JP7583201B2 - Semiconductor Device - Google Patents

Description

The present invention relates to a semiconductor device.

In recent years, there has been an increasing demand for measuring integrated power consumption by time period in measuring instruments such as power meters that measure integrated power consumption. Accordingly, some measuring instruments are designed to measure power and time by configuring a semiconductor device by providing an oscillator and an integrated circuit inside the measuring instrument. There is also a piezoelectric oscillator in which an integrated circuit is mounted on the front surface of a lead frame and a piezoelectric vibrator (oscillator) is mounted on the back surface of the lead frame, with the integrated circuit and the terminals of the lead frame, and the integrated circuit and the oscillator connected by bonding wires (for example, Patent Document 1).

However, after mounting the integrated circuit on the front side of the lead frame, the lead frame is flipped over and the oscillator is mounted on the back side, making it difficult to improve production efficiency. To address this issue, a configuration could be considered in which the oscillator and integrated circuit are mounted side by side on one side of the lead frame, but because the oscillator is thicker than the integrated circuit, it interferes with the bonding wires that connect the integrated circuit to the terminals of the lead frame, making it difficult to connect the integrated circuit to the lead frame.

JP 2007-234994 A

In consideration of the above, the present invention aims to provide a semiconductor device that improves production efficiency and facilitates the connection between an integrated circuit and a lead frame.

The semiconductor device according to claim 1 comprises a sealing resin having a front surface, a back surface opposite to the front surface, and a side surface connecting the front surface and the back surface, a first surface constituted by a first region on which an integrated circuit having an electrode pad is mounted and a second region adjacent to the first region, and a second surface opposite the first surface constituted by a third region and a fourth region adjacent to the third region on which an oscillator having an external terminal is mounted, and the second surface comprises a die pad sealed in the sealing resin, a sealing portion disposed between the back surface and the die pad and sealed in the sealing resin, and an exposed portion including a bent portion bent toward the back surface and exposed from the side surface of the sealing resin. and a lead for connecting the first and fourth regions to the die pad, the first and third regions do not overlap in the surface direction of the die pad, the first and third regions overlap at least partially in the surface direction of the die pad, and the second and fourth regions overlap at least partially in the surface direction of the die pad, the die pad further includes an opening facing the external terminal, the external terminal and the electrode pad are connected through the opening by a first bonding wire, the die pad is disposed at a first distance from the back surface, the sealing portion is disposed at a second distance from the back surface that is shorter than the first distance, and the second distance is shorter than a third distance that is the distance from the front surface to the sealing portion.

The present invention has the above configuration, and therefore can provide a semiconductor device that improves production efficiency and facilitates the connection between the integrated circuit and the lead frame.

1 is a perspective view of an integrating watt-hour meter including a semiconductor device according to a first embodiment; 1 is a partially cutaway view of a semiconductor device according to a first embodiment, as viewed from the back surface. This is a cross-sectional view taken along line 3-3 in Figure 2. FIG. 2 is an exploded perspective view showing the oscillator according to the first embodiment. 1 is a block diagram for explaining an LSI of a semiconductor device according to a first embodiment. 1A to 1E are explanatory diagrams showing a procedure for arranging an oscillator and an LSI on a lead frame and performing wire bonding in the method for manufacturing the semiconductor device according to the first embodiment. 4A to 4D are explanatory diagrams showing a procedure for sealing a lead frame, an oscillator, and an LSI with resin in the method for manufacturing the semiconductor device according to the first embodiment. FIG. 4 is a partially cutaway view showing a modified example of the semiconductor device according to the first embodiment. 5 is a flowchart showing a flow of a first frequency correction process according to the first embodiment. 10 is a flowchart showing a flow of a second frequency correction process according to the first embodiment. 4 is a diagram showing the relationship between temperature and frequency deviation in the semiconductor device according to the first embodiment. FIG. 13 is a block diagram for explaining an LSI of a semiconductor device according to a second embodiment. 1A is a diagram showing an example of a clock value of an oscillator of a semiconductor device according to a second embodiment, and FIG. 1B is a diagram showing an example of a clock value of a reference signal oscillator of a semiconductor device according to the second embodiment. 13 is a flowchart showing a flow of a first frequency correction process according to the second embodiment. 10 is a flowchart showing a flow of a frequency error derivation process according to the second embodiment. 13A and 13B are timing charts illustrating a frequency error derivation process according to the second embodiment, in which FIG. 13A illustrates the time when counting starts, and FIG. 13 is a flowchart showing a flow of a second frequency correction process according to the second embodiment. FIG. 11 is a block diagram for explaining another example of the LSI of the semiconductor device according to the second embodiment. FIG. 11 is a block diagram for explaining another example of the LSI of the semiconductor device according to the second embodiment. FIG. 11 is a partially cutaway view of a semiconductor device according to a third embodiment, as viewed from the back surface. This is a cross-sectional view taken along line 21-21 in Figure 20. FIG. 13 is a partially cutaway view of a semiconductor device according to a fourth embodiment, as viewed from the back surface. 13 is an explanatory diagram for explaining a lead frame of the semiconductor device according to the fourth embodiment; FIG. FIG. 13 is a partially cutaway view of a semiconductor device according to a fifth embodiment, as viewed from the back surface. This is a cross-sectional view taken along line 14-14 in Figure 24. 13A to 13E are explanatory diagrams showing a procedure for arranging an oscillator and an LSI on a lead frame and performing wire bonding in a manufacturing method for a semiconductor device according to a fifth embodiment. 13A to 13D are explanatory diagrams showing a procedure for sealing a lead frame, an oscillator, and an LSI with resin in a manufacturing method for a semiconductor device according to a fifth embodiment. FIG. 13 is a partially cutaway view of a semiconductor device according to a sixth embodiment, as viewed from the back surface. This is a cross-sectional view taken along line 18-18 in Figure 28. FIG. 1 is a block diagram showing an example of a state in which a conventional semiconductor device having a built-in timing function and an oscillator are connected to each other; FIG. 1 is a block diagram showing an example of a state in which a conventional semiconductor device having a built-in timing function and an oscillator are connected to each other; 1 is a schematic cross-sectional view showing a typical conventional packaged semiconductor device;

First Embodiment
Hereinafter, a semiconductor device according to the present invention will be described in detail with reference to the accompanying drawings.

<Composition>

As shown in FIG. 1, an integrated watt-hour meter 10 equipped with the semiconductor device of embodiment 1 is attached to the upper surface of a fixed plate 102 fixed to an exterior wall 100 of a house or the like, and is mainly composed of a main body 12, a transparent cover 14 that covers the main body 12, and a connection part 16 provided at the bottom of the main body 12.

The power supply side wiring 18 and the load side wiring 20 are connected from below the connection part 16, and supply current to the electric energy meter 10. The main body 12 is a rectangular box in a plan view, and inside the main body 12, a semiconductor device 24 (described later) and an electric energy measurement circuit 22 as a measuring means for measuring the amount of electric energy in response to a signal output from the semiconductor device 24 are mounted on a board (not shown). Note that in FIG. 1, the sizes of the electric energy measurement circuit 22 and the semiconductor device 24 are exaggerated for ease of explanation.

A horizontally long liquid crystal display 15 is provided on the front of the main body 12. The liquid crystal display 15 displays the amount of electricity used per unit time measured by the power measurement circuit 22, the accumulated amount of electricity used by time period, and the like. Note that the integrated watt-hour meter 10 according to this embodiment is an electronic watt-hour meter that uses the power measurement circuit 22 as a measuring means, but is not limited to this, and may be, for example, an induction-type watt-hour meter that measures the amount of electricity by rotating a disk.

Next, the detailed configuration of the semiconductor device 24 according to this embodiment will be described. In the following description, the left-right direction in the plan view of the semiconductor device 24 shown in FIG. 2 is the arrow X direction, the up-down direction is the arrow Y direction, and the height direction in the cross-sectional view of the semiconductor device 24 shown in FIG. 3 is the Z direction. As shown in FIGS. 2 and 3, the external shape of the semiconductor device 24 is rectangular in plan view, and includes a lead frame 26 as a skeleton, an oscillator 28 mounted on the front surface (first surface) of the lead frame 26, an LSI 30 as an integrated circuit mounted on the back surface (second surface) of the lead frame 26, and a molded resin 32 as a sealing material.

The lead frame 26 is a plate material formed by punching a flat plate made of metal such as copper (Cu) or an alloy of iron (Fe) and nickel (Ni) with a press, and is composed of a die pad 26A as a mounting part provided in the center, hanging leads 26B extending diagonally outward from the die pad 26A, and a number of leads (terminals) 38 provided between adjacent hanging leads 26B.

