JP2001185577A - Electronics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic appliance equipped with mounting configuration for easy rework. SOLUTION: A mounting configuration connects a bump of a semiconductor device with an electrode terminal of the wiring substrate. A metallic layer with lower melting point than the bump is formed on the electrode terminal, and the bump is connected to the electrode terminal forming the metallic layer via a conductive adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic apparatus having a mounting structure in which a semiconductor chip or a semiconductor device (semiconductor package) having a bump is connected to an electrode terminal of a wiring board via a conductive adhesive. The present invention relates to an electronic device having a mounting structure suitable for reworking the semiconductor chip or semiconductor device (semiconductor package).

[0002]

2. Description of the Related Art At present, personal computers (PC: Per)
Sonal Computer) and other mounting boards have a microprocessor with a number of input / output pins of 400 to 600
ASIC for various controllers called chipset of 0-400 pin class and graphic controller
(Application Specified Integrated Circuit) occupies a large proportion, and the number of pins is increasing year by year due to demands for faster input / output performance of the PC body. Conventionally, in order to meet the demand for increasing the number of input / output pins, a QFP (Quad Fl
At-package), SOP (Small Outline Package), and other packages with peripheral pin arrangement have been narrowed in pin pitch. However, due to the mounting problem such as soldering and reliability issues, the pitch limit has become practically limited to about 0.5 mm pitch. BGA (Ball Grid Array) where certain solder bumps are arranged in the area under the semiconductor package
The rate of adopting the type semiconductor package is increasing.
In addition, since the BGA type semiconductor package can be miniaturized and multi-pin even at a relatively coarse pitch as compared with a package having a peripheral pin arrangement, it has been widely adopted as a multi-pin and high-speed semiconductor package.

[0003] Bare chip mounting, in which a semiconductor chip itself is mounted, has also become widespread for the purpose of improving the mounting density.

[0004]

However, the BGA
In a mounting structure in which a semiconductor package is mounted on a substrate, the solder balls (bumps) of the semiconductor package are melted and connected to the electrode terminals on the substrate side, so that there is a problem that rework, that is, package replacement, is difficult. . The rework method after the BGA type semiconductor package is mounted on the substrate is described in, for example, Electronics Packaging Technology; vol.
12 No. 1, pp. 48-52, 1996.1, a hot air nozzle method is known. In this method, the solder portion of the melted and connected BGA type semiconductor package is melted again to remove the BGA type semiconductor package body (not including solder balls). In this method, the molten solder is placed on the electrode on the substrate side. Is left behind, which causes a problem when a new BGA type semiconductor package is remounted.

On the other hand, as a method for mounting a semiconductor chip on a substrate, there are a method using a thermoplastic or thermosetting conductive adhesive and a method using an anisotropic conductive adhesive.

A technique using a conductive adhesive is, for example, LS
An Au bump is formed on the I electrode, and a conductive adhesive layer is formed by stamping the Au bump into a conductive paste in which Ag flakes are dispersed. After the completion of the electrical temporary connection, a thermosetting insulating adhesive is formed. An agent is filled in the gap between the LSI and the substrate to make a final connection.

The method using an anisotropic conductive adhesive is as follows.
For example, an anisotropic conductive adhesive in which metal balls or the like are filled in a film-like or gel-like adhesive layer is supplied onto the electrodes of the substrate, and then the electrical connection and the semiconductor chip / substrate are simultaneously formed by thermocompression bonding. Filling with a thermosetting insulating adhesive is performed.

In these cases, the semiconductor chip is removed and reworked by melting the conductive adhesive or the anisotropic conductive adhesive with a solvent, but even in this case, the adhesive is applied to the electrodes. Some remain. In addition, the effect on other mounted components due to the use of the solvent cannot be ignored.

An object of the present invention is to facilitate rework of a semiconductor chip or a semiconductor package in a mounting structure of an electronic device.

[0010]

According to the present invention, there is provided a semiconductor device comprising: a semiconductor device; a wiring board on which the semiconductor device is mounted; a bump of the semiconductor device; and an electrode terminal of the wiring substrate. A metal layer having a lower melting point than the bump is formed on the electrode terminal, and the bump and the electrode terminal on which the metal layer is formed are connected via a conductive adhesive layer. It was done.

