WIRING SUBSTRATE DEVICE

A wiring substrate device includes a wiring substrate, a plurality of terminals each of which is provided upright on the wiring substrate and has a lower end, an upper end and a narrowed part between the lower end and the upper end, and a plurality of solders each of which has a melting point lower than the terminals and covers a surface of the corresponding terminal.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2017-183549 filed on Sep. 25, 2017, the entire content of which is incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to a wiring substrate device.

Related Art

There are various types of terminals for connecting components such as a semiconductor device to a wiring substrate. Among them, solder bumps have been widely used because they are melted by reflow and the semiconductor device can be thus easily mounted on the wiring substrate.

However, when the solder bumps are melted by the reflow, the adjacent solder bumps are contacted to each other, so that the solder bumps may be electrically shorted. Furthermore, the melted solder bumps are squashed, so that an interval between the wiring substrate and the semiconductor device is reduced and the semiconductor device may be thus contacted to the wiring substrate, in some cases.

SUMMARY

Exemplary embodiments of the present invention provides a wiring substrate device capable of keeping an interval between a wiring substrate and a component and suppressing electrical short of terminals adjacent to each other.

A wiring substrate device according to an exemplary embodiment comprises:

a wiring substrate;

a plurality of terminals each of which is provided upright on the wiring substrate and has a lower end, an upper end and a narrowed part between the lower end and the upper end; and

a plurality of solders each of which has a melting point lower than the terminals and covers a surface of the corresponding terminal.

According to one aspect, since the melted solder is accumulated at the narrowed part of the terminal, it is possible to prevent the melted solder from spreading in a horizontal direction of the substrate and to suppress electrical short of the adjacent terminals via the solder.

DETAILED DESCRIPTION

Before describing exemplary embodiments, the matters that have been examined by the inventor are described.

FIG. 1is an entire sectional view of a wiring substrate used for examination.

The wiring substrate1is a multi-layered wiring substrate, and is configured by stacking alternately insulation layers6and wirings4,7on both surfaces of a core base material2.

The core base material2is a glass epoxy substrate in which epoxy resin is impregnated in glass cloth, and has a plurality of through-holes2a.The through-hole2aand opening ends thereof are formed with copper plated films, so that a through-electrode3is provided in the through-hole2aand the wiring4is provided on the core base material2around the through-electrode3.

Also, the insulation layer6is a resin layer such as a phenol resin, a polyimide resin and the like. The resin layer6is formed with a via hole6areaching the wiring4by laser processing or the like, and the wiring7is formed in the via hole6aand on the insulation layer6around the via hole by copper plating.

An upper main surface of both main surfaces of the wiring substrate1is formed with a first solder resist layer11. The first solder resist layer11is provided with first openings11aexposing the wiring7of the uppermost layer. A surface of the wiring7in the first opening11ais formed with a first diffusion prevention layer12.

The first diffusion prevention layer12is a metal layer for preventing a solder, which is to be formed later on the first diffusion prevention layer, from diffusing into the wiring7, and is also referred to as a UBM (Under Barrier Metal). In this example, a nickel layer, a palladium layer and a gold layer are formed in corresponding order, as the first diffusion prevention layer12.

In the meantime, a lower main surface of both the main surfaces of the wiring substrate1is formed with a second solder resist layer13. The second solder resist layer13is formed with second openings13aexposing the wiring7of the lowest layer. A surface of the wiring7in the second opening13ais formed with a second diffusion prevention layer14.

Like the first diffusion prevention layer12, the second diffusion prevention layer14is a stacked film formed by stacking a nickel layer, a palladium layer and a gold layer in corresponding order.

In this example, a semiconductor device is mounted on the wiring substrate1, as follows.

FIGS. 2A to 3Bare enlarged sectional views depicting states where a wiring substrate device using the wiring substrate1is being manufactured.

First, as shown inFIG. 2A, a terminal16is erected in the first opening11a.

