Patent Description:
In a conventional flow sensor composed of a semiconductor device equipped with an air flow sensing unit, an electric control circuit and a board, gold wires electrically connecting the semiconductor device and the board are protected and fixed via a potting resin. The fixing using the potting resin is normally performed without clamping the semiconductor device via molds or the like, so that the shrinkage of the potting resin may cause the semiconductor device to be displaced. Therefore, the fixing performed via the potting resin has a drawback in that the dimensional accuracy of the semiconductor device may be deteriorated. Further, since a relatively long time is required for curing the potting resin, the manufacturing costs become high.

This problem can be solved by providing a structure that molds and fixes the semiconductor device including the air flow sensing unit to the board or the lead frame with the air flow sensing unit portion exposed, instead of performing potting as in the prior art.

At this time, molding can be performed while clamping the semiconductor device via the mold so as to improve the positioning accuracy of the semiconductor device and the board after molding and to shorten the resin curing time by the heat transfer from the mold to the resin.

Patent documents <NUM> and <NUM> disclose known mold integrated structures in which the semiconductor device including the air flow sensing unit and the lead frame are molded integrally.

Patent document <NUM> (<CIT>, <CIT>) and patent document <NUM> (<CIT>, <CIT>) disclose a structure in which one end of a semiconductor sensor device not having a cavity section or a heating resistor is integrally molded with a lead frame.

According to the structure disclosed in patent documents <NUM> and <NUM>, the area of a surface of the semiconductor device other than the air flow sensing unit is not surrounded via resin or a lead frame, so that the structure has a drawback in that the flow of air on the air flow sensing unit side cannot be detected accurately since air flows into the diaphragm having a narrow passage.

Furthermore, upon manufacturing the structure disclosed in patent documents <NUM> and <NUM>, during the process for placing the semiconductor device and the lead frame in a mold and integrally molding the same via resin, the semiconductor device and the lead frame must be clamped and fixed via the mold to prevent flash and to determine the position of the semiconductor device.

The structural drawback of patent documents <NUM> and <NUM> according to this manufacturing process is that when the semiconductor device is clamped via the mold, the dimensional variation of the semiconductor device or the adhesive for bonding the semiconductor device to the lead frame may cause flash or chip crack of the air flow sensing unit on the semiconductor device when the device is clamped via the mold.

The present invention aims at solving the problems mentioned above by providing a flow sensor structure in which surfaces of a resin mold, a board or a pre-mold component molded in advance surround the semiconductor device in such a manner that they are not in continuous contact with three walls of the semiconductor device orthogonal to a side on which the air flow sensing unit portion is disposed on the semiconductor device.

The present invention further provides a manufacturing method capable of absorbing the dimensional variation of the semiconductor device via the deformation of springs or deformation of an elastic film in the thickness direction by supporting an insert of a mold clamping the semiconductor device via springs or by disposing an elastic film on the surface of the mold. In other words, the present invention enables to prevent the occurrence of flash or chip crack even when the dimension of the semiconductor device is varied.

According to the coventional flow sensor, the gold wires electrically connecting the semiconductor device and the board are protected and fixed via potting resin. The fixture using potting resin is performed without clamping the semiconductor device via the mold or the like, so that the shrinkage of the potting resin may cause the semiconductor device to be displaced. Therefore, the fixture using potting resin not only deteriorates dimensional accuracy but also requires a long time for curing the potting resin, so that the costs related thereto become high.

The present problem can be solved by adopting structure to fix the semiconductor device having the air flow sensing unit to the board or the lead frame via molding while having the air flow sensing unit exposed, instead of performing the prior art potting.

The problem of the structure for fixing the components via molding is to prevent air from flowing into the diaphragm portion having a narrow passage. The present invention provides a flow sensor structure in which the walls composed of a resin mold or a board or a pre-mold component molded in advance surrounds the semiconductor device without being in continuous contact with three walls of the semiconductor device orthogonal to a side of the semiconductor device on which the air flow sensing unit is disposed.

The problem to be solved related to the manufacturing method of the flow sensor is to prevent the occurrence of flash or chip crack of the semiconductor device when the device is clamped via the mold.

<CIT> discloses a sensor chip in which a detection part and a wiring part connected to the detection part are formed on a substrate, having a cavity and a resistor composing the detection part, is formed on a thin portion above the cavity, and a lead frame including a support lead and an external connection lead are prepared. After a laminate is formed by fixing the prepared sensor chip on the support lead via an adhesive member, the external connection lead is electrically connected to the wiring part. The laminate and a stopper, having hardness closer to that of the substrate than that of the adhesive member; are disposed in the cavity configured in a pair of molds, and molding is performed with the stopper being held in between the two molds, while the one of the molds is in contact with the top surface of the sensor chip.

<CIT> discloses a semiconductor chip that is electrically connected to a circuit board overlapping with and fixing to its one end of the circuit board in the direction of thickness, and a lid frame is used for a semiconductor device which is configured so as to cover the semiconductor chip with resin through the hollow cavity. The lid frame is equipped with a lid unit which is provided to the one end of the circuit board so as to cover the semiconductor chip to form the cavity; and a projection which is nearly cylindrical, projects outward out of the cavity from the lid unit, and makes the cavity communicate with the external space. The projection provides a lid frame which extends furthermore in the direction of thickness from the upper end of the lid unit.