An electronic device comprising a semiconductor chip and a wiring board on which the semiconductor chip is mounted, wherein the electronic device comprises a bump provided on the semiconductor chip and an electrode terminal provided on the wiring board, wherein the bump is provided on the electrode terminal. Forming a metal layer having a lower melting point than the above, connecting the bump and the electrode terminal on which the metal layer is formed via a conductive adhesive layer, and forming a thermosetting resin between the semiconductor chip and the wiring board. Is filled with.

Further, the bump is a solder bump or a conductive bump.

Further, the metal layer is made of solder.

Further, the diameter of the conductive adhesive layer is smaller than the diameter of the electrode terminal on which the metal layer is formed.

Further, a part of the bump is flattened.

Further, a part of the solder bump is roughened.

Further, the bump is formed of a low elastic conductive adhesive having a glass transition temperature near room temperature.

According to the above configuration, the metal layer on the electrode terminal of the wiring board can be in a molten state, so that the semiconductor chip or semiconductor device (semiconductor package) including the conductive adhesive layer can be connected to the electrode of the wiring board. It can be separated at the terminal interface. Since the conductive adhesive layer and the metal layer are not metal-connected, the semiconductor chip or the semiconductor device (semiconductor package) including the conductive adhesive layer can be easily removed. After removal, the metal layer remains on the electrode terminals of the wiring board, but does not pose a problem because it is remounted via the conductive adhesive layer. Further, the leveling operation is also easy.

When the semiconductor chip is mounted, before the semiconductor chip is filled with an underfill (thermosetting resin), that is, the bumps of the semiconductor chip and the metal layer on the electrode terminals on the wiring board are electrically conductive adhesive. It is preferable to judge whether or not to rework after connecting via an underfill. Underfill (thermosetting resin) for those judged as having no problem
It is preferable to fill with.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a semiconductor device mounting structure and a mounting method according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of a semiconductor device mounting structure according to the present invention. FIG. 2 is an enlarged cross-sectional view of the vicinity of the connection portion according to the first embodiment.

In the figure, 1 is a semiconductor package body,
1a is a resin seal, 1b is a substrate, 2 is a wiring board, 3 is a metal pad, 4 is a bump, 5 is an electrode terminal, 6 is a metal layer, 7 is a conductive adhesive layer, and 11 is a semiconductor package.

The semiconductor package body 1 is packaged by mounting an LSI chip (not shown) on a substrate 1b such as a small ceramic, glass epoxy or resin film.
A plurality of metal pads 3 mainly made of Cu (for example, formed by coating Cu with Au or the like) are provided on the lower surface of the substrate 1b.

In the semiconductor package 11, a bump 4 having a flat surface 4a formed on a metal pad 3 of a semiconductor package body 1 is joined. The solder bump 4 is formed by soldering (fusing) a solder bump made of a Pb-Sn eutectic solder or a lead-free solder having a flattened top, and fixed. As a lead-free solder, for example, Sn-Ag-
An alloy solder such as Cu or Sn-Ag-Cu-Bi having a melting point of about 190 to 220 ° C. is considered. Pb-
In the case of Sn eutectic solder, the melting point is slightly lower from about 180 to 190 ° C., which is advantageous when mounting at a low temperature.
As an example of the semiconductor package 11, a BGA (Ball Gr
id Alley) and CSP (Chip Size Package).

The wiring board 2 is provided with a plurality of electrode terminals 5 mainly made of Cu on a glass epoxy board or the like.
A solder coat layer 6 made of Pb-Sn eutectic solder, lead-free solder, or the like is formed on the outermost surfaces of these electrode terminals 5. The thickness of the solder coat layer 6 is desirably about 10 to 20 μm.

