Contact force sensor package, blood pressure meter with the same, and method for fabricating the contact force sensor package

A contact force sensor package includes a substrate layer having a vibration detection unit and a pair of first junction pads that are electrical connection ports which are provided on an upper surface of the substrate layer, a flexible circuit substrate layer having a pair of second junction pads provided at a position corresponding to the first junction pads and electrically connected to the first junction pad, a vibration transfer unit having one side contacting the vibration detection unit and the other side contacting a human body and transferring a sphygmus wave of the human body to the vibration detection unit, and an adhesion layer formed between the substrate layer and the flexible circuit substrate layer to reinforce a junction force between the substrate layer and the flexible circuit substrate layer, the adhesion layer being not formed in an area overlapping at least the vibration transfer unit.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2008-0001429, filed on Jan. 4, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contact force sensor package for detecting the sphygmus wave of a human body to measure blood pressure, blood pressure meter with the contact force sensor package, and a method for fabricating the contact force sensor package.

2. Description of the Related Art

A blood pressure meter is a device to measure blood pressure using the relationship between the blood pressure and a sphygmus wave according to the repeated contraction of a heart. The blood pressure meter includes a contact force sensor package.

FIG. 1is a cross-sectional view of an example of a typical contact force sensor package50. Referring toFIG. 1, the contact force sensor package50contacts a wrist1where a radial artery5passes to detect a sphygmus wave. In the contact force sensor package50, a substrate layer54having a thin film55is mounted on a circuit substrate layer51and the substrate layer54having the thin film55and the circuit substrate layer51are electrically connected via a bonding wire60. To protect the bonding wire60, the substrate layer54is sealed with an elastic material such as a silicon gel65.

A vibration, that is, a sphygmus wave, generated from the radial artery5is transferred to the thin film55via the silicon gel65. Accordingly, blood pressure is measured through a change of the thin film55. However, since the bonding wire60that is tens of nanometers thick is weak to an impact, to prevent disconnection of the bonding wire60due to the vibration transferred to the silicon gel65, the silicon gel65on the thin film55is formed to have a thickness M that is relatively thick.

For this reason, it is difficult to reduce the size of the contact force sensor package. Also, as the distance between the radial artery and the thin film increases, the sensitivity of detection of the sphygmus wave is deteriorated.

SUMMARY OF THE INVENTION

The present invention provides a contact force sensor package which can be manufactured to be compact and have an improved sphygmus wave detection sensitivity, a blood pressure meter with the contact force sensor package, and a method for fabricating the contact force sensor package.

According to an aspect of the present invention, a contact force sensor package comprises a substrate layer having a vibration detection unit and a pair of first junction pads that are electrical connection ports which are provided on an upper surface of the substrate layer, a flexible circuit substrate layer having a pair of second junction pads provided at a position corresponding to the first junction pad and electrically connected to the first junction pad, a vibration transfer unit having one side contacting the vibration detection unit and the other side contacting a human body and transferring a sphygmus wave of the human body to the vibration detection unit, and an adhesion layer formed between the substrate layer and the flexible circuit substrate layer to reinforce a junction force between the substrate layer and the flexible circuit substrate layer, the adhesion layer being not formed in an area overlapping at least the vibration transfer unit.

The vibration transfer unit is formed of an elastic material.

The elastic coefficient of the vibration transfer unit is less than that of the vibration detection unit.

The vibration transfer unit includes a portion of the flexible circuit substrate layer combined to the vibration detection unit.

The contact force sensor package further comprises an anisotropic conductive layer to electrically connect the first and second junction pads, wherein the vibration transfer unit includes a portion of the anisotropic conductive layer contacting the vibration detection unit and a portion of the flexible circuit substrate layer contacting the portion of the anisotropic conductive layer.

The flexible circuit substrate layer includes an opening formed to expose the vibration detection unit, and the vibration transfer unit includes a vibration transfer member provided in the opening, contacting the vibration detection unit, and capable of covering the opening.

The vibration transfer member is formed of an elastic material.

The vibration transfer unit includes an outermost layer formed of an elastic material that is harmless to the human body.

The contact force sensor package further comprises a pair of metal bumps providing electric connection between the first and second junction pads.

