JP5672769B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof.

  Advances in microfabrication technology have led to higher integration of LSIs (Large Scale Integrated Circuits), and it has become possible to mount LSIs with many functions in one package. As a result, the number of electrode terminals required for one package has increased. As a mounting technique corresponding to this, there is flip chip bonding, which is currently applied to many electronic devices.

  A feature of flip chip bonding is that the shape of solder bumps becomes a drum shape due to the weight of the semiconductor package. This shape change causes the following problems.

  First, the packaging density is limited. In the drum shape, the solder diameter is inevitably larger than the electrode diameter. Therefore, there is a concern that the solder bumps may be bridged unless a sufficient distance is maintained between the electrodes. In recent years, the number of cores of semiconductor elements mounted on one package tends to increase, and the number of electrode terminals also increases accordingly. As is currently done, if the number of electrode terminals is increased by increasing the package size, the stress applied to the solder joints also increases, leading to a decrease in reliability. Therefore, it is required to increase the number of electrode terminals without increasing the package size.

  Secondly, in the drum-shaped shape, an extremely large stress is generated in a portion close to the electrode, so that the failure of the electronic device is accelerated. In flip chip bonding, when the solder bumps are in a drum shape, stress concentrates on the bonding portion. Cracks grow from stress-concentrated parts, causing a phenomenon that accelerates the failure of electronic devices. For this reason, it is necessary to prevent stress from concentrating on only a part.

  As a method for preventing a short circuit between bump electrodes of a semiconductor package, a method of sandwiching an insulating film 123 between a semiconductor package 111 having solder bumps 112 and a wiring board 121 as shown in FIG. Patent Document 1 and Patent Document 2). A hole 122 is formed in the insulating film 123 at a position corresponding to the solder bump 112 of the semiconductor package 111. The semiconductor package 111 is BGA bonded to the wiring substrate 121 through the hole 122, so that the shape of the solder bump 112 is maintained in a substantially cylindrical shape. However, in this method, since the insulating film 123 is inserted between the semiconductor package 111 and the wiring substrate 121 without a gap, rework cannot be performed, and the semiconductor device cannot be repaired in the event of a malfunction. Therefore, there is a need for a mounting structure capable of reworking while solving the above-described problems of crack generation due to stress concentration at the joint and prevention of short circuit between electrodes.

JP 2000-340607 A JP 2001-223463 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device and a manufacturing method thereof capable of reworking while preventing a short circuit and stress concentration between electrodes in a joint portion in a configuration in which a semiconductor package is flip-chip bonded to a wiring board. To do.

  In order to solve the above-described problems, a heat shrink mold is used at the joint between the semiconductor package and the wiring board to enable flip chip bonding while maintaining the shape of the connection electrodes such as solder bumps in a predetermined shape.

Specifically, in one aspect of the present invention, in a semiconductor device in which a semiconductor package is flip-chip bonded to a wiring board,
A protruding electrode for bonding the semiconductor package and the wiring board;
The protruding electrode includes a solder electrode and a heat shrink mold that covers the solder electrode.

In another aspect of the present invention, in a method for manufacturing a semiconductor device,
Form a mold electrode filled with solder material in a heat shrink mold,
Placing the mold electrode on the connection electrode on the semiconductor package;
While shrinking the heat shrink mold in the radial direction by reflow, the mold electrode is joined to the connection electrode of the semiconductor package,
The semiconductor package to which the mold electrode is bonded is flip-chip bonded to the wiring board.

In still another aspect of the present invention, in a method for manufacturing a semiconductor device,
A mask having an opening at a position corresponding to the connection electrode is disposed on the semiconductor package having the connection electrode,
Inserting a hollow heat-shrinkable mold having both ends opened in the opening of the mask, exposing the connection electrode in the opening of the heat-shrinkable mold,
Filling the heat shrink mold with a solder material,
While shrinking the heat shrinkable mold in the radial direction by a reflow process, the solder material is melt bonded to the connection electrode to form a protruding electrode,
The mask is removed from the semiconductor package.

  With the above configuration and method, in a semiconductor device in which a semiconductor package is flip-chip bonded to a wiring board, it is possible to increase the density of electrode terminals and facilitate reworking while preventing short-circuiting and stress concentration between electrodes at the bonding portion. Is possible.

