Circuit module having a substrate, semiconductor chip, and molding material formed by dicing

A circuit module including: a wiring substrate having a shape elongated in one direction; a semiconductor chip mounted on the wiring substrate; and a molding material that molds the semiconductor chip, wherein end faces of the molding material that extend along a lengthwise direction of the wiring substrate and intersect with a lateral direction of the wiring substrate are formed by dicing performed along end faces of a partial region of the wiring substrate.

BACKGROUND

1. Technical Field

The present invention relates to a circuit module including at least one semiconductor chip that is mounted on a wiring substrate and molded with a molding material, and a method for manufacturing such a circuit module.

2. Related Art

With a miniaturized circuit module, a semiconductor chip (bare chip) that is not encapsulated in a package is mounted on a wiring substrate by wire bonding or flip chip bonding, and then the semiconductor chip on the wiring substrate is molded with a molding material in order to protect the semiconductor chip and the like.

For example, a plurality of semiconductor chips are mounted on a mother board in which a plurality of wiring substrates are continuously arranged, the semiconductor chips are molded with a molding material, and thereafter the mother board is cut by punching with a die (die cutting). The plurality of wiring substrates are thereby separated. At this time, if the wiring substrates have a small width, the molding material spreads over the widthwise sides of the wiring substrates, and thus the molding material is undesirably cut by the die during punching.

However, the molding material is brittle, and thus if cracking occurs in the cut surfaces of the molding material, a molding defect occurs, resulting in a low manufacturing yield of the circuit modules. There is another problem in that if, for example, a residue of the molding material adheres to the end faces of the wiring substrates, an additional step of removing the residue of the molding material is necessary.

In particular, according to a transfer molding method, a plurality of semiconductor chips mounted on a plurality of wiring substrates are collectively and continuously molded with a molding material, and thus when the molding material and the mother board are cut by punching using a die, cracking is likely to occur in the molding material. Also, even when the molding material and the mother board are cut by using a scribing method, cracking is likely to occur in the molding material. For these reasons, it has been difficult to remove the molding material along the end faces of the wiring substrates.

As a related technique, JP-A-2013-105992 (paragraphs 0006, 0048 and 0065, and FIG. 12) discloses a method for manufacturing a substrate module with a built-in semiconductor device, with which it is possible to achieve high integration and miniaturization of semiconductor devices having a specific function, as well as achieving simplification and improved efficiency of the manufacturing steps relating to mounting components. According to this manufacturing method, a plurality of substrate modules with a built-in semiconductor device are obtained by cutting a core substrate, in which a plurality of core substrate regions (substrate module forming regions) applied to a substrate device portion are continuously provided, along dicing streets into substrate module forming regions so as to singulate the substrate modules.

According to JP-A-2013-105992, a plurality of substrate modules can be obtained by cutting the core substrate, in which a plurality of substrate module forming regions are provided, along the dicing streets. However, JP-A-2013-105992 contains no disclosure of cutting a core substrate on which a plurality of semiconductor devices molded with a molding material are mounted. Also, if the core substrate is cut from one end to the other by dicing, a large amount of residue of the core substrate or insulating layer is generated, and the problem of contamination occurs.

SUMMARY

Accordingly, in view of the points described above, an advantage of some aspects of the invention is to provide a circuit module including a semiconductor chip that is mounted on a wiring substrate and molded with a molding material, wherein cracking that occurs in the molding material is reduced.

In order to solve the problems described above, a circuit module according to one aspect of the invention includes: a wiring substrate having a shape elongated in one direction; a semiconductor chip mounted on the wiring substrate; and a molding material that molds the semiconductor chip, wherein end faces of the molding material that extend along a lengthwise direction of the wiring substrate and intersect with a lateral direction of the wiring substrate are formed by dicing performed along end faces of a partial region of the wiring substrate.

According to the circuit module according to one aspect of the invention, the end faces of the molding material that extend along the lengthwise direction of the wiring substrate and intersect with the lateral direction of the wiring substrate are formed by dicing performed along the end faces of a partial region of the wiring substrate, and it is therefore possible to remove the molding material along the end faces of the wiring substrates without causing a crack in the molding material. Also, when the molding material is cut by dicing, a region of the wiring substrate other than the partial region is not cut, and it is therefore possible to reduce contamination caused by a residue of the substrate material.

