JP2015179688A - Flexible substrate and manufacturing method of flexible substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy a constraint condition in manufacturing while mounting an electronic component in high density.SOLUTION: A flexible substrate of one embodiment is provided with: a unit substrate including a plurality of surface electrodes that are provided on the surface and mount electronic components, reverse surface electrodes that are provided on the reverse surface and connected to any of the surface electrodes, and a plurality of conductive layers that is provided inside and connects the surface electrodes with a terminal provided on an end surface; and an extension unit substrate which is disposed on the reverse surface side of the unit substrate via an anisotropic electroconductive film and includes a surface auxiliary electrode provided at a position opposite to the reverse surface electrode, and a plurality of conductive layers that is provided inside and connects the surface auxiliary electrode with a terminal on an end surface.

Description

  Embodiments described herein relate generally to a flexible substrate and a flexible substrate manufacturing method.

  A medical diagnostic apparatus acquires biological information by a built-in sensing component (electronic component) and is used for diagnosis of a patient in the medical field. For example, an ultrasonic probe of an ultrasonic diagnostic apparatus uses a piezoelectric element (electronic component) mounted on a flexible substrate to transmit an ultrasonic wave to a subject and receive a reflected wave to image an affected part of the subject. It is used for diagnosis. In recent years, in order to perform highly accurate diagnosis, a two-dimensional array of ultrasonic probes in which piezoelectric elements are arranged in a matrix has been used.

JP 2005-507581 A

  In the ultrasonic probe, it is necessary to increase the density of the wiring of the flexible substrate in accordance with the number of piezoelectric elements. For this purpose, the substrate is multilayered and the wiring is miniaturized. Due to manufacturing restrictions, the number of layers is about 6 layers, and the minimum is 10 μm / 30 μm for the line / space width, and the upper limit of the density of the piezoelectric elements is determined accordingly.

  In recent years, there has been an increasing need for high accuracy in small medical diagnostic apparatuses. For this reason, there is a need for a flexible substrate that satisfies manufacturing constraints while mounting sensing components at high density.

  A flexible substrate according to an embodiment of the present invention includes a plurality of front surface electrodes provided on the front surface for mounting electronic components, a rear surface electrode provided on the rear surface and connected to any one of the front surface electrodes, the inner surface, and the front surface A unit substrate on which a plurality of conductive layers that connect the electrodes and terminals provided on the end surface are formed, and is disposed on the back side of the unit substrate via an anisotropic conductive film, at a position facing the back electrode. A surface auxiliary electrode provided, and an extension unit substrate provided with a plurality of conductive layers for connecting the surface auxiliary electrode and a terminal provided on an end face are provided.

Explanatory drawing which shows typically the small medical diagnosis apparatus by which the flexible substrate which concerns on 1st Embodiment was mounted. Explanatory drawing which shows the flexible substrate typically. Explanatory drawing which shows the manufacturing process of the flexible substrate typically. Explanatory drawing which shows typically the small medical diagnostic apparatus by which the flexible substrate which concerns on 2nd Embodiment was mounted. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically. Explanatory drawing which shows the manufacturing process of the small medical diagnosis apparatus typically.

  FIG. 1 is an explanatory diagram schematically showing an ultrasonic probe (small medical diagnostic apparatus) 100 on which a flexible substrate 110 according to the first embodiment is mounted. FIG. 2 is an explanatory diagram schematically showing the flexible substrate 110. FIG. 3 is an explanatory view schematically showing a manufacturing process of the flexible substrate 110.

  The ultrasonic probe 100 includes a probe main body 101, a plurality of control boards 102 arranged in the probe main body 101, a flexible board 110 connected to the control board 102, and a plurality of stacked layers mounted on the flexible board 110. And a piezoelectric vibrator (electronic component) 150. In FIG. 1, reference numeral 103 denotes a cable, and 104 denotes a control panel.

  The flexible substrate 110 is formed by stacking a unit substrate 120 and an extension unit substrate 130 with an anisotropic conductive film 140 interposed therebetween.

  The unit substrate 120 includes a substrate body 121 made of a polyimide material. The substrate body 121 is provided with a plurality of front surface electrodes 122 for mounting the laminated piezoelectric vibrator 150 on the front surface, and a rear surface electrode 123 connected to the front surface electrode 122 on the back surface. Further, the substrate body 121 is formed with about 6 to 8 conductive layers 124 (only four layers are shown in FIG. 2 for simplicity), and a part of them connects the front surface electrode 122 and the back surface electrode 123, and others This part is drawn out to the terminal 125 on the end face side. That is, the front electrode 122 is connected to either the back electrode 123 or the terminal 125 via the conductive layer 124. The conductive layers 124 are connected by through holes 124a. Further, the terminal 125 is connected to the control board 102.