According to a first aspect of the present invention there is provided a flow sensor as specified in claim <NUM>.

The flow sensor according to the first aspect of the present invention may optionally be as specified in any one of claims <NUM> to <NUM>.

According to a second aspect of the present invention there is provided a method for manufacturing a flow sensor as specified in claim <NUM>.

The method according to the second aspect of the present invention may optionally be as specified in claim <NUM>.

Now, the preferred embodiments of the present invention will be described with reference to <FIG>, and <FIG>. The embodiments of the flow sensor illustrated in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> are not encompassed in the wording of the claims but are considered as useful for understanding the invention.

The embodiments of the manufacturing method illustrated in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> are not encompassed in the wording of the claims but are considered as useful for understanding the invention. <FIG> shows a plan view of a flow sensor prior to molding. <FIG> shows a plan view of a rear side of <FIG> is an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding comprises a semiconductor device <NUM> having formed thereon an air flow sensing unit <NUM> and a diaphragm <NUM>, and a board <NUM> having an opening with a stepped portion <NUM> arranged on one side and an electric control circuit <NUM> for controlling the semiconductor device <NUM> arranged on the other side, wherein the semiconductor device <NUM> is mounted on the stepped portion formed in the opening <NUM>, and electric signals are transmitted via gold wires <NUM> and wirings <NUM> disposed on the board <NUM>. Further, the electric control circuit <NUM> and the semiconductor device <NUM> are bonded via an adhesive <NUM> or the like to the board <NUM>.

Now, the semiconductor device <NUM> includes at least a heating resistor and a resistance thermometer as the air flow sensing unit <NUM>, wherein the electric control circuit <NUM> performs control so that the temperature of the heating resistor becomes higher by a certain temperature than the resistance thermometer corresponding to air temperature. When the temperature of the resistance thermometer is varied by air flow, the heating current supplied to the heating resistor to raise the temperature by a certain temperature is detected as flow.

The air flow sensing unit <NUM> is only required to include at least a heating resistor and a resistance thermometer, and should be capable of detecting the flow based on the temperature difference between the upstream side and the downstream side of air flow of the resistance thermometer.

The heating resistor and the resistance thermometer are formed by creating a metal film formed for example of platinum or a semiconductor thin film formed for example of polycrystalline silicon via methods such as sputtering or CVD, and then processing the same via ion etching or the like.

A cavity for forming the diaphragm <NUM> for thermal insulation is formed on the semiconductor device <NUM> constituting the air flow sensing unit <NUM> via methods such as anisotropic etching.

Further, glass epoxy can be used as the material for the board <NUM>, and thermosetting resin such as epoxy or phenol can be used as the material for the mold resin <NUM>, or thermosetting resin such as polycarbonate or polyethylene terephtharate can be used having a filler material such as glass or mica mixed therein.

Now, <FIG> shows a manufacturing method for subjecting a structure including a semiconductor device <NUM> mounted on the board <NUM> shown in <FIG> and the control board <NUM> to resin-sealing using a mold.

<FIG> is an A-A cross-section of <FIG>, showing a cross-sectional view of the structure prior to molding of <FIG> placed in a mold and subjected to molding.

The dimensional accuracy of the semiconductor device <NUM> during molding can be improved by inserting a lower mold <NUM> to an opening <NUM> formed on the board <NUM>, clamping the semiconductor device <NUM> from above and below via an upper mold <NUM> and a lower mold <NUM>, and thereby fixing the semiconductor device.

Further, resin <NUM> can be filled through a gate <NUM> into the mold with a space <NUM> formed to the upper mold <NUM> so that the upper mold <NUM> does not contact the air flow sensing unit <NUM>, according to which the electric control circuit <NUM>, the gold wires <NUM> and a portion of the semiconductor device <NUM> can be sealed via the resin <NUM>.

The B-B cross-section of <FIG> is either formed as shown in <FIG>. Here, the clearance between the semiconductor device <NUM> and the board <NUM> shown in the B-B cross-section should be blocked so as to stop the flow of resin <NUM> in order to prevent the resin <NUM> from reaching the diaphragm <NUM>.

Resin <NUM> can be prevented from entering the clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section by disposing an elastic member <NUM> such as a Teflon block as illustrated in <FIG> or via an insert <NUM> disposed on the upper mold <NUM> as illustrated in <FIG>.

Now, since the semiconductor device <NUM> has varied dimensions, when carrying out the manufacturing method of <FIG>, resin <NUM> will leak on the semiconductor device <NUM> if the dimension of the semiconductor device <NUM> is smaller than the mold clamp dimension, and the semiconductor device <NUM> may crack if the size of the semiconductor device <NUM> is greater than the mold clamp dimension.

<FIG>, <FIG> and <FIG> are A-A cross-sections of <FIG>, showing a state in which the structure prior to molding of <FIG> is placed in the mold and subjected to molding.

Now, as shown in <FIG>, it is possible to use a mold having a structure where at least one of the molds for clamping the semiconductor device <NUM> from above and below is composed of a movable insert <NUM> capable of moving in sliding motion within the mold, wherein the side of the movable insert <NUM> opposite from the side in contact with the semiconductor device <NUM> is supported by an elastic member such as a spring <NUM>. Further, the spring <NUM> is fixed in the mold via a spring presser <NUM>.