The terminal16has a column shape obtained by cutting a nickel wire rod into a predetermined length, and a solder17is formed on a surface thereof by barrel plating,

Subsequently, as shown inFIG. 2B, the solder17is reflowed and melted, so that the terminal16is joined to the wiring7via the solder17and the first diffusion prevention layer12. Upon the reflow, the solder17is formed to have a schematically spherical shape by surface tension.

By the above processes, a basic structure of a wiring substrate device25relating to this example is completed.

Then, the wiring substrate device25is subjected to a process of mounting thereon a semiconductor device.

First, as shown inFIG. 3A, a semiconductor device2.0having a plurality of electrodes21is prepared, and the electrodes21and the terminals16are positionally aligned. Although the electrode21is not particularly limited, a copper post is formed as the electrode21, in this example.

Then, as shown inFIG. 3B, while pressing the semiconductor device20toward the wiring substrate1, the solders17are reflowed and melted, so that the terminals16and the electrodes21are interconnected via the solders17.

During the reflow, a heating temperature is set to a temperature higher than a melting point of the solder17and lower than a melting point of the terminal16. For this reason, the solder17is melted by the reflow but the terminal16keeps the column shape without being melted.

By the above processes, the basic processes of this example are over.

According to the wiring substrate device25, since the nickel terminal16having the melting point higher than the solder17is adopted, the terminal16is not melted even when the solder17is reflowed in the process ofFIG. 3B. Thereby, even when the semiconductor device20is pressed upon the reflow, the terminal16is not squashed, Accordingly, an interval between the first wiring substrate1and the semiconductor device20is kept by the terminals16and it is possible to prevent the semiconductor device20from contacting the first wiring substrate1.

However, following problems may occur in the wiring substrate device25.

FIGS. 4 to 6are enlarged sectional views for illustrating the problems.

In an example ofFIG. 4, when the solders17are reflowed in the process ofFIG. 2B or 3B, the solders17are spread in a horizontal direction due to the surface tension, so that the adjacent terminals16are electrically shorted via the solders17.

In order to avoid the above problem, it is considered to reduce an amount of the solder17on the surface of the terminal16. However, according to this method, an amount of the solder16is insufficient at a lower end16aand an upper end16bof the terminal16, so that joining strength between the lower end16aand the wiring7and joining strength between the upper end16aand the electrode21may be insufficient.

FIG. 5is an enlarged sectional view depicting a case where heights of the plurality of electrodes21are not uniform due to a manufacturing error.

In this case, the solder17is not contacted to the electrode21of which height is low, so that the electrode21and the terminal16corresponding to the electrode are not electrically connected to each other.

FIG. 6is an enlarged sectional view depicting a case where the semiconductor device20is bent due to thermal expansion and the like.

In this case, a part of the electrodes21is detached from the terminal16due to the bending of the semiconductor device20, so that the terminal16and the electrode21cannot be connected to each other by the solder17.

In the below, each exemplary embodiment capable of avoiding the above problems is described.

First Exemplary Embodiment

First, a terminal that is used in a first exemplary embodiment is described.

FIG. 7Ais a top view of the terminal, andFIG. 7Bis a sectional view taken along a line I-I ofFIG. 7A.

As shown inFIG. 7A, a terminal30has a circular shape, as seen from above.

Also, as shown inFIG. 7B, the terminal30has a lower end30aand an upper end30b,and a narrowed part30chaving a width narrower than each of the lower end30aand the upper end30bis provided between the lower and upper ends.

In this example, the narrowed part30cis provided with a narrow portion30dhaving a smallest width W1, as seen from a cross sectional view. A sectional shape of the terminal30is narrowed in a tapered shape from the lower end30atoward the narrow portion30d,and a sectional shape of the terminal30is widened in a tapered shape from the narrow portion30dtoward the upper end30b.

A size of the terminal30is not particularly limited. For example, a height H of the terminal30is about 10 μm to 1000 μm, and a width W2of each of the lower end30aand the upper end30bis about 10 μm to 500 μm. Also, the width W1of the narrow portion30dis about 5 μm to 495 μm, and more preferably about 300 μm.

