JP2001044319A - Wiring board and mounting structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mechanical strength of the bases of connection terminals for jointing by brazing and hence improve their long-term connection reliability, by relaxing thermal stress, mechanical stress, impact, and stress concentration caused during mounting or at use. SOLUTION: A metallized interconnection layer 2 is formed on the surface and/or in the interior of an insulating substrate, and a plurality of terminal electrodes 3 which are in electrical conduction with the layer 2 are formed on the main surface of the substrate. A connection terminal 14, having the shape of a truncated cone or of a truncated polygonal pyramid, whose top is smaller than its base 14a for joint, is jointed to the corresponding electrode 3 via a solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board such as a package for housing a semiconductor element made of an insulator such as ceramics, glass ceramics or synthetic resin. The present invention relates to a mounting structure of a wiring board for mounting a semiconductor element, which is brazed to a surface of a circuit board such as a motherboard made of an insulator.

[0002]

2. Description of the Related Art Conventionally, a ceramic wiring substrate has a structure in which a metallized wiring layer is provided on the surface and / or inside of an insulating substrate. Typical examples are semiconductor devices,
Particularly, there is a semiconductor device housing package (hereinafter, referred to as a semiconductor package) for housing a semiconductor integrated circuit device such as an LSI (large-scale integrated circuit device). Generally, a semiconductor package is made of ceramics such as alumina ceramics.
It consists of glass ceramics, organic resin, etc. Particularly, in a semiconductor package using alumina ceramics, a plurality of metallized wiring layers made of a refractory metal such as tungsten (W) and molybdenum (Mo) are provided on the surface and inside of an insulating substrate, and a semiconductor mounted on the surface is provided. It is electrically connected to the element.

[0003] A connection terminal electrode (hereinafter abbreviated as terminal electrode) for electrically connecting to an external circuit board is provided on the lower surface or side surface of the insulating substrate. The terminal electrode is connected to a metallized wiring layer. Electrically connected. Further, an electrode for connection to the semiconductor element is formed at the center of the upper surface of the insulating substrate, and after the semiconductor element is mounted, it is sealed with a resin adhesive or the like. Alternatively, at the center of the upper surface of the insulating substrate,
A cavity for accommodating the semiconductor element is formed, and the semiconductor element is placed and accommodated in the cavity, and hermetically sealed with a lid.

In general, as the degree of integration of a semiconductor device increases, the number of electrodes formed on the semiconductor device also increases. With this, in a semiconductor package containing the semiconductor device, the number of terminal electrodes for connecting to an external circuit board also increases. Increase. The external circuit board is generally a so-called printed board made of glass-epoxy resin or the like. However, when the number of terminal electrodes is increased, the size of the package is increased. Therefore, it is necessary to increase the formation density of the terminal electrodes of the package in combination with the demand for downsizing of the package.

Conventionally, as a structure of a terminal electrode in a semiconductor package, a pin grid array (PGA) in which metal pins such as Kovar (Fe-Ni-Co alloy) are connected to the lower surface of the package is generally and commercialized. Recently, a quad flat package (QFP) in which gull-wing (L-shaped) metal pins are connected to metallized wiring layers led out on four sides of the package, and electrode pads on four sides of the package With lead pins and leadless chip carrier (LC
C), a chip size package (CSP) in which a Si chip is flip-chip mounted, and a ball grid array (BGA) in which a number of spherical terminals made of solder are arranged on the lower surface of an insulating substrate. Of these, BGA has the highest density. Is possible.

The terminal electrodes of the ball grid array (BGA) are formed by brazing spherical terminals made of a metal brazing material such as solder (hereinafter also referred to as brazing material) to the terminal electrode pads. The spherical terminal is placed and abutted on a wiring conductor of an external circuit board, and thereafter, the spherical terminal is heated and melted at about 200 to 400 ° C. and bonded to the wiring conductor to be mounted on the circuit board. With such a mounting structure, each electrode of the semiconductor element housed inside the semiconductor package is electrically connected to an external circuit board via the metallized wiring layer and the terminal electrode.

[0007]

However, when a semiconductor element is housed in a semiconductor package having a wiring board and mounted on a circuit board such as a printed board, heat generated during operation of the semiconductor element is applied to both the wiring board and the circuit board. Heat is repeatedly transmitted, thereby generating a large thermal stress due to a difference in thermal expansion between the wiring board and the circuit board. In particular, in the case of a semiconductor package having a number of connection terminals exceeding 300 or a large semiconductor package, the influence of the thermal stress increases. Therefore, the thermal stress is repeatedly applied to the outer peripheral portion of the terminal electrode on the lower surface of the wiring board by repeatedly operating and stopping the semiconductor element. And acts on the bonding interface between the wiring conductor of the circuit board and the connection terminal, and as a result, a situation occurs in which the terminal electrode peels off from the wiring board, the connection terminal peels off from the wiring conductor, or the wiring board body is destroyed, There has been a problem that a wiring board for a semiconductor package and a circuit board such as a printed board cannot be stably electrically connected for a long period of time.

Further, when ceramics or glass ceramics are used as a wiring board used for such a semiconductor package, an organic resin is used in view of strength, hermetic sealing properties, and a technique of forming a multilayer with a metallized wiring layer. High reliability is obtained as compared with the case of using. However, the thermal expansion coefficient of a wiring board made of ceramics and glass ceramics is about 4 to 7 × 10 ⁻⁶ / ° C., whereas the thermal expansion coefficient of a printed board often used as a circuit board for mounting a semiconductor package. The coefficient is 11-18 × 10 ^-6 / ° C.
Is very large, a large thermal stress is generated due to a large difference in thermal expansion coefficient between the two. As a result, it has been difficult to stably connect a wiring board for a semiconductor package to a circuit board for a long time.

FIG. 9 shows a process of mounting a conventional BGA type semiconductor package on a circuit board and its mounting structure. FIG. 9 shows a cross section of a connection terminal portion when the conventional BGA type semiconductor package is mounted on a circuit board. The figure is shown in FIG.