Moreover, as shown in <FIG>, it is also possible to use a mold having a structure in which an elastic insert <NUM> such as Teflon is placed in at least one of the molds clamping the semiconductor device <NUM> from above and below.

Polymeric material such as Teflon and fluorine resin can be used as the elastic member.

Further, as shown in <FIG>, it is possible to use a mold having a lower mold <NUM> inserted from an opening <NUM> on the board <NUM> to support the semiconductor device <NUM> and having an elastic film <NUM> disposed on the upper mold <NUM> in contact with the mold resin material <NUM>, thereby clamping the semiconductor device <NUM> from above and below via the elastic film <NUM>.

Further, <FIG> is a cross-sectional view showing an A-A cross-section of <FIG> in which the structure prior to molding of <FIG> is placed in a mold and subjected to molding, wherein <FIG> show the B-B cross-section of <FIG>.

Now, it is necessary to stop the flow of resin <NUM> by blocking the clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section so as to prevent resin <NUM> from flowing into the diaphragm <NUM> section.

The clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section can be blocked to prevent resin <NUM> from flowing therein by placing an elastic member <NUM> such as a Teflon block <NUM> as shown in <FIG> or by adopting an insert <NUM> disposed on the upper mold <NUM> as shown in <FIG>.

Now, it is possible to use a polymeric material such as Teflon or fluorine resin as the elastic film <NUM>, and the variation in dimension of the elastic film <NUM> in the thickness direction can prevent the occurrence of resin leak or crack during molding even when the dimension of the semiconductor device <NUM> is varied.

As described, the use of molds having structures shown in <FIG>, <FIG> or <FIG> enables molding to be performed without causing resin <NUM> leak or semiconductor device <NUM> crack even when the dimension of the semiconductor device <NUM> is varied.

Further, it is possible to adopt the movable insert <NUM> supported via the elastic member shown in <FIG> or the elastic insert <NUM> shown in <FIG> in the portion for clamping the semiconductor device <NUM> shown in <FIG>.

<FIG>, <FIG> and <FIG> illustrate a structure in which the diaphragm <NUM> is supported via an insert from the opening <NUM> of the board <NUM>, but it is also possible to adopt a structure as illustrated in <FIG> in which the diaphragm <NUM> of the semiconductor device <NUM> is not supported via an insert.

Moreover, in the mold illustrated in <FIG>, it is possible to place an insert such as an elastic insert <NUM> formed for example of Teflon to either the upper mold <NUM> or the lower mold <NUM>.

In the mold illustrated in <FIG>, it is possible to place an insert <NUM> supported via an elastic member such as springs <NUM> to either the upper mold <NUM> or the lower mold <NUM>.

<FIG> is a plan view of a flow sensor formed by molding a structure including the semiconductor device <NUM> and the control board <NUM> prior to molding illustrated in <FIG> in the mold illustrated in <FIG>.

<FIG> is an A-A cross-section of <FIG>, wherein the goldwires <NUM> for electrically connecting the semiconductor device <NUM> and the board <NUM> or the electric control circuit <NUM> and the board <NUM> are insulated via a mold resin <NUM>, and the detected flow is output via an electric signal output section <NUM>.

Further, the present flow sensor can adopt a structure in which the semiconductor device <NUM>, the resin mold <NUM> and the board <NUM> are not in contact with each other except for the area where the semiconductor <NUM>, the gold wires <NUM> for transmitting the electric signal from the semiconductor device <NUM> and the board <NUM> are integrated via the resin mold.

In other words, the present embodiment enables to provide a flow sensor structure in which the walls <NUM> of the board <NUM> form a continuous space with three walls <NUM> of the semiconductor device <NUM> orthogonal to the side on which the air flow sensing unit portion of the semiconductor device <NUM> is disposed, thereby surrounding the semiconductor device <NUM>.

<FIG> shows a plan view prior to molding of the flow sensor. <FIG> shows a plan view of a rear side of <FIG> shows an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding comprises a semiconductor device <NUM> having an air flow sensing unit <NUM> and a diaphragm <NUM> formed thereto, and a lead frame <NUM> having an opening <NUM> formed on one side and an electric control circuit <NUM> for controlling the semiconductor device <NUM> formed on the other side, wherein the semiconductor device <NUM> is mounted on the projected area of the opening <NUM>. The electric control circuit <NUM> and the semiconductor device <NUM> are attached via an adhesive <NUM> or the like to the lead frame <NUM>. Furthermore, a dam <NUM> of the lead frame portion is clamped in the mold to prevent resin from flowing out of the mold, and the dam <NUM> is cut away after molding so that electric signals are output from the output terminals <NUM>.

Now, a manufacturing method for sealing the structure including the semiconductor device <NUM> and the electric control board <NUM> disposed on the lead frame <NUM> of <FIG> in a mold using resin will be illustrated in <FIG>.

<FIG> is an A-A cross-section of <FIG>, showing a cross-sectional view in which the structure prior to molding of <FIG> is placed in the mold and subjected to molding.

A lower mold <NUM> is inserted to an opening <NUM> formed on the lead frame <NUM> so as to clamp and fix the semiconductor device <NUM> from above and below via molds, and while having a part of the semiconductor device <NUM> exposed, a resin layer <NUM> is formed on a surface including a part of the semiconductor device <NUM>.

