/or a metal film formed by plating or sputtering. In the example of FIG. 1, the conductor layer 12 has a multilayer structure composed of these metal foils and metal films. The conductor layers 31 to 33, through-hole conductor 13, and via conductor 20 are also shown as having a single layer structure in FIG. 1, but may have a multilayer structure including two or more metal layers. The conductor layer 12 and the conductor layers 31 to 33 may each include an arbitrary conductor pattern. As described above, the conductor layer 32 includes the first conductor pad 321 and the second conductor pad 322.

In the wiring board 1 shown in FIG. 1, the metal bumps 5 formed on the first conductor pads 321 protrude from the upper surface 4a through the through holes 4b formed in the solder resist layer 4. That is, the through hole 4b is provided on the first conductive pad 321, and at least a portion of the upper surface of the first conductive pad 321 is exposed from the solder resist layer 4 through the through hole 4b. A metal bump 5 is formed in the exposed portion, and the inside of the through hole 4b is filled with the metal bump 5. As shown in FIG. 3, the metal bumps 5 are formed on the first conductor pad 321, on the inner wall surface of the solder resist layer 4 exposed inside the through hole 4b, and on the upper surface 4a of the solder resist layer 4. The main body layer 53 is formed on the base layer 52 and the base layer 52 .

The protrusion 6 has a surface 6a facing in the opposite direction to the insulating layer 22, as shown in FIG. The component E may be placed on the surface 6a depending on the thickness of the connection layer 7. Furthermore, the component E may be placed on the surface 6a when the connection layer 7 is melted. The contact between the component E and the surface 6a may prevent the end surface 5a of the metal bump 5 from coming too close to the electrode E1 of the component E. The protrusion 6 in the example of FIGS. 1 and 3 has a flat surface 6a. Since the protrusion 6 has the flat surface 6a, the component E may be stably mounted in an appropriate position, for example, without being significantly tilted relative to the wiring board 1. Note that regarding the surface 6a of the protrusion 6, "flat" means that the surface 6a is not curved in the opposite direction to the insulating layer 22 at a height of 20% or more of the width of the surface 6a. Here, the "width" of the surface 6a is the distance between two farthest points on the outer circumference of the surface 6a.

In the example of FIGS. 1 and 3, the protrusion 6 is connected to the second conductive pad 322 from the upper surface 4a of the solder resist layer 4 through the solder resist layer 4. That is, in the example of FIGS. 1 and 3, the protrusion 6 is formed on the second conductive pad 322. The protrusion 6 passes through a through hole 4c formed in the solder resist layer 4 and projects from the upper surface 4a of the solder resist layer 4. That is, the through hole 4c is provided on the second conductive pad 322, and at least a portion of the upper surface of the second conductive pad 322 is exposed from the solder resist layer 4 through the through hole 4c. A projection 6 is formed on the exposed portion, and a portion of the projection 6 fills the inside of the through hole 4c. As shown in FIG. 3, the protrusion 6 is formed on the second conductor pad 322, on the inner wall surface of the solder resist layer 4 exposed inside the through hole 4c, and on the upper surface 4a of the solder resist layer 4. It includes a base layer 62 and a main body layer 63 formed on the base layer 62.

The base layer 52 and main body layer 53 of the metal bump 5 are formed using any metal such as copper or nickel, similarly to the conductor layers 31 to 33 and the like. In the example of FIG. 3, the base layer 62 and main body layer 63 of the protrusion 6 are also formed using an arbitrary metal such as copper or nickel. The base layer 52 of the metal bump 5 and the base layer 62 of the protrusion 6 may be, for example, an electroless plating film made of a metal such as copper or nickel, or a sputtering film made of an alloy of these metals. Further, the main body layer 53 of the metal bump 5 and the main body layer 63 of the protrusion 6 may be, for example, an electroplated film formed by electrolytic plating using a metal film including the base layer 52 and the base layer 62 as a power supply layer. Note that the material forming the protrusion 6 may be any material that has at least enough rigidity to not be deformed by the weight of the component E, and is not limited to metals such as copper and nickel.