Also, a material of the terminal30is not particularly limited. For example, the terminal30may be formed of any one of nickel, copper, gold and aluminum.

In the first exemplary embodiment, a solder is provided on a surface of the terminal30, as follows.

FIG. 8is a sectional view of the terminal30having a solder31provided on the surface thereof.

The solder31is formed to have a thickness of about 5 μm to 100 μm on the entire surface of the terminal30by barrel plating, for example.

Also, a material of the solder31is not particularly limited inasmuch as it is a material having a melting point lower than the terminal30. For example, tin or lead may be adopted.

Subsequently a manufacturing method of the terminal30is described.

FIG. 9Ais a sectional view depicting a manufacturing method of the terminal30. Also,FIG. 9Bis a partial sectional side view taken along a line II-II ofFIG. 9A.

As shown inFIGS. 9A and 9B, in this example, jigs33are arranged above and below a linear nickel wire rod30x.The jig33is formed with an inclined surface33acorresponding to the narrowed part30c(refer toFIG. 7B). The wire rod30xis rotated and pinched several times by the jigs33, so that the wire rod30xis processed into a tapered shape.

In the meantime, the wire rod30xmay be processed into a tapered shape by a rolling processing method or the like.

After processed into the tapered shape, the wire rod30xis cut into a predetermined length, so that the terminal30having the narrowed part30cis obtained.

Subsequently, a wiring substrate device having the terminals30is described with reference to a manufacturing method thereof.

FIGS. 10A to 11Bare enlarged sectional views depicting states where a wiring substrate device of the first exemplary embodiment is being manufactured. InFIGS. 10A to 11B, the same elements as those described inFIGS. 1 to 3Bare denoted with the same reference numerals as those inFIGS. 1 to 3Band the descriptions thereof are omitted.

In the first exemplary embodiment, the terminal30is provided upright on the wiring substrate1, as follows.

First, as shown inFIG. 10A, the terminals30are erected in the first openings11aof the first solder resist layer11with the lower ends30abeing located downward.

Then, as shown inFIG. 10B, the solders31are reflowed and melted, so that the terminals30are connected to the wiring7via the solders31and the first diffusion prevention layers12. During the reflow, a heating temperature is set to a temperature higher than the melting point of the solder31and lower than the melting point of the terminal30, for example, about 100° C. to 400° C.

In the first exemplary embodiment, during the reflow, since the melted solder31is accumulated at the narrowed part30cby the surface tension, it is possible to prevent the solder31from spreading in a horizontal direction and to reduce a risk that the adjacent terminals30will be electrically shorted by the solder31.

In the meantime, as described above, since the heating temperature of the reflow is lower than the melting point of the terminal30, the terminal30is not melted by the reflow.

By the above processes, a wiring substrate device35of the first exemplary embodiment is completed. In this embodiment, as shown inFIG. 8, the solder31is provided on the entire surface of the terminal30. However, the solder31may not be provided on the lower end30aof the terminal30and the lower end30aof the terminal30may be in direct contact with the wiring7without the solder31and the first diffusion prevention layer12.

In the wiring substrate device35, the first solder resist layer11is formed on the wiring7around the terminal30, and the terminal30protrudes from the first solder resist layer11.

Subsequently, a process of mounting a component such as a semiconductor device on the terminal30of the wiring substrate device35is performed.

First, as shown inFIG. 11A, a semiconductor device20having a plurality of electrodes21is prepared, and the electrodes21and the terminals30are positionally aligned. A type of the semiconductor device20is not particularly limited. For example, a processor such as a CPU (Central Processing Unit) may be adopted as the semiconductor device20.

Also, like the example ofFIG. 3A, the electrode21is a metal post such as a copper post.

Then, as shown inFIG. 11B, the solders31are reflowed and melted while pressing the semiconductor device20toward the wiring substrate1, so that the terminals30and the electrodes21are interconnected via the solders31.