FIG. 9A shows that the semiconductor package A
Has a wiring board 1, a metallized wiring layer 2 and a terminal electrode 3 for connection, and a semiconductor element 4
Are bonded and fixed via an adhesive such as glass frit or resin, and the semiconductor element 4 is electrically connected to the metallized wiring layer 2 by bonding wires 5.
The top is sealed by covering (mounting) with a synthetic resin 6 or the like.

Then, as shown in FIG. 9B, a solder layer 8 made of Pb37-Sn63 eutectic solder containing 37% by weight of Pb and 63% by weight of Sn is screen-printed on the terminal electrode 3. Etc., and apply the same Pb
Solder balls 7 made of 37-Sn63 eutectic solder or the like are joined and reflowed during mounting, so that the solder balls 7 are joined and fixed on the terminal electrodes 3 as shown in FIG. 9C. Reference numeral 12 denotes a connection terminal in which the solder ball 7 is melted at the time of reflow and bonding and diffuses with the solder layer 8 to be flattened by its own weight.

On the other hand, as shown in FIG. 9C, Pb 37 is also formed on the wiring conductor 10 on the circuit board B in the same manner as described above.
After forming the solder layer 9 made of -Sn63 eutectic solder or the like, the connection terminal 12 is positioned on the solder layer 9 so as to be in contact therewith, and then reflowed as shown in FIG. 9D. Then, the semiconductor package A is mounted on the circuit board B.

As described above, in the mounting structure of the conventional BGA type semiconductor package A, the solder ball 7, the solder layer 8 for joining the solder ball 7 to the terminal electrode 3 on the wiring board 1, and the circuit board B The solder layer 9 formed on the wiring conductor 10 is made of the same material, for example, Pb37-Sn63 eutectic solder. Therefore, the solder ball 7 melts and diffuses with the solder layers 8 and 9 at the time of reflow and is flattened by its own weight, so that the solder ball 7 cannot maintain its original shape, and the connection terminal 12 having a substantially elliptical shape as shown in FIG. It is formed.

The thermal stress is mainly concentrated on the interface between the connection terminal 12 and the terminal electrode 3 and acts in the direction W in FIG.
In FIG. 10, the right side is the outside of the semiconductor package (dotted arrow). Further, this thermal stress can be divided into two components of an X-direction component in the shear direction and a Y-direction component in the tensile direction. Generally, since the X-direction component of the thermal stress is large, the mode in which the crack progresses from the outside of the semiconductor package toward the center side along the interface between the connection terminal 12 and the terminal electrode 3 is most frequently destroyed. . Alternatively, cracks may progress in the connection terminal 12 body. aside from that,
The interface between the wiring board 1 and the terminal electrode 3 may be exfoliated or the main body of the wiring board 1 may be broken due to the Y-direction component of the thermal stress.

At this time, if the shape of the connection terminal 12 is substantially elliptical as shown in FIG.
At the interface of the connection portion, necking occurs, and a large stress concentration occurs along the interface. As a result, cracks easily progress at the interface. Further, if the height h of the connection between the semiconductor package A and the circuit board B is insufficient, the X-direction component of the thermal stress in the shear direction increases, and the crack at the interface between the connection terminal 12 and the terminal electrode 3 is increased. Progress is further promoted.

Furthermore, the solder layers 8 and 9 and the solder balls 7
However, as they melt and diffuse with each other at the time of reflow, the solder and especially the impurity components and air contained in the solder paste diffuse and rise, and a flame such as a void is generated at the interface between the connection terminal 12 and the terminal electrode 3. Produces and reduces the mechanical strength of the interface. In addition, Pb37-
When the Sn63 eutectic solder is used, the connection terminals 1
Since the whole 2 is melted, it is difficult to maintain the parallelism between the semiconductor package A and the circuit board B at the time of mounting, and as a result, there is a problem that a portion having low mechanical strength is easily formed locally.

Further, besides the thermal stress, there are mechanical stresses and circuit stresses generated when the circuit board B on which the semiconductor package A is mounted is mounted on various electronic device bodies by using screws, pins, adhesives and the like. Various stresses such as mechanical stress due to bending and deformation of the board B and impact applied when the electronic device body falls down are connected to the outer peripheral portion of the terminal electrode 3 on the lower surface of the wiring board 1 and the wiring conductor 10 of the circuit board B. It acts on the joint interface with the terminal 12. As a result, the terminal electrode 3 peels off from the wiring board 1 or the connection terminal 12 peels off from the wiring conductor 10, and it has been difficult to stably connect the semiconductor package A to the circuit board B for a long time.

In order to solve such a problem, for example, as shown in FIG.
And a mounting structure using solder layers 8 and 9 made of low melting point Pb37-Sn63 eutectic solder. In this configuration, since the solder balls 13 are mounted at a temperature at which the solder balls 13 do not melt during reflow, the distance h between the connecting portions between the semiconductor package A and the circuit board B can be kept high, and stress concentration can be reduced to some extent. However, even in this configuration,
Since the connection interface has a constricted structure in which stress concentration is likely to occur, further improvement in long-term reliability has been required.

Further, when the wiring density is further improved,
If the height h of the connection portion is to be ensured in order to reduce the stress concentration at the interface of the connection portion, the distance between the terminal electrodes 3 is limited to the diameter of the solder ball 7, so that the height between the terminal electrodes 3 is higher than the distance between the terminal electrodes 3. In addition, it was not possible to secure the high density, and it was a big obstacle to high density mounting.

In order to solve the above-mentioned various problems, the following improved techniques have been proposed for a mounting technique for mounting a semiconductor package on a circuit board using solder balls and brazing material. In a semiconductor device for conducting a plurality of terminals formed on the surface of a semiconductor chip to a conductive portion of a mounting board through a conductor, the conductor is made of conductive spheres that do not melt at the time of mounting, and is further soldered to the surface of the conductive spheres. (See, for example, Japanese Unexamined Patent Publication No.
No. 115997). However, even in the conventional example 1, it cannot be said that it is sufficient in terms of relaxation of the stress concentration and the like, and therefore, a configuration which sufficiently solves the above various problems has not been found yet.