The leads 38 are elongated members extending toward the center of the die pad 26A, and multiple leads are formed at a predetermined interval around the die pad 26A. In this embodiment, 16 leads 38 are formed between adjacent hanging leads 26B. The leads 38 are composed of an inner lead 38A located on the die pad 26A side and an outer lead 38B located on the outer peripheral end side of the semiconductor device 24, and the inner lead 38A is pressed down by a press machine so as to be lower than the die pad 26A and extends parallel to the die pad 26A (see FIG. 3). The tip of the inner lead 38A closest to the die pad 26A is covered with a plating film 40. In this embodiment, the plating film 40 is formed of silver (Ag) as an example, but is not limited to this, and the plating film may be formed of a metal such as gold (Au).

The outer lead 38B is exposed from the molded resin 32 and bent downward, with its tip parallel to the inner lead 38A. In other words, it is a gull-wing lead. The outer lead 38B is also covered with a solder plating film. The solder plating film may be made of tin (Sn), an alloy of tin (Sn) and lead (Pb), or an alloy of tin (Sn) and copper (Cu).

The die pad 26A in the center of the lead frame 26 is a flat member formed into a rectangular shape in a plan view, and two openings 26C are formed to the right of the center of the die pad 26A, penetrating the die pad 26A in the thickness direction. The openings 26C are formed into a horizontally long rectangle, and are arranged to face the external electrodes 34 of the oscillator 28 described below (see FIG. 4).

The area between the two openings 26C is an oscillator mounting beam 42 that extends in the left-right direction and serves as an oscillator mounting area, and the oscillator 28 is mounted on the oscillator mounting beam 42 on the surface of the lead frame 26 via adhesive (not shown) (see FIG. 4). In other words, openings 26C are provided on both sides of the oscillator mounting beam 42. The oscillator 28 is a rectangular electronic component with the vertical direction as the longitudinal direction, and in this embodiment, an oscillator 28 that can be externally attached to a general-purpose semiconductor device 24 with a frequency of 32.768 kHz that is mounted on a general electronic device is used.

As shown in FIG. 4, the oscillator 28 includes a vibrating piece 44, a package body 46 that houses the vibrating piece 44, and a cover 48, and has a rectangular shape in a plan view. The vibrating piece 44 is a quartz vibrating piece in which an excitation electrode 44A is formed on the surface of a tuning-fork-shaped quartz piece made of artificial quartz. When a current is passed through the excitation electrode 44A, the vibrating piece 44 oscillates due to the piezoelectric effect. Here, the vibrating piece 44 is not limited to a tuning-fork-shaped quartz piece, and an AT-cut quartz piece may be used. In addition to quartz, a vibrating piece made of lithium tantalate (LiTaO ₃ ) or lithium niobate (LiNbO ₃ ) may be used. Furthermore, a MEMS vibrating piece made of silicon may be used.

The package body 46 is a box with an open top, and a base 47 to which the vibrating arm 44 is fixed is formed at the bottom of one longitudinal end. The base of the vibrating arm 44 is fixed to this base 47 to enable it to vibrate, and the vibrating arm 44 is hermetically sealed by joining the package body 46 and the lid 48 in a vacuum state. In addition, external electrodes 34 serving as terminals electrically connected to the excitation electrodes 44A of the vibrating arm 44 are formed at both ends of the underside of the package body 46 at a predetermined distance L1. In addition, the width L2 of the oscillator mounting beam 42 is formed narrower than the distance between the external electrodes 34.

The external electrode 34 is formed to have the same width as the package body 46, and as shown in FIG. 2, the size of the external electrode 34 is larger than the electrode pad 50 formed on the LSI 30, which will be described later, and the electrode pad 54 for the oscillator. In addition, the opening 26C of the die pad 26A is formed to be larger than the external electrode 34.

As shown in Figures 2 and 3, an LSI 30 serving as an integrated circuit or semiconductor chip is mounted on the center of die pad 26A on the back surface of lead frame 26 via an adhesive (not shown). LSI 30 is a rectangular, thin-walled electronic component, and the right end of LSI 30 covers about half of opening 26C. Therefore, when projected in a plan view, oscillator 28 and LSI 30 are arranged to overlap. Furthermore, when lead frame 26 is viewed from the LSI 30 side, external electrode 34 of oscillator 28 is exposed from opening 26C.

At the outer peripheral end of the lower surface along each side of the rectangular LSI 30, a plurality of electrode pads 50 electrically connected to the internal wiring of the LSI 30 are provided. The electrode pads 50 are formed of metal such as aluminum (Al) or copper (Cu), and 16 electrode pads are provided on each side of the LSI 30. The number of electrode pads 50 may be the same on each side, or may be different, such as fewer or more on the side on which the oscillator electrode pads 54 described later are provided. In addition, each electrode pad 50 is connected to the inner lead 38A by a bonding wire 52. In this embodiment, the number of electrode pads 50 is 16 on each side of the LSI 30 so as to match the number of leads 38, but this is not limited thereto, and may be more than the number of leads 38 and used for other purposes.

At the outer peripheral end of the LSI 30 on the oscillator 28 side, an oscillator electrode pad 54 is provided separately from the electrode pad 50. Two oscillator electrode pads 54 are provided in the vertical center of the LSI 30, and are located between the electrode pads 50. That is, an oscillator electrode pad 54 arrangement area (first area) is formed in the center, and electrode pad 50 arrangement areas (second areas) are formed in the areas from this center to the ends of the sides on which the oscillator electrode pads 54 are provided, and on the remaining three sides. In addition, the oscillator electrode pad 54 is connected to the external electrode 34 of the oscillator 28 by a bonding wire 52 through the opening 26C. The bonding wire is a linear conductive member made of a metal such as gold (Au) or copper (Cu).

The two oscillator electrode pads 54 provided in the vertical center of the LSI 30 are provided away from the electrode pads 50 provided on the same side. In other words, the distance between the oscillator electrode pads 54 and the electrode pads 50 adjacent to the oscillator electrode pads 54 is longer than the distance between the electrode pads 50.

The distance between the oscillator electrode pad 54 and the adjacent electrode pad 50 may be made equal to the distance between the electrode pads 50, and the oscillator electrode pad 54 and the adjacent electrode pad 50 may not be wire-bonded, so that the distance between the wire-bonded electrode pad 50 and the oscillator electrode pad 54 is longer than the distance between the wire-bonded electrode pads 50. In other words, on the electrode pad 50 of the LSI 30, the distance between the bonding wire 52 connecting the oscillator electrode pad 54 and the external electrode 34 and the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A is longer than the distance between the bonding wires 52 connecting the electrode pad 50 and the inner lead 38A.

Here, the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34 and the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A cross each other at a three-dimensional intersection. As shown in FIG. 3, the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A is formed so as to straddle the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34. In other words, in order to prevent short-circuiting of the bonding wire 52, the apex of the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34 is formed to be lower than the apex of the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A.

The height of the apex of the bonding wire 52 connecting the oscillator electrode pad 54 and the external electrode 34 may be lower than the height of the apex of the bonding wire 52 connecting all the electrode pads 50 and the inner lead 38A, or may be lower than the height of the apex of the bonding wire 52 connecting the electrode pad 50 between the oscillator electrode pad 54 and the external electrode 34 and the inner lead 38A.

The LSI 30 and the rectangular parallelepiped oscillator 28 are arranged parallel to each other so that their centers are approximately aligned on the X axis. In other words, the deviation of the center CP of the oscillator 28 from the X axis in the Y axis direction is smaller than the width of the central portion in the Y axis direction. In this arrangement, the oscillator electrode pad 54 provided near the center of any one side of the LSI 30 is connected by a bonding wire 52 to the external electrodes 34 arranged at a distance on both ends of the oscillator 28 in the longitudinal direction. At the same time, the electrode pads 50 arranged side by side to sandwich the oscillator electrode pad 54 are connected by a bonding wire 52 to the inner lead 38A arranged parallel to the electrode pad 50 in the Y axis direction.

Furthermore, since the electrode pad 54 for the oscillator is provided away from the electrode pad 50, the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A passes through a portion of the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34 that is lower than the oscillator 28. In other words, it is possible to avoid passing through and crossing the vicinity of the apex of the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34, and to efficiently cross over in a three-dimensional manner. Furthermore, since the height of the apex of the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A can be kept low, it is also possible to reduce the height of the package.

In addition, the connection position of the bonding wire 52 on the external electrode 34 of the oscillator 28 is shifted toward the inner lead 38A from the center position of the oscillator 28 in the X-axis direction. By connecting in this manner, it is possible to reduce the contact of the bonding wire 52 with the end of the LSI 30. On the other hand, in the X-axis direction, it is shifted toward the center of the oscillator 28 from the center of the external electrode 34. By connecting in this manner, it is possible to reduce the number of intersections with the bonding wire 52 connecting the electrode pad 50 and the inner lead 38A.