As described, the dimensional accuracy of the semiconductor device <NUM> during molding can be improved by clamping the semiconductor device <NUM> from above and below via the mold. Here, the dam <NUM> of the lead frame portion is clamped via the mold to prevent resin <NUM> from flowing out of the mold.

Furthermore, resin <NUM> is filled in the mold through a gate <NUM> while having a space <NUM> formed within the mold so that the flow sensor <NUM> will not contact the mold, according to which the electric control circuit <NUM>, the gold wires <NUM>, and a part of the semiconductor device <NUM> can be sealed via the resin <NUM>.

The B-B cross-section of <FIG> is formed as shown in <FIG>. Now, it is necessary to block the flow of resin <NUM> by blocking the clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section so as to prevent the resin <NUM> from flowing into the diaphragm <NUM> portion.

The clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section is blocked by disposing an elastic member <NUM> such as a Teflon block as shown in <FIG> or by disposing an insert <NUM> attached to the lower mold <NUM> as shown in <FIG> to block the flow of resin <NUM>.

<FIG>, <FIG> and <FIG> show an A-A cross-section of <FIG>, which are cross-sectional views showing the structure prior to molding of <FIG> placed in the mold and subjected to molding.

As shown in <FIG>, the mold can adopt a structure in which at least one of the molds for clamping the semiconductor device <NUM> from above and below is composed of a movable insert <NUM> capable of moving in sliding motion within the mold, and the side of the movable insert <NUM> opposite from the side in contact with the semiconductor device <NUM> is supported via an elastic member such as springs <NUM>. The springs <NUM> are fixed within the mold via a spring presser <NUM>.

Further, as shown in <FIG>, the mold can adopt a structure in which an elastic insert <NUM> formed for example of Teflon is placed in at least one of the molds for clamping the semiconductor device <NUM> from above and below.

Now, the elastic insert <NUM> can be formed of a polymeric material such as Teflon and fluorine resin.

Even further, as shown in <FIG>, the mold can adopt a structure in which a lower mold <NUM> is inserted from the opening of the lead frame <NUM> to support the semiconductor device <NUM> and an elastic film <NUM> is disposed on the surface of an upper mold <NUM>, to thereby clamp the semiconductor device <NUM> from above and below via the elastic film <NUM>.

Now, the elastic film <NUM> can be formed of a polymeric material such as Teflon and fluorine resin, and since the dimension of the elastic film <NUM> can be varied in the thickness direction, molding can be performed without causing leak of resin <NUM> or crack of semiconductor device <NUM> even if the dimension of the semiconductor device <NUM> is varied, and the change in the dimension in the thickness direction of the elastic film <NUM> can prevent the resin <NUM> from leaking or the semiconductor device <NUM> from cracking during molding even when the dimension of the semiconductor device <NUM> is varied.

As described, by using a mold having the structure illustratedinFig. <NUM>, <FIG> or <FIG>, moldingcanbeperformed without causing leak of resin <NUM> or crack of semiconductor device <NUM> even when the dimension of the semiconductor device <NUM> is varied.

It is also possible to adopt a structure in which the movable mold <NUM> supported via the elastic member shown in <FIG> or the elastic insert <NUM> shown in <FIG> is placed in the section for clamping the semiconductor device <NUM> shown in <FIG>.

<FIG>, <FIG> and <FIG> adopt a structure in which the diaphragm <NUM> is supported via an insert from the opening of the board <NUM>, but it is also possible to adopt a structure as shown in <FIG> in which the diaphragm <NUM> of the semiconductor device <NUM> is not supported via the movable insert <NUM>.

Furthermore, the mold shown in <FIG> can have an insert such as an elastic insert <NUM> formed of Teflon disposed on either the upper mold <NUM> or the lower mold <NUM>.

The mold shown in <FIG> can have a movable insert <NUM> supported via an elastic member such as springs <NUM> disposed on either the upper mold <NUM> or the lower mold <NUM>.

<FIG> shows a plan view in which the structure including the semiconductor device <NUM> and the control board <NUM> prior to molding shown in <FIG> is molded via the mold shown in <FIG>.

<FIG> is an A-A cross-section of <FIG>. As shown, the gold wires <NUM> electrically connecting the semiconductor device <NUM> and the lead frame <NUM> or the electric control circuit <NUM> and the lead frame <NUM> are insulated via the mold resin <NUM>.

Further, <FIG> illustrates a structure in which the dam <NUM> of the lead frame <NUM> excluding the output terminals <NUM> is cut away, so that the detected flow is output as electric signals through the output terminals <NUM>.

Further, it is possible to adopt a structure in which the semiconductor device <NUM> and the resin <NUM> mold are not in contact with each other except for the area where the semiconductor <NUM>, the gold wires <NUM> for transmitting the electric signals of the semiconductor <NUM> and the lead frame <NUM> are integrally molded via resin <NUM>.

In other words, it is possible to provide a structure of a flow sensor in which resin walls <NUM> formed of the molded portion of resin <NUM> define a continuous space with three sides <NUM> orthogonal to the surface on which the air flow sensing unit is disposed on the semiconductor device <NUM>, thereby surrounding the semiconductor device <NUM>.