Accordingly, the present invention has been completed in view of the above circumstances, and an object of the present invention is to provide a wiring board for a semiconductor package made of, for example, ceramics or glass ceramics having a small coefficient of thermal expansion by using glass-epoxy resin or the like. When mounting on an external circuit board having a larger coefficient of thermal expansion than the wiring board, the wiring board has high reliability because it can maintain a strong and stable connection state for a long time, and a wiring board capable of supporting high-density mounting. It is to provide the mounting structure.

[0022]

According to the present invention, there is provided a wiring board having a plurality of terminal electrodes provided on the main surface of an insulating substrate having a wiring conductor layer formed on the surface and / or inside thereof, the terminal electrodes being electrically connected to the wiring conductor layer. A connection terminal having a truncated cone shape or a truncated polygonal pyramid shape having a tip portion smaller than a joining base portion is joined to the terminal electrode via a brazing material.

According to the present invention, when a wiring board for a semiconductor package or the like is mounted on another circuit board such as a printed circuit board by the above configuration, thermal stress, various mechanical stresses and impacts generated during mounting or use are reduced. It reduces the relaxation, reduces the stress concentration, and improves the mechanical strength of the joint base to be brazed, thereby improving the long-term reliability of the connection. In the present invention, the connection terminals at least at the four corners of the main surface on which the connection terminals of the wiring board are installed may be configured as in the present invention, which is effective in improving the long-term reliability of the connection portion.

In the present invention, preferably, instead of the truncated cone-shaped or polygonal truncated pyramid-shaped connection terminal, a drum-shaped connection terminal having a constricted central portion is provided. Thereby, the height of the connection part by the connection terminal can be sufficiently maintained,
It is possible to reduce the shear stress component of the thermal stress and suppress the occurrence of cracks and the like.

In the present invention, preferably, the base angle of the joint base of the connection terminal is 60 ° to 85 °, and the ratio R2 / R1 of the maximum diameter R1 of the joint base to the minimum diameter R2 of the tip is 0.4. ０．９0.95. Preferably, in the case of a drum-shaped connection terminal, the base angle of the joint base is 4 mm.
5 ° to 85 °, and the ratio R4 / R3 of the maximum diameter R3 of the joining base portion and the minimum diameter R4 of the constricted portion is 0.3 to 0.95. By setting the base angle within the above range, the height of the connection portion can be sufficiently maintained and stress concentration can be reduced. By setting the ratio between the maximum diameter and the minimum diameter within the above range, the size of the tip of the connection terminal can be maintained, the strength at the time of mounting can be maintained, and stress concentration can be reduced.

The connection terminal of the present invention is preferably made of a metal or an alloy having a higher melting point than the brazing material, or a conductive resin having a higher thermal decomposition temperature than the melting point of the brazing material. With such a configuration, the initial shape of the connection terminal is maintained, so that the necking generated at the interface between the connection terminal and the terminal electrode can be reduced, and the stress concentration generated along this interface is alleviated. Thus, it is possible to suppress the crack from advancing rapidly. Furthermore, the height of the connection between the wiring board and the circuit board is sufficiently maintained,
It is possible to prevent the shear stress component of the thermal stress from increasing. In the present invention, the conductive resin means a resin excellent in conductivity or an insulating resin provided with conductivity by containing a conductive substance.

The conductive resin is made of Au, Ag, Cu, A
1, Ni, Fe, Pd, Pt, W, Mo, Mn, Pd,
It preferably contains at least one element of Sn, Bi, Sb, In, and C, and these elements have excellent conductivity and high chemical stability. The conductive resin desirably contains a thermosetting resin or an ultraviolet curable resin.

Preferably, the conductive resin has a Young's modulus lower than that of the wiring conductor. The conductive resin preferably has a Young's modulus of 60 GPa (gigapascal) or less, and is effective in reducing stress by making the connection terminal easily deformable to some extent.

A mounting structure of a wiring board according to the present invention is characterized in that the wiring board is joined to a wiring conductor of another circuit board by a brazing material via the connection terminal. As a result, the wiring board on which the semiconductor element and the like are mounted is reduced in thermal stress,
A mounting structure having excellent durability against stresses such as mechanical stress and impact can be mounted on another circuit board, so that a semiconductor element or the like can be used with high reliability for a long time.

The wiring board of the present invention basically comprises
A semiconductor element is mounted and fixed on one main surface of an insulating substrate such as ceramics, glass ceramics or resin, and a metallized wiring layer as a wiring conductor layer is formed on the surface and / or inside, and connection terminals are formed on the other main surface. Electrode (pad)
Is provided, and a protruding connection terminal is joined to the terminal electrode via solder as a brazing material.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wiring board and a mounting structure thereof according to the present invention will be described below. FIG. 1 shows a first embodiment of the present invention, and is a cross-sectional view of a wiring board constituting a semiconductor package A, FIG. 2 is an enlarged cross-sectional view of a connection terminal portion of the wiring board of FIG. 1, and FIG. FIG. 4 is an enlarged sectional view of the connection terminal portion shown in FIG. 5 shows a second embodiment of the present invention, and is a cross-sectional view of a wiring board constituting the semiconductor package A, FIG. 6 is an enlarged cross-sectional view of a connection terminal portion of the wiring board of FIG. 5, and FIG.
8 is a cross-sectional view of a mounting structure in which this wiring board is mounted on another circuit board B, and FIG. 8 is an enlarged cross-sectional view of the connection terminal portion of FIG.