A thermosetting conductive adhesive layer 7 (a circular conductive adhesive layer corresponding to each bump) is provided between the flat surface 4a of the solder bump 4 and each electrode terminal 5 on which the solder coat layer 6 is formed. Or a square pattern), which electrically and mechanically connects them. That is, the conductive adhesive is electrically connected by a conductive powder mainly composed of flake Ag or Ag-Pd contained in the conductive adhesive, and is mechanically bonded and connected by an adhesive base material of the conductive adhesive. When a thermosetting conductive adhesive is used, each conductive adhesive layer (each conductive paste part) remains in paste form, and the package and wiring board are aligned and mounted. It is desirable to completely heat-harden the layer to connect each solder bump 4 and each electrode terminal 5. Here, as the thermosetting conductive adhesive, an adhesive base mainly composed of an epoxy resin or the like, and a flake-like Ag or Ag having a length of about 5 μm to 20 μm and a diameter of about 0.6 μm to 2 μm. It is desirable to use one containing conductive powder containing -Pd as a main component. In addition, the conductive adhesive layer 7
It is preferable that the thermosetting resin be adhesively connectable at a lower temperature than the solder bumps 4 and the solder coat layer 6. This is because the conductive adhesive is thermally cured without substantially melting the solder bump 4 and the solder coat layer 6 (at a temperature at which the solder bump 4 and the solder coat layer 6 do not melt).

Further, by forming the diameter of the conductive adhesive layer 7 smaller than the diameter of the electrode terminal 5 on which the solder coat layer 6 is formed, at the time of rework, that is, at the time of package replacement, the semiconductor package 11 ( (Including the conductive adhesive layer 7) can be easily removed.

As shown in the figure, by providing a solder coat layer 6 on the electrode terminals 5, the solder coat layer 6 is heated and melted, and the semiconductor package 1 including the conductive adhesive layer 7 is heated.
1 can be easily removed. Semiconductor package 1
If the solder coat layer 6 having a lower melting point than the one solder bump 4 is formed, the semiconductor package can be removed at a lower temperature. Therefore, the temperature at which the semiconductor package is removed can be determined based on the melting point of the solder coat layer 6. Even if the melting point of the bumps of the semiconductor package and the melting point of the solder coat layer are the same, since the conductive adhesive layer can be removed from the melted solder coat layer, the solder bumps of the semiconductor package melt, Even if the semiconductor package and the conductive adhesive layer are separated at that portion, the semiconductor package and the conductive adhesive layer can be removed as a result.

Further, since the flat surfaces 4a which are flattened at the same height with respect to the apexes of the plurality of solder bumps 4 formed on the semiconductor package 11 are formed, the connected portions of the solder bumps can be uniformly formed. As a result, the semiconductor package 11 is partially formed by the group (collection) of the conductive adhesive layers 7 only between the flat surface 4a of each of the opposed solder bumps 4 and each of the electrode terminals 5. Thus, electrical and mechanical connection reliability comparable to that of solder connection can be ensured without an underfill. As shown in FIG. 2, the conductive adhesive component 7 of each of the solder bumps 4 and the electrode terminals 5 slightly covers the side surfaces of the flat surface 4a of the solder bumps, and also covers the electrode terminals 5.

FIG. 3 shows a structure provided with a plurality of mounting structures shown in FIG. FIG. 3 shows a plurality of semiconductor packages 21.
(11), 22 (11) and 23 (11) are mounted on the wiring board 2 from the mounting structure (20) of the semiconductor package having the multi-chip module structure.
This is an example in which (11) is replaced and reworking is performed, but even in this case, the desired solder coating layer 6 formed on the outermost surface of the electrode terminal 5 on the wiring board 2 can be easily melted by heating. The semiconductor package 21 (11) can be removed, and rework (package replacement) can be easily performed. That is, rework can be performed at a temperature lower than the melting point of the desired solder bump of the semiconductor package 21 (11). Further, the thermosetting conductive adhesive layer 7 provided between each solder bump 4 of the semiconductor package 11 and the electrode terminal 5 of the wiring board 2 serves as a thermal expansion coefficient between the semiconductor package body 1 and the wiring board 2. In order to absorb the stress caused by the difference between the two, high connection reliability is secured.

Next, the semiconductor package 1 according to the present invention will be described.
A first example of a mounting method for obtaining the first embodiment of the first mounting structure will be described with reference to FIGS.

FIGS. 4 and 5 are cross-sectional views showing changes in the mounting structure of the semiconductor package.

First, FIGS. 4 (a) and 4 (b), FIGS.
As shown in (b), the electrode terminal 5 mainly made of Cu on the wiring board 2 is formed to a thickness of 10 to 20 μm by, for example, electrolytic / electroless plating or solder paste reflow on the electrode terminal.
Approximately a solder coat layer is formed. Here, the temperature of the solder coat is desirably set to a temperature higher by about 20 to 30 ° C. than the melting point of the solder, and it is desirable that the reflow is performed for 60 seconds or more.