<FIG> is a plan view showing the surface of the flow sensor prior to molding. <FIG> is an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding adopts a structure in which a semiconductor device <NUM> having an air flow sensing unit <NUM> and a diaphragm <NUM> formed thereto is exposed from the end of a board <NUM>, and on the other end of the board <NUM> is disposed an electric control circuit <NUM> for controlling the semiconductor device <NUM>.

Now, a manufacturing method for sealing the structure including the semiconductor device <NUM> disposed on the board <NUM> and the control board <NUM> illustrated in <FIG> via a mold using resin <NUM> will be shown in <FIG>.

<FIG> is an A-A cross-section of <FIG>, which is a cross-sectional view showing the state where the structure prior to molding of <FIG> is placed in a mold and subjected to molding.

The semiconductor device <NUM> is clamped and fixed from above and below via a mold, and a resin <NUM> layer is formed on the surface including a part of the semiconductor device <NUM> while exposing a part of the semiconductor device <NUM>. As shown, the mold can adopt a structure in which at least one of the molds clamping the semiconductor device <NUM> from above and below is composed of a movable insert <NUM> capable of moving in sliding motion within the mold, and the side of the movable insert <NUM> opposite to the side in contact with the semiconductor device <NUM> is supported via an elastic member such as springs <NUM>.

Further, the mold shown in <FIG> can adopt a mold structure in which an elastic insert <NUM> formed for example of Teflon can be disposed on at least one of the molds clamping the semiconductor device <NUM> from above and below, as shown in <FIG>.

Furthermore, the mold shown in <FIG> can adopt a mold structure in which an elastic film <NUM> is placed on the side of the upper mold <NUM> in contact with the resin <NUM> material of the mold and clamping the semiconductor device <NUM> from above and below via the elastic film <NUM>, as shown in <FIG>.

By adopting the movable insert <NUM> supported via elastic members as shown in <FIG>, it becomes possible to mold the semiconductor device <NUM> without causing leak of resin <NUM> or crack even when the dimension of the semiconductor device <NUM> is varied.

<FIG> is a plan view of a structure in which the structure including the semiconductor device <NUM> and the control board <NUM> prior to molding shown in <FIG> is molded in the mold shown in <FIG>.

<FIG> is an A-A cross-section of <FIG>. As illustrated, gold wires <NUM> for electrically connecting the semiconductor device <NUM> and the board <NUM> or the electric control circuit <NUM> and the board <NUM> are insulated via a mold resin <NUM>, and the detected flow is output via an electric signal output section <NUM>.

Further, when using the flow sensor illustrated in <FIG>, a structure having a continuous space with the semiconductor device <NUM> should be disposed to surround the semiconductor device <NUM> to thereby prevent air from flowing into the diaphragm <NUM> section.

<FIG> is a plan view of a surface of the flow sensor prior to molding. <FIG> is an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding adopts a structure in which a semiconductor device <NUM> including an air flow sensing unit <NUM> and a diaphragm <NUM> is exposed from the end of a lead frame <NUM>, and on the other side of the lead frame <NUM> is disposed an electric control circuit <NUM> for controlling the semiconductor device <NUM>.

Now, <FIG> illustrates a manufacturing method for sealing via resin the structure including the air flow sensing unit <NUM> and the control board <NUM> disposed on the lead frame <NUM> using a mold.

<FIG> is a cross-sectional view showing the A-A cross-section of <FIG> in which the structure prior to molding of <FIG> is placed in a mold and subjected to molding.

The semiconductor device <NUM> is clamped from above and below via a mold, and a resin <NUM> layer is formed on a surface including a part of the semiconductor device <NUM> while having a part of the semiconductor device <NUM> exposed. As shown, the mold can adopt a structure in which at least one of the molds for clamping the semiconductor device <NUM> from above and below is formed of a movable insert <NUM> capable of moving in sliding motion within the mold, and the side of the movable mold opposite from the side in contact with the semiconductor device <NUM> is supported via an elastic member such as springs <NUM>.

Moreover, the dam <NUM> of the lead frame portion is clamped via the mold so as to prevent resin <NUM> from flowing out of the mold.

Furthermore, the mold shown in <FIG> can adopt a structure in which an elastic insert <NUM> formed for example of Teflon can be disposed on at least one of the molds for clamping the semiconductor device <NUM> from above and below, as shown in <FIG>.

Further, the mold shown in <FIG> can adopt a mold structure in which an elastic film <NUM> is placed on the side of the upper mold <NUM> in contact with the resin <NUM> material of the mold and clamping the semiconductor device <NUM> from above and below via the elastic film <NUM>, as shown in <FIG>.

By adopting the movable insert supported via elastic members as shown in <FIG>, the semiconductor device <NUM> can be molded without causing leak of resin <NUM> or crack of semiconductor device even when the dimension of the semiconductor device <NUM> is varied.

<FIG> is an A-A cross-section of <FIG>. As illustrated, gold wires <NUM> for electrically connecting the semiconductor device <NUM> and the lead frame <NUM> or the electric control circuit <NUM> and the board <NUM> are insulated via a mold resin <NUM>, and after the dam <NUM> portion of the lead frame is cut away, the detected flow is output via electric signal output terminals <NUM>.