As shown in FIG. 1, a semiconductor package A according to a first embodiment of the present invention has a wiring board 1 as a main body,
A metallized wiring layer 2 as a wiring conductor layer is formed on the surface and / or inside thereof, and a terminal electrode 3 that is electrically connected to the metallized wiring layer 2 and joins the connection terminal 14 is provided on a lower surface for mounting the wiring board. A semiconductor element 4 is adhered and fixed to the center of the upper surface of 1 via an adhesive such as glass or resin. The semiconductor element 4 is electrically connected to the metallized wiring layer 2 by a bonding wire 5, and is sealed by covering (mounting) it with a synthetic resin 6 or the like. In addition, as a configuration in which the semiconductor element 4 is mounted on the wiring board 1 and electrically connected thereto, other examples include flip-chip mounting in which the semiconductor element 4 is directly mounted on a central portion of the upper surface of the wiring board 1 using a solder bump or the like; There is a configuration in which a cavity is formed on the upper surface, placed in the cavity, and hermetically sealed with a lid from above.

Further, a metallized wiring layer 2 is formed on the surface and / or inside of the wiring board 1 to electrically connect the semiconductor element 4 to the terminal electrodes 3 on the lower surface of the wiring board 1. The connection terminal 14 is joined to the terminal electrode 3 via solder as a brazing material. And the terminal electrode 14 of the present invention
2, as shown in FIG.
b is a small truncated cone or a truncated polygon. Also, as shown in FIGS. 1 and 2, a large number of terminal electrodes 3 are formed on the lower surface of the wiring board 1, and connection terminals 14 are joined to the terminal electrodes 3 via solder 8.

The connection terminal 14 of the present invention is installed as follows. Solder 8 is formed on terminal electrode 3 of wiring board 1 by various printing application methods such as screen printing method, gravure printing method, or dispenser method, dip method, and the like, and connection terminal 1 previously formed into a predetermined shape thereon.
4 is mounted such that the joint base 14 a having a larger cross-sectional shape than the tip 14 b is on the lower surface side of the wiring board 1. Thereafter, the solder 8 is melted by a reflow oven, an infrared oven, or the like to a temperature at which the solder 8 is melted but the connection terminal 14 is not melted or decomposed.
Is adhered and fixed to the lower surface of the wiring board 1. Then, as shown in FIGS. 3 and 4, the connection terminals 14 of the semiconductor package A are joined and mounted on the wiring conductors 10 of the circuit board B via solder 9 by soldering (brazing).

In such a mounting structure of the present invention, the solder 9 is formed on the surface of the wiring conductor 10 of the circuit board B, and the connection terminals 14 of the semiconductor package A are positioned so as to contact the solder 9 on the circuit board B. It is obtained by mounting together, melting the solder 9 and bonding and fixing the connection terminal 14 on the circuit board B. In the present invention, the connection procedure of the connection terminal 14 is not limited to the above procedure. After the connection terminal 14 is bonded and fixed on the wiring conductor 10 of the circuit board B, the connection terminal 14 is bonded to the semiconductor package A side. No problem.

In the second embodiment of the present invention, as shown in FIG. 5, a drum-shaped connection terminal 15 having a central portion is attached to a terminal electrode 3 on the lower surface of a semiconductor package A similar to that of FIG. Join. This connection terminal 15 has two connection terminals 15
a, 15b, and is brazed onto the terminal electrode 3 with the connection base of the connection terminal 15a in the shape of a truncated cone or a truncated polygonal pyramid facing the lower surface of the semiconductor package A, and is shaped like a truncated cone or Frustum-shaped connection terminal 15
The connection terminal 15b is brazed so that the front end of the connection terminal 15b and the front end of the connection terminal 15a are joined. Then, a large number of terminal electrodes 3 are formed on the lower surface of the wiring board 1, and as shown in FIG.
The connection terminal 15 is formed by bonding the upper end of the connection terminal 15b to the upper end of the connection terminal 15a with the solder 16 via the solder 16. Further, the connection terminal 15 may be integrally formed as a whole.

The connection terminal 15 of the present invention is installed as follows. The connection terminal 15a is joined in the same manner as the connection terminal 14 of the first embodiment. And
The solder 16 is formed on the tip of the connection terminal 15a by various printing coating methods such as screen printing and gravure printing, or by a dispenser method, dipping method, or the like, and the tip of the connection terminal 15b is brought into contact with the solder 16. Next, solder 16
Is melted but the connection terminals 15a and 15b are not melted, or the solder 16 is melted but the connection terminals 15a and 15b are melted.
b is heated to a temperature at which it does not decompose by the same means as described above, and the connection terminal 15b is joined and fixed on the connection terminal 15a, whereby the connection terminal 15 is obtained.

Then, the connection terminals 15 of the semiconductor package A of FIG. 5 are mounted on the wiring conductors 10 of the circuit board B by brazing. At this time, as shown in FIG. 8, a wiring conductor 10 is formed on a main surface of a circuit board B having an insulating substrate 11 such as a printed board as a main body so as to correspond to the terminal electrode 3. The semiconductor package A and the circuit board B are electrically connected to each other via the solders 8, 9, 16 and the connection terminals 15. In such a mounting structure according to the second embodiment of the present invention, the solder 9 is formed on the surface of the wiring conductor 10 of the circuit board B in the same manner as described above, and the connection terminal 15 on the semiconductor package A side contacts the solder 9. Are aligned so that they touch each other, and the solder 9 is melted in the same manner as above.
It is obtained by joining the connection terminal 15 on the wiring conductor 10.

The process for producing and installing the connection terminals 15 is not limited to the above-described process. The connection terminals 15 are bonded in advance on the wiring conductors 10 of the circuit board B, and the semiconductor package A and the circuit board B are bonded. Alternatively, the connection terminal 15a is placed on the terminal electrode 3 of the wiring board 1,
Are placed on the wiring conductors 10 of the circuit board B, respectively.
The connection terminal 15a and the connection terminal 15b may be brazed. Furthermore, the solders 8, 9, and 16 do not necessarily need to be made of the same material, and can be changed to another brazing material or conductive resin if necessary.