On the other hand, as shown in FIGS. 4 (a) and 4 (b), 5 (a) and 4 (b), the semiconductor package 11 having A flat plate 8 made of a material that is smooth with the bumps 4 facing down, hardly warps even at high temperatures, and does not wet with solder, for example,
After being mounted on ceramic or glass, the solder bumps 4 are heated and melted, and the apex portion is flattened only by the weight of the package without flux and the flat surface 4a serving as an adhesive surface is formed with the same height. Here, the flattening temperature of the solder bump 4 is set to a temperature higher by about 20 to 30 ° C. than the melting point of the solder, and it is desirable that the solder is reflowed for 60 seconds or more. By performing these steps in advance and forming the flat surfaces 4a of 50% or more of the diameter of the solder bumps 4 at the same height, the conductive adhesive layer (thermosetting conductive adhesive) is thereafter formed. 7 can be easily formed by paste printing.

At the time of heating and melting, the area of the flattened portion (adhered area) can be controlled by pressing the semiconductor package at about 0.02 gf / bump.

The vertex side of the solder bump 4 of the semiconductor package 11 has a flat plate 8 made of a material which is smooth and does not wet with solder.
After being mounted on the reflow furnace, the solder bumps 4 are conveyed into a reflow furnace, and the solder bumps 4 are heated and melted.
It is also possible to perform the processes up to flattening and cooling all at once. At this time, the flattening area and the bump height of the solder bump 4 can be adjusted by applying a load from the upper surface of the package.

In the above embodiment, the solder bumps 4 are flattened by heating and melting. However, by pressing and heating the solder bumps 4 at a temperature lower than the melting point, the top side and the height are made uniform and smooth. In order to perform such flattening, it is not possible to apply an excessive load to the semiconductor package body 1. Therefore, the number of bumps has increased, especially in response to the increase in the number of pins, the size of the packages has increased, the solder bumps have become lead-free solder, and the melting point has increased. It becomes increasingly difficult. Therefore, flattening at a temperature equal to or higher than the solder melting point, which can flatten the solder bumps without applying a large load to the semiconductor package 11, is effective.

Next, as shown in FIG. 4C, the flat surface 4a of the solder bump 4 of the semiconductor package 11 is turned upside down and held, and the flat surface 4a of the inverted solder bump 4 is After the openings of the mask 9 are aligned, a paste-like thermosetting conductive adhesive 12 is locally applied only to the flat portions 4a of the solder bumps 4 by a screen printing method.

Note that, as shown in FIG.
After the opening of the metal mask 9 is aligned with the electrode terminal 5 on which the upper solder coat layer 6 is formed, a paste-like thermosetting conductive adhesive 12 is locally applied only to the electrode terminal 5 side by a screen printing method or the like. May be applied.

Here, in the case of a thermosetting conductive adhesive, a semi-cured state can be obtained only by standing at room temperature without heating.

In each of FIGS. 4C and 5C, the thickness of the metal mask 9 depends on the thickness of the semiconductor package 1.
(1) The amount of warpage deformation during mounting (the amount of warpage deformation of the wiring board 2 or the semiconductor package 11; however, regarding the amount of warpage deformation of the semiconductor package 11, the temperature when the flat surface 4a of the solder bump 4 is formed, the conductive adhesive layer 7 using solder bump 4
And a temperature at the time of connecting and mounting between the solder-coated electrode terminals 5, there is a temperature difference of about 30 to 40 ° C., which is caused by the temperature difference) and heat curing of the thermosetting conductive adhesive. Determined in consideration of the volume reduction.

In this case, the thermosetting shrinkage of the thermosetting conductive adhesive is so small as to be negligible compared to the warpage of the semiconductor package 11. That is, the thickness of the metal mask 9 is set to be equal to the thickness (80 μm) of the conductive adhesive layer 7 capable of absorbing the height variation of the solder bumps 4 having the flattened tops and the warpage of the wiring board 2 and the semiconductor package 11.程度 100 μm).

As described above, if the conductive adhesive layer 7 is applied by the screen printing method, the conductive adhesive layer 7 can be easily formed even on the semiconductor package 11 having a larger number of solder bumps. Become.