The oscillator 28, the LSI 30, and the lead frame 26 are sealed with the molded resin 32, and the outer shape of the semiconductor device 24 is formed. The molded resin 32 is filled so as not to leave any voids inside, and the height of the molded resin 32 is more than twice the height of the inner lead 38. In other words, the distance H1 from the surface of the molded resin 32 on the oscillator 28 mounting side to the center of the inner lead 38 is longer than the distance H2 from the surface of the molded resin 32 on the LSI 30 mounting side to the center of the inner lead 38. In addition, the distance H3 from the surface of the molded resin 32 on the LSI 30 mounting side to the center of the die pad 26 is longer than the distance H2 from the surface of the molded resin 32 on the LSI 30 mounting side to the inner lead 38. In this embodiment, a thermosetting epoxy resin containing a silica-based filler is used as the molded resin 32, but this is not limited to this, and for example, a thermoplastic resin may be used.

Next, the internal configuration of the LSI 30 will be described. As shown in FIG. 5, the LSI 30 includes an oscillator circuit 51, a divider circuit 53, a timer circuit 56, a temperature sensor 58, a control unit 60, and a register unit 70. The oscillator circuit 51 is connected to the oscillator 28 and causes the oscillator 28 to oscillate. The divider circuit 53 divides the signal output from the oscillator 28 (in this embodiment, a frequency of 32.768 kHz) to a predetermined clock (for example, 1 Hz). The timer circuit 56 measures time based on the signal divided by the divider circuit 53 and transmits the time to the control unit 60. The temperature sensor 58 measures the temperature of the LSI 30 and transmits it to the control unit 60. The oscillator 28 is arranged on the same lead frame near the LSI 30 and is electrically connected to the LSI 30, and the temperature of the oscillator 28 can be regarded as the same as the temperature of the LSI 30. That is, the temperature sensor 58 can accurately measure the temperature of the oscillator 28 arranged around the LSI 30. The control unit 60 displays the integrated amount of power per unit time measured by the power measurement circuit 22 on the liquid crystal display 15 based on the time measured by the timer circuit 56 (see FIG. 1). The register unit 70 is composed of multiple registers for storing various data used when correcting the oscillation frequency of the oscillator 28. The multiple registers will be explained in detail in the explanation of the correction of the oscillation frequency later. The LSI 30 also contains an arithmetic circuit that performs calculations and an internal power supply.

<Manufacturing Procedure>
The manufacturing procedure of the semiconductor device 24 will now be described.
6A, the lead frame 26 is placed on the mounting table 2 of the bonding device 1 so that the leads 38 are positioned downward. The mounting table 2 is formed with a recess 3 for accommodating the oscillator 28 when the lead frame 26 is turned upside down with the oscillator 28 fixed to the first surface. The oscillator 28 is transported sealed in a package 29 on a tape with the external electrodes 34 facing downward. An opening 26C is formed in the lead frame 26 in advance by pressing or the like.

Next, as shown in FIG. 6(b), the package 29 is opened, the oscillator 28 is taken out with the picker 4, and the oscillator 28 is placed on the first surface of the die pad 26A, i.e., the upper surface in FIG. 6(b), so that the external terminal 34 of the oscillator 28 overlaps the opening 26C, and is fixed to the die pad 26A with adhesive. Note that when the oscillator 28 is sealed in the package 29 with the external electrode 34 facing upward, it is preferable to use a picker 4 with a rotation mechanism, and after taking out the oscillator 28 with the picker 4, to turn the oscillator 28 upside down with the rotation mechanism and place it on the first surface of the die pad 26A with the external terminal 34 facing downward.

After the oscillator 28 is fixed to the first surface of the die pad 26A, the lead frame 26 is turned upside down and placed on the mounting table 2 as shown in FIG. 6(c). As a result, the lead frame is placed on the mounting table 2 with the first surface facing downward. At this time, the oscillator 28 is accommodated in the recessed portion 3 of the mounting table 2.

After the lead frame 26 is placed upside down on the mounting table 2, as shown in FIG. 6(d), the LSI 30 is fixed to the portion adjacent to the opening 26C on the second surface of the die pad 26A, which is opposite the first surface. Note that in FIG. 6(d), the second surface is the upper surface of the die pad 26A.

Finally, as shown in FIG. 6(e), the electrode pad 50 of the LSI 30 and the lead 38 are connected with a bonding wire 52, and the electrode pad 54 for the oscillator of the LSI 30 and the external electrode 34 of the oscillator 28 are connected with a bonding wire 52 to form the semiconductor device 24. At this time, the height of the top of the bonding wire 52 connecting the electrode pad 54 for the oscillator of the LSI 30 and the external electrode 34 of the oscillator 28 is connected so that it is lower than the height of the top of the bonding wire 52 connecting the electrode pad 50 of the LSI 30 and the lead 38. In addition, after first connecting the electrode pad 54 for the oscillator of the LSI 30 and the external electrode 34 of the oscillator 28 with a bonding wire, the electrode pad 50 of the LSI 30 and the lead 38 are connected with a bonding wire 52 so as to jump over the bonding wire 52. Also, the bonding wire 52 connecting the electrode pad 54 for the oscillator of the LSI 30 to the external electrode 34 of the oscillator 28 and the bonding wire 52 connecting the electrode pad 50 to the lead 38 are connected so as to cross over each other. At this time, the bonding wire 52 connecting the electrode pad 50 of the LSI 30 to the lead 38 is connected so as to cross over at a position shifted from the apex of the bonding wire 52 connecting the electrode pad 54 for the oscillator of the LSI 30 to the external electrode 34 of the oscillator 28.

By fixing the oscillator 28 and LSI 30 to the lead frame 26 (die pad 26A) and connecting the LSI 30 to the oscillator 28 in the procedure shown in Figures 6(a) to 6(e), even though the LSI 30 is fixed to the second surface of the die pad 26A opposite to the first surface to which the oscillator 28 is fixed, the connection between the LSI 30 and the oscillator 28 can be made from the second surface of the die pad 26A in the same way as the connection between the LSI 30 and the lead frame lead 38, which is efficient. In addition, since the oscillator 28 and the LSI 30 are directly connected by the bonding wire 32 without going through the lead frame 26, the wiring resistance can be reduced compared to when the oscillator 28 and the LSI 30 are connected through the lead frame 26 or when the bonding wire is routed around the back side of the lead frame 26.

Next, a procedure for sealing the semiconductor device 24 with the molding resin 32 will be described.
First, as shown in Fig. 7A, the semiconductor device 24 is fixed inside the cavity 6 of the mold 5 so that the first surface of the lead frame 26 (die pad 26A), i.e., the surface on which the oscillator 28 is fixed, becomes the upper surface, and the second surface of the lead frame 26 (die pad 26A), i.e., the surface on which the LSI 30 is fixed, becomes the lower surface. Here, since the oscillator 28 is thicker than the LSI 30, the semiconductor device 24 is disposed inside the cavity 6 so that the lead frame 26 (die pad 26A) is located below the center of the cavity 6 in the height direction of the mold 5. In addition, the outer lead 38B is made to protrude outside the mold 5 with the semiconductor device 24 fixed inside the cavity 6.

Once the semiconductor device 24 is fixed inside the cavity 6, the molding resin 32 is injected from the injection port 7 provided along the lower surface of the lead frame 26, as shown by the arrow a in FIG. 7(b). As described above, the lead frame 26 (die pad 26A) is fixed so as to be located lower than the center of the height direction of the cavity 6 in the mold 5, so the molding resin 32 is initially injected along the lead frame 26 (die pad 26A). The injected molding resin 32 has the property of flowing into the direction of a larger space, so it tries to flow upward from the gap between the rear end of the lead frame 26 and the die pad 26A, for example, but the path is blocked by the oscillator 28, so it flows around to the bottom of the lead frame 26, as shown by the arrow b in FIG. 7(c).

Then, as shown by the arrow c in FIG. 7(d), the mold resin 32 flows into the upper surface side of the lead frame 26. Then, when the lower surface side of the lead frame 26 is filled with the mold resin 32, the upper surface side of the lead frame 26 is also filled with the mold resin 32.

Once both sides of the lead frame 26 are filled with the molding resin 32, the mold 5 is heated to harden the molding resin 32.

In the semiconductor device 24, the oscillator 28 is fixed to the upper surface of the lead frame 26 (die pad 26A) and the LSI 30 is fixed to the lower surface. Therefore, when sealing the semiconductor device 24 with molded resin 32, the lead frame 26 needs to be positioned below the center of the height of the cavity 6 of the mold 5. When there is a large space above the lead frame 26 like this, the molded resin 32 tends to flow into the upper side of the lead frame 26.