The metal bump 5 illustrated in FIG. 3 and the like further includes a coating layer 51 (first coating layer). The covering layer 51 is formed on the main body layer 53 and covers the upper surface of the main body layer 53. In the example shown in FIG. 3, the upper surface of the coating layer 51 constitutes the end surface 5a of the metal bump 5. Similarly, the protrusion 6 illustrated in FIG. 3 and the like further includes a covering layer 61 (second covering layer). The covering layer 61 is formed on the main body layer 63 and covers the upper surface of the main body layer 63. In an example such as FIG. 3, the upper surface of the covering layer 61 constitutes a surface 6a of the protrusion 6 facing in the opposite direction to the insulating layer 22 (see FIG. 1). The covering layer 51 and the covering layer 61 may be, for example, electroplated films formed by electrolytic plating using a metal film including the base layer 52 and the base layer 62 as a power supply layer, similarly to the main body layer 53 and the main body layer 63. . However, the covering layer 51 and the covering layer 61 are not limited to electroplated films, and may be, for example, electroless plated films or sputtered films.

Examples of materials constituting the covering layer 51 and the covering layer 61 include nickel and gold. The covering layer 51 and the covering layer 61 may be formed of different materials, or may be formed of the same material. By using the same material for forming the covering layer 51 and the covering layer 61, the covering layer 51 and the covering layer 61 may be formed efficiently. The covering layer 51 and the covering layer 61 may be able to slow down the corrosion progress of the body layer 53 and/or the body layer 63, which is made of copper, for example. Furthermore, the covering layer 51 may prevent the constituent material of the connection layer 7 from diffusing into the main body layer 53 . However, the materials of the covering layer 51 and the covering layer 61 are not limited to nickel and gold, but are preferably any material that can have some beneficial effect on the body layer 53, the body layer 63, and/or the connection layer 7. is used.

In the example of FIG. 3 in which the connection layer 7 is provided on the metal bump 5, the protrusion 6 is higher than the surface 7a of the connection layer 7 facing in the opposite direction to the metal bump 5 with respect to the height from the upper surface 4a of the solder resist layer 4. is also low. In the example of FIG. 3 in which the surface 7a is curved so as to be convex in the direction opposite to the solder resist layer 4, the protrusions 6 are at least at the top of the surface 7a with respect to the height from the upper surface 4a of the solder resist layer 4. lower than. Since the height H6 of the protrusion 6 with respect to the upper surface 4a of the solder resist layer 4 is smaller than the height H7 of the surface 7a of the connection layer 7 from the upper surface 4a, the connection layer 7 and the electrode E1 of the component E are brought into substantially reliable contact. be able to.

Furthermore, in the example of FIG. 3, the height of the protrusion 6 from the top surface 4a of the solder resist layer 4 is higher than the end surface 5a of the metal bump 5. Since the height H6 of the protrusion 6 with respect to the upper surface 4a of the solder resist layer 4 is greater than the height H5 of the end surface 5a of the metal bump 5 from the upper surface 4a, there is a distance between the end surface 5a and the electrode E1 of the component E of an appropriate size. It is easy to secure a gap. For example, as in the example of FIG. 3, even when the electrode E1 protrudes from the lower surface Ea that contacts the projection 6 of the component E, it is possible to ensure an appropriately sized gap between the end surface 5a and the electrode E1. be.

Note that the height of the protrusion 6 from the upper surface 4a of the solder resist layer 4 may be the same as or higher than the surface 7a of the connection layer 7. For example, if the electrode E1 largely protrudes from the lower surface Ea of the component E, the electrode E1 may come into contact with the connection layer 7 or the metal bump 5 even if the protrusion 6 is higher than the surface 7a of the connection layer 7. . Further, the height of the protrusion 6 from the upper surface 4a of the solder resist layer 4 may be the same as or lower than the end surface 5a of the metal bump 5. For example, if the connection surface of the electrode E1 is recessed than the lower surface Ea of the component E, even if the protrusion 6 is lower than the end surface 5a of the metal bump 5, there is a gap of an appropriate size between the end surface 5a and the electrode E1. It may be possible to ensure that Alternatively, if the contact portion of the lower surface Ea of the component E with the protrusion 6 protrudes beyond the surrounding lower surface Ea or the surface surface of the electrode E1, an appropriate size may be provided between the end surface 5a and the electrode E1. Sometimes it is possible to secure a gap.