<FIG> is a plan view of an example where the flow sensor of <FIG> sealed via resin is disposed on a structure <NUM> having a passage for air formed therein, wherein the structure <NUM> including the air passage has an air passage groove <NUM> formed thereto.

<FIG> is an A-A cross-section of <FIG>. As shown, by inserting and fixing a positioning projection <NUM> of the structure <NUM> having the air passage to the opening <NUM> of the flow sensor, the positioning accuracy of the structure <NUM> having the air passage and the flow sensor can be improved and the assembly time thereof can be shortened.

<FIG> is a cross-sectional view of an example where a cover <NUM> is disposed on the structure <NUM> having the air passage equipped with the flow sensor shown in the cross-section of <FIG>.

The air passage <NUM> shown in <FIG> is designed so that the air taken in through an inlet <NUM> shown in <FIG> flows through the air passage <NUM>, passes the upper portion of the flow sensor, and exits through an outlet <NUM> formed on an upper portion shown in <FIG>.

<FIG> shows a plan view of a surface of the flow sensor prior to molding. <FIG> shows a first embodiment of the A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding comprises a semiconductor device <NUM> having an air flow sensing unit <NUM> and a diaphragm <NUM> formed thereto, and a board <NUM> having an electric control circuit <NUM> disposed for controlling the semiconductor device <NUM>, wherein the semiconductor device <NUM> is mounted on a stepped portion and electric signals are transmitted through gold wires <NUM> and wirings <NUM> disposed on the board <NUM>. Further, the electric control circuit <NUM> is attached to the board <NUM> via an adhesive <NUM> or the like.

The present structure has a varied thickness in the stepped portion of the board <NUM> on which the semiconductor device <NUM> is disposed, wherein the side of the semiconductor device <NUM> close to the electric control circuit <NUM> is attached to the board <NUM> via an adhesive <NUM> or the like, and the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is in contact with a portion <NUM> where the stepped portion has greater thickness.

<FIG> illustrates a second embodiment of the A-A cross-section of <FIG>. As illustrated, the side of the semiconductor device <NUM> close to the electric control circuit <NUM> is attached to the board <NUM> via an adhesive <NUM> or the like, and the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is supported via the stepped portion of the board <NUM> and a spacer <NUM>.

The spacer <NUM> can be formed of organic materials such as Teflon, fluorine resin, epoxy resin or polycarbonate resin, and the semiconductor device <NUM> can either be bonded to or not bonded to the board <NUM>.

Now, a manufacturing method for sealing via resin the structure including the semiconductor device <NUM> disposed on the board <NUM> and the control board <NUM> via a mold is shown in <FIG>.

<FIG> illustrates an example where the structure prior to molding shown in the A-A cross-section of <FIG> is placed in a mold and subjected to molding.

A mold is used in which an elastic film <NUM> is disposed on a surface of an upper mold <NUM> and the semiconductor device <NUM> is clamped from above and below via the elastic film <NUM>.

In the example, as shown in <FIG>, the portion of the semiconductor device <NUM> facing the diaphragm <NUM> and opposite from the electric control circuit <NUM> is in contact with a portion where the thickness of the stepped portion is greater, so that even when the semiconductor device <NUM> is clamped by the upper mold <NUM> via the elastic film21, the device can be accurately positioned in the mold in the clamping direction.

<FIG> illustrate the B-B cross-section of <FIG>.

The flow of resin <NUM> must be blocked by closing the clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section, so that resin <NUM> will not flow into the diaphragm <NUM> section.

The clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section can be blocked by disposing an elastic member <NUM> such as a Teflon block as shown in <FIG> or by an insert <NUM> disposed on the upper mold <NUM> as shown in <FIG>.

Polymeric materials such as Teflon and fluorine resin can be used for the elastic film <NUM>, and the variation of dimension in the thickness direction of the elastic film <NUM> enables the semiconductor device to be molded without causing leak of resin <NUM> or crack of semiconductor device even when the dimension of the semiconductor device <NUM> is varied.

According to the present flow sensor formed after molding, the semiconductor device <NUM> is not in contact with the resin <NUM> mold except for the area where the semiconductor device <NUM>, the gold wires <NUM> for transmitting electric signals from the semiconductor device <NUM> and the board <NUM> are integrally molded via resin <NUM>.

In other words, the present flow sensor enables to provide a flow sensor structure in which the walls <NUM> of the board <NUM> form a continuous space with three sides <NUM> of the semiconductor device <NUM> orthogonal to the mounting surface of the air flow sensing unit section of the semiconductor device <NUM>, thereby surrounding the semiconductor device <NUM>.

<FIG> shows a plan view of a surface of the flow sensor prior to molding. <FIG> is an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding comprises a semiconductor device <NUM> having an air flow sensing unit <NUM> and a diaphragm <NUM> formed thereto, and a lead frame <NUM> including an electric control circuit <NUM> for controlling the semiconductor device <NUM>, wherein electric signals from the semiconductor device <NUM> are transmitted via the lead frame <NUM> having a conductive property. Further, the electric control circuit <NUM> is attached to the board <NUM> via an adhesive <NUM> or the like.

As shown in <FIG>, the side of the semiconductor device <NUM> close to the electric control circuit <NUM> is attached to the lead frame <NUM> for example via an adhesive <NUM>, and the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is in contact with and supported via a spacer <NUM> and the lead frame <NUM>.