During the reflow, the heating temperature is set to a temperature higher than the melting point of the solder31and lower than the melting point of the terminal30, for example, about 100° C. to 400° C. For this reason, during the reflow, the terminals30are not melted and an interval between the wiring substrate1and the semiconductor device20can be kept by the terminals30even when the semiconductor device20is pressed toward the wiring substrate1, so that the semiconductor device20can be prevented from contacting the wiring substrate1.

Furthermore, the melted solder31is accumulated at the narrowed part30cof the terminal30, so that the solder31does not spread in the horizontal direction and it is thus possible to reduce a possibility that the adjacent terminals30will be electrically shorted due to the solder31.

In particular, like this example, the narrow portion30dis positioned above an upper surface11xof the first solder resist layer11, so that it is possible to prevent the narrow portion30dfrom being screened by the first solder resist layer11. As a result, the more solder31can be accumulated at the narrowed part30c,so that it is possible to effectively suppress the solder31from spreading in the horizontal direction.

Also, the narrow portion30dis exposed, so that the solder31can be accumulated between the narrow portions30d,which are most distant from each other between the adjacent terminals30. Accordingly, it is possible to suppress the solder31from spreading in the horizontal direction.

In this way, the basic processes of the first exemplary embodiment are completed.

FIG. 12is an entire sectional view including the semiconductor device20.

In this example, after the semiconductor device20is mounted on the wiring substrate1, as described above, an underfill resin38is filled between the wiring substrate1and the semiconductor device20. Also, a solder bump functioning as an external connection terminal39is formed on the wiring7exposed from the second opening13aof the second solder resist layer13.

In the meantime, the underfill resin38and the external connection terminal39may be omitted if they are not necessary. This applies to each exemplary embodiment to be described later, as well.

According to the first exemplary embodiment, the terminals30having the melting point higher than the solder31are arranged between the wiring substrate1and the semiconductor device20. Thereby, even when the solder31is reflowed, it is possible to keep the interval between the wiring substrate1and the semiconductor device20and to reduce a contact possibility of the wiring substrate1and the semiconductor device20.

In particular, when using the underfill resin38, as shown inFIG. 12, the interval between the wiring substrate1and the semiconductor device20is kept, so that the underfill resin38can be easily filled therebetween.

Also, as shown inFIG. 11B, the terminal30is provided with the narrowed part30c,so that it is possible to prevent the solder31from spreading in the horizontal direction of the substrate and to reduce a possibility that the adjacent terminals30will be interconnected via the solder31.

Furthermore, since it is not necessary to reduce an amount of the solder31so as to prevent the solder31from spreading in the horizontal direction, a sufficient amount of the solder31is uniformly spread to each of the lower end30aand the upper end30bof the terminal30. As a result, it is possible to sufficiently secure connection strength between the terminal30and the wiring substrate1and connection strength between the terminal30and the semiconductor device20by the solder31, so that it is possible to maintain connection reliability between the wiring substrate1and the semiconductor device20.

Also, according to the first exemplary embodiment, following effects can also be accomplished.

FIGS. 13 and 14are enlarged sectional views for illustrating effects to be accomplished in the first exemplary embodiment.

FIG. 13is a sectional view depicting a case where the heights of the plurality of electrodes21are not uniform due to a manufacturing error.

In this case, when the semiconductor device20is pressed in the process ofFIG. 11B, the narrowed parts30c,which are mechanically weak, are squashed, so that it is possible to absorb the non-uniformity of the heights of the respective electrodes21by the terminals30. For this reason, unlike the example ofFIG. 5, it is possible to suppress a situation where a part of the plurality of terminals30is not connected to the electrode21, so that it is possible to suppress a yield of the wiring substrate device from being lowered.

FIG. 14is a sectional view depicting a case where the semiconductor device20is bent due to thermal expansion or the like.

In this case, when the semiconductor device20is pressed in the process ofFIG. 11B, the terminal30is bent at the narrowed part30c,so that the upper end30bof the terminal30conforms to the bending of the semiconductor device20. Thereby, unlike the example ofFIG. 6, it is possible to connect each of the plurality of terminals30to the electrode21.