In this way, the height H6 of the protrusion 6 with respect to the upper surface 4a of the solder resist layer 4 is arbitrarily selected. However, as described above, when the height H6 of the protrusion 6 is smaller than the height H7 of the surface 7a of the connection layer 7 and larger than the height H5 of the end surface 5a of the metal bump 5, the mounting of the component E is prevented. There are some advantages in terms of suppressing open defects and short circuit defects. When the height H6 of the protrusion 6 is larger than the height H5 of the end surface 5a of the metal bump 5 and smaller than the height H7 of the connection layer 7, the difference between the height H6 and the height H5 is, for example, The thickness is 30% or more and 70% or less of the thickness T7 of No.7. Both open defects and short circuit defects may be difficult to occur.

As shown in FIG. 4, the wiring board 1 in the example shown in FIG. 1 includes a group of metal bumps 50 made up of a plurality of metal bumps 5. A component E (see FIG. 1) is mounted on a group of metal bumps 50. In the example of FIG. 4, the wiring board 1 includes a plurality of protrusions 6. The plurality of protrusions 6 are provided adjacent to the metal bumps 5, respectively, and surround the group of metal bumps 50 as a whole. Therefore, in the wiring board 1 of the example shown in FIG. 4, it is considered that the component E is stably placed without significant inclination. Further, the spread of the connecting material such as the connecting layer 7 from the area between the metal bump 5 and the electrode E1 of the component E (see FIG. 1) to the surrounding area can be easily suppressed evenly between the metal bumps 5. Conceivable. In this way, the wiring board 1 may include a plurality of protrusions 6, and the plurality of protrusions 6 as a whole may surround one or more metal bumps 5 in plan view. Note that "planar view" means viewing the wiring board of the embodiment from a line of sight parallel to its thickness direction.

Note that the plurality of protrusions 6 included in the wiring board 1 do not have to surround the metal bumps 5 as in the example of FIG. It may also include two protrusions 6, each disposed at a sandwiching position. For example, when a group of metal bumps 50 are arranged in a matrix as in the example of FIG. A pair of protrusions 6 sandwiching the protrusions 50 may be provided.

5A and 5B respectively show a protrusion 6α and a protrusion 6β, which are other examples of protrusions on the wiring board 1 of this embodiment.

The entire protrusion 6α in the example of FIG. 5A is formed on the upper surface 4a of the solder resist layer 4. That is, the protrusion 6α in the example of FIG. 5A does not have a portion that penetrates the solder resist layer 4. Further, the protrusion 6α does not have a multilayer structure including the base layer 62, the main body layer 63, and the covering layer 61 like the protrusion 6 in the example of FIG. 3, but has an integral structure as a whole. The protrusion 6α may be provided on the upper surface 4a of the solder resist layer 4 by any method. For example, the projections 6α may be formed separately from the formation of the metal bumps 5, and may be attached to the upper surface 4a of the already formed solder resist layer 4 using an appropriate adhesive.

Further, the material forming the protrusion 6α may be selected from various materials. For example, the protrusion 6α may be formed of a material different from the material constituting the metal bump 5. The protrusion 6α may be formed of, for example, metal (conductor) such as stainless steel or aluminum, resin (organic insulator) such as epoxy resin or phenol resin, or ceramic (inorganic insulator) such as alumina.

The protrusion 6β in FIG. 5B is formed on the second conductor pad 322 and connected to the second conductor pad 322, like the protrusion 6 in the example of FIG. , a main body layer 63 , and a cover layer 61 . The protrusion 6β in the example of FIG. 5B includes a base portion 6b including the base layer 62, the main body layer 63, and the covering layer 61, and a surface portion 6c formed on the base portion 6b. In the example of FIG. 5B, the base portion 6b including the base layer 62, the main body layer 63, and the covering layer 61 is formed of the same metal as the metal that constitutes the metal bump 5 including the base layer 52, the main body layer 53, and the covering layer 51. has been done. Therefore, the base portion 6b can be formed simultaneously with the formation of the metal bumps 5 by the same formation method as that of the metal bumps 5.