The spacer <NUM> can be formed of organic materials such as Teflon, fluorine resin, epoxy resin or polycarbonate resin, and the semiconductor device <NUM> can either be bonded to or not bonded to the lead frame <NUM>.

<FIG> shows a manufacturing method for sealing via resin the structure including the semiconductor device <NUM> and the electric control circuit <NUM> disposed on the board <NUM> shown in <FIG> in a mold.

In the example, as shown in <FIG>, the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is in contact with a lead frame <NUM> via a spacer <NUM>, so that even when the semiconductor device <NUM> is clamped by the upper mold <NUM> via the elastic film <NUM>, the device can be accurately positioned in the mold in the clamping direction.

The dam <NUM> of the lead frame is clamped via the mold so as to prevent resin from flowing out of the mold.

Polymeric materials such as Teflon and fluorine resin <NUM> can be used for forming the elastic film <NUM>, and the variation of dimension in the thickness direction of the elastic film <NUM> enables the semiconductor device to be molded without causing leak of resin <NUM> or crack of semiconductor device <NUM> even when the dimension of the semiconductor device <NUM> is varied.

When molding is completed, as shown in <FIG> and <FIG>, the dam <NUM> of the lead frame <NUM> excluding output terminals <NUM> is cut away to form the flow sensor, and the detected flow is output as electric signals via the output terminals <NUM>.

According to the present flow sensor, the semiconductor device <NUM> is not in contact with the resin <NUM> mold except for the area where the semiconductor device <NUM>, the gold wires <NUM> for transmitting electric signals from the semiconductor device <NUM> and the board <NUM> are integrally molded via resin <NUM>.

In other words, the present invention enables to provide a flow sensor structure in which the wall <NUM> formed by the resin <NUM> mold forms a continuous space with three sides <NUM> of the semiconductor device <NUM> orthogonal to the mounting surface of the air flow sensing unit section of the device <NUM>, thereby surrounding the semiconductor device <NUM>.

<FIG> is a plan view of the surface of a flow sensor prior to molding. <FIG> shows an A-A cross-section of <FIG>.

As shown in <FIG>, the flow sensor prior to molding comprises a semiconductor device <NUM> having an air flow sensing unit <NUM> and a diaphragm <NUM> mounted on a pre-mold component <NUM>, and a lead frame having an electric control circuit <NUM> for controlling the semiconductor device <NUM> disposed thereon, wherein electric signals from the semiconductor device <NUM> are transmitted via the lead frame <NUM> having conductive property. Further, the pre-mold component <NUM> and the electric control circuit <NUM> are attached to the board <NUM> via an adhesive <NUM> or the like.

Now, <FIG> shows a plan view of the pre-mold component <NUM> formed of resin, and <FIG> is an A-A cross-section of <FIG>. The pre-mold component <NUM> comprises a mounting surface <NUM> of the semiconductor device <NUM> and sides <NUM> orthogonal to the mounting surface <NUM> of the semiconductor device <NUM>, wherein projections <NUM> are formed at parts of the mounting surface <NUM> of the semiconductor device <NUM>.

As shown in <FIG>, the side of the semiconductor device <NUM> close to the electric control circuit <NUM> is attached via an adhesive <NUM> or the like to the pre-mold component <NUM>, and the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is formed so that parts of the semiconductor device <NUM> contact the projections <NUM>.

The pre-mold component <NUM> can be formed of thermosetting resin such as epoxy resin or phenol resin, or of thermoplastic resin such as polycarbonate resin or PBT resin.

According to the present example illustrated in <FIG>, the projections <NUM> of the pre-mold component <NUM> are formed as three semispherical parts, but the present example is not restricted to such design, and the number of the projections can be any arbitrary number and the cross-sectional shapes of the projections can be any arbitrary shape such as a rectangular shape or a triangle.

<FIG> shows a manufacturing method for sealing via resin the structure including the semiconductor device <NUM> mounted on the pre-mold component <NUM> and the control board <NUM> shown in <FIG> via a mold.

<FIG> is a cross-sectional view showing the structure prior to molding of the A-A cross-section of <FIG> placed in a mold and subjected to molding.

A mold is used in which an elastic film <NUM> is disposed on a surface of an upper mold <NUM> and the semiconductor device <NUM> is clamped from above and below via the elastic film <NUM>. Further, the dam <NUM> of the lead frame portion is clamped via the mold so as to prevent resin <NUM> from flowing out of the mold.

In the example, as shown in <FIG> and <FIG>, the side of the semiconductor device <NUM> opposite from the electric control circuit <NUM> is in contact with projections <NUM> of the pre-mold component <NUM>, so that even when the semiconductor device <NUM> is clamped by the upper mold <NUM> via the elastic film <NUM>, the device can be accurately positioned in the mold in the clamping direction.

The B-B cross-section of <FIG> is either formed as shown in <FIG>.

The flow of resin <NUM> must be blocked by closing the clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section so as to prevent resin <NUM> from flowing into the diaphragm <NUM> section.

The clearance between the semiconductor device <NUM> and the board <NUM> in the B-B cross-section is blocked by disposing an elastic member <NUM> such as a Teflon block as shown in <FIG> or by an insert <NUM> disposed on the upper mold <NUM> as shown in <FIG> to block the resin <NUM>.