Therefore, it is believed that the pressure from the molding resin 32 injected into the cavity 6 from the injection port 7 is not applied evenly to both sides of the lead frame 26, but is applied more strongly to the top surface of the lead frame 26.

However, by adjusting the flow path of the molded resin 32 using the oscillator 28 and causing the molded resin 32 to flow below the lead frame 26 first, it is expected that the molded resin 32 injected into the cavity 6 will support the lead frame 26 from below. Therefore, the lead frame 26 is prevented from shifting vertically inside the cavity 6 while the molded resin 32 is being injected.

＜Action＞

Next, the operation of the semiconductor device 24 and the watt-hour meter 10 according to this embodiment will be described. In the semiconductor device 24 according to this embodiment, the oscillator 28 and the LSI 30 are integrated by being sealed with the molded resin 32, and the LSI 30 has an oscillation circuit 51, a frequency divider circuit 53, and a timing circuit 56 built in. Therefore, time can be measured simply by mounting the semiconductor device 24 on the board inside the watt-hour meter 10 shown in FIG. 1. In other words, there is no need to mount the oscillator 28, the frequency divider circuit 53, etc. separately on the board. Therefore, there is no need to take the trouble of adjusting the connection between the oscillator 28 and the semiconductor device 24.

The LSI 30 also has a built-in temperature sensor 58, which allows the temperature around the oscillator 28 to be accurately measured. This allows the frequency to be corrected with high precision even if the signal (frequency) output from the oscillator 28 fluctuates due to temperature changes. This means that the frequency can be made highly accurate even with an inexpensive oscillator, without the need for an expensive high-precision oscillator.

2, the external electrode 34 of the oscillator 28 and the oscillator electrode pad 54 of the LSI 30 are directly connected through the opening 26C by the bonding wire 52. This allows wiring over the shortest distance without going through the lead frame 26, reducing wiring resistance. In addition, the lengths of the two bonding wires 52 connecting the external electrode 34 and the oscillator electrode pad 54 are uniform, so that the tension on the bonding wires 52 can be made uniform, preventing contact due to breakage or bending of the bonding wires 52. In addition, since wiring can be performed without going through the lead frame 26, it is less susceptible to the effects of noise, and signals can be transmitted smoothly from the oscillator 28 to the LSI 30. In addition, noise is likely to occur between the bonding wires 52 formed in parallel, but the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34 crosses over the other bonding wires 52, so interference between the bonding wire 52 connecting the electrode pad 54 for the oscillator and the external electrode 34 and the other bonding wires 52 can be reduced, and in particular, the effect of noise from the other bonding wires 52 on the oscillator 28 can be reduced. Furthermore, since the external electrode 34 is larger than the electrode pad 54 for the oscillator, wire bonding can be easily performed.

In addition, the oscillator 28 and the LSI 30 are mounted on the front and back surfaces of the lead frame 26 and are arranged so as to overlap when projected in a plan view, so the vertical and horizontal sizes of the semiconductor device 24 can be made smaller than when the oscillator 28 and the LSI 30 are mounted side by side on one side of the lead frame 26.

In addition, since the LSI 30 is located in the center of the die pad 26A, the length of the bonding wire 52 connecting the electrode pad 50 and the inner lead 38 can be made constant. This makes the wire bonding process easier and improves yield.

In this embodiment, all the inner leads 38A are connected to the electrode pads 50 of the LSI 30, but this is not limited thereto. As shown in the modified example in FIG. 6, any inner lead 38A may be connected to the die pad 26A with a bonding wire 52, and the outer lead 38B may be connected to earth to ground the die pad 26A. In this case, it is possible to prevent the die pad 26A from being charged. In addition, since the LSI 30 and the oscillator 28 are arranged separately on both sides of the lead frame so as to sandwich the lead frame, noise from the LSI 30 to the oscillator 28 can be shielded by the die pad 26A.

In addition, in this modified example, the oscillator circuit 51 is placed near the electrode pad 54 for the oscillator, and the digital circuit section 55 is placed so as to surround this oscillator circuit 51. The digital circuit section 55 is a circuit section that processes digital signals, and is less susceptible to noise compared to other elements. This reduces the effect of noise on the oscillator circuit 51 from other elements (particularly the analog circuit section) built into the LSI 30. An example of the digital circuit section 55 is a CPU.

<Oscillation frequency correction>

Next, we will explain the frequency correction process that corrects temperature-dependent errors in the oscillation frequency of the oscillator 28 in the semiconductor device 24 according to this embodiment.

For example, at the time of shipment, the semiconductor device 24 measures the temperature using the temperature sensor 58 when the temperature of the LSI 30 inside the semiconductor device 24 is at room temperature (here, 25°C), at a reference temperature lower than room temperature (hereinafter also referred to as "low temperature"), and at a reference temperature higher than room temperature (hereinafter also referred to as "high temperature"). Then, for example, after shipment, the semiconductor device 24 uses the temperature obtained by this measurement as trimming data and corrects the frequency error of the oscillator 28, taking into account measurement errors that occur due to manufacturing variations in the temperature sensor 58.

The register unit 70 (see FIG. 5) includes a temperature measurement value register 71 that stores data indicating the temperature measured by the temperature sensor 58, a low temperature register 72 that stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is low, a normal temperature register 73 that stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is normal, a high temperature register 74 that stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is high, and a frequency correction register 75 for storing a correction value for the oscillation frequency of the oscillator 28 derived from the data indicating these temperatures. Each register is connected to the control unit 60 via a data bus 76, and the control unit 60 reads and writes to each register via the data bus 76.

In order to correct the frequency error of the oscillator 28, the semiconductor device 24 performs a first frequency correction process in which the temperature of the semiconductor device 24 is measured by the temperature sensor 58 when the temperature of the semiconductor device 24 is set to low temperature, room temperature, and high temperature, and the measured temperatures are stored as trimming data in the low temperature register 72, the room temperature register 73, and the high temperature register 74, respectively.

For example, during a shipping test, a tester first places the semiconductor device 24 inside a thermostatic chamber with the temperature inside the chamber set to room temperature. Then, the user inputs a measurement operation signal to the semiconductor device 24 to start measuring the temperature, for example, using the temperature sensor 58, thereby causing the semiconductor device 24 to execute the first frequency correction process. At this time, the user inputs the measurement operation signal to the semiconductor device 24, for example, by connecting a device that outputs the measurement operation signal to the lead 38 of the semiconductor device 24. In addition, the measurement operation signal includes information indicating whether the temperature set in the thermostatic chamber is room temperature, high temperature, or low temperature.

Figure 9 is a flowchart showing the flow of the first frequency correction process in the semiconductor device 24 according to this embodiment. The program for executing the first frequency correction process is a program executed at the timing when the measurement operation signal is input, and is stored in advance in a storage means possessed by the control unit 60. Note that the timing of execution is not limited to this.

In step S101, the control unit 60 determines whether a predetermined time (e.g., several hours) has elapsed since the measurement operation signal was input. The predetermined time is preferably the time required for the internal temperature of the semiconductor device 24 (the temperature of the LSI 30) to match the temperature of the thermostatic chamber.

If it is determined in step S101 that the predetermined time has elapsed, in step S103, the control unit 60 acquires a measurement value by the temperature sensor 58. The measurement value by the temperature sensor 58 is stored in the temperature measurement value storage register 71. When acquiring a measurement value by the temperature sensor 58, a measurement may be performed every predetermined time (e.g., one minute), and the measurement value may be an average value of multiple measurement values obtained by multiple measurements.

In step S105, the control unit 60 stores the acquired measurement value in the room temperature register 73 if the temperature set in the thermostatic chamber is room temperature (here, 25°C), stores it in the high temperature register 74 if the temperature set in the thermostatic chamber is high, and stores it in the low temperature register 72 if the temperature set in the thermostatic chamber is low, and ends the first frequency correction process. Note that the first frequency correction process may be performed in advance when the wafer is in a wafer state.

The tester causes the semiconductor device 24 to perform the above steps S101 to S105 in each of the following states: when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to room temperature; when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to high; and when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to low. As a result, the values measured by the temperature sensor 58 are stored in the room temperature register 73, the high temperature register 74, and the low temperature register 72, respectively.

The semiconductor device 24 according to this embodiment is shipped after the above-mentioned processing is performed, and the second frequency correction processing described below is performed at a predetermined timing after the shipment.

For example, after shipment, the user causes the semiconductor device 24 to execute the second frequency correction process by inputting a derivation operation signal to the semiconductor device 24 to start deriving a frequency correction value. At this time, the user inputs the derivation operation signal by, for example, connecting a device that outputs the derivation operation signal to the lead 38 of the semiconductor device 24. Alternatively, the semiconductor device 24 may execute the second frequency correction process at regular intervals.