It is a figure which shows the example of mounting structure of the conventional semiconductor device. It is a figure which shows the example of joining of the semiconductor device in embodiment. It is a figure which shows the preparation example of the mold electrode using a heat shrink mold. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the manufacturing process of the semiconductor device using the mold electrode of FIG. It is a figure which shows the example of the mold electrode of another shape. It is a figure which shows the manufacturing process of the semiconductor device of another embodiment. It is a figure which shows the manufacturing process of the semiconductor device of another embodiment. It is a figure which shows the manufacturing process of the semiconductor device of another embodiment. It is a figure which shows the manufacturing process of the semiconductor device of another embodiment.

  FIG. 2 is a schematic configuration diagram of a semiconductor device 1 according to an embodiment of the present invention. In the semiconductor device 1, the semiconductor package 11 is flip-chip bonded to the wiring substrate 21 through the protruding electrodes 30. The protruding electrode 30 includes a heat shrink mold 31 and a solder electrode 32 held in a predetermined shape by the heat shrink mold 31. The connection electrode 12 of the semiconductor package 11 and the connection electrode 22 of the wiring substrate 21 are electrically connected by a solder electrode 32. Although not shown, the wiring board 21 is a multilayer wiring board in which insulating layers and wiring layers are alternately laminated on a glass epoxy substrate, for example. The surface region other than the connection electrode 22 on the wiring substrate 21 is covered with an insulating layer 23 such as a resin film.

  In the example of FIG. 2, the solder electrode 32 is held in a cylindrical shape by a heat shrink mold 31. A heat-shrink mold is a mold-molded product made of a material that shrinks into a shape stored in advance by heat. Examples of the mold material include thermoplastic resins, silicon elastomers (silicon-based resins), fluorine-based resins, vinyl chloride-based resins, polyolefin-based resins, and the like. The heat shrinkable mold 31 used in the embodiment has heat resistance at the reflow temperature of flip chip bonding, shrinks toward the center in the radial direction when a temperature above a certain level is applied, and heat shrinks and expands in the axial direction. Select those that do not. The reflow temperature varies depending on the material of the solder electrode 32, but is in the range of 150 ° C to 240 ° C. When the reflow temperature is 250 ° C. or lower, for example, a heat shrink mold 31 made of silicon rubber can be used. Silicone rubber has a shrinkage temperature of 80 ° C. to 200 ° C. and exhibits heat resistance up to 250 ° C. The shrinkage rate is 50%. When the reflow temperature exceeds 250 ° C., it is desirable to use, for example, a fluorine resin such as TFE (heat-resistant temperature is 250 to 330 ° C.) as the heat shrinkable mold 31. In this case as well, the shrinkage due to heat is 50%.

  The solder electrode 32 is, for example, Sn—Bi, Sn—Ag, Sn—Ag—Cu, Sn—Cu, Sn—Zn, Sn—In, Sn—Pb, Sn—Pb—Ag. , Sn—Pb—Bi, Sn—Pb—Sb, In—Cu, and Sn—Sb solder materials. When using a Sn—Bi-based or Sn-In-based solder material, the reflow temperature is relatively low, and therefore it is desirable to combine it with the silicon mold 31. Similarly, columnar solder bumps can be formed by using a conductive paste. In this case, the curing temperature is about 120 ° C.

  Since the heat shrink mold 31 holds the solder electrode 32 in a predetermined shape, partial stress concentration due to deformation of the solder electrode 31 can be prevented. As a result, the lifetime of the electronic device to which the semiconductor device 1 is applied can be extended. Further, since the surface of the solder electrode 32 is insulated by the heat shrinkable mold 31, the protruding electrodes 30 can be disposed close to each other, and high-density mounting is realized. Further, unlike the conventional example of FIG. 1, the protruding electrodes 30 are separated from each other by air, unlike the configuration in which the gaps of the solder electrodes 32 are completely filled with resin or the like. Therefore, even when rework is required after the product is completed, the semiconductor package 11 can be easily separated from the wiring board 21 and re-joined. Since the protruding electrode 30 is held in a predetermined shape by the heat shrinkable mold 31 as described above, in the following description, it will be appropriately referred to as a “mold electrode”.

  FIG. 3 is a diagram illustrating an example of manufacturing the mold electrode 30. As shown in FIG. 3A, a heat shrink mold 41 having a certain length L is filled with a solder material. The shape of the solder material is arbitrary, such as a powdered solder material 42a, a rod-shaped solder material 42b, and a spherical solder material 42c. The inner diameter D1 of the heat-shrinkable mold 41 is selected so as to have a size that substantially matches the diameters of the connection electrode 12 of the semiconductor package 11 and the connection electrode 22 of the wiring board 21 after the reflow process. If the inner diameter of the heat-shrinkable mold 41 after shrinkage is D2, the diameter of the rod-shaped solder material 42b is also set to D2, so that it can be easily inserted into the heat-shrinkable mold 41 before heat treatment. When the powder solder material 42a or the spherical solder material 42c is used, the filling amount is set so that the volume of the solder material after melting and solidification substantially coincides with the internal volume of the heat shrink mold 41 after shrinkage.