Furthermore, the surface 6ba of the base portion 6b included in the projection 6β on the surface portion 6c side is approximately the same as the end surface 5a of the metal bump 5 with respect to the height from the upper surface 4a of the solder resist layer 4. That is, the height of the base portion 6b with respect to the upper surface 4a of the solder resist layer 4 is approximately the same as the height of the end surface 5a of the metal bump 5 from the upper surface 4a. In the example of FIG. 5B, the height of the surface 6ba of the base portion 6b from the top surface of the second conductor pad 322 is approximately the same as the height of the end surface 5a of the metal bump 5 from the top surface of the first conductor pad 321. Furthermore, the height of the upper surface of the main body layer 63 of the protrusion 6β from the upper surface of the second conductive pad 322 is approximately the same as the height of the upper surface of the main body layer 53 of the metal bump 5 from the upper surface of the first conductive pad 321. Therefore, the main body layer 53 and the main body layer 63 may be formed by electrolytic plating as described above in approximately the same time period. Further, the coating layer 51 of the metal bump 5 and the coating layer 61 of the protrusion 6β may be formed by electrolytic plating in approximately the same time period. Therefore, it is considered that the wiring board 1 can be manufactured efficiently.

The surface portion 6c of the protrusion 6β in the example of FIG. 5B has a melting point higher than that of the constituent material of the connection layer 7 formed on the end surface 5a of the metal bump 5. Since the surface portion 6c has a higher melting point than the connection layer 7, the surface portion 6c remains solid even while the connection layer 7 is melting when the component E (see FIG. 1) is mounted on the wiring board 1. The protrusion 6β including the protrusion 6β can prevent the electrode E1 of the component E (see FIG. 1) from coming too close to the metal bump 5. An example of the material for the surface portion 6c is a solder classified as a so-called high melting point solder. For example, the surface portion 6c is formed of an alloy of gold, tin, antimony, bismuth, zinc, or the like.

In the example of FIG. 5B, the surface 6ca of the surface portion 6c of the protrusion 6β is curved so as to be convex in the direction opposite to the base portion 6b. However, the surface 6ca may be flat like the surface 6a of the protrusion 6 in the example of FIG. In the example of FIG. 5B, the height of the top of the surface 6ca from the top surface 4a of the solder resist layer 4 is approximately the same as the height of the top of the surface 7a of the connection layer 7 from the top surface 4a. However, the height of the surface 6ca from the top surface 4a of the solder resist layer 4 is not limited to the example of FIG. may be greater than the height of the end surface 5a of the metal bump 5. Both open defects and short circuit defects may be difficult to occur.

With reference to FIGS. 6A to 6F, a method for manufacturing the wiring board according to the embodiment will be described, taking as an example the case where the wiring board 1 shown in FIG. 1 is manufactured. First, as shown in FIG. 6A, the core substrate 10 is prepared, and the insulating layer 21, the conductor layer 31, the insulating layer 22, and the conductor layer 32 are formed on the first surface 10a side of the core substrate 10. Two sets of insulating layers 23 and conductive layers 33 are formed on the second surface 10b side of core substrate 10 by alternately forming insulating layers 23 and conductive layers 33.

In preparing the core substrate 10, for example, a double-sided copper-clad laminate including the insulating layer 11 is prepared. Then, a conductor layer 12 including a predetermined conductor pattern is formed on both sides of the insulating layer 11 by a subtractive method or the like, and a through-hole conductor 13 is formed in the insulating layer 11. The cavity of the through-hole conductor 13 is filled with a filler 14 by injecting epoxy resin or the like. In the example of FIG. 6A, the metal film covering both ends of the filling body 14 is formed by electroless plating and electrolytic plating. Therefore, a conductor layer 12 including a metal film covering both ends of the filler 14 is formed on both sides of the insulating layer 11.