FIG. 12 shows a third embodiment of the present invention.
In the figure, a drum-shaped connection terminal 20 having a central portion constricted is integrally formed. Incidentally, reference numeral 22 denotes the side surface, and the side surface 22 may be formed linearly or curvedly.
The installation process of the connection terminal 20 is performed according to the connection terminal 15.
Is the same as However, it goes without saying that the solder 16 is unnecessary. In addition, 21 is an upper surface which is a joining base of the connection terminal 20, and 23 is a lower surface which is joined to the wiring conductor 10 of the circuit board B.

The connection terminals 14, 15, and 20 of the present invention have a metal or alloy having a melting point higher than the melting points of the solders 8, 9, and 16, or have a thermal decomposition temperature higher than the melting points of the solders 8, 9, and 16. Preferably, it is made of a conductive resin,
Optimally, the melting point and the thermal decomposition temperature of the material of the connection terminals 14, 15, 20 are preferably higher than the heat treatment temperature at the time of brazing. As an example of such a combination, the connection terminals 14, 15, 20 are connected to Pb90-Sn10 (Pb
Wt%, containing 10% by weight of Sn)
There is a configuration in which a g-epoxy resin (Ag-containing epoxy resin) -based conductive resin and solders 8, 9, and 16 are Pb37-Sn63 eutectic solders. The "high temperature" of the Pb90-Sn10 high-temperature solder refers to the melting point of the connection terminals 14, 15, 20 with respect to the metal brazing material for the solders 8, 9, 16 melted during reflow of the solders 8, 9, 16. Alternatively, it means that the thermal decomposition temperature is relatively higher than the melting point of the metal brazing material.

When the connection terminals 14, 15, and 20 are made of a conductive resin, the long-term reliability of the connection portion is further improved by the stress relaxation effect of the conductive resin, and solder containing Pb, which is a harmful substance, is not used. Therefore, environmental pollution can be reduced. However, in this case, the molten solder 8, 9, 1
Since the self-alignment effect due to the surface tension of No. 6 cannot be obtained, positioning accuracy at the time of mounting is required. When the connection terminals 14, 15, 20 are made of conductive resin,
It is assumed that conductive resin or insulating resin contains conductive particles such as metal powder and alloy powder. Examples of the conductive resin include polyacetylene resin, polyphenylene resin, and ionic resin. Examples of the insulating resin include epoxy resin, urethane resin, acrylic resin, polyimide resin, polyester resin, and pheno resin. −
Metal-based resin is good.

The conductive particles contained in the insulating resin include Au, Ag, Cu, Al, Ni, Fe, Pd, P
t, W, Mo, Mn, Pb, Sn, Bi, Sb, In,
A powder of one or more elements of the element group consisting of C (for example, metal powder) or a compound containing at least one element of the above element group (for example, alloy powder) is preferable. These elements have excellent conductivity and high chemical stability. More preferably, Au, Ag, Cu, Ni, Pd, P
It is a powder of at least one element of t and C, or a compound containing at least one of these elements.
Most preferably, it is a powder of one or more of Au, Ag, and Cu, or a compound containing at least one of these elements.

The conductive resin preferably contains a thermosetting resin or a UV-curable resin.
It is desirable to perform a hardening treatment at the time of molding of 4, 15, and 20 in order to maintain the initial shape. The thermosetting resin and the ultraviolet curing resin have a thermal decomposition temperature of solder 8,
It is preferable that the melting point is higher than the melting points 9 and 16, and most preferably higher than the heat treatment temperature during brazing. further,
The connection terminals 14, 15a, 15b are connected to the semiconductor package A
It is desirable that the curing process be completed before joining on top to maintain its shape. Examples of the thermosetting resin and the ultraviolet curing resin include an epoxy resin, a urethane resin, an acrylic resin, a polyimide resin, a polyester resin, and a phenol resin.

The conductive resin for the connection terminals 14, 15, 20 preferably has a Young's modulus smaller than the Young's modulus of the wiring conductor 10, and is effective in relieving stress. Specifically, the Young's modulus of the conductive resin is preferably 60 GPa (gigapascal) or less, more preferably 30 GPa or less, and most preferably 15 GPa or less. Such a desired Young's modulus is obtained by appropriately selecting the resin component and the conductive particles, their mixing ratio, curing conditions and the like.

The connection terminal 14 according to the first embodiment
Is a ratio R2 / R1 between the maximum diameter R1 of the joining base 14a and the minimum diameter R2 of the tip 14b, the base angle α of which is 60 ° to 85 °.
Is preferably 0.4 to 0.95. α <60 °
In the case of, the height w1 of the connection portion cannot be sufficiently maintained,
If 85 ° <α, the effect of reducing stress concentration cannot be sufficiently obtained. More preferably α = 65 ° to 83 °, optimally α =
70 ° to 80 ° is desirable. Also, R2 / R1 <0.4
In the case of (1), the interface between the wiring conductor 10 and the connection terminal 14 becomes too small and the strength is reduced. When 0.95 <R2 / R1, the effect of reducing stress concentration cannot be sufficiently obtained. More preferably, R2 / R1 = 0.45 to 0, 90, and most preferably, R2 / R1 = 0.50 to 0.85.

The connection terminal 1 according to the second embodiment of the present invention
5, the base angle β is 45 ° to 85 °, and the ratio R4 / R3 of the maximum diameter R3 of the joint base and the minimum diameter R4 of the constricted portion is 0.3 to 0.3.
It is preferably 0.95. When β <45 °, the height w2 of the connection portion cannot be sufficiently maintained, and 85 ° <β
In the case of (1), the effect of reducing stress concentration cannot be sufficiently obtained. More preferably β = 50 ° to 83 °, optimally β = 55 ° to 8
0 ° is desirable. In the case of R4 / R3 <0.3, the interface between the wiring conductor 10 and the connection terminal 15 is too small, and the strength is reduced. In the case of 0.95 <R4 / R3, the effect of relaxing stress concentration is sufficiently obtained. I can't. More preferably R4 / R
3 = 0.45-0,90, and optimally R4 / R3 =
It is 0.50 to 0.85.