For example, the end faces of the molding material that extend along the lengthwise direction of the wiring substrate and intersect with the lateral direction of the wiring substrate may be formed together with the end faces of the partial region of the wiring substrate by dicing after the molding material has been cured. In this case, the cut surfaces that extend in the lengthwise direction of the wiring substrate and intersects with the lateral direction of the wiring substrate are formed at positions flush with the cut surfaces of the partial region of the wiring substrate, the shape of the molding material is accurately formed, and the cut surfaces of the molding material become dense.

Here, if the end faces of another region of the wiring substrate are formed by, for example, punching the mother board with a die, the end faces of the partial region of the wiring substrate and the end faces of the other region of the wiring substrate are formed by different methods. In this case, an appropriate cutting method can be used depending on the region of the wiring substrate.

Also, it is desirable that the end faces of the partial region of the wiring substrate protrude in a widthwise direction of the wiring substrate with respect to the end faces of the other region in the lengthwise direction of the wiring substrate. It is thereby possible to cut the molding material without affecting the other region in the lengthwise direction of the wiring substrate.

Furthermore, it is desirable that the molding material is not cut in a direction substantially perpendicular to the lengthwise direction of the wiring substrate. In this case, the cut direction of the molding material is limited to one direction, and thus the circuit module manufacturing process can be simplified.

Also, it is desirable that the wiring substrate has a width that is smaller than a length of the molding material in the lengthwise direction of the wiring substrate. In this case, it is possible to achieve a circuit module having a size that is small in the widthwise direction of the wiring substrate.

In the above configuration, the semiconductor chip may include a semiconductor chip that is not encapsulated in a package, and be mounted on the wiring substrate by wire bonding. By using such a semiconductor chip that is not encapsulated in a package, it is possible to miniaturize the wiring substrate.

A method for manufacturing a circuit module according to one aspect of the invention includes: (a) preparing a mother board including a plurality of wiring substrates that each have a shape elongated in a first direction and are continuous via a connecting portion in a second direction that is perpendicular to the first direction, and a frame that supports at least connecting portions located at both outermost ends in the second direction of the plurality of wiring substrates; (b) mounting a semiconductor chip on each of the plurality of wiring substrates; (c) molding the plurality of semiconductor chips mounted on the plurality of wiring substrates by a molding material that is continuous in the second direction, and heating and curing the molding material; and (d) after the molding material has been cured, cutting the connecting portion of the plurality of wiring substrates together with the molding material formed on the connecting portion by dicing.

With the method for manufacturing a circuit module according to one aspect of the invention, the connecting portions of the wiring substrates are cut together with the molding material formed on the connecting portions by dicing, it is thereby possible to remove the molding material along the end faces of the wiring substrates without causing a crack in the molding material.

Here, the step (d) may include cutting the connecting portion of the plurality of wiring substrates together with the molding material formed on the connecting portion by dicing, without cutting the mother board in a region other than the connecting portion of the plurality of wiring substrates. In this case, the mother board in a region other than the connecting portions is not cut by dicing, and it is therefore possible to reduce contamination caused by a residue of the substrate material.

Also, if the frame of the mother board supports, in addition to the connecting portions located at both outermost ends in the second direction of the plurality of wiring substrates, opposing end portions in the first direction of each of the wiring substrates, the method for manufacturing a circuit module may further include (e) cutting the opposing end portions in the first direction of each of the wiring substrates so as to separate each of the wiring substrates from the frame of the mother board, which is performed after the step (d). In this case, each of the wiring substrates can be separated after completion of processing such as the inspection of electrical characteristics performed on the plurality of wiring substrates supported by the frame of the mother board.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. Note that the same constituent elements are given the same reference numerals, and redundant descriptions are omitted.