Figure 10 is a flowchart showing the flow of the second frequency correction process in the semiconductor device 24 according to this embodiment. The program for executing the second frequency correction process is a program that is executed when the derivation operation signal is input after the semiconductor device 24 is shipped, and is stored in advance in a storage means included in the control unit 60.

In step S201, the control unit 60 acquires the measurement values stored in the room temperature register 73, the high temperature register 74, and the low temperature register 72.

In step S203, the control unit 60 uses the measurement value acquired in step S201 to derive a correction value for the oscillation frequency of the oscillator 28 (hereinafter also referred to as the "frequency correction value").

11 is a diagram showing the relationship between temperature and frequency deviation in the semiconductor device according to this embodiment. Note that FIG. 11 shows a theoretical value obtained by calculation using a quadratic function, not a frequency error obtained in an actual temperature environment. The quadratic function is expressed by the following formula (1). Note that in the following formula (1), f is the frequency deviation, a is a quadratic temperature coefficient, T is the measured temperature, _T0 is the peak temperature, and b is the peak error. The quadratic temperature coefficient a is a constant that is predetermined according to the individual difference of the oscillator 28, and is stored in advance in a storage means of the control unit 60.

In the first embodiment, the frequency deviation f is unknown, but the apex error b can be derived from the known secondary temperature coefficient a, the measurement value at room temperature stored in the room temperature register 73, the measurement value at high temperature stored in the high temperature register 74, and the measurement value at low temperature stored in the low temperature register 72. Then, the control unit 60 sets the value of the apex error b as the frequency correction value so that the frequency deviation is smallest at temperature T0 at room temperature.

In deriving the frequency correction value, for example, if the measurement value by temperature sensor 58 is -8°C in a measurement environment of -10°C, a correction corresponding to +2°C is required. At the shipping stage, the product reads out the measurement values at three points, room temperature, high temperature, and low temperature stored in each register via data bus 76, and the temperature in the actual environment is derived using the read data as trimming data. If the measurement value by temperature sensor 58 is a value not stored in each register, the temperature in the actual environment can be derived using the values of the two adjacent registers.

In step S205, the control unit 60 stores data indicating the frequency correction value derived in step S203 in the frequency correction register 75. Then, in the semiconductor device 24, the frequency divider circuit 53 uses the frequency correction value stored in the frequency correction register 75 to generate a clock signal from the signal input from the oscillation circuit, thereby correcting the oscillation frequency of the oscillator 28.

In this way, according to the semiconductor device 24 of the first embodiment, at the time of shipment, the measurement values by the temperature sensor 58 at three environmental temperatures of the semiconductor device 24 are prepared as trimming data, and a frequency correction value is derived based on the trimming data, so that a frequency correction value based on highly accurate temperature information can be obtained without depending on manufacturing variations in the temperature sensor 58 for each individual semiconductor device 24.

In a conventional packaged semiconductor device, as shown in FIG. 32, when the semiconductor device is operated, the ambient temperature Ta (°C), package surface temperature Tc (°C), and chip surface temperature Tj (°C) of the semiconductor device are all different. For example, the chip surface temperature Tj is expressed by the following formula (2), where θja is the package thermal resistance (between the junction and the atmosphere) and P is the power consumption (maximum or average) of the chip.

However, in the semiconductor device 24 according to this embodiment, the temperature sensor 58 and the oscillator 28 are sealed together, so that the temperature around the temperature sensor 58 and the temperature around the oscillator 28 are the same, and the temperature of the oscillator 28 can be measured with high accuracy by the temperature sensor 58 of the LSI 30. This prevents the accuracy of the frequency correction from being reduced due to the temperature difference between the oscillator 28 and the temperature sensor 58.

(Second embodiment)

Next, a semiconductor device 24 according to a second embodiment of the present invention will be described. Note that the same components as those in the first embodiment are given the same reference numerals and will not be described.

As shown in FIG. 12, the semiconductor device 24 according to the second embodiment is connected to a clock generator including a reference signal oscillator 80 that inputs a clock signal (hereinafter also referred to as a "reference clock signal") that is used as a reference when correcting the oscillation frequency of the oscillator 28 to the LSI 30A. In addition to the configuration of the LSI 30 of the semiconductor device 24 according to the first embodiment, the LSI 30A of the semiconductor device 24 according to the second embodiment further includes a measurement counter 81, a reference counter 82, and an output terminal 83 that outputs a clock signal from the oscillator circuit 57 to the outside.

As shown in Figures 13(a) and (b), the reference signal oscillator 80 is an oscillator such as a quartz crystal resonator having a higher oscillation frequency than the oscillator 28. In the second embodiment, the oscillation frequency of the oscillator 28 is 32.768 KHz, and the oscillation frequency of the reference signal oscillator 80 is 10 MHz.

The measurement counter 81 is connected to the oscillator circuit 51 and receives a clock signal (hereinafter also referred to as a "measurement clock signal") from the oscillator circuit 51 under the control of the control unit 60, and counts the number of clocks of the clock signal. The reference counter 82 is connected to a clock generating device equipped with a reference signal oscillator 80 and receives a clock signal from the reference signal oscillator 80 under the control of the control unit 60, and counts the number of clocks of the clock signal. As shown in Figures 13(a) and (b), the reference counter 82 and the measurement counter 81 count the number of clocks approximately at the same time while synchronizing with each other. The measurement counter 81 and the reference counter 82 may be operated in synchronism with each other based on an operation signal, or a synchronous counter may be used.

In the second embodiment, in the register unit 70, the temperature measurement value register 71 stores data indicating the temperature measured by the temperature sensor 58, the low temperature register 72 stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is set to a reference temperature lower than room temperature (25°C) and the frequency error at that temperature, the room temperature register 73 stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is set to room temperature (25°C) and the frequency error at that temperature, the high temperature register 74 stores data indicating the temperature measured by the temperature sensor 58 when the ambient temperature is set to a reference temperature higher than room temperature (25°C) and the frequency error at that temperature, and the frequency correction register 75 stores data indicating the frequency correction value derived from the data indicating the frequency error described above.

<Oscillation frequency correction>

For example, during a shipping test, the user first places the semiconductor device 24 inside a thermostatic chamber with the temperature inside the chamber set to room temperature (here, 25°C). The user then inputs a measurement operation signal to the semiconductor device 24 to start measuring the temperature, for example, using the temperature sensor 58, thereby causing the semiconductor device 24 to execute the first frequency correction process. At this time, the user inputs the measurement operation signal to the semiconductor device 24, for example, by connecting an instrument that outputs the measurement operation signal to the lead 38 of the semiconductor device 24. The measurement operation signal also includes information indicating whether the temperature set in the thermostatic chamber is room temperature, high temperature, or low temperature.

Figure 14 is a flowchart showing the flow of the first frequency correction process in the semiconductor device 24 according to this embodiment. The program for executing the first frequency correction process is a program that is executed when the measurement operation signal is input at the time of shipment of the semiconductor device 24, and is stored in advance in a storage means included in the control unit 60.

In step S301, the control unit 60 determines whether a predetermined time (e.g., several hours) has elapsed since the measurement operation signal was input. The predetermined time may be the time required for the internal temperature of the semiconductor device 24 (the temperature of the LSI 30) to match the temperature of the thermostatic chamber.

If it is determined in step S301 that the predetermined time has elapsed, in step S303, the control unit 60 acquires a measurement value by the temperature sensor 58. The measurement value by the temperature sensor 58 is stored in the temperature measurement value storage register 71. Furthermore, the measurement accuracy of the temperature sensor 58 has been confirmed by testing to be equal to or greater than a predetermined reference value, and it is guaranteed that the temperature sensor 58 can measure temperature with high accuracy. Alternatively, the measurement value by the temperature sensor 58 may be used to perform correction.

In step S305, the control unit 60 performs a frequency error derivation process to derive an error in the oscillation frequency of the oscillator 28. FIG. 15 is a flowchart showing the flow of the frequency error derivation process according to this embodiment. FIG. 16 is a timing chart of the frequency error derivation process according to this embodiment, where (a) shows when counting starts and (b) shows when counting stops.

In step S401, the control unit 60 outputs a correction operation signal to the measurement counter 81. In step S403, the measurement counter 81, which has received the correction operation signal, starts operation, starts counting the clock value of the clock signal generated by the oscillator 28, and outputs a start signal to the reference counter 82.

In step S405, the reference counter 83, which has received the start signal, starts counting the clock value of the clock signal generated by the reference signal oscillator 80. That is, as shown in FIG. 16(a), when the correction operation signal is turned on, the measurement counter 81 starts counting, and the reference counter 82 also starts counting in synchronization with the measurement counter 81.