The insulating layers 21 to 23 are each formed, for example, by thermocompression bonding a film-like insulating resin. The conductor layers 31 to 33 are each formed using an arbitrary method such as a semi-additive method after forming through holes in the insulating layer 21, the insulating layer 22, or the insulating layer 23 by irradiating laser light, respectively. . The conductor layer 32 is provided with a first conductor pattern 321 and a second conductor pattern 322. Inside the through holes formed in the insulating layers 21 to 23, the via conductors 20 are formed together with the formation of the conductor layers 31 to 33.

As shown in FIG. 6B, a solder resist layer 4 is formed on the insulating layer 22 and the conductor layer 32, and a solder resist layer 41 is formed on the outer insulating layer 23 and the conductor layer 33, respectively. A through hole 4b that exposes the first conductor pad 321 and a through hole 4c that exposes the second conductor pad 322 are formed in the solder resist layer 4. A through hole 41a is formed in the solder resist layer 41 to expose a part of the outer conductor layer 33.

The solder resist layer 4 and the solder resist layer 41 are formed, for example, by forming a resin film containing a photosensitive epoxy resin, polyimide resin, or the like by a method such as spray coating, curtain coating, or lamination. Then, the through holes 4a to 4c are formed by exposure using an exposure mask having an appropriate pattern depending on the formation position of the through holes 4a to 4c, and development.

As shown in FIGS. 6C to 6F, metal bumps 5 and protrusions 6 (see FIG. 6F) are formed on the conductor layer 32. Note that when no processing is performed on the insulating layer 23, conductive layer 33, and solder resist layer 41 shown in FIG. 6B together with the formation of the metal bumps 5 and protrusions 6, the exposed portions of these layers are, for example, , by applying a protective film (not shown) made of a suitable material. In FIGS. 6C to 6F, illustration of a portion below the insulating layer 22 is omitted.

As shown in FIG. 6C, first, the upper surface 4a of the solder resist layer 4, the wall surface of the solder resist layer 4 exposed to the through holes 4b and 4c, the exposed surface of the first conductor pad 321 to the through hole 4b, and the through hole. A metal film 562 is formed on the entire surface of the second conductor pad 322 exposed to the second conductor pad 4c. For example, a metal film 562 made of a metal having appropriate conductivity such as copper or nickel is formed by electroless plating or sputtering. A part of the metal film 562 constitutes the base layer 52 of the metal bump 5 and the base layer 62 of the protrusion 6 (see FIG. 6F), as will be described later.

A plating resist R is formed on the metal film 56, for example, by laminating dry film resists. An opening R1 is formed in the plating resist R by exposure using an exposure mask having an appropriate pattern according to the formation positions of the metal bumps 5 and projections 6 (see FIG. 6F) and development.

As shown in FIG. 6D, a metal film 563 is formed on the metal film 562 exposed in the opening R1 of the plating resist R. For example, the metal film 563 made of a metal having appropriate conductivity, such as copper or nickel, is formed by electrolytic plating in which the metal film 562 is used as a power supply layer. The metal film 563 in each opening R1 constitutes the main body layer 53 of the metal bump 5 and the main body layer 63 of the protrusion 6 (see FIG. 6F), as described later.

In the example of FIG. 6D, a metal film 563 is formed in the opening R1 on the second conductive pad 322, which is thicker than the metal film 563 formed in the opening R1 on the first conductive pad 321. For example, by adjusting the density of the plating current during electrolytic plating, the deposition rate of the plating metal in the opening R1 on the first conductor pad 321 and the deposition rate of the plating metal in the opening R1 on the second conductor pad 322 can be adjusted. be done. By doing so, metal films 563 having mutually different thicknesses can be formed in each opening R1. Alternatively, after completing the formation of the metal film 563 with a desired thickness in the opening R1 on the first metal film 321, a protective film (not shown) made of an appropriate material may be attached to the first conductor pad 321. The opening R1 may be closed. The formation of the metal film 563 within the opening R1 on the second conductor pad 322 may then be continued.