In the connection terminal 15, the connection terminal 15
a and the connection terminal 15b do not necessarily have to have the same shape, and it is preferable that the base angle β1 of the connection terminal 15a is smaller than the base angle β2 of the connection terminal 15b. Height w2 can be further secured.

The connection terminal 2 according to the third embodiment of the present invention
0, the base angle β is 45 ° to 85 °, and the ratio R4 / R3 of the maximum diameter R3 of the joining base portion and the minimum diameter R4 of the constricted portion is 0.3 to
It is preferably 0.95. When β <45 °, the height w3 of the connection portion cannot be sufficiently maintained, and 85 ° <β
In the case of (1), the effect of reducing stress concentration cannot be sufficiently obtained. More preferably β = 50 ° to 83 °, optimally β = 55 ° to 8
0 ° is desirable. When R4 / R3 <0.3, the interface between the wiring conductor 10 and the connection terminal 20 becomes too small, and the strength is reduced. When 0.95 <R4 / R3, the effect of reducing stress concentration is sufficiently obtained. I can't. More preferably R4 / R
3 = 0.55-0,90, and optimally R4 / R3 =
0.60 to 0.85.

In the connection terminal 20, the diameter of the upper surface 21 and the diameter of the lower surface 23 do not necessarily have to be the same.
It is preferable that the diameter of the upper surface 21 is larger than the diameter of the lower surface 23. In this case, stress concentration at the connection portion is reduced, and the height w3 of the connection portion can be further secured.

Thus, the present invention provides a method for turning on and off a semiconductor element.
The wiring board 1 and the circuit board B
When thermal stress occurs due to the difference in thermal expansion between
Since the initial shape of the connection terminals 14, 15, and 20 is maintained, and the shape of the joint between the connection terminals 14, 15, and 20 and the terminal electrode 3 is not constricted at the interface, a structure in which a large stress concentration occurs. But not as a result of cracking,
The progress and the like are suppressed, and the semiconductor package A can be stably connected to the circuit board B for a long time, and high long-term reliability can be obtained.

When a conductive resin is used as the material for the connection terminals 14, 15, 20 of the present invention, the stress concentrated between the solder 8 and the terminal electrode 3 is reduced to a certain level by a conductive material having some elasticity. As a result of being further alleviated by the resin, the occurrence of cracks and the like is suppressed, and the long-term reliability of the connection portion is further improved. The stress relaxation effect of the conductive resin is effective not only for thermal stress but also for various stresses, and at least the connection terminals 14 and 1 made of the conductive resin are provided on the terminal electrodes 3 at the four corners.
By providing 5 and 20, a stress relaxation effect can be obtained.

Further, since the connection terminals 14, 15, 20 are made of a metal, an alloy or a conductive resin having a higher melting point than the solders 8, 9, 16 as shown in FIG.
Solder balls made of Sn63 eutectic solder and solders 8, 9
Since the connection terminals 14, 15, and 20 do not soften or melt at the time of joining, the height w1 of the connection portion (FIG. 4),
w2 (FIG. 8) can be sufficiently maintained, and the shear direction component (X-direction component) of the thermal stress can be reduced. Furthermore, it is easy to maintain the parallelism between the semiconductor package A and the circuit board B at the time of mounting, no locally weak connection portion is formed, and the thermal stress shear direction (X
Direction) component can be reduced, and generation of cracks and the like is suppressed. Further, as a result of the mutual diffusion of the solders 8 and 9 being prevented by the connection terminals 14, 15 and 20, impurity components and air contained in the solder paste are diffused and rise, and voids are formed at the interface between the solder 8 and the terminal electrodes 3. And the like, and the mechanical strength at the interface can be prevented from lowering. As a result, the long-term reliability of the connection is improved.

Further, conventionally, the diameter of the solder ball 13 (FIG. 11) having an improved mounting density and a high melting point has an influence on the mounting density, so that a sufficient connection portion height h cannot be ensured. In the mounting structure of the present invention, the required heights w1 and w2 of the connection portion can be secured without being influenced by the interval between the terminal electrodes 3, and high-density wiring and high-density mounting can be easily achieved.

The connection terminals 14, 15, 20 of the present invention
Is not necessarily the terminal electrode 3 on the entire lower surface of the semiconductor package A.
It is not necessary to apply to the four corners, preferably by applying to at least four corners where the stress is most concentrated, desirably at and around the four corners, to exert a stress relaxation effect.

The present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0057]

Embodiments of the present invention will be described below.

Example 1 The mounting structure of FIG. 3 was manufactured by the following steps [1] to [4].

[1] Holes for through holes and the like are formed in a plurality of ceramic green sheets mainly containing alumina for the wiring board 1 by punching, and a metal paste mainly containing tungsten is formed in the holes. A metal paste for the metallized wiring layer 2 including the filled and through-hole connected terminal electrodes 3 was formed on the lower surface of the ceramic green sheet by screen printing.

[2] The thickness of the fired wiring board 1 is 1 mm
Then, a plurality of ceramic green sheets were laminated under pressure to obtain a laminate, and the laminate was simultaneously fired together with the metallized wiring layer 2, through-holes and terminal electrodes 3.

[3] Ni—Au plating is applied to the surface of the surface wiring conductor and the terminal electrode 3, and the connection terminal 14 of FIG.
The bonding was performed by solder 8 made of b37-Sn63 eutectic solder.

[4] Put the tip of the connection terminal 14 on the wiring conductor 10 of the circuit board B of the printed board by Pb37-Sn
Bonding was performed with solder 9 made of 63 eutectic solder.

The reflow temperature of the solders 8 and 9 is 230 ° C.
And the material of the connection terminal 14 is Pb90-Sn1 having a high melting point.
A thermosetting epoxy resin containing no solder or Ag powder was used. As connection terminals, P as shown in FIG.
b37-Sn63 eutectic solder using a solder ball,
Pb90-Sn1 as shown in FIG. 11 having a substantially elliptical shape having a flat shape in the horizontal direction after bonding (sample No. 1).
Using a solder ball made of No. 0 solder, a ball having a ball shape after bonding (sample No. 2) was manufactured as a comparative example.