Further, other flat surface 4a of solder bump 4
As a conductive adhesive layer forming method other than the screen printing method of forming a local conductive adhesive layer 12 connectable at a lower temperature than solder on the electrode terminals 5 of the wiring board 2, a conductive paste is transferred. Although a method and a method of transferring an uncured thermosetting conductive adhesive in a sheet form by thermocompression bonding are also conceivable, there are variations in the amount of conductive paste transferred and the amount of conductive adhesive sheet transferred. Since it is difficult to control the shape of the semiconductor package, the screen printing method is most suitable for connection and rework (package replacement) of semiconductor package bumps.

Thereafter, as shown in FIG. 4D, the solder bumps 4 of the semiconductor package 11 on which the conductive adhesive layer 12 has been locally formed and the electrode terminals 5 of the wiring board 2 are aligned and mounted. By heating below the melting point of the solder bumps 4 and the solder coat layer 6, the solder bumps 4 and the electrode terminals 5 are electrically and mechanically connected via the conductive adhesive layer 7, A mounting structure of a semiconductor package as shown in FIG. 4E can be obtained.

The above-mentioned alignment is obtained by optically observing a desired electrode terminal 5 or a reference mark (not shown) on the wiring board 2 placed on a stage (not shown). And the solder bump 4 of the semiconductor package 11 held by a vacuum chuck or the flat surface 4 thereof, for example.
a) by double-exposing an image obtained by optically observing the conductive adhesive layer 12 formed on a) and controlling the relative position between the stage and the vacuum chuck based on the image. can do.

As shown in FIG. 5D, the semiconductor package 11 has a flat portion 4a of the solder bump 4 and a solder coat layer 6 on the wiring board 2 on which a conductive adhesive layer 12 is locally formed. The electrode terminal 5 is aligned and mounted.
By heating the solder bumps 4 and the solder coat layer 6 at a temperature equal to or lower than the melting point, the solder bumps 4 and the electrode terminals 5 are electrically and mechanically connected via the conductive adhesive layer 7. A semiconductor package mounting structure as shown in FIG. 5 (e) can be obtained.

In this case, since the conductive adhesive substrate is a thermosetting resin, the connection is made by a thermosetting reaction.

4 (a) to 4 (d) and FIGS. 5 (a) to 5 (d)
4 (e) and 5 (c), the adhesive connection by the conductive adhesive layer 7 of the semiconductor package 11 is completed.
A mounting structure of a semiconductor package as shown in (e) can be obtained.

As described above, the thermosetting conductive adhesive layer 12 which can be bonded and connected at a temperature lower than the melting points of the solder bumps 4 and the solder coat layer 6 is provided on the flat surface 4a of the solder bumps 4 and the wiring board. An electrode having the flat surface 4a of the solder bump 4 and the solder coat layer 6 is formed locally only between the electrode terminal 5 on which the solder coat layer 6 is formed and heated at a temperature lower than the melting point of the solder bump. Since the adhesive connection including the electrical connection is made between the terminal 5 and the local conductive adhesive layer 7 via the conductive adhesive layer 7, the semiconductor package 11 can be reworked at a low temperature.

Further, if the adhesive force of the printed thermosetting conductive paste 12 is used, the semiconductor package can be mounted.
It is possible to prevent the semiconductor package bumps 4 from being displaced from the electrode terminals 5 of the wiring board during the heating connection process. In addition, since the local conductive adhesive layer 12 may be heated to a temperature equal to or lower than the melting point of the solder bumps 4 and the solder coat layer 6, rework using a conventional facility such as a reflow furnace becomes possible. Also, when the semiconductor package 11 is connected, the conductive paste 12 is applied to the semiconductor package 11.
It is also possible to absorb the height variation of the solder bumps 4.

Further, according to this method, the variation in the height of the solder bumps of the semiconductor package is uniformly absorbed by forming the flat surface 4 a on the top of the solder bump 4, and the conductive paste 12 is used to absorb the variation in the height of the wiring board 2. Since the semiconductor package 11 is configured to absorb the warp deformation, the semiconductor package can be connected and reworked, which is difficult to connect by heating accompanied by pressurization of the semiconductor package. The curing temperature of the thermosetting conductive adhesive is from 130 to 1 which does not greatly exceed the glass transition point 130 ° C. of the mounting substrate.
It is desirable to be in the range of 60 ° C.