In step S407, the measurement counter 81 determines whether the count value of the measurement counter is equal to or greater than a predetermined value (in this embodiment, 32.768, which corresponds to one second). If the count value is not equal to or greater than the predetermined value in step S407, the measurement counter 81 continues counting.

If it is determined in step S407 that the count is equal to or greater than the predetermined value, in step S409, the measurement counter 81 stops counting and outputs a stop signal to the reference counter 82.

The reference counter 82, which has received the stop signal, stops counting in step S411. That is, as shown in FIG. 16(b), when the correction operation signal is turned off, the measurement counter 81 stops counting, and the reference counter 82 also stops counting in synchronization with the measurement counter 81.

In step S413, the control unit 60 acquires the count value of the reference counter 82.

In step S415, the control unit 60 derives the error in the oscillation frequency of the oscillator 28 from the count value of the reference counter 82 acquired in step S413. That is, the control unit 60 derives the error in the oscillation frequency of the oscillator 28 by comparing the count value (i.e., 32,768) obtained in the same time period in the measurement clock signal by the oscillator 28 with the count value of the reference clock signal by the reference signal oscillator 80, which can measure time with higher accuracy than the oscillator 28.

For example, since the oscillation frequency of the reference signal oscillator 80 is 10 MHz, if the count value of the reference counter 82 is "10000000 (decimal)", it can be assumed that the oscillator 28 is measuring one second accurately, and there is no need to correct the error in the oscillation frequency to 0, so the error in the oscillation frequency (frequency correction value) is set to 0. On the other hand, if the count value of the reference counter 82 is "10000002 (decimal)", it can be assumed that the oscillation frequency of the oscillator 28 is slower by 0.2 ppm, and it is necessary to correct the oscillation frequency of the oscillator 28 by the amount of that error, i.e., 0.2 ppm, so that the error in the oscillation frequency (frequency correction value) is +0.2 ppm. Also, for example, if the value of the reference counter 82 is "9999990 (decimal)", the oscillation frequency of the oscillator 28 is 1.0 ppm faster, so the oscillation frequency of the oscillator 28 needs to be slowed down by that error, i.e., 1.0 ppm, and the oscillation frequency error (frequency correction value) is set to -1.0 ppm.

In step S417, the control unit 60 stops outputting the correction operation signal to the measurement counter 81 and ends the frequency error derivation processing program. In addition, the measurement counter 81 and the reference counter 82 stop operating when the input of the correction operation signal stops.

In step S307, the control unit 60 stores the temperature measurement value acquired in step S303 and the frequency error derived in step S415 in the room temperature register 73 if the temperature set in the thermostatic bath is room temperature, in the high temperature register 74 if the temperature set in the thermostatic bath is high, and in the low temperature register 72 if the temperature set in the thermostatic bath is low, and ends the first frequency correction processing program.

The user causes the semiconductor device 24 to perform the above steps S301 to S309 in each of the following states: when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to room temperature; when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to a high reference temperature; and when the semiconductor device 24 is placed inside a thermostatic chamber whose temperature is set to a low reference temperature. As a result, the temperature measurement value by the temperature sensor 58 and the error in the oscillation frequency of the oscillator 28 are stored in the room temperature register 73, high temperature register 74, and low temperature register 72, respectively.

The semiconductor device 24 according to this embodiment is shipped after the above-mentioned processing, and at a predetermined timing after the shipment, the oscillation frequency of the oscillator 28 is corrected based on the above-mentioned formula (1) using the data indicating the frequency correction value stored in the frequency correction register 75. The secondary temperature coefficient a and the apex error b in the second embodiment are determined by the frequency error derived at each temperature. The frequency error may be obtained by linear approximation from the difference between the oscillation frequency error values stored in the register of a higher temperature than the temperature at which the frequency error is to be determined and the register of a lower temperature. Then, the second frequency correction processing described later is performed at the time of system reset, periodically, in response to the input of a predetermined signal via the lead 38, or when the oscillation frequency of the oscillator 28 is corrected using the above-mentioned formula (1).

The user causes the semiconductor device 24 to execute the second frequency correction process by, for example, inputting a derivation operation signal to start deriving a frequency correction value to the semiconductor device 24. At this time, the user inputs the derivation operation signal, for example, by connecting a device that outputs the measurement operation signal to the lead 38 of the semiconductor device 24.

Figure 17 is a flowchart showing the flow of the second frequency correction process in the semiconductor device 24 according to this embodiment. The program for executing the second frequency correction process is a program executed when the measurement operation signal is input, and is stored in advance in a storage means included in the control unit 60.

In step S503, the control unit 60 measures the current ambient temperature using the temperature sensor 58 and acquires the measured value. The measured value by the temperature sensor 58 is stored in the temperature measurement value storage register 71.

In step S505, the control unit 60 determines whether the temperature acquired in step S503 is different from the temperature measured in the thermostatic chamber (for example, the temperature acquired in step S303). If this determination is not necessary, the process may proceed to step S505 after performing the process of step S503 without performing the process of step S505.

If it is determined in step S505 that the temperatures are not different, the control unit 60 determines that there is no need to change the frequency correction value and ends the second frequency correction process.

If it is determined in step S505 that the temperatures are different, the control unit 60 performs the same process as in step S305 described above in step S507 to derive the frequency error. Also, in step S507, the control unit 60 substitutes the data stored in each register of the register unit 70 into the above-mentioned formula (1) to derive the quadratic temperature coefficient a and the apex error b.

In step S511, the control unit 60 stores the frequency correction value in the frequency correction register 75. At this time, if it is determined in step S505 that the temperatures are not different, the control unit 60 derives and stores the frequency correction value using the temperatures and frequency errors stored in the low temperature register 72, the normal temperature register 73, and the high temperature register 74. On the other hand, if it is determined in step S505 that the temperatures are different, the control unit 60 derives and stores the frequency correction value using the frequency error derived in step S507.

In the semiconductor device 24, the frequency divider circuit 53 corrects the signal input from the oscillator circuit based on the frequency correction value stored in the frequency correction register 75, thereby correcting the oscillation frequency of the oscillator 28.

As described above, the semiconductor device 24 according to the second embodiment can measure the frequency error at the actual temperature, thereby enabling a stable timekeeping even if the frequency deviation varies depending on the temperature due to manufacturing variations in the oscillator 28.

In addition, according to the semiconductor device 24 of the second embodiment, by incorporating a time correction circuit inside the LSI 30A of the semiconductor device 24, it is possible to perform time measurement with high accuracy even if the frequency accuracy of the clock signal supplied from the outside is low.

In addition, in the semiconductor device 24 according to the second embodiment, the unused terminals resulting from the incorporation of the oscillator 28 can be replaced with other functions (e.g., the addition of serial communication or I2C), thereby achieving high functionality even with a limited number of terminals.

In this embodiment, the error in the oscillation frequency of the oscillator 28 is derived using the reference signal oscillator 80, the measurement counter 81, and the reference counter 82, but the method of deriving the error is not limited to this. It is also possible to measure how long it actually takes for the oscillator 28 to time a specific time (in this embodiment, 1 second (32,768 CLK)) by comparing the time measured by the clock signal output from the oscout terminal output from the oscillation circuit 51 with the specific time accurately measured by another method.

In addition, after correcting the error in the oscillation frequency of the oscillator 28 in the semiconductor device 24 according to the second embodiment, a correction may be made, if necessary, taking into account the measurement error of the temperature sensor 58 in the semiconductor device 24 according to the first embodiment.

Figures 18 and 19 are block diagrams showing another example of the electrical configuration of LSI 30A of semiconductor device 24 according to this embodiment.

As shown in FIG. 18, the semiconductor device 24 may have an output terminal 84, and the error (frequency correction value) of the oscillation frequency of the oscillator 28 derived by the control unit 60 may be output to the outside of the semiconductor device 24 via the output terminal 84. This makes it possible to perform periodic calibration to find deterioration of the characteristics of the reference clock generating device.

19, the LSI 30A of the semiconductor device 24 may connect a high-precision clock generator 85, which serves as a calibration reference, to the measurement counter 81. In this case, in step S413 described above, the control unit 60 acquires the count value of the measurement counter 81 and the count value of the reference counter 82, and compares the count value of the measurement counter 81 with the count value of the reference counter 82. For example, if the frequency of the clock signal of the measurement counter 81 is 10 MHz and the frequency of the clock generator 85 connected to the reference counter 82 is 10 MHz, if the clock generator having the reference signal oscillator 80 and the clock generator 84 connected to the reference counter 82 generate clock signals of the same frequency, the count value of the measurement counter 81 and the count value of the reference counter 82 will be the same value, but if the characteristics of the reference signal oscillator 80 have changed, a difference will occur between the count value of the measurement counter 81 and the count value of the reference counter 82. If a difference occurs between the count value of the measurement counter 81 and the count value of the reference counter 82, the control unit 60 determines whether the difference is within a predetermined allowable error range and outputs the determination result to the output terminal 84. This makes it possible to perform regular calibration to find deterioration in the characteristics of the clock generating device equipped with the reference signal oscillator 80.