Second Exemplary Embodiment

In a second exemplary embodiment, an amount of the solder31to be accumulated at the narrowed part30cis larger than the first exemplary embodiment.

FIG. 15Ais a top view of the terminal30of the second exemplary embodiment, andFIG. 15Bis a side view of the terminal30.

Meanwhile, inFIGS. 15A and 15B, the same elements as those described in the first exemplary embodiment are denoted with the same reference numerals as those in the first exemplary embodiment and the descriptions thereof are omitted.

As shown inFIGS. 15A and 15B, in the second exemplary embodiment, a side of the terminal30is formed with a plurality of grooves30gextending from the lower end30ato the upper end30b.

FIG. 16Ais a top view depicting a case where the terminal30is provided with the solder31, andFIG. 16Bis a sectional view taken along a line III-III ofFIG. 16A.

Like the first exemplary embodiment, the solder31is formed on the surface of the terminal30by the barrel plating.

In particular, as shown inFIG. 16A, in the second exemplary embodiment, since a surface area of the side of the terminal30increases due to the grooves30g,it is possible to provide the more solder31on the terminal30, as compared to a configuration where the grooves30gare not provided.

Subsequently, a manufacturing method of the terminal30is described.

FIG. 17Ais a sectional view depicting a manufacturing method of the terminal30relating to the second exemplary embodiment. Also,FIG. 17Bis a partial sectional side view taken along a line IV-IV ofFIG. 17A.

As shown inFIGS. 17A and 17B, also in the second exemplary embodiment, the wire rod30xis rotated and pinched several times by the pair of jigs33and is thus formed with the narrowed part30c(refer toFIG. 15B).

In the meantime, the wire rod30xmay be processed into a tapered shape by a rolling processing method or the like.

Also, as shown inFIG. 17B, the jig33is provided with a concavity and convexity33bcorresponding to the groove30g(refer toFIG. 15A), so that it is possible to form the groove30gby transferring the concavity and convexity33bto the wire rod30x.

FIG. 18is a partial sectional side view of a wiring substrate device35having the terminals30in accordance with the second exemplary embodiment.

Meanwhile, inFIG. 18, the same elements as those described in the first exemplary embodiment are denoted with the same reference numerals as those in the first exemplary embodiment and the descriptions thereof are omitted.

The wiring substrate device35is manufactured by performing the same processes asFIGS. 10A to 11Bof the first exemplary embodiment, and has a structure where the wiring substrate1and the semiconductor device20are connected to each other by the terminals30.

In the second exemplary embodiment, the grooves30gare formed, so that it is possible to provide the more solder31on the surface of the terminal30. Therefore, the solder31is difficult to be insufficient at the lower end30aand the upper end30bof the terminal30. As a result, it is possible to sufficiently secure the connection strength between the terminal30and the wiring substrate1and the connection strength between the terminal30and the semiconductor device20by the solders31.

Third Exemplary Embodiment

In a third exemplary embodiment, a shape of the narrowed part30cis different from the first exemplary embodiment.

FIG. 19Ais a top view of the terminal30relating to the third exemplary embodiment, andFIG. 19Bis a sectional view taken along a line V-V ofFIG. 19A.

Meanwhile, inFIGS. 19A and 19B, the same elements as those described in the first exemplary embodiment are denoted with the same reference numerals as those in the first exemplary embodiment and the descriptions thereof are omitted.

As shown inFIGS. 19A and 19B, the terminal30of the third exemplary embodiment has an upper plate30eincluding the upper end30b,a lower plate30fincluding the lower end30a,and a column-shaped part30hconnecting the upper plate30eand the lower plate30feach other.

The column-shaped part30his a part becoming the above-described narrowed part30c,and has a width W3that is constant between the lower end30aand the upper end30b.

The width W3is, for example, about 5 μm to 495 μm, and a height h of the column-shaped part30his, for example, about 5 μm to 800 μm. Also, the width W2of each of the lower end30aand the upper end30bis about 10 μm to 500 μm, like the first exemplary embodiment. A height H of the terminal30is about 10 μm to 1000 μm.