As shown in FIG. 6E, a metal film 561 is further formed on the metal film 563 in each opening R1. For example, the metal film 561 containing a metal such as nickel or gold is formed by electrolytic plating in which the metal film 562 is used as a power supply layer. The metal film 561 may be formed by electroless plating or sputtering. The metal film 561 in each opening R1 constitutes the coating layer 51 of the metal bump 5 and the coating layer 61 of the protrusion 6 (see FIG. 6F), as described later.

A metal film 564 is further formed on the metal film 561 on the first conductor pad 321. For example, the metal film 564 containing a metal such as tin, silver, copper, bismuth, zinc, and/or indium is formed by electrolytic plating in which the metal film 562 is used as a power supply layer. The metal film 564 constitutes the connection layer 7 (see FIG. 6F) provided on the metal bump 5, as described below. Note that when forming the metal film 564, the opening R1 on the second conductor pad 322 is closed by, for example, pasting a protective film (not shown) made of an appropriate material.

After forming the metal film 564, the plating resist R is removed using a suitable solvent. Thereafter, the exposed portion of the metal film 562 due to removal of the plating resist R is removed by quick etching or the like.

As a result, as shown in FIG. 6F, metal bumps 5 and protrusions 6 that are separated from each other are obtained. In the example of FIG. 6F, the metal bump 5 includes a base layer 52 in contact with the first conductor pad 321 and the solder resist layer 4, a body layer 53 formed on the base layer 52 and filling the through hole 4b, and a body layer 53 that is formed on the base layer 52 and fills the through hole 4b. A coating layer 51 that covers the upper surface of 53 is included. A connection layer 7 is provided on the covering layer 51. In the example of FIG. 6F, the protrusion 6 includes a base layer 62 in contact with the second conductor pad 322 and the solder resist layer 4, a main body layer 63 formed on the base layer 62 and filling the through hole 4c, and a main body layer 63 that is formed on the base layer 62 and fills the through hole 4c. A covering layer 61 covering the upper surface of the layer 63 is included. The connection layer 7 is shaped by heat treatment such as reflow at a temperature exceeding the melting point of the material constituting the connection layer 7 so that its upper surface is curved so as to be convex in the direction opposite to the metal bumps 5. Through the above steps, the wiring board 1 of the example shown in FIG. 1 is completed.

Incidentally, the protrusion 6α in the example of FIG. 5A referred to above is formed separately from the metal bump 5 using any conductive material or insulating material, as described above, by attaching a member that will become the protrusion 6α with appropriate adhesive. It can be formed by attaching it to the upper surface 4a of the solder resist layer 4 using an agent.

When the protrusion 6β in the example of FIG. 5B is formed, a metal film 563 of approximately the same thickness is formed in each opening R1 of the plating resist R by a method similar to that described with reference to FIG. 6D. be done. A metal film 561 is formed on the metal film 563 in a manner similar to that described with reference to FIG. 6E. Then, the surface portion 6c of the protrusion 6β (see FIG. 5B) is formed on the metal film 561 in the opening R1 on the second conductor pad 322, for example, by electrolytic plating using the metal film 562 as a power supply layer. The surface portion 6c may be shaped into a shape that curves in the opposite direction to the metal film 561 by heat treatment such as high temperature reflow exceeding the melting point of the constituent material of the surface portion 6c. Thereafter, a metal film 564 is formed as described with reference to FIG. 6E, and a heat treatment such as reflow for shaping the connection layer 7 shown in FIG. 6F may be performed. Alternatively, the surface portion 6c of the protrusion 6β may be formed after the metal film 564 is formed. Then, the connection layer 7 and the surface portion 6c of the protrusion 6β may be shaped simultaneously by heat treatment such as the high-temperature reflow described above.