Also, as shown in FIG. 19, even if the LSI 30A of the semiconductor device 24 has a built-in clock generating device 85, a selector 86 may be connected inside the LSI 30A to selectively input either the clock signal output from the oscillator circuit 51 or the clock signal output from the clock generating device 85 and output it to the measurement counter 81. By connecting the selector 86, the semiconductor device 24 shown in FIG. 19 can function in the same way as the semiconductor device 24 shown in FIG. 18.

(Third embodiment)

Next, a semiconductor device 200 according to a third embodiment of the present invention will be described. The same components as those in the first embodiment are given the same reference numerals and will not be described. As shown in Figures 9 and 10, an oscillator 28 is mounted via adhesive on an oscillator mounting beam 206 on the front surface of a lead frame 202 constituting the semiconductor device 200 according to this embodiment, and an LSI 30 is mounted via adhesive on a die pad 202A on the back surface of the lead frame 202.

Here, the LSI 30 is mounted shifted to the left of the center of the die pad 202A so that it does not overlap with the opening 202C formed in the die pad 202A. Therefore, the entire surface of the LSI 30 is bonded to the die pad 202A.

The procedure for fixing the oscillator 28 to the first surface of the die pad 202A and the LSI 30 to the second surface opposite the first surface, and connecting the electrode pad 54 for the oscillator of the LSI 30 to the external electrode 34 of the oscillator 28, and the electrode pad 50 of the LSI 30 to the inner lead 38A with bonding wires 52 to form the semiconductor device 200 is as shown in Figures 6(a) to (e) in the same manner as the semiconductor device 24 of embodiment 1. The procedure for sealing the semiconductor device 200 with the mold resin 32 is also as shown in Figures 7(a) to (d).

In the semiconductor device 200 according to this embodiment, the adhesive strength of the LSI 30 can be improved compared to the semiconductor device 24 according to the first embodiment. In addition, since the entire surface of the external electrode 34 of the oscillator 28 is exposed, the electrode pad 54 for the oscillator and the external electrode 34 can be easily connected with the bonding wire 52.

(Fourth embodiment)

Next, a semiconductor device 300 according to a fourth embodiment of the present invention will be described. The same components as those in the first embodiment are given the same reference numerals and will not be described. As shown in Figures 22 and 23, the lead frame 302 constituting the semiconductor device 300 according to this embodiment has a shape in which a circular die pad 302A and an outer frame portion 302B provided on the outer periphery of the die pad 302A are bridged by a support beam 302C and an oscillator mounting beam 302D.

The die pad 302A is located in the center of the lead frame 302 and is smaller than the LSI 30 mounted on the back surface of the die pad 302A. The support beam 302C extends above and below the die pad 302A and to the left, and the oscillator mounting beam 302D extends to the right side of the die pad 302A. The oscillator mounting beam 302D is formed to be wider than the support beam 302C, and the width of the oscillator mounting beam 302D is formed to be narrower than the distance between the external electrodes 34 of the oscillator 28, and the oscillator 28 is mounted via an adhesive.

The procedure for fixing the oscillator 28 to the first surface of the die pad 302A and the LSI 30 to the second surface opposite the first surface, and connecting the electrode pads 54 for the oscillator of the LSI 30 to the external electrodes 34 of the oscillator 28, and the electrode pads 50 of the LSI 30 to the leads 38 with bonding wires 52 to form the semiconductor device 300 is as shown in Figures 6(a) to (e) in the same manner as the semiconductor device 24 of embodiment 1. The procedure for sealing the semiconductor device 300 with the mold resin 32 is also as shown in Figures 7(a) to (d).

In the semiconductor device 300 according to this embodiment, the die pad 302A is formed as small as possible and the outside of the die pad 302A is punched out, so the material cost of the lead frame 302 can be reduced compared to the semiconductor device 24 according to the first embodiment.

In addition, by making the die pad 302A smaller, the contact area between the molded resin 32 and the LSI 30 is larger than that of the first embodiment. Here, since the adhesive strength between the LSI 30 and the molded resin 32 is greater than that between the LSI 30 and the die pad 302A, the LSI 30 is less likely to peel off due to the increased contact area between the molded resin 32 and the LSI 30. In particular, when mounting the semiconductor device 300 on a substrate by reflow or the like, the semiconductor device 300 is heated, which may reduce the adhesive strength between the die pad 302A and the molded resin 32. However, by making the die pad 302A smaller and increasing the contact area between the molded resin 32 and the LSI 30, the adhesive strength can be ensured even when heated.

Furthermore, the support beams 302C and the oscillator mounting beams 302D are arranged in a cross shape (grid shape) inside the outer frame portion 302B, and the oscillator 28 is mounted so as to cross perpendicularly to the oscillator mounting beams 302D, so that it is possible to prevent the support beams 302C and the external electrodes 34 of the oscillator 28 from coming into contact and shorting out. Note that the support beams 302C supporting the die pad 302A may be removed, and the outer frame portion 302B and the die pad 302A may be connected to each other by only the oscillator mounting beam 302D as a cantilever.

(Fifth embodiment)

Next, a semiconductor device 400 according to a fifth embodiment of the present invention will be described. The same components as those in the first embodiment are given the same reference numerals and will not be described. As shown in FIGS. 24 and 25, a step portion 404 is provided on a die pad 402A located in the center of a lead frame 402 according to this embodiment. The step portion 404 extends in the vertical direction of the die pad 402A, and as shown in FIG. 14, it is inclined upward from left to right. Therefore, the die pad 402A is divided by the step portion 404 into a first mounting surface 402B located below and a second mounting surface 402C located above.

The first mounting surface 402B and the second mounting surface 402C are provided continuously on the back surface of the lead frame 402 and are formed parallel to the inner lead 408A. The LSI 30 is also mounted on the first mounting surface 402B via an adhesive, and the electrode pad 50 provided on the underside of the LSI 30 and the inner lead 408A are electrically connected by a bonding wire 412.

The oscillator 28 is mounted on the second mounting surface 402C via adhesive. Here, the second mounting surface 402C is located above the first mounting surface 402B by the difference in thickness between the integrated circuit 30 and the oscillator 28, and the bottom surface of the LSI 30 and the bottom surface of the oscillator 28 are at the same height.

As shown in FIG. 25, the bonding wire 412 connecting the electrode pad 50 and the inner lead 408A is formed so as to straddle the bonding wire 412 connecting the oscillator electrode pad 54 and the external electrode 34. In other words, in order to prevent a short circuit of the bonding wire 412, the apex of the bonding wire 412 connecting the oscillator electrode pad 54 and the external electrode 34 is formed so as to be lower than the apex of the bonding wire 412 connecting the electrode pad 50 and the inner lead 408A.

<Production procedure>

The manufacturing procedure for the semiconductor device 400 is described below.

First, as shown in FIG. 26(a), the lead frame 402 is placed on the mounting table 2 of the bonding device 1 so that the inner lead 408A is located at the top and the die pad 402A is located at the bottom. The mounting table 2 has a step 8 formed thereon to hold the portion of the die pad 402A on which the second mounting surface 402C is formed. In this state, both the first mounting surface 402B and the second mounting surface 402C face upward. The oscillator 28 is transported sealed in a package 29 on a tape with the external electrode 34 facing upward. The step 404 is formed in advance in the lead frame 402 by pressing or the like.

Next, as shown in FIG. 26(b), the package 29 is opened, the oscillator 28 is removed with the picker 4, and the oscillator 28 is placed on the first mounting surface 402B of the die pad 402A so that the external electrode 34 of the oscillator 28 faces upward as shown in FIG. 26(c), and fixed to the first mounting surface 402B with adhesive. Note that when the oscillator 28 is sealed in the package 29 with the external electrode 34 facing downward, it is preferable to use a picker 4 with a rotation mechanism, remove the oscillator 28 with the picker 4, then turn the oscillator 28 upside down with the rotation mechanism, and place it on the first surface of the die pad 26A with the external electrode 34 facing upward.