  The surface electrode 122, the back surface electrode 123, and the terminal 125 described above are surface plated with, for example, nickel / gold. For example, the conductive layer 124 is a good conductor such as copper and a copper alloy.

  The extension unit substrate 130 includes a substrate body 131 made of a polyimide material. The substrate body 131 is provided with a front surface auxiliary electrode 132 provided at a position facing the back surface electrode 123 on the front surface, and a back surface auxiliary electrode 133 that is electrically connected to the front surface auxiliary electrode 132 on the back surface. . The substrate body 131 is formed with a plurality of conductive layers 134, connecting the front surface auxiliary electrode 132 and the back surface auxiliary electrode 133, and further leading out to the auxiliary terminal 135 on the end surface side. The conductive layers 134 are connected by through holes 134a. The auxiliary terminal 135 is connected to the control board 102. The surface auxiliary electrode 132, the back surface auxiliary electrode 133, and the auxiliary terminal 135 described above are subjected to surface plating with nickel / gold. The conductive layer 134 is a good conductor such as copper and a copper alloy.

  Further, the extension unit substrate 130 can be further connected via the anisotropic conductive film 140 below the extension unit substrate 130 in FIG. 2 in accordance with the mounting density of the laminated piezoelectric vibrators 150.

  Next, a process of pressure bonding the unit substrate 120 and the auxiliary unit substrate 130 in the above-described method for manufacturing the flexible substrate 110 will be described. FIG. 3 shows a pulse heat type thermocompression bonding apparatus 300. The pulse heat type thermocompression bonding apparatus 300 includes a support base 310 and a thermocompression bonding tool 320 disposed to face the support base 310.

  The support base 310 has a smooth upper surface. For example, the support base 310 is made of quartz. In another example, the support base 310 may have a configuration in which a recess 311 is provided at the center of the upper surface, and a stage 312 made of glass material is fitted in the recess 311.

  The thermocompression bonding tool 320 includes a heater tool 321 serving as a heating source by resistance heat generation, and a smooth plate member 322 provided at the lower end of the heater tool 321. The heater tool 321 is formed in a hollow shape using, for example, super invar, cemented carbide, Ti, or the like. Further, the smooth plate member 322 has a highly accurate smooth surface and is formed with little thermal deformation. For example, the smooth plate material 322 is formed of a ceramic material such as AIN.

  In such a pulse heat type thermocompression bonding apparatus 300, the auxiliary unit substrate 130 and the anisotropic conductive film 140 are disposed, and temporary bonding is performed using the heater tool 321 at, for example, 80 ° C., 1 to 3 seconds, and a pressure of 1 MPa. Next, the unit substrate 120 is positioned and laminated, the smooth plate material 322 is sandwiched, the heater tool 321 is heated and pressure is applied downward to melt the anisotropic conductive film 140, and the back surface of the unit substrate 120. The electrode 123 and the surface auxiliary electrode 132 of the auxiliary unit substrate 130 are joined. At this time, for example, the pressure is 2 to 4 MPa at 150 to 200 ° C. for 5 to 10 seconds. In FIG. 3, Q indicates a thermocompression bonding part.

  Here, for example, the smooth plate material 322 may be suspended from the heater tool 321 and integrated with the heater tool 321.

  At this time, since the smooth plate material 322 is sandwiched, the smoothness of the heater tool 321 may not be so high. For example, when the tool width is 13 mm and there is an unevenness difference of about 10 to 15 μm on the bottom surface of the tool, there is a risk of poor connection of the anisotropic conductive film 140, but when a 3 mm thick smooth plate material 322 is sandwiched, The unevenness difference can be improved to 8 μm or less.

  In the heater tool 321, the temperature profile can be freely set, and the processing temperature can be set to a desired state. Moreover, since it can cool in the pressurization state after thermocompression bonding, there is an effect of preventing springback and suppressing warpage of the sample. Further, since it can be set not to heat during standby, there is an advantage that no thermal damage is given to the unit substrate or the like during alignment.

  Next, a signal flow when the flexible substrate 110 is used will be described. That is, signals output from the plurality of laminated piezoelectric vibrators 150 are transmitted to the conductive layer 124 in the substrate body 121 through the surface electrode 122 of the unit substrate 120. Here, part of the conductive layer 124 is transmitted to the terminal 125 and input to the control board 102. The conductive layer 124 that is not connected to the terminal 125 is connected to the back electrode 123 and is transmitted to the front surface auxiliary electrode 132 of the auxiliary unit substrate 130 via the anisotropic conductive film 140. The signal transmitted to the front surface auxiliary electrode 132 is transmitted to the auxiliary terminal 135 or the rear surface auxiliary electrode 133 through the conductive layer 134. Here, a part of the conductive layer 134 is transmitted to the auxiliary terminal 135 and input to the control board 102.