FIG. 1schematically shows a work piece in a molding step for manufacturing a circuit module according to an embodiment of the invention.FIG. 1Ais a plan view of the work piece, andFIG. 1Bis a side view of the work piece. The work piece includes a mother board10, a plurality of semiconductor chips20arranged in at least one column, and a molding material30that molds the semiconductor chips20.

The mother board10includes a plurality of wiring substrates11arranged in at least one column, and a frame12that supports the wiring substrates11. The mother board10is made by, for example, punching out a glass epoxy substrate with a die. In order to manufacture a plurality of circuit modules at a time, such a mother board10including a plurality of wiring substrates11is used.FIG. 1Ashows, as an example, the mother board10on which a large number of wiring substrates11are arranged in a plurality of rows and a plurality of columns. As used herein, the term “row” refers to an array of a plurality of wiring substrates11in an X axis direction in the diagrams, and the term “column” refers to an array of a plurality of wiring substrates11in a Y axis direction in the diagrams.

As shown inFIG. 1A, each of the wiring substrates11has a shape elongated in a first direction (the X axis direction in the diagram). Also, a plurality of wiring substrates11arranged in each column are continuous via connecting portions11ain a second direction (the width direction of the wiring substrates11, the Y axis direction in the diagram) perpendicular to the first direction, which is the lengthwise direction of the wiring substrates11.

The frame12of the mother board10supports at least the connecting portions11alocated at both outermost ends in the Y axis direction of the plurality of wiring substrates11arranged in each column. Furthermore, as shown inFIG. 1A, the frame12of the mother board10may support opposing end portions in the X axis direction of each of the wiring substrates11.

At least one semiconductor chip20is mounted on each of the wiring substrates11. The semiconductor chip20may be a semiconductor chip (bare chip) that is not encapsulated in a package. The use of bare chips enables miniaturization of the wiring substrates11. The bare chips are mounted on the wiring substrates11by wire bonding or flip chip bonding.

Because the wiring substrates11have a small width, it is difficult to independently mold the individual semiconductor chips20. For this reason, the molding material30is continuous in the Y axis direction so as to mold the plurality of semiconductor chips20mounted on the plurality of wiring substrates11arranged in one column in the Y axis direction. The molding material30is formed by a transfer molding method, a screen printing method, or the like. As the molding material30, for example, a thermosetting resin is used, and in particular, thermosetting epoxy resin is suitable.

FIG. 1Ashows a pot41and a runner42that are used in a transfer molding method. The pot41is a container that contains resin tablets made by compacting thermosetting resin powders. Thermosetting resin temporarily melts upon heating. With continued heating, the chemical reaction proceeds, and the thermosetting resin cures. The runner42is a small path through which the melted thermosetting resin flows.

In the transfer molding method, a die is fixed above the mother board10on which a plurality of semiconductor chips20are mounted, a thermosetting resin heated and temporarily melted in the pot41is injected into the die through the runner42, and the thermosetting resin cures in the heated die. After the die has been cooled, the die is removed from the wiring substrates11.

With the mold encapsulation performed in this way, the semiconductor chips20and gold (Au) wires for use in wire bonding can be protected from external stress, moisture and contaminants. However, if the wiring substrates11have a small width, the molding material30spreads over the widthwise sides of the wiring substrates11. Accordingly, it is necessary to remove the spread molding material30so as to bring the width of the circuit module within a predetermined range.

FIG. 2schematically shows the work piece in a dicing step for manufacturing a circuit module according to an embodiment of the invention.FIG. 2Ais a plan view of the work piece, andFIG. 2Bis a side cross sectional view of the work piece taken along the line B-B′ shown inFIG. 2A. InFIG. 2A, dotted arrows indicate the paths of movement of a dicing blade50.

As shown inFIG. 2A, the dicing blade50is moved down to a height lower than the bottom surface of the mother board10at a position at which the frame12of the mother board10is not present, then moved in a direction substantially parallel to the X axis direction so as to cut the connecting portions11aand the molding material30of the wiring substrates11, and thereafter moved up before the dicing blade50reaches the frame12of the mother board10. Accordingly, in a region other than the connecting portions11aof the wiring substrates11, the mother board10is not cut.