The adhesion layer is formed as a liquid material implanted between the substrate layer and the flexible circuit substrate layer is cured.

The vibration detection unit includes a shape deformation element whose shape is changed by a contact force and the shape deformation element has piezoresistance, piezoelectricity, and capacitance, at least one of which measurably varies according to the contact force.

The shape deformation element is one of a thin film, a cantilever beam, and a bridge.

According to another aspect of the present invention, a blood pressure meter comprises a blood pressure measuring block having at least one contact force sensor package detecting a sphygmus wave of a human body and measuring blood pressure based on the detected sphygmus wave, and a contact maintaining device maintaining a state in which the blood pressure measuring block contacts the human body, wherein the contact force sensor package comprises a substrate layer having a vibration detection unit and a pair of first junction pads that are electrical connection ports which are provided on an upper surface of the substrate layer, a flexible circuit substrate layer having a pair of second junction pads provided at a position corresponding to the first junction pads and electrically connected to the first junction pads, a vibration transfer unit having one side contacting the vibration detection unit and the other side contacting a human body and transferring a sphygmus wave of the human body to the vibration detection unit, and an adhesion layer formed between the substrate layer and the flexible circuit substrate layer to reinforce a junction force between the substrate layer and the flexible circuit substrate layer, the adhesion layer being not formed in an area overlapping at least the vibration transfer unit.

The blood pressure block includes a plurality of the contact force sensor packages and, when one of the contact force sensor packages detects an effective sphygmus wave, blood pressure is measured based on the detected sphygmus wave.

According to another aspect of the present invention, a method for fabricating a contact force sensor package comprises preparing a substrate layer having a vibration detection unit and a pair of first junction pads that are electrical connection ports which are provided on an upper surface of the substrate layer, providing a flexible circuit substrate layer having a pair of second junction pads at a position overlapping the first junction pads, and electrically connecting the first and second junction pads, forming a vibration transfer unit having one side contacting the vibration detection unit and the other side contacting a human body and transferring a sphygmus wave of the human body to the vibration detection unit, and forming an adhesion layer by implanting and curing a liquid material between the substrate layer and the flexible circuit substrate layer to reinforce a junction force between the substrate layer and the flexible circuit substrate layer, wherein the liquid material is not implanted in an area overlapping the vibration detection unit.

The forming of the vibration transfer unit is performed at the same time when the flexible circuit substrate layer is mounted, or before or after the flexible circuit substrate layer is mounted.

The vibration transfer unit is formed of an elastic material.

The forming of the vibration transfer unit includes combining a portion of the flexible circuit substrate layer to the vibration detection unit.

Electrically connecting of the first and second junction pads and the forming of the vibration transfer unit are simultaneously performed, and the above method further comprises providing an anisotropic conductive layer between the flexible circuit substrate layer and the substrate to electrically connected the first and second junction pads, and pressing the flexible circuit substrate layer against the substrate layer to allow one side of the anisotropic conductive layer to contact the vibration detection unit and the other side of the anisotropic conductive layer to contact the flexible circuit substrate layer.

The method further comprises forming an opening in the flexible circuit substrate layer to expose the vibration detection unit, wherein the forming of the vibration transfer unit comprises providing a vibration transfer member in the opening that is capable of contacting the vibration detection unit and covering the opening.

The vibration transfer member is formed of an elastic material.

Electrically connecting of the first and second junction pads includes forming a pair of metal bumps that electrically connect the first and second junction pads.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2is a cross-sectional view of a blood pressure meter10according to an embodiment of the present invention.FIG. 3Ais a cross-sectional view showing a method for fabricating a contact force sensor package according to an embodiment of the present invention.FIG. 3Bis a cross-sectional view showing a completed contact force sensor package.