After the heat shrink mold 41 is filled with the solder materials 42a to 42c, the whole is heated to shrink the heat shrink mold 41 in the inner diameter direction (the radial direction toward the center). The temperature at which the heat-shrinkable mold 41 is shrunk is arbitrary as long as it has heat resistance, but is preferably a temperature that leaves room for further shrinkage during reflow when bonding to a semiconductor package. As a result, as shown in FIG. 3B, a mold electrode material 40L in which the solder electrode material 42 is covered with the heat shrink mold 41 is obtained. In the mold electrode material 40L, the inner diameter of the heat shrink mold 41 is shrunk to D2, but the length L in the axial direction is not changed. As shown in FIG. 3C, each mold electrode 40 is obtained by cutting the mold electrode material 40L according to the distance d between the semiconductor package 11 and the wiring substrate 21. The height d of the cylindrical mold electrode 40 is, for example, 500 μm.

  4 to 9 are diagrams showing a manufacturing process of the semiconductor device 1 using the mold electrode 40 manufactured in FIG. First, as shown in FIG. 4, a solder paste 14 or a flux 14 is applied as an adhesive material on the connection electrode 12 of the semiconductor package 11. For applying the solder paste or flux, for example, a printing metal mask (not shown) is arranged on the semiconductor package 11, and the solder paste 14 is printed using a squeegee or the like. The metal mask for printing (not shown) has an opening at a position corresponding to the connection electrode 14 of the semiconductor package 11, fills the opening with the solder paste 11, and then removes the metal mask. As a result, as shown in FIG. 4, the solder paste 14 is applied on the connection electrode 12 of the semiconductor package 11.

  Next, as shown in FIG. 5, a bonding mask 51 having a predetermined opening 52 is disposed on the semiconductor package 11. The diameter of the opening 52 of the bonding mask 51 is selected to be slightly larger than the diameter of the connection electrode 12 on the semiconductor package 11 and substantially equal to the outer diameter of the mold electrode 40. In the opening 52, the half connection electrode 12 to which the solder paste 14 is applied is exposed. The bonding mask 51 has heat resistance against the reflow temperature and has a thickness corresponding to the height of the mold electrode 30.

  Next, as shown in FIG. 6, the mold electrode 40 is inserted into the opening 52, and the bonding mask 51 is reflowed. By reflow, the solder paste 14 and the solder electrode material 42 are melted to form the solder electrode 42 </ b> B as shown in FIG. 7 and are joined to the connection electrode 12 of the semiconductor package 11. Further, since the heat shrink mold 41 contracts in the inner diameter direction, the diameter of the mold electrode 40B after reflow is slightly smaller than the diameter of the opening 52 of the bonding mask 51. Therefore, the bonding mask 51 can be easily removed. Thereby, the mold electrode 40 can be joined to the semiconductor package 11 to form the protruding electrode 40.

  On the other hand, as shown in FIG. 8, a solder paste or flux 24 is applied on the connection electrodes 22 of the wiring board 21. Also in this case, for example, a metal mask (not shown) for screen printing is arranged on the wiring substrate 21 and solder paste is printed with a squeegee or the like, and then the metal mask is removed. The semiconductor package 11 is aligned with the wiring substrate 21 on which the solder paste 24 is applied on the connection electrodes 22 by using, for example, a mounter.

  Next, as shown in FIG. 9, reflow is performed in a state where the mold electrode 40 </ b> B of the semiconductor package 11 is aligned with the connection electrode 22 on the wiring substrate 21. By reflow, the solder electrode 42B and the solder paste 24 are melted to form the solder electrode 42C, and are joined to the connection electrode 22 on the wiring board 21. The heat-shrinkable mold 41 shrinks to a certain inner diameter once heated, but does not shrink in the axial direction, that is, the height direction of the protruding electrode 40B. Therefore, even when the solder pastes 12 and 24 applied on the electrodes and the solder electrode material 42 filled in the mold are melted, there is a possibility that excess solder spreads on the package substrate 11 and the wiring substrate 21 from the electrodes. Absent.