Next, the mounting method shown in FIG. 4 will be described in more detail. In this case, as the semiconductor package 11, a BGA package having a pitch of the solder bumps 4 of 0.8 mm and about 729 bumps was used. Further, the conductive adhesive 12
The base material of the adhesive is epoxy-based, and the length is 3 to 8μ.
A thermosetting material in which a flake-like Ag conductive filler having a size of about m and a diameter of about 0.5 to 1 μm was dispersed was used. Also, for printing conductive paste, the thickness of 150μm
A plastic mask 9 having a hole diameter of about 450 μm was used.

First, as shown in FIGS. 4A and 4B, 1 m
After placing the apex side of the solder bumps 4 of the semiconductor package 11 on the glass plate 8 having a thickness of m below, the flux is conveyed into a reflow furnace without flux and with a static load of about 0.02 gf / bump applied. The Pb-Sn eutectic solder bump 4 was flattened under heating conditions of about 210 ° C. for about 60 seconds to form a flat surface 4a.

As shown in FIGS. 4 (a) and 4 (b), a Pb-Sn eutectic solder paste is applied to electrode terminals mainly made of Cu on the wiring board 2 and then reflowed. From about 20 μm. Here, the temperature of the solder coat is Pb-Sn
The melting point of the eutectic solder was raised from 183 ° C. to about 30 ° C., that is, 210 ° C., and reflow was performed for about 60 seconds to form the solder coat layer 6.

Thereafter, as shown in FIG. 4C, the semiconductor package 11 is turned over and the plastic mask 9 is turned on.
Thus, a paste-like epoxy-based thermosetting conductive adhesive 12 was screen-printed on each flat surface 4 a of the solder bump 4.

Thereafter, as shown in FIG. 4D, the solder bumps 4 of the semiconductor package 11 and the electrode terminals 5 of the wiring board 2 are aligned and mounted, and heated at about 150 ° C. for about 15 minutes to form a conductive paste. 12 was cured and an adhesive connection was made. With these connection methods, it is possible to obtain a connection resistance and a connection strength equivalent to those of the solder connection without performing any resin reinforcement of the connection portion such as the underfill.

FIG. 6 shows an example of the connection state. As is clear from FIG. 6, a fillet-shaped thermosetting conductive adhesive layer 7 is also formed on the side surface of the solder bump 4, and blowholes are generated in the conductive adhesive layer 7. Since there is no connection, high connection reliability can be obtained.

According to the bump connection in this state, an initial connection strength of about 280 gf / bump at the maximum could be obtained in the adhesive connection on the solder coat surface.

Next, the semiconductor package 1 according to the present invention
A second embodiment of the first mounting structure will be described with reference to FIG.

That is, the second embodiment is characterized in that a rough surface 4b is formed on the vertex side of the solder bump 4 in the mounting structure of the semiconductor package 11 in the first embodiment.

FIG. 4 shows a first embodiment of a mounting method for obtaining the first embodiment of the mounting structure of the semiconductor package 11 in the first embodiment.
5 (a) and 5 (b) and FIGS. 5 (a) and 5 (b), in the step of flattening the top of the solder bump, a rough surface is mechanically formed with the solder bump 4 side down, and even at a high temperature. After placing the solder bumps 4 on a surface plate 8 made of a material which hardly warps and is not wetted by solder, for example, ceramic or glass, the solder bumps 4 are heated and melted only by the own weight of the package without flux and almost by its own weight. It is characterized in that the apex portion is flattened and roughened, and the rough surface 4b serving as an adhesive surface is formed with a uniform height. According to the second embodiment, it is possible to increase the connection strength at the bonding interface between the solder bump 4 and the conductive adhesive layer 7, and it is possible to obtain high connection reliability.

Even with such a structure, the semiconductor package 11 is interposed via the solder coat layer and the conductive adhesive layer 7.
And the wiring board 2 are connected, so that rework can be easily realized as in the first embodiment.

Next, the semiconductor package 1 according to the present invention
Third and fourth embodiments of the first mounting structure will be described with reference to FIGS.

That is, the third and fourth embodiments are similar to the first embodiment.
Instead of the solder bumps 4 of the semiconductor package 11 in the embodiment, a flexible thermosetting or
The conductive bump 10 is formed of a low-elasticity thermoplastic conductive adhesive layer having a glass transition point near room temperature.