Referring toFIG. 2, the blood pressure meter10according to the present embodiment is wearable on a wrist1where a radial artery5passes so that a sphygmus wave is easily detected, and includes blood pressure measuring block15measuring blood pressure and a contact maintaining device maintaining a state in which the blood pressure measuring block15contacts a human body, that is, the wrist1. Although in the drawings the contact maintaining device includes a band20wrapping around the wrist, the present invention is not limited thereto. The blood pressure measuring block15includes a plurality of contact force sensor packages100A detecting the sphygmus wave of a human body through the vibration of the radial artery5, a processor (not shown) measuring blood pressure based on the detected sphygmus wave, and a display panel (not shown) visually indicating the measured blood pressure. The contact force sensor packages100A are arranged close to one another in the minimum interval. When an arbitrary one of the contact force sensor packages100A detects an effective sphygmus wave, the processor measures blood pressure based on the detected sphygmus wave.

Referring toFIGS. 3A and 3B, each of the contact force sensor packages100A includes a base layer101, a substrate layer102deposited on the base layer101, a flexible circuit substrate layer110mounted on the substrate layer102, and an adhesion layer130A to reinforce a junction force between the substrate layer102and the flexible circuit substrate layer110.

In the present embodiment, the base layer101is formed of glass and the substrate layer102is formed of silicon (Si). The substrate layer102includes a vibration detection unit and a pair of first junction pads107that are electric connection ports, on an upper surface of the substrate layer102. The vibration detection unit includes a shape deformation element having a shape varying according to an applied contact force. The shape deformation element has piezoresistance, piezoelectricity, and capacitance, at least one of which measurably varies according to the contact force. In the present embodiment, the shape deformation element is a thin film105. The thin film105is an example of the shape deformation element and a cantilever beam or a bridge can be adopted as the shape deformation element.

A cavity103forming the thin film105is formed in the substrate layer102. As the thin film105vibrates, piezoresistive resistance that is sensitive to the strain of the thin film105varies. By applying a known current or voltage to thin film105, a change in the voltage or current can be detected. Thus, the vibration of the thin film105due to the sphygmus wave can be detected through the change of the voltage or current.

In a method for fabricating the contact force sensor package100A, as shown inFIG. 2A, the substrate layer102is prepared and deposited on the base layer101. Next, the flexible circuit substrate layer110having a pair of second junction pads112is arranged at a position corresponding to the first junction pads107. The flexible circuit substrate layer110is mounted on the substrate layer102by electrically and one to one connecting the first junction pads107and the second junction pads112. The flexible circuit substrate layer110transfers an electric signal formed by detecting the sphygmus wave to the processor (not shown) of the blood pressure measuring block15ofFIG. 2. The flexible circuit substrate layer110also protects the thin film105that is easily breakable by foreign materials and impacts such as scratches.

In the above-described embodiment, a metal bump120provides an electric connection between the first and second junction pads107and112. The metal bump120is formed by dropping melted conductive metal such as gold (Au) in a ball shape on one of the first junction pad107.

As shown inFIG. 3B, a vibration transfer unit150A is formed to transfer the sphygmus wave of a human body to the thin film105. In the present embodiment, the vibration transfer unit150A is formed by combining the thin film105and the central portion of the flexible circuit substrate layer110that overlaps the thin film105. The combination of the flexible circuit substrate layer110and the thin film105can be achieved in a method such as pressing, heating, ultrasonic welding, chemical junction, and adhesive coating. The formation of the vibration transfer unit150A is not necessarily performed after the flexible circuit substrate layer110is mounted on the substrate layer102. The vibration transfer unit150A can be formed at the same time when the flexible circuit substrate layer110is mounted on the substrate layer102, or before the flexible circuit substrate layer110is mounted on the substrate layer102.

The lower surface of the vibration transfer unit150A contacts the thin film105and the upper surface thereof contacts a human body, that is, the wrist1, to detect the sphygmus wave. Since the flexible circuit substrate layer110is formed of an flexible elastic material, the vibration of the radial artery5due to the sphygmus wave can be well transferred to the thin film105. For the improvement of the sensitivity in the vibration transferal, an elastic coefficient of the vibration transfer unit150A can be lower than that of the shape deformation element of the vibration detection unit, that is, the thin film105. Since the adhesion layer130A is formed of a relatively non-elastic and solid material such as cured resin or molding compound, when the adhesion layer130A is extended to overlap the thin film105, a sphygmus wave detection performance may be deteriorated. To address this problem, in the present embodiment, the vibration transfer unit150A is formed by combining the central portion of the flexible circuit substrate layer110and the thin film105prior to the formation of the adhesion layer130A.