As shown inFIG. 2B, the dicing blade50passes outside end faces11bof the wiring substrates11in the X axis direction (see the left side in the diagram), and cuts the connecting portions11aof the wiring substrates11together with the molding material30formed on the connecting portions11a. As a result, as shown inFIG. 2A, end faces of the molding material30extending in a direction substantially parallel to the X axis direction are formed by dicing performed along the end faces11cof partial regions of the wiring substrates11(raised regions remaining after the connecting portions11ahave been cut).

On the other hand, if the molding material30is punched with a die after the molding material30has been cured, because the molding material30is brittle, the cut surfaces of the molding material30become rough, and cracking may occur in the cut surfaces of the molding material30. Also, if the entire mother board10is cut by the dicing blade50, a large amount of residue of the substrate material is generated, and the problem of contamination occurs.

According to the present embodiment, the end faces of the molding material30in a direction substantially parallel to the X axis direction are formed by dicing performed along the end faces11cof a partial region of a wiring substrate11, and it is therefore possible to remove the molding material30along the end faces of the wiring substrates11without causing a crack in the molding material30. Also, when the molding material30is cut by dicing, a region of a wiring substrate11other than the partial region is not cut, and it is therefore possible to reduce contamination caused by a residue of the substrate material.

However, if dicing is performed before the molding material30is cured, the shape of the molding material30is deformed. Accordingly, it is desirable that the end faces of the molding material30in a direction substantially parallel to the X axis direction are formed together with the end faces11cof the partial regions of the wiring substrates11by dicing after the molding material30has been cured.

In this case, the cut surfaces of the molding material30in a direction substantially parallel to the X axis direction are formed at positions flush with the cut surfaces of the partial regions of the wiring substrates11, the shape of the molding material30is accurately formed, and the cut surfaces of the molding material30become dense. Accordingly, whether or not the end faces of the molding material30were formed by dicing after curing of the molding material30can be determined by observing the shape of the molding material30or measuring the surface roughness of the cut surfaces of the molding material30.

Here, if the end faces of another region of a wiring substrate11are formed by, for example, punching the mother board10with the use of a die, the end faces11cof a partial region of the wiring substrate11and the end faces11bof the other region of the wiring substrate11are formed by different methods. As used herein, the term “different methods” means methods that use different means and different conditions for cutting the substrate. In this case, an appropriate cutting method can be used depending on the region of the wiring substrate11.

Also, it is desirable that the end faces11cof a partial region of a wiring substrate11protrude in the widthwise direction of the wiring substrate11with respect to the end faces11bof another region in the lengthwise direction of the wiring substrate11. It is thereby possible to cut the molding material30without affecting the other region in the lengthwise direction of the wiring substrate11.

In this way, the connecting portions11aof all of the wiring substrates11are cut together with the molding material30. Also, in the case in which electronic components other than the semiconductor chips20(FIG. 1) are mounted on the wiring substrates11, the electronic components are mounted on a first or second primary surface of the plurality of wiring substrates11supported by the mother board10. Furthermore, the electrical characteristics of the circuits formed on the plurality of wiring substrates11are inspected. After that, opposing end portions of each of the wiring substrates11in the X axis direction are cut, the plurality of wiring substrates11are thereby separated from the frame12of the mother board10, and individual circuit modules are obtained.

FIG. 3is a plan view showing an example of an outer configuration of a circuit module according to an embodiment of the invention. This circuit module includes a wiring substrate11having a shape elongated in one direction, at least one semiconductor chip20(FIG. 1) mounted on the wiring substrate11, and a molding material30molding the at least one semiconductor chip20. A feature of the circuit module is that end faces30aof the molding material30in a direction substantially parallel to the lengthwise direction of the wiring substrate11are formed by dicing performed along the end faces11cof a partial region of the wiring substrate11. The end faces30aof the molding material30extend along the lengthwise direction of the wiring substrate11and intersect with the lateral direction of the wiring substrate11.

Here, it is desirable that the molding material30is not cut in a direction substantially perpendicular to the lengthwise direction of the wiring substrate11. In this case, the cut direction of the molding material30is limited to one direction, and thus the circuit module manufacturing process can be simplified. Also, it is desirable that the wiring substrate11has a width smaller than the length of the molding material30in the lengthwise direction of the wiring substrate11. In this case, it is possible to achieve a circuit module having a size that is small in the widthwise direction of the wiring substrate11.