  The unit substrate 120 and the extension unit substrate 130 are provided with 6 to 8 conductive layers 124 and 134, respectively, and the internal wiring is fine wiring such as a pitch of 40 to 60 μm and a line / space of 20 μm / 40 μm. It is necessary to ensure manufacturing restrictions. For this reason, when the laminated piezoelectric vibrators 150 are arranged at a higher density, an additional unit board 130 is further added in order to maintain restrictions on the number of conductive layers stacked and the manufacturing of fine wiring.

  In the flexible substrate 110 configured in this way, even when the laminated piezoelectric vibrators 150 are arranged in high density, the number of the extension unit substrates 130 is increased to increase the number of extension unit substrates 130 and the conductive layers in the extension unit substrates 130. Signals can be transmitted to the control board 102 without increasing the number or miniaturizing the wiring. Therefore, it is possible to increase the accuracy of the ultrasonic probe 100 while maintaining manufacturing restrictions.

  FIG. 4 is an explanatory view schematically showing the portable medical diagnostic apparatus 200 on which the flexible substrate 210 according to the second embodiment is mounted, and FIGS. 5 to 10 schematically show the manufacturing process of the portable medical diagnostic apparatus 200. It is explanatory drawing shown. In FIG. 4, M indicates a human body.

  As shown in FIG. 4, the portable medical diagnostic device 200 includes a device main body 210 and an adhesive tape 290 for fixing the device main body 210 to the chest or wrist of a human body. The apparatus main body 210 includes a hollow casing 211 made of a flexible elastomer material, and an electrical component 220 accommodated in the casing 211.

  The casing 211 is provided with a lid portion 211a so that batteries can be exchanged.

  The electrical component 220 includes a flexible substrate 230, an electronic component 240 such as a sensor and a battery 241 mounted on the front surface side of the flexible substrate 230, and an electrocardiogram electrode 250 mounted on the back surface side.

  The flexible substrate 230 includes two unit substrates 231 and 232 and an anisotropic conductive film 233 sandwiched between them. The unit substrate 231 is configured in the same manner as the unit substrate 130 described above, and the unit substrate 232 is configured in the same manner as the extension unit substrate 140 described above. The flexible substrate 230 has a bent portion 230a of 10 ° or more at the center as a whole, and a reinforcing material 239 is inserted. The flexible substrate 230 is formed so as to be swingable in the right and left directions in FIG. The reinforcing member 239 becomes the center of swing when the casing 211 and the flexible substrate 230 are bent.

  The electrocardiogram electrode 250 is further connected to the human body sticking electrode 251 and exposed to the outside from the opening of the sticking tape 290 described above.

  The portable medical diagnostic apparatus 200 configured as described above can detect a current inside the human body from the human body sticking electrode 251 by being attached to the surface of the human body, and the electronic component 240 can be detected based on the detection information. Diagnosis can be made by this. At this time, since the casing 211 and the flexible substrate 230 move flexibly, they can follow the movement of the human body. In addition, when the number of electronic components 240 to be mounted is large, the unit substrate 232 is provided even when the necessary conductive layer is increased. The number of layers can be kept to a number that can maintain flexibility. If the number of electronic components 240 to be mounted increases, the number of unit substrates 232 is further increased, so that the number of conductive layers in each of the unit substrates 231 and 232 is not increased, and the internal wiring is miniaturized. It is possible to cope with ensuring manufacturing restrictions.

  Next, a method for manufacturing the portable medical diagnostic apparatus 200 will be described. As shown in FIG. 5, an anisotropic conductive film 233 is temporarily attached on the unit substrate 232. At this time, the separator 233a is attached to the anisotropic conductive film 233 in advance.

  Next, the separator 233a is peeled off from the anisotropic conductive film 233. Then, as shown in FIG. 6, the unit substrate 231 is positioned on the unit substrate 232 on which the anisotropic conductive film 233 is temporarily attached, and placed on the glass substrate stage 400 having the recess 401. And it heat-presses with the heat tool 410 which has the convex part 411 from upper direction, and this crimps | bonds. At this time, since the flexible 230 is flexible, the central portion is recessed into the recess 401, and a bent portion 230a is formed as shown in FIG.

  Next, as shown in FIG. 8, the flexible substrate 230 is mounted on the magic resin plate 500, the electronic component 240 and the electrocardiogram electrode 250 are mounted by double-sided reflow plate soldering, and the electrical component 220 is assembled.

  Next, as shown in FIG. 9, the electrical component 220 is put together with the reinforcing material 239 into the mold 600, and molten rubber (elastomer) is