Next, the semiconductor package A and the circuit board B having these mounting structures are respectively removed by -40 in the air atmosphere.
A maximum of 1,000 cycles were repeated, in which one cycle was a case where the temperature was kept alternately in a thermostat controlled at a temperature of 125 ° C. and a temperature of 125 ° C., and both were held for 15 minutes. Then, the electrical resistance between the wiring conductor 10 of the circuit board B and the terminal electrode 3 of the wiring board 1 was measured every 50 cycles, and Table 1 shows the number of cycles until the electrical resistance changed. In Table 1, those marked with * are outside the scope of the present invention, and those marked with triangles are outside the preferred ranges of α and R2 / R1.

[0065]

[Table 1]

As shown in Table 1, the sample No. 1
In the case of Sample No. using a high melting point solder ball, the solder ball melted during reflow and became substantially elliptical, causing a change in resistance in 100 cycles, making it impossible to ensure long-term reliability of the connection portion. 2, the electrical resistance changed at 250 cycles, and the long-term reliability of the connection portion was insufficient. In Nos. 3 to 19, the number of cycles in which the electric resistance does not change is excellent at 300 or more. Therefore, they are accurately and firmly connected for a long period of time, and are sufficient for increasing the number of terminals and increasing the density of the semiconductor element 4 by increasing the size of the semiconductor element 4. A highly reliable mounting structure that can be used was realized.

The base angle α of the connection terminal 14 is
Within the range of 60 to 85 °, the stress relaxation effect by the connection terminal 14 was high, and the reliability of the connection portion was high. Further, the ratio R2 between the maximum diameter R1 and the minimum diameter R2 of the connection terminal 14 is R2.
Regarding / R1, the effect of reducing stress concentration was high in the range of 0.4 to 0.95, and the reliability of the connection portion was high. Then, α = 60 ° to 85 °, R2 / R1 = 0.4
~ 0.95 sample NO. 5,8-10,1
In Nos. 3, 16 to 19, the number of cycles was particularly excellent at 500 or more.

(Example 2) The mounting structure shown in FIG. However, on the terminal electrode 3, the connection terminal 15 of FIG.
Bonding was performed by solder 8 made of Sn63 eutectic solder. The connection terminal 15 connects the connection terminals 15a and 15b to Pb37-Sn.
63 eutectic solder is used for joining,
The tip of the connection terminal 15 was joined to the wiring conductor 10 of the printed circuit board B by the solder 9 made of Pb37-Sn63 eutectic solder. The reflow temperature of the solders 8, 9, and 16 is 230 ° C., and the material of the connection terminals 15 is high melting point P.
b90-Sn10 solder or thermosetting epoxy resin containing Ag powder.

Next, the semiconductor package A and the circuit board B each having these mounting structures are mounted in an air atmosphere at −40.
A maximum of 1,000 cycles were repeated, in which one cycle was a case where the temperature was kept alternately in a thermostat controlled at a temperature of 125 ° C. and a temperature of 125 ° C., and both were held for 15 minutes. Then, the electrical resistance between the wiring conductor 10 of the circuit board B and the terminal electrode 3 of the wiring board 1 was measured every 50 cycles, and Table 2 shows the number of cycles until the electrical resistance changed. In Table 2, those marked with * are outside the range of the present invention, and those marked with triangles are outside the preferred ranges of β and R4 / R3.

[0070]

[Table 2]

As shown in Table 2, the sample N of the present invention
O. In Nos. 20 to 36, no change in resistance was observed up to 300 cycles. Therefore, they were accurately and firmly connected for a long period of time. A high mounting structure was realized.

The base angle β of the connection terminal 15 is
Within the range of 45 ° to 85 °, the effect of relaxing the stress by the connection terminal 15 was high, and the reliability of the connection portion was high. Furthermore, the ratio R4 between the maximum diameter R3 and the minimum diameter R4 of the connection terminal 15
Regarding / R3, the effect of reducing stress concentration was high in the range of 0.3 to 0.95, and the reliability of the connection portion was high. Then, β = 45 ° to 85 °, R4 / R3 = 0.3
~ 0.95 sample NO. 22, 23, 25
For ~ 28,39,31,33 ~ 36, the number of cycles is 5
It was particularly excellent at 00 or more.

(Example 3) A mounting structure using the connection terminals 20 shown in FIG. However, the connection terminal 2 made of various shapes and materials (Table 3) is provided on the terminal electrode 3.
No. 0 was joined by solder 8 made of Pb37-Sn63 eutectic solder. The connection terminal 20 has a lower surface 2 which is a tip portion thereof.
3 on the wiring conductor 10 of the printed circuit board B,
Bonding was performed with solder 9 made of Pb37-Sn63 eutectic solder. The reflow temperature of the solders 8 and 9 was 230 ° C., and the material of the connection terminals 20 was a high melting point Pb90-Sn10 solder or a thermosetting epoxy resin containing Ag powder.

Next, the semiconductor package A and the circuit board B having these mounting structures are respectively removed by -40 in the air atmosphere.
A maximum of 1,000 cycles were repeated, in which one cycle was a case where the temperature was kept alternately in a thermostat controlled at a temperature of 125 ° C. and a temperature of 125 ° C., and both were held for 15 minutes. Then, the electric resistance between the wiring conductor 10 of the circuit board B and the terminal electrode 3 of the wiring board 1 was measured every 50 cycles, and Table 3 shows the number of cycles until the electric resistance changed. In Table 3, those marked with * are outside the range of the present invention, and those marked with triangles are outside the preferred ranges of β and R4 / R3.

[0075]

[Table 3]

As shown in Table 3, the sample N of the present invention was used.
O. In Nos. 37 to 53, no change in resistance was observed up to 300 cycles. Therefore, they were accurately and firmly connected for a long period of time. A high mounting structure was realized.