Next, a method for manufacturing a circuit module according to a first embodiment of the invention will be described with reference toFIGS. 1 to 4.FIG. 4is a flowchart illustrating a method for manufacturing a circuit module according to the first embodiment of the invention. In this manufacturing method, the molding material30is formed by a transfer molding method.

In step S11shown inFIG. 4, for example, a mother board10as shown inFIG. 1is prepared. The mother board10includes a plurality of wiring substrates11that each have a shape elongated in the X axis direction and are continuous via connecting portions11ain the Y axis direction perpendicular to the X axis direction, and a frame12that supports at least the connecting portions11alocated at both outermost ends in the Y axis direction of the plurality of wiring substrates11.

In step S12, at least one semiconductor chip20is mounted on a first primary surface of each of the wiring substrates11. For example, an adhesive such as a silver (Ag) paste is applied to a predetermined region of the first primary surface of the wiring substrate11. A bare chip is mounted on the predetermined region of the wiring substrate11, with a plurality of outer connecting electrodes (pads) of the bare chip facing to the side opposite to the wiring substrate11, and the adhesive is heated and cured. The bare chip is thereby fixed to the wiring substrate11. Furthermore, wire bonding is performed by connecting the plurality of outer connecting electrodes of the bare chip to a plurality of electrodes provided on the first primary surface of the wiring substrate11respectively with the use of gold (Au) wires or the like.

In step S13, a molding material30is formed by a transfer molding method. To be specific, as shown inFIG. 1, the plurality of semiconductor chips20mounted on a plurality of wiring substrates11in each column are molded by a molding material30that is continuous in the Y axis direction, and the molding material30is heated and cured. The molding material30formed by the transfer molding method can withstand reflow processing performed later.

In step S14, after the molding material30has been cured, for example, as shown inFIG. 2, the connecting portions11aof the plurality of wiring substrates11are cut together with the molding material30formed on the connecting portions11aby dicing. As a result of the connecting portions11aof the wiring substrates11being cut together with the molding material30formed on the connecting portions11aby dicing in this way, it is possible to remove the molding material30along the end faces of the wiring substrates11without causing a crack in the molding material30.

At this time, it is desirable that the connecting portions11aof the plurality of wiring substrates11are cut together with the molding material30formed on the connecting portions11aby dicing, without cutting the mother board10in a region other than the connecting portions11aof the plurality of wiring substrates11. In this case, the mother board10in the region other than the connecting portions11ais not cut by dicing, and it is therefore possible to reduce contamination caused by a residue of the substrate material.

In step S15, at least one electronic component other than the semiconductor chip20is surface-mounted on the first primary surface of each of the plurality of wiring substrates11. For example, a cream solder is printed on the first primary surface of the plurality of wiring substrates11by a cream solder printing machine, and electronic components are mounted on the first primary surface of the plurality of wiring substrates11by a chip mounter. After that, the plurality of wiring substrates11are allowed to pass through a reflow furnace so as to melt the solder, and the electronic components are fixed to the first primary surface of the plurality of wiring substrates11by the solder solidified by cooling.

In step S16, at least one electronic component is surface-mounted on a second primary surface that is opposite the first primary surface of the plurality of wiring substrates11. The method for mounting an electronic component in step S16is the same as that of step S15.

In step S17, a plurality of probes are respectively brought into contact with a plurality of measurement electrodes (pads) provided on the first or second primary surface of the wiring substrates11, and inspection is performed for the electrical characteristics of the circuit formed on each of the wiring substrates11with the use of a measuring instrument.

In the above processing, the frame12of the mother board10may support, in addition to the connecting portions11alocated at both outermost ends in the Y axis direction of the plurality of wiring substrates11, opposing end portions in the X axis direction of each of the wiring substrates11. In this case, step S15to S17are performed in a state in which the plurality of wiring substrates11are supported by the frame12of the mother board10.