Further, the surface portion 6c of the protrusion 6β in the example of FIG. 5B may be formed by the method illustrated in FIG. 7. That is, the surface portion 6c may be formed using a metal ball 6d containing an alloy having a melting point higher than that of the connection layer 7, such as gold, tin, antimony, bismuth, and zinc. In the example of FIG. 7, metal layers 563 having the same thickness are formed in each opening R1 by the method described with reference to FIG. 6D. Further, a mask M having an opening M1 is placed on the metal film 564 after the steps from forming the metal film 564 to removing the exposed portion of the metal film 562 by the method described with reference to FIG. 6D. The mask M is positioned such that the opening M1 is located on the base portion 6b of the protrusion 6β. Then, the metal ball 6d is placed on the base portion 6b using a ball placer or the like. Thereafter, the metal ball 6d is melted by heat treatment such as the above-mentioned high-temperature reflow and then solidified, thereby forming the surface portion 6c in the example of FIG. 5B. By using the metal balls 6d, variations in volume of the surface portion 6c may be reduced. Therefore, it may be possible to easily form the protrusion 6b having a desired height.

The wiring board of the embodiment is not limited to the structure illustrated in each drawing and the structure, shape, and material illustrated in this specification. For example, the wiring board of the embodiment may not include the connection layer 7 as described above. The surface 7a of the connection layer 7 may be flat. Further, the metal bump 5 may not include the coating layer 51, and the protrusion 6 may not include the coating layer 61 either. The wiring board of the embodiment may be a so-called coreless board that does not include the core board 10. Furthermore, any electrical component, including a semiconductor integrated circuit device in a packaged or bare chip state, may be mounted on the metal bumps of the wiring board of the embodiment.

1 Wiring board 11, 21-23 Insulating layer 22a Surface 12, 31-33 of insulating layer 22 Conductor layer 321 First conductor pad 322 Second conductor pad 4, 41 Solder resist layer 4a Top surface 5 Metal bump 5a End surface 51 Covering layer ( 1st coating layer)
6, 6α, 6β Protrusion 6a Surface 6b Base portion 6c Surface portion 61 Coating layer (second coating layer)
7 Connection layer 7a Surface E Component E1 Electrode H5 Height of the end surface of the metal bump from the top surface of the solder resist layer H6 Height of the protrusion with respect to the top surface of the solder resist layer H7 Height of the surface of the connection layer from the top surface of the solder resist layer

Claims (9)

an insulating layer;
a first conductor pad formed on the surface of the insulating layer;
a solder resist layer formed on the surface and having an upper surface facing in a direction opposite to the insulating layer;
a metal bump connected to the first conductor pad and protruding from the upper surface through the solder resist layer;
A wiring board comprising:
The metal bump has an end surface on a protrusion side from the solder resist layer, which is a connection surface with an electrode of a component mounted on the wiring board,
The wiring board further includes a protrusion that protrudes from the upper surface of the solder resist layer and prevents the end surface of the metal bump and the electrode from coming closer to each other than a predetermined distance. The wiring board according to claim 1, further comprising a connection layer formed on the end surface of the metal bump and connecting the electrode and the metal bump. 3. The wiring board according to claim 2, wherein the protrusion is lower in height from the upper surface of the solder resist layer than a surface of the connection layer facing in a direction opposite to the metal bump, and higher than the end face of. 2. The wiring board according to claim 1, wherein the protrusion has a flat surface facing in a direction opposite to the insulating layer. The wiring board according to claim 1,
The metal bump includes a first coating layer forming the end surface,
The protrusion includes a second covering layer forming a surface of the protrusion facing in a direction opposite to the insulating layer,
The first covering layer and the second covering layer are formed of the same material. The wiring board according to claim 1, further comprising a second conductor pad formed on the surface of the insulating layer,
The protrusion penetrates the solder resist layer and is connected to the second conductor pad. 2. The wiring board according to claim 1, wherein the protrusion is formed on the upper surface of the solder resist layer. The wiring board according to claim 1, further comprising a connection layer formed on the end surface of the metal bump and connecting the electrode and the metal bump,
The protrusion includes a base portion made of the same metal as the metal that constitutes the metal bump, and a surface portion formed on the base portion and having a higher melting point than the connection layer. 9. The wiring board according to claim 8, with respect to the height of the solder resist layer from the top surface, a surface of the base portion on the surface portion side is approximately the same as the end surface of the metal bump.

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