After the oscillator 28 is fixed to the first mounting surface 402B, as shown in FIG. 26(d), the LSI 30 is fixed to the second mounting surface 402C of the die pad 402A with adhesive so that the electrode pads 50 and the oscillator electrode pads 54 face upward. Note that since the second mounting surface 402C is formed so as not to overlap with the first mounting surface 402B in a planar view, the LSI 30 is also fixed so as not to overlap with the oscillator 28 in a planar view. Furthermore, the LSI 30 and the oscillator 28 are fixed to the same side of the die pad 402A.

After the LSI 30 is fixed to the second mounting surface 402C, as shown in FIG. 26(e), the electrode pad 50 of the LSI 30 is connected to the inner lead 408A of the lead frame 402 with a bonding wire 412, and the oscillator electrode pad 54 of the LSI 30 is connected to the external electrode 34 of the oscillator 28 with a bonding wire 412.

Next, the procedure for sealing the semiconductor device 400 with the mold resin 32 will be described.

As shown in FIG. 27(a), the semiconductor device 400 is fixed inside the cavity 6 of the mold 5 in a state in which it is turned upside down from the state shown in FIG. 27(e). At this time, it is preferable to arrange the semiconductor device 400 so that the side of the semiconductor device 400 on which the LSI 30 is mounted is closer to the injection port 7 for injecting the molding resin 32 in the mold 5 than the side on which the oscillator 28 is mounted, and the portion of the die pad 402A on which the LSI 30 is mounted is located near the center of the height direction of the cavity 6. In addition, the semiconductor device 400 is arranged so that the outer lead 408B protrudes outside the mold 5.

Once the semiconductor device 400 is fixed inside the cavity 6, the molding resin 32 is injected into the cavity 6 through the injection port 7, as shown by the arrow a in FIG. 27(b).

As shown in FIG. 27(c), the molding resin 32 injected from the injection port 7 flows evenly above and below the lead frame 402 in the portion of the lead frame 402 (die pad 402A) where the LSI 30 is fixed.

However, a step 404 is formed in the lead frame 402 (die pad 402A) in the thickness direction, and the portion of the die pad 402A where the oscillator 28 is fixed is bent upward in Figures 27(a) to (d) with respect to the portion where the LSI 30 is fixed, with the step 404 as the boundary.

Therefore, as shown by the arrow c in FIG. 27(d), in the portion of the die pad 402A where the oscillator 28 is fixed, the flow velocity below the die pad 402A is lower than the flow velocity above the die pad 402A. As a result, in the above portion of the die pad 402A, the molding resin fills preferentially downward, so that the lead frame 402 (die pad 402A) is supported from below by the injected molding resin 32.

Once both sides of the lead frame 402 are filled with molding resin 32, the mold 5 is heated to harden the molding resin 32.

In the semiconductor device 400 according to this embodiment, the oscillator 28 and the LSI 30 are mounted on the back surface of the lead frame 402, so there is no need to invert the lead frame 402 when mounting the oscillator 28 and the LSI 30. This improves the production efficiency of the semiconductor device 400 compared to the first embodiment.

In addition, if the surface on which the bonding wire 412 is formed is considered the upper surface, the second mounting surface 402C is located below the first mounting surface 402B, so when the electrode pad 50 of the LSI 30 and the inner lead 408A are connected by the bonding wire 412 across the oscillator 28, the oscillator 28 does not get in the way of the bonding wire 412.

In this embodiment, the first mounting surface 402B and the second mounting surface 402C are provided on the back surface of the lead frame 402, but this is not limiting and they may be provided on the front surface of the lead frame 402. Even in this case, the surface on which the bonding wire 412 is formed is the upper surface, and the second mounting surface 402C is formed below the first mounting surface 402B, so that the oscillator 28 does not interfere with the bonding wire 412.

In addition, in this embodiment, the second mounting surface 402C is provided above the first mounting surface 402B by the difference in thickness between the LSI 30 and the oscillator 28, but this is not limited thereto. As long as there is a step that does not interfere with the bonding wires 412, the bottom surface of the oscillator 28 may protrude downward from the bottom surface of the LSI 30.

(Sixth embodiment)

Next, a semiconductor device 500 according to a sixth embodiment of the present invention will be described. The same components as those in the first embodiment are given the same reference numerals and will not be described. As shown in FIGS. 28 and 29, a step portion 504 is formed in the die pad 502A located in the center of the lead frame 502 according to this embodiment, as in the fifth embodiment. As shown in FIG. 29, the step portion 504 is inclined upward from left to right, and the die pad 502A is divided by the step portion 504 into a first mounting surface 502B located below and a second mounting surface 502C located above.

The first mounting surface 502B and the second mounting surface 502C are both provided continuously on the back surface of the lead frame 502 and are parallel to the inner lead 508A. The LSI 30 is mounted on the first mounting surface 502B via an adhesive, and the oscillator 28 is mounted on the second mounting surface 502C via an adhesive. As shown in FIG. 28, the LSI 30 is located in the center of the lead frame 502, and the right end of the LSI 30 covers part of the oscillator 28. In other words, the oscillator 28 and the LSI 30 are arranged to overlap when projected in a plan view.

The procedure for fixing the oscillator 28 to the first mounting surface 502B of the die pad 502A, fixing the LSI 30 to the second mounting surface 502C, and connecting the electrode pads 54 for the oscillator of the LSI 30 to the external electrodes 34 of the oscillator 28, and connecting the electrode pads 50 of the LSI 30 to the leads 38 with bonding wires 512 to form the semiconductor device 500 is as shown in Figures 26(a) to (e) in the same manner as the semiconductor device 400 of the fourth embodiment. The procedure for sealing the semiconductor device 500 with the mold resin 32 is also as shown in Figures 27(a) to (d).

In the semiconductor device 500 according to this embodiment, the LSI 30 is mounted in the center of the lead frame 502, so the distance between the electrode pads 50 of the LSI 30 and the inner leads 508A can be made constant on each side of the LSI 30. This makes it easy to perform wire bonding. Other functions are the same as those of the fifth embodiment.

Although the first to sixth embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the first to sixth embodiments may be used in combination, and the present invention may be embodied in various forms without departing from the spirit of the present invention. For example, an oscillator with a built-in oscillator circuit 51 may be used as the oscillator 28. Also, the opening 26C in FIG. 2 may be a slit-shaped hole.

REFERENCE SIGNS LIST 1 Bonding device 2 Placement table 5 Mold 6 Cavity 10 Integrated watt-hour meter 22 Watt-hour measurement circuit (measurement means)
24 Semiconductor device 26 Lead frame 26C Opening 28 Oscillator 30 LSI (integrated circuit)
34 External electrode (oscillator terminal)
50 Electrode pad (terminal of integrated circuit)
51 Oscillator circuit 52 Bonding wire 54 Electrode pad for oscillator (terminal of integrated circuit)
55 Digital circuit section 58 Temperature sensor 60 Control section 70 Register section 80 Reference signal oscillator 81 Measurement counter 82 Reference counter 85 Clock generating circuit 86 Selector 200 Semiconductor device 202 Lead frame 202C Opening 300 Semiconductor device 302 Lead frame 400 Semiconductor device 402 Lead frame 402B First mounting surface 402C Second mounting surface 412 Bonding wire 500 Semiconductor device 502 Lead frame 502B First mounting surface 502C Second mounting surface 512 Bonding wire

Claims (3)

a sealing resin having a front surface, a back surface opposite to the front surface, and a side surface connecting the front surface and the back surface;
a first surface including a first region on which an integrated circuit having an electrode pad is mounted and a second region adjacent to the first region, and a second surface opposite to the first surface including a third region and a fourth region adjacent to the third region on which an oscillator having an external terminal is mounted, the second surface being a third surface on the opposite side to the first surface, the fourth surface being a fourth region on which an oscillator having an external terminal is mounted, the die pad being sealed in the sealing resin;
a lead having a sealing portion disposed between the back surface and the die pad and sealed in the sealing resin, and an exposed portion including a bent portion bent toward the back surface and exposed from the side surface of the sealing resin;
Equipped with
the first region and the fourth region do not overlap in a surface direction of the die pad,
the first region and the third region at least partially overlap with each other in a surface direction of the die pad,
the second region and the fourth region at least partially overlap with each other in a surface direction of the die pad,
the die pad further includes an opening facing the external terminal,
the external terminal and the electrode pad are connected by a first bonding wire through the opening;
the die pad is disposed at a first distance from the backside;
the sealing portion is disposed at a second distance from the rear surface that is shorter than the first distance,
The semiconductor device, wherein the second distance is shorter than a third distance which is a distance from the surface to the sealing portion. The semiconductor device according to claim 1, wherein the integrated circuit has the electrode pads on the rear surface, and the oscillator has the external terminals on the rear surface. 3. The semiconductor device according to claim 1, further comprising a second bonding wire connecting the electrode pad of the integrated circuit and a surface of the sealing portion on the rear side.