Accordingly, after completion of processing such as the inspection of electrical characteristics performed on the plurality of wiring substrates11supported by the frame12of the mother board10, in step S18, the opposing end portions in the X axis direction of each of the wiring substrates11are cut by, for example, punching with a die, and each of the wiring substrates11is thereby separated from the frame12of the mother board10. Through this, individual circuit modules as shown inFIG. 3are obtained.

Next, a method for manufacturing a circuit module according to a second embodiment of the invention will be described with reference toFIGS. 1 to 3and5.FIG. 5is a flowchart illustrating a method for manufacturing a wiring substrate according to the second embodiment of the invention. In this manufacturing method, the molding material30is formed by a screen printing method.

In step S21shown inFIG. 5, for example, a mother board10as shown inFIG. 1is prepared. The mother board10includes a plurality of wiring substrates11that each have a shape elongated in the X axis direction and are continuous via connecting portions11ain the Y axis direction perpendicular to the X axis direction, and a frame12that supports at least the connecting portions11alocated at both outermost ends in the Y axis direction of the plurality of wiring substrates11.

In step S22, at least one electronic component other than a semiconductor chip20is surface-mounted on the first primary surface of each of the plurality of wiring substrates11. The detailed processing in step S22is the same as that of step S15of the first embodiment. However, a molding material30formed by a screen printing method is susceptible to reflow processing. For this reason, the reflow processing performed on the first primary surface of the wiring substrates11is performed prior to molding processing.

In step S23, at least one semiconductor chip20is mounted on the first primary surface of each of the wiring substrates11. The detailed processing in step S23is the same as that of step S12of the first embodiment.

In step S24, a molding material30is formed by a screen printing method. As the molding material30, for example, a thermosetting resin in paste form is used. The screen printing method refers to a printing method in which a screen having a pattern defined by openings is placed on a printing object, and a paste is applied onto the screen so as to cause the paste to adhere only to the printing object in the openings of the screen. With the screen printing method, the plurality of semiconductor chips20mounted on a plurality of wiring substrates11in each column are molded by the molding material30that is continuous in the Y axis direction. Next, debubbling processing is performed so as to remove the air bubbles contained in the molding material30. After that, the molding material30is heated and cured.

In step S25, after the molding material30has been cured, for example, as shown inFIG. 2, the connecting portions11aof the plurality of wiring substrates11are cut together with the molding material30formed on the connecting portions11aby dicing. The detailed processing in step S25is the same as that of step S14of the first embodiment.

In step S26, at least one electronic component is surface-mounted on a second primary surface that is opposite the first primary surface of the plurality of wiring substrates11. The method for mounting an electronic component in step S26is the same as step S16of the first embodiment.

In step S27, a plurality of probes are respectively brought into contact with a plurality of measurement electrodes (pads) provided on the first or second primary surface of the wiring substrates11, and inspection is performed for the electrical characteristics of the circuit formed on each of the wiring substrate11with the use of a measuring instrument.

In the above processing, the frame12of the mother board10may support, in addition to the connecting portions11alocated at both outermost ends in the Y axis direction of the plurality of wiring substrates11, opposing end portions in the X axis direction of each of the wiring substrates11. In this case, steps S26and S27are performed in a state in which the plurality of wiring substrates11is supported by the frame12of the mother board10.

Accordingly, after completion of processing such as the inspection of electrical characteristics performed on the plurality of wiring substrates11supported by the frame12of the mother board10, in step S28, the opposing end portions in the X axis direction of each of the wiring substrates11are cut by, for example, punching with a die, and each of the wiring substrates11is thereby separated from the frame12of the mother board10. Through this, individual circuit modules as shown inFIG. 3are obtained.

The above embodiments have been described taking the case in which a double-sided substrate is used as the wiring substrate, but the invention is not limited to the embodiments described above. For example, the invention is applicable to the case in which a single-sided substrate is used as the wiring substrate, and various other modifications can be made by those skilled in the art within the technical concept of the invention.

The entire disclosure of Japanese Patent Application No. 2013-219025, filed Oct. 22, 2013 is expressly incorporated by reference herein.