In the third embodiment, as shown in FIG.
The fourth embodiment comprises a conductive bump 10 formed of an uncured thermosetting or low-elastic thermoplastic conductive adhesive layer having a glass transition point near room temperature. As shown, a conductive adhesive bump 10 and a conductive adhesive layer 12 each composed of two or more conductive adhesive layers having different properties.
Can be formed, and the mounting structure can be formed by adhesively connecting through the adhesive layer 7 obtained by curing the adhesive layer 12.

In the case of these mounting forms, in the semiconductor package 11, the bump height must be such that a sufficient connection height can be secured to the metal pad (input / output pad) of the package-side base substrate 1b. In the case of a 27 mm bump pitch BGA package, 600 to 70
Desirably, it is about 0 μm.

As a method of forming the conductive adhesive bump 10 in the third embodiment, in the semiconductor package body 1 having a plurality of metal pads, only the metal pad 3 of the package is thermoset by a screen printing method or the like. Alternatively, the solid conductive bump 10 is formed by a thermoplastic conductive adhesive layer.

The method of forming the conductive adhesive bump 10 in the fourth embodiment is as follows. In the semiconductor package body 1 having a plurality of metal pads, only the metal pad 3 of the package is heat-cured by screen printing or the like. A solid conductive bump 10 is formed by a thermoplastic conductive adhesive layer, and a thermosetting conductive adhesive layer 12a is locally applied and formed only on the bump 10 by a screen printing method or the like. Things. In the third embodiment, the second thermosetting conductive adhesive layer 7 may be formed by screen printing or the like on the electrode terminal 5 on which the solder coat layer 6 of the wiring board 2 is formed. good.

Even with such a structure, the semiconductor package 1 is interposed via the solder coat layer 6 and the conductive adhesive layer 7.
1 and the wiring board 2 are connected, so that rework can be easily realized as in the first embodiment.

FIGS. 10 and 11 show a semiconductor package of a type having a semiconductor chip 1a on a film 1b. The solder coat layer 6 and the conductive adhesive layer 7 are also applied to such a type of semiconductor package. Since the semiconductor package 11 and the wiring board 2 are connected through the intermediary, it goes without saying that rework can be easily realized as in the first embodiment. The semiconductor chip 1a and the film 1b are connected via an anisotropic conductive sheet.

Although the mounting of a semiconductor package such as a BGA has been described above, the present invention can also be applied to a bare chip mounting for mounting a semiconductor chip as shown in FIGS. In this case, the bump 4 of the semiconductor chip 1 a and the terminal electrode 5 of the substrate 2 are connected via the solder coat layer 5 and the conductive adhesive layer 7.

In the case of bare chip mounting, it is determined whether or not rework is to be performed in this state, and an underfill between the semiconductor chip 1a and the substrate 2 is performed by using an underfill, for example, a thermosetting resin 8 for an object that does not require rework. Is filled, the structure shown in the figure is obtained.

Even with such a structure, the semiconductor package 1 is provided via the solder coat layer 6 and the conductive adhesive layer 7.
1 and the wiring board 2 are connected, so that rework can be easily realized as in the first embodiment.

According to the embodiment described above, the metal layer on the electrode terminal of the wiring board is brought into a molten state,
A semiconductor chip or a semiconductor device (semiconductor package) including a conductive adhesive layer can be separated at an electrode terminal interface of a wiring board. Since the conductive adhesive layer and the metal layer are not metal-connected, the semiconductor chip or the semiconductor device (semiconductor package) including the conductive adhesive layer can be easily removed. After removal, the metal layer remains on the electrode terminals of the wiring board, but does not pose a problem because it is remounted via the conductive adhesive layer. Further, the leveling operation is also easy.

In particular, by combining the solder bump 4 with a flattened structure, not only the package connection and reworking at a solder melting point or lower can be performed, but also the shape of the conductive adhesive layer 7 is changed to the flat surface 4a of the solder bump. In addition, by adopting a shape that covers both the side surface and the side surface, it is possible to obtain connection strength and connection resistance similar to those of solder connection without performing resin reinforcement such as underfill. Since this conductive adhesive layer has high flexibility, it can absorb warpage and distortion generated when a semiconductor chip or a semiconductor package is connected by heating and heating under pressure, and can reduce thermal stress. And connection reliability can be improved. Further, by making the conductive adhesive layer cover the side surfaces of the bumps, it is possible to further improve connection reliability such as connection resistance and temperature cycle resistance.