FIG. 20is a sectional view depicting a case where the terminal30is provided with the solder31.

Like the first exemplary embodiment and the second exemplary embodiment, the solder31is formed on the surface of the terminal30by the barrel plating.

Subsequently, a manufacturing method of the terminal30is described.

FIG. 21Ais a sectional view depicting a manufacturing method of the terminal30relating to the third exemplary embodiment. Also,FIG. 21Bis a partial sectional side view taken along a line VI-VI ofFIG. 21A.

As shown inFIGS. 21A and 21B, also in the third exemplary embodiment, the wire rod30xis rotated and pinched several times by the pair of jigs33and is thus formed with the narrowed part30c(refer toFIG. 19B).

In the meantime, the wire rod30xmay be formed with the narrowed part30cby a rolling processing method or the like.

As shown inFIG. 21B, each jig33is provided with a convex part33chaving a semicircular shape corresponding to the column-shaped narrowed part30c,It is possible to form the column-shaped narrowed part30cby transferring the shape of the convex part33cto the wire rod30x.

FIG. 22is an enlarged sectional view of a wiring substrate device having the terminals30in accordance with the third exemplary embodiment.

Meanwhile, inFIG. 22, the same elements as those described in the first exemplary embodiment are denoted with the same reference numerals as those in the first exemplary embodiment and the descriptions thereof are omitted.

The wiring substrate device is manufactured by performing the same processes asFIGS. 10A to 11Bof the first exemplary embodiment, and has a structure where the wiring substrate1and the semiconductor device20are connected to each other by the terminals30.

In the third exemplary embodiment, the narrowed part30cis formed to have a column shape, as described above. Therefore, it is possible to largely retreat the surface of the narrowed part30cfrom a surface of each of the lower end30aand the upper end30b,and to largely separate the narrowed parts30cof the adjacent terminals30. For this reason, even when the solder31is reflowed in the process ofFIG. 11B, it is possible to effectively suppress the adjacent terminals30from being connected each other due to the solder31.

Also, even when the narrowed part30cis formed to have a column shape, following effects are accomplished, like the first exemplary embodiment.

FIGS. 23 and 24are sectional views for illustrating effects to be accomplished in the third exemplary embodiment.

FIG. 23is a sectional view depicting a case where the heights of the plurality of electrodes21are not uniform due to a manufacturing error.

In this case, the narrowed parts30care squashed, so that it is possible to absorb the non-uniformity of the heights of the respective electrodes21by the terminals30and to connect each of the plurality of terminals30to the electrode21.

FIG. 24is a sectional view depicting a case where the semiconductor device20is bent due to thermal expansion or the like.

In this case, the narrowed part30cis bent, so that the upper end30bof the terminal30conforms to the bending of the semiconductor device20and it is thus possible to connect each of the plurality of terminals30to the electrode21.

Fourth Exemplary Embodiment

In the first to third exemplary embodiments, the semiconductor device20is used as a component that is connected to the wiring substrate1via the terminals30. However, in a fourth exemplary embodiment, a wiring substrate is used as the component.

FIG. 25is an enlarged sectional view of a wiring substrate device in accordance with the fourth exemplary embodiment.

Meanwhile, inFIG. 25, the same elements as those described in the first exemplary embodiment are denoted with the same reference numerals as those in the first exemplary embodiment and the descriptions thereof are omitted.

As shown inFIG. 25, in a wiring substrate device50, the two wiring substrates1are made to face each other. Then, the solders31are reflowed and melted, so that the wirings7of the wiring substrates1are connected to each other via the terminals30.

Since the terminal30is provided with the narrowed part30c,as described above, the melted solder31is accumulated at the narrowed part30c,so that it is possible to prevent the solder31from spreading in the horizontal direction of the substrate. As a result, it is possible to suppress the adjacent terminals30from being connected to each other due to the solder31, so that it is possible to improve the yield of the wiring substrate device50.