Although it is not illustrated in the drawings, the vibration transfer unit150A can further include an outermost layer that directly contacts human skin outside the flexible circuit substrate layer110. The outermost layer is formed of an elastic material that is harmless to the human body.

Next, a liquid material, for example, resin or molding compound, is implanted between the substrate layer102and the flexible circuit substrate layer110and heated and cured in an appropriate condition so that the adhesion layer130A is formed. Since a gap G1between the flexible circuit substrate layer110and the upper surface of the substrate layer102is merely tens of micrometers, the gap G1can be filled with the liquid material by a capillary force. The adhesion layer130A reinforces the junction force between the substrate layer102and the flexible circuit substrate layer110and protects the junction portion between the first and second junction pads107and112.

In the contact force sensor package100A, since the thin flexible circuit substrate layer110and the substrate layer102are combined to each other, the distance between the radial artery5and the thin film105can be reduced. Thus, the sensitivity in the detection the sphygmus wave is improved. Also, since the size of the contact force sensor package can be reduced compared to the conventional contact force sensor package in a wire bonding method, the contact force sensor package100A can be more densely arranged in the blood pressure measuring block15ofFIG. 2. Thus, when blood pressure is measured by wearing the blood pressure meter10ofFIG. 2, the possibility of generation of a measurement error is reduced. That is, the blood pressure measuring performance can be improved.

FIG. 4Ais a cross-sectional view showing a method for fabricating a contact force sensor package according to another embodiment of the present invention.FIG. 4Bis a cross-sectional view showing a completed contact force sensor package which can be applied to the blood pressure meter ofFIG. 2like the contact force sensor package100A ofFIG. 3B. In the following description, the same reference numerals as those ofFIGS. 3A and 3Bindicate the same constituent elements.

Referring toFIGS. 4A and 4B, the contact force sensor package100B includes the base layer101, the substrate layer102deposited on the base layer101and having the thin film105, the pair of first junction pads107, and the cavity103, the flexible circuit substrate layer110mounted on the substrate layer102and having the pair of second junction pads112, and an adhesion layer130B to reinforce a junction force between the substrate layer102and the flexible circuit substrate layer110.

In the method for fabricating the contact force sensor package10B, as shown inFIG. 4A, the substrate layer102is prepared and deposited on the base layer101. The metal bump120is formed on the first junction pad107. An anisotropic conductive layer135is provided between the flexible circuit substrate layer110and the first junction pad107. The anisotropic conductive layer135is of a film type.

As shown inFIG. 4B, the flexible circuit substrate layer110presses against the substrate layer102such that the lower surface of the central portion of the anisotropic conductive layer135can contact the thin film105and the upper surface of the anisotropic conductive layer135can contact the flexible circuit substrate layer110. Thus, the first and second junction pads107and112are electrically connected via the metal bump120and the anisotropic conductive layer135.

At the same time when the first and second junction pads107and112are electrically connected, a vibration transfer unit150B to transfer the sphygmus wave to the thin film105is formed. The vibration transfer unit150B includes the central portion of the anisotropic conductive layer135contacting the thin film105and the central portion of the flexible circuit substrate layer110contacting the human body, that is, the wrist1, to detect the sphygmus wave. Since the anisotropic conductive layer135and the flexible circuit substrate layer110are all formed of an elastic material, have an elastic coefficient lower than that of the thin film105, and closely contact each other, the vibration of the radial artery5due to the sphygmus wave can be well transferred to the thin film105.

Next, the liquid material such as resin or molding compound is implanted between the substrate layer102and the flexible circuit substrate layer110and heated and cured in an appropriate condition to form the adhesion layer130B. The adhesion layer130B reinforces a junction force between the substrate layer102and the flexible circuit substrate layer110.

In the contact force sensor package10B, since the thin flexible circuit substrate layer110and the substrate layer102are combined to contact each other, the distance between the radial artery5and the thin film105can be reduced. Thus, the sensitivity in the detection of the sphygmus wave can be improved. Also, since the size of the contact force sensor package can be reduced compared to the conventional contact force sensor package in a wire bonding method, the contact force sensor package100B can be more densely arranged in the blood pressure measuring block15ofFIG. 2. Thus, when blood pressure is measured by wearing the blood pressure meter10ofFIG. 2, the possibility of generation of a measurement error is reduced. That is, the blood pressure measuring performance can be improved.