The base angle β of the connection terminal 20 is
Within the range of 45 ° to 85 °, the stress relaxation effect by the connection terminal 20 was high, and the reliability of the connection portion was high. Further, the ratio R4 between the maximum diameter R3 and the minimum diameter R4 of the connection terminal 20 is R4.
Regarding / R3, the effect of reducing stress concentration was high in the range of 0.3 to 0.95, and the reliability of the connection portion was high.

Then, β = 45 ° to 85 °, R4 / R3
= 0.3 to 0.95. 39,4
In the case of 0, 42 to 45, 47, 48, 50 to 53, the number of cycles was particularly excellent at 500 or more.

As described above, in the first to third embodiments, the wiring board 1 is made of alumina ceramic, and the circuit board B
Is obtained by forming a Cu wiring conductor layer or the like on an insulating substrate of glass-epoxy resin, but the same effect can be obtained by changing the type of constituent material, such as by exchanging materials between the two. Further, the mounting structure of the present invention can be applied not only to BGA type semiconductor packages, but also to CSP (chip scale semiconductor packages), MCMs (multi-chip modules), and various module substrates mounted using connection terminals. The same effect can be obtained.

[0080]

According to the present invention, a wiring substrate for a semiconductor package or the like is formed by joining a connection terminal of a truncated cone shape or a truncated polygonal pyramid shape having a tip portion smaller than a joining base portion on a terminal electrode via a brazing material. When mounted on other circuit boards such as printed circuit boards, connection terminals that are brazed by reducing and reducing thermal stress, various mechanical stresses, and shocks that occur during mounting or use, and by reducing stress concentration And the long-term reliability of the connection is improved.

Further, since the connection terminal is made of a metal, an alloy or a conductive resin having a higher thermal decomposition temperature than the melting point of the brazing material, it does not soften or melt at the time of joining. , And as a result, it is easy to maintain the parallelism between the semiconductor package and the circuit board at the time of mounting and after mounting, without forming a locally weak connection portion, The shear direction component of the thermal stress can be reduced, and the occurrence of cracks and the like can be suppressed. In addition, as a result of the inter-diffusion of solder, which is a brazing material, being prevented by the connection terminals, impurity components and air contained in the solder paste diffuse and rise, and defects such as voids occur at the interface between the solder and the terminal electrode, A decrease in the mechanical strength of the interface can be prevented. As a result, the long-term reliability of the connection is improved.

Further, since the required height of the connection portion can be secured without being influenced by the interval between the terminal electrodes, high-density wiring and high-density mounting can be easily achieved.

[Brief description of the drawings]

FIG. 1 shows a BGA type semiconductor package of the present invention;
FIG. 3 is a cross-sectional view of the wiring board according to the first embodiment.

FIG. 2 is an enlarged sectional view of a connection terminal portion provided on the wiring board of FIG. 1;

FIG. 3 is a sectional view of a mounting structure in which the semiconductor package of FIG. 1 is mounted on another circuit board.

FIG. 4 is an enlarged sectional view of a connection terminal part in the mounting structure of FIG. 3;

FIG. 5 shows a BGA type semiconductor package of the present invention;
It is sectional drawing of the wiring board by 2nd embodiment.

FIG. 6 is an enlarged sectional view of a connection terminal portion provided on the wiring board of FIG. 5;

FIG. 7 is a sectional view of a mounting structure in which the semiconductor package of FIG. 5 is mounted on another circuit board.

FIG. 8 is an enlarged sectional view of a connection terminal portion in the mounting structure of FIG.

9A and 9B are diagrams illustrating a mounting process of a conventional BGA type semiconductor package, in which FIG. 9A is a cross-sectional view of the semiconductor package before mounting, and FIG. 9B is a diagram in which solder balls are bonded to terminal electrodes of a wiring board. Sectional view of the semiconductor package in a state,
(C) is a cross-sectional view of the semiconductor package and another circuit board when the solder balls are melted, and (d) is a state of the semiconductor package and the circuit board in a state where the semiconductor package is mounted on the circuit board via the solder balls. It is sectional drawing.

FIG. 10 is a sectional view of a solder ball portion used for mounting a conventional BGA type semiconductor package.

FIG. 11 is a sectional view of a high melting point solder ball portion used for mounting a conventional BGA type semiconductor package.

FIG. 12 is an enlarged sectional view of a connection terminal portion according to a third embodiment of the present invention.

[Explanation of symbols]

 1: Wiring board 2: Metallized wiring layer 3: Terminal electrode 4: Semiconductor element 5: Bonding wire 8, 9, 16: Solder 10: Wiring conductor 11: Insulating substrate 14, 15, 20: Connection terminal

Claims (6)

[Claims] A plurality of terminal electrodes are provided on a main surface of an insulating substrate having a wiring conductor layer formed on the surface and / or inside thereof, the terminal electrodes being electrically connected to the wiring conductor layer. A wiring substrate, wherein a connection terminal in the shape of a truncated pyramid is joined to the terminal electrode via a brazing material. 2. The wiring board according to claim 1, wherein the connection terminal is a drum-shaped connection terminal with a central portion instead of the truncated conical or polygonal truncated connection terminal. 3. The connection terminal according to claim 2, wherein the base angle of the connection base is 60 ° or more.
2. The wiring board according to claim 1, wherein the ratio R2 / R1 of the maximum diameter R1 of the joining base portion and the minimum diameter R2 of the tip end portion is 0.4 to 0.95. 4. A base angle of a connecting base of the connection terminal is 45 ° or more.
The wiring board according to claim 2, wherein the ratio R4 / R3 of the maximum diameter R3 of the joining base portion and the minimum diameter R4 of the constricted portion is 0.3 to 0.95. 5. The connecting terminal is made of a metal or alloy having a higher melting point than the brazing material, or a conductive resin having a higher thermal decomposition temperature than the melting point of the brazing material. The wiring board according to any one of the above. 6. The mounting of the wiring board according to claim 1, wherein the wiring board according to claim 1 is joined to a wiring conductor of another circuit board via the connection terminal with a brazing material. Construction.