Although the case where the solder coat layer is formed has been mainly described above, it goes without saying that the same effect can be obtained if the metal layer is in a molten state during rework. However, also in this case, the melting point must be such that the semiconductor chip or the bump of the semiconductor package does not melt before melting.

Also, when re-mounting a new semiconductor chip or semiconductor package, the mounting is performed via a thermosetting conductive adhesive. Therefore, package replacement at a low temperature below the melting point of the solder bumps, that is, Rework becomes possible.

[0079]

According to the present invention, there is an effect that the rework of a semiconductor chip or a semiconductor package is facilitated in a mounting structure of an electronic device.

[Brief description of the drawings]

FIG. 1 shows a first example of a mounting structure of a semiconductor device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 2 shows a first example of a mounting structure of a semiconductor device according to the present invention.
It is sectional drawing which expanded and showed the vicinity of the connection part in embodiment.

FIG. 3 is a perspective view showing the entire mounting structure of the semiconductor device according to the present invention.

FIG. 4 is a schematic explanatory diagram for explaining a first embodiment of a mounting method according to the present invention.

FIG. 5 is a schematic explanatory diagram for explaining a first embodiment of a mounting method according to the present invention.

FIG. 6 is a diagram showing a cross section of a BGA package connection of 0.8 / 729 bumps.

FIG. 7 shows a second example of the mounting structure of the semiconductor device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 8 shows a third example of the mounting structure of the semiconductor device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 9 shows a fourth example of the mounting structure of the semiconductor device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 10 is a schematic explanatory diagram for explaining a fifth embodiment of the mounting method according to the present invention.

FIG. 11 is a schematic explanatory view for explaining a fifth embodiment of the mounting method according to the present invention;

FIG. 12 is a schematic explanatory view for explaining a sixth embodiment of the mounting method according to the present invention;

FIG. 13 is a schematic explanatory view for explaining a sixth embodiment of the mounting method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Multi-pin area bump type package body (semiconductor device and package body), 2 ... Wiring board, 3 ... Metal pad, 4 ... Solder bump, 5 ... Electrode terminal, 6 ... Solder coat layer, 7 ... Conductive adhesive layer , 8 ... plate, 9
... metal mask (printing mask), 10: conductive adhesive bump (solid bump), 11: semiconductor package,
12: conductive adhesive (conductive paste), 20: multi-chip module substrate 21, 22, 23: semiconductor package.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masaaki Sato 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside of Hitachi, Ltd. 5F044 KK01 KK13 LL07 QQ03 RR01

Claims (8)

[Claims] 1. An electronic device comprising a semiconductor device and a wiring board on which the semiconductor device is mounted, wherein the electronic device is connected to a bump of the semiconductor device and an electrode terminal of the wiring board. An electronic device, wherein a metal layer having a lower melting point than a bump is formed, and the bump and the electrode terminal on which the metal layer is formed are connected via a conductive adhesive layer. 2. An electronic device comprising: a semiconductor chip; and a wiring board on which the semiconductor chip is mounted, wherein the bump is provided on the semiconductor chip and an electrode terminal on the wiring board is connected. Forming a metal layer having a lower melting point than the above, connecting the bump and the electrode terminal on which the metal layer is formed via a conductive adhesive layer, and forming a thermosetting resin between the semiconductor chip and the wiring board. An electronic device characterized by being filled with: 3. The electronic device according to claim 1, wherein the bump is a solder bump or a conductive bump. 4. The electronic device according to claim 1, wherein said metal layer is made of solder. 5. The electronic device according to claim 1, wherein the diameter of the conductive adhesive layer is smaller than the diameter of the electrode terminal on which the metal layer is formed. 6. The electronic device according to claim 1, wherein a part of said bump is flattened. 7. The electronic device according to claim 1, wherein a part of said solder bump is roughened. 8. The electronic apparatus according to claim 1, wherein said bump is formed of a low-elasticity conductive adhesive having a glass transition temperature near room temperature.