  FIG. 10 shows an example of a mold electrode using another type of heat-shrinkable mold material. A mold electrode 60A in FIG. 10A is an example using a heat-shrinkable mold 61a that contracts into a shape (a drum shape) in which the central portion in the axial direction is constricted by heating. An example of such a molding material is a fluoropolymer. FIG. 10B shows a mold electrode 60B using a heat shrink mold 61b having a rectangular cross-sectional shape perpendicular to the axis. In this case as well, the mold shrinks in the inner diameter direction without changing the height. The mold electrode 60B in FIG. 10B has a rectangular cross-sectional shape, but may have a polygonal cross-sectional shape such as a hexagonal shape or an octagonal shape. In any case, the heat shrinks in the direction toward the center (referred to as “inner diameter direction” for convenience), but does not shrink in the axial direction (height direction).

  11 to 14 are diagrams showing a manufacturing process of a semiconductor device in another embodiment. First, as shown in FIG. 11, using a printing metal mask (not shown), for example, solder paste or flux is printed on the connection electrode 12 of the semiconductor package, and then the metal mask (not shown) is removed. The solder paste 14 is disposed on the connection electrode 12.

  Next, as shown in FIG. 12, a heat-resistant mask 51 having an opening 52 having the same size and shape as the mold diameter before thermal shrinkage is disposed on the semiconductor package. The electrode 12 to which the solder paste 14 is applied is exposed in the opening 52. A hollow heat-shrinkable mold 71 having both ends opened is inserted into the opening 52 of the mask 51. The heat shrink mold 71 is cut in advance according to the height of the mold electrode (that is, the distance between the semiconductor package 11 and the wiring substrate 21 (see FIG. 2)). The solder material 72 c is filled into the heat shrink mold 71 in the opening 52. Although a spherical solder material is illustrated in FIG. 12, the powdered solder material 42a, the rod-shaped solder material 42b, and the like shown in FIG. 3 may be used. Reflow is performed in a state where the solder material 72 c is filled in the heat shrink mold 71.

  As a result of the reflow, as shown in FIG. 13, the solder material 72 c and the solder paste 14 melt and the solder electrode 72 is joined to the connection electrode 12 of the semiconductor package 11. Although the heat shrink mold 71 shrinks in the inner diameter direction by the reflow process, the length in the axial direction, that is, the height of the heat shrink mold 71 does not change. The mold electrode 70 is composed of the solder electrode 72 and the heat-shrinkable mold 72 after shrinkage.

  Next, the heat resistant mask 51 is removed from the semiconductor package 11. Since the diameter of the mold electrode 70 is smaller than the opening 52 of the heat resistant mask 51 by the reflow, the heat resistant mask 51 can be easily removed. As shown in FIG. 8, the semiconductor package 11 formed in this way is opposed to the wiring substrate 21 in which the solder paste 24 is previously applied on the electrode 22, and the mold electrode (projection electrode) 70 is connected to the electrode 22 of the wiring substrate 21. To join. Thereby, the semiconductor device is completed.

  Also by this method, since the shape of the solder electrode is maintained after reflow, local stress concentration can be prevented. Further, since the solder electrodes are held in the insulating mold, a short circuit between the electrodes can be prevented. Furthermore, even when rework is required after the completion of the semiconductor device, the semiconductor package can be easily removed.