FIGS. 5A and 5Bare cross-sectional views sequentially showing a method for fabricating a contact force sensor package according to another embodiment of the present invention.FIG. 5Cis a cross-sectional view of a completed contact force sensor package which can be applied to the blood pressure meter ofFIG. 2like the contact force sensor packages100A and100B shown inFIGS. 3B and 4B. In the following description, the same reference numerals as those ofFIGS. 3A and 3Bindicate the same constituent elements.

Referring toFIGS. 5A-5C, the contact force sensor package100C includes the base layer101, a substrate layer102having the thin film105, the pair of first junction pads107, and the cavity103, the flexible circuit substrate layer110mounted on the substrate layer102and having the pair of second junction pads112, an adhesion layer130C to reinforce a junction force between the substrate layer102and the flexible circuit substrate layer110, and a vibration transfer member150C.

In the method for fabricating the contact force sensor package100C, as shown inFIG. 5A, the substrate layer102is prepared and deposited on the base layer101. Next, the pair of metal bumps120are formed on the pair of first junction pads107. The flexible circuit substrate layer110is pressed against the substrate layer102to allow the pair of second junction pads112to contact the pair of metal bumps120, thereby mounting the flexible circuit substrate layer110on the substrate layer102. Accordingly, the first and second junction pads107and112are electrically connected via the metal bumps120. Prior to the mounting of the flexible circuit substrate layer110on the substrate layer102, an opening115is formed in the flexible circuit substrate layer110so that the thin film can be exposed.

Next, after the flexible circuit substrate layer110is mounted on the substrate layer102, as shown inFIG. 5B, a liquid material, for example, resin or molding compound, is implanted between the substrate layer102and the flexible circuit substrate layer110and heated and cured in an appropriate condition so that the adhesion layer130C is formed. As it is described above with reference toFIG. 3B, since the gap between the flexible circuit substrate layer110and the upper surface of the substrate layer102is merely tens of micrometers, the gap can be filled with the liquid material by a capillary force. However, since a portion where the opening115is formed cannot be filled with the liquid material due to surface tension, the thin film105may still remain exposed.

The vibration transfer member150C includes an end portion153contacting the thin film105and a head portion154covering the opening115. A vibration transfer unit is formed by inserting the end portion153of the vibration transfer member150C in the opening115after the adhesion layer130C is formed. In the embodiment shown inFIG. 5C, the vibration transfer unit to transfer the sphygmus wave of a human body to the thin film105includes the vibration transfer member150C. The end portion153of the vibration transfer member150C inserted in the opening115contacts the thin film105and the head portion154contacts the human body, that is, the wrist1, to detect the sphygmus wave. The vibration transfer member150C is formed of a material, such as rubber or silicon resin, having an elastic coefficient lower than that of the thin film105. Thus, the vibration of the radial artery5due to the sphygmus wave can be well transferred to the thin film105.

The contact force sensor package100C can reduce the distance between the radial artery5and the thin film105because the thin flexible circuit substrate layer110and the substrate layer102are combined to closely contact each other. Thus, the sensitivity of the detection of the sphygmus wave is improved. Also, since the size of the contact force sensor package100C can be reduced compared to the conventional contact force sensor package in a wire bonding method, the contact force sensor package100C can be more densely arranged in the blood pressure measuring block15ofFIG. 2. Thus, when blood pressure is measured by wearing the blood pressure meter10ofFIG. 2, the possibility of generation of a measurement error is reduced. That is, the blood pressure measuring performance can be improved.

Also, since the portion contacting the human body is limited to the vibration transfer member150C, even when many persons use the single blood pressure meter10ofFIG. 2, the vibration transfer member150C only can be separated from the flexible circuit substrate layer110and sterilized for reuse which is good for sanitary reasons. Also, a trouble of the flexible circuit substrate layer110can be avoided which is good for economical reasons.