Now, the elastic film <NUM> can be formed of a polymeric material such as Teflon or fluorine resin, and since the dimension of the elastic film <NUM> can be varied in the thickness direction, molding can be performed without causing leak of resin <NUM> or crack of semiconductor device <NUM> even if the dimension of the semiconductor device <NUM> is varied.

<FIG> is an A-A cross-section of <FIG>, wherein gold wires <NUM> for electrically connecting the semiconductor device <NUM> and the lead frame <NUM> or the electric control circuit <NUM> and the lead frame <NUM> are insulated via a mold resin <NUM>, and the detected flow is output via an electric signal output section.

The post-mold structure as shown in <FIG> is used as a flow sensor by cutting away the dam <NUM> of the lead frame <NUM> excluding the output terminals <NUM> as shown in <FIG> and <FIG>, and the detected flow is output via output terminals <NUM> as electric signals.

The present flow sensor can adopt a structure in which the semiconductor device <NUM> and the resin <NUM> mold or the pre-mold component <NUM> are not in contact with each other excluding the portion where the semiconductor device <NUM>, the gold wires <NUM> for transmitting electric signals from the semiconductor device <NUM>, the pre-mold component <NUM> and the lead frame <NUM> are integrally molded via resin <NUM>.

In other words, the present embodiment provides a flow sensor structure in which three sides <NUM> of the semiconductor device <NUM> orthogonal to the surface on which the air flow sensing unit is disposed on the semiconductor device <NUM> and the pre-mold portion form a continuous space, thereby surrounding the semiconductor device <NUM>.

The structure including the pre-mold component <NUM> shown in <FIG> adopts a structure in which the pre-mold component <NUM> and the semiconductor device <NUM> or the pre-mold component <NUM> and the lead frame <NUM> are attached via the adhesive <NUM>, but the structure is not restricted to such example, and can adopt a structure in which the pre-mold component <NUM> and the semiconductor device <NUM> or the pre-mold component <NUM> and the lead frame <NUM> are joined via a snap-fit structure <NUM> disposed on the pre-mold component <NUM>, as shown in <FIG>.

<FIG> shows a plan view of surface of a flow sensor prior to molding, and <FIG> is an A-A cross-section of <FIG>.

Now, <FIG> shows a plan view of a pre-mold component <NUM> formed of resin, <FIG> is an A-A cross-section of <FIG> is a B-B cross-section of <FIG>. The pre-mold component <NUM> comprises amounting surface <NUM> of the semiconductor device <NUM> and sides <NUM> orthogonal to the mounting surface <NUM> of the semiconductor device <NUM>, wherein projections <NUM> are formed at parts of the mounting surface <NUM> of the semiconductor device <NUM>, constituting a snap-fit <NUM> for joining the lead frame <NUM> and the pre-mold component <NUM> as shown in <FIG> or a snap-fit structure <NUM> for joining the semiconductor device <NUM> and the pre-mold component <NUM> as shown in <FIG>.

The illustrated embodiments adopt a structure in which the pre-mold component <NUM> and the semiconductor device <NUM> or the pre-mold component <NUM> and the lead frame <NUM> are joined via an adhesive <NUM> as shown in <FIG> or a structure in which the pre-mold component <NUM> and the semiconductor device <NUM> or the pre-mold component <NUM> and the lead frame <NUM> are joined via a snap-fit <NUM> as shown in <FIG>, but the structure is not restricted thereto, and can adopt a structure in which the pre-mold component <NUM> and the semiconductor device <NUM> or the pre-mold component <NUM> and the lead frame <NUM> are joined via press-fitting <NUM> as shown in <FIG>.

Further, <FIG> shows a plan view of the surface of a flow sensor prior to molding, and <FIG> is an A-A cross-section of <FIG>. Moreover, after molding the pre-molding structure shown in <FIG> or <FIG>, the dam <NUM> of the lead frame <NUM> other than the output terminals <NUM> is cut away as shown in <FIG> and <FIG> to form the flow sensor, wherein the detected flow rate is output as electric signals via the output terminals <NUM>.

Claim 1:
A flow sensor comprising:
a semiconductor device (<NUM>) having an air flow sensing unit (<NUM>) and a diaphragm (<NUM>) formed thereto;
an electric control circuit (<NUM>) for controlling the semiconductor device (<NUM>);
a lead frame (<NUM>), to which the semiconductor device (<NUM>) and the electric control circuit (<NUM>) are mounted; and
a spacer (<NUM>),
wherein the spacer (<NUM>) is disposed in a clearance between the lead frame (<NUM>) and the semiconductor device (<NUM>) on a side of the semiconductor device (<NUM>) opposite from the electric control circuit (<NUM>); and
wherein a surface of the electric control circuit (<NUM>) and a part of a surface of the semiconductor device (<NUM>) is covered with resin (<NUM>) while the air flow sensing unit (<NUM>) is exposed;
characterized in that:
at a joint portion on a side of the semiconductor device (<NUM>) close to the electric control circuit (<NUM>), the semiconductor device (<NUM>) is attached to the lead frame (<NUM>) only via an adhesive (<NUM>), wherein
the diaphragm (<NUM>) is disposed between the spacer (<NUM>) and the joint portion.