The following notes are presented for the above explanation.
(Appendix 1)
In a semiconductor device in which a semiconductor package is flip-chip bonded to a wiring board,
A protruding electrode for bonding the semiconductor package and the wiring board;
The protruding electrode includes a solder electrode and a heat shrink mold that covers the solder electrode.
(Appendix 2)
The semiconductor device according to appendix 1, wherein the heat shrink mold has heat resistance at a reflow temperature of the solder electrode.
(Appendix 3)
The semiconductor device according to appendix 1 or 2, wherein the heat shrink mold has a circular or polygonal columnar cross-sectional shape perpendicular to the axis.
(Appendix 4)
The semiconductor device according to any one of appendices 1 to 3, wherein the heat-shrinkable mold is a columnar shape having a constricted central portion along an axis.
(Appendix 5)
The solder material is Sn-Ag, Sn-Ag-Cu, Sn-Bi, Sn-Zn, Sn-In, Sn-Pb, Sn-Pb-Ag, Sn-Pb-Bi. The semiconductor device according to any one of appendices 1 to 4, wherein the semiconductor device is a Sn-Pb-Sb-based, In-Cu-based, Sn-Sb-based solder or conductive paste.
(Appendix 6)
The semiconductor device according to any one of appendices 1 to 5, wherein the heat shrinkable mold material includes a thermoplastic resin, a silicon resin, a fluorine resin, a vinyl resin, and a polyolefin resin.
(Appendix 7)
Form a mold electrode filled with solder material in a heat shrink mold,
Placing the mold electrode on the connection electrode on the semiconductor package;
While shrinking the heat shrink mold in the radial direction by reflow, the mold electrode is joined to the connection electrode of the semiconductor package,
A method for manufacturing a semiconductor device, comprising: flip chip bonding a semiconductor package to which the mold electrode is bonded to a wiring board.
(Appendix 8)
The step of disposing the mold electrode on the connection electrode includes:
A mask having an opening at a position corresponding to the connection electrode is disposed on the semiconductor package to expose the connection electrode in the opening.
Inserting the mold electrode into the opening of the mask;
The method for manufacturing a semiconductor device according to appendix 7, which includes a step.
(Appendix 9)
9. The method of manufacturing a semiconductor device according to appendix 8, wherein the mask is a mask having heat resistance, and the reflow is performed while the mask is placed on the semiconductor package.
(Appendix 10)
A mask having an opening at a position corresponding to the connection electrode is disposed on the semiconductor package having the connection electrode,
Inserting a hollow heat-shrinkable mold having both ends opened in the opening of the mask, exposing the connection electrode in the opening of the heat-shrinkable mold,
Filling the heat shrink mold with a solder material,
While shrinking the heat shrinkable mold in the radial direction by a reflow process, the solder material is melt bonded to the connection electrode to form a protruding electrode,
Removing the mask from the semiconductor package;
A method for manufacturing a semiconductor device.
(Appendix 11)
The method of manufacturing a semiconductor device according to appendix 10, wherein the size of the opening of the mask is substantially equal to the outer diameter of the heat shrink mold before shrinkage.
(Appendix 12)
The method of manufacturing a semiconductor device according to appendix 10 or 11, further comprising a step of applying a solder paste or a flux on the connection electrode of the semiconductor package.

  The present invention can be applied to a semiconductor device mounting configuration and process.

DESCRIPTION OF SYMBOLS 1 Semiconductor device 11 Semiconductor package 12 Connection electrode (package side)
21 Wiring board 22 Connection electrode (wiring board side)
23 Insulating layer 30, 40, 60A, 60B, 70 Projection electrode (mold electrode)
31, 41, 61a, 61b, 71 Heat shrinkable molds 32, 42, 72 Solder electrodes 42a, 42b, 42c Solder material

Claims (6)

In a semiconductor device in which a semiconductor package is flip-chip bonded to a wiring board,
A protruding electrode for bonding the semiconductor package and the wiring board;
The protruding electrode includes a solder electrode and a heat shrink mold that covers the solder electrode,
The heat shrinkable mold has heat resistance at the reflow temperature of the solder electrode and shrinks in the radial direction of the protruding electrode at the reflow temperature, but the axial length of the protruding electrode does not change. Semiconductor device.   2. The semiconductor device according to claim 1, wherein the heat shrink mold has a columnar shape having a circular or polygonal cross section perpendicular to the axis.   The semiconductor device according to claim 1, wherein the heat-shrinkable mold is a columnar shape with a constricted central portion along the axis. A mold electrode filled with a solder material in a heat shrink mold having heat resistance at a reflow temperature is formed separately from the semiconductor package,
The mold electrode is disposed on a connection electrode on the semiconductor package;
While shrinking the heat shrink mold in the radial direction by reflow, the mold electrode is joined to the connection electrode of the semiconductor package,
A method of manufacturing a semiconductor device , comprising: flip chip bonding a semiconductor package to which the mold electrode is bonded to a wiring board , wherein the heat shrinkable mold does not change its axial length at the reflow temperature . The step of disposing the mold electrode on the connection electrode includes:
A mask having an opening at a position corresponding to the connection electrode is disposed on the semiconductor package to expose the connection electrode in the opening.
Inserting the mold electrode into the opening of the mask;
The method of manufacturing a semiconductor device according to claim 4, further comprising a step. A mask having an opening at a position corresponding to the connection electrode is disposed on the semiconductor package having the connection electrode,
Inserting a hollow heat-shrinkable mold having both ends opened in the opening of the mask, exposing the connection electrode in the opening of the heat-shrinkable mold,
Filling the heat shrink mold with a solder material,
While shrinking the heat shrinkable mold in the radial direction by a reflow process, the solder material is melt bonded to the connection electrode to form a protruding electrode,
Removing the mask from the semiconductor package;
A method of manufacturing a semiconductor device , comprising: a step, wherein the heat shrinkable mold has heat resistance at a reflow temperature, and the axial length is not changed by the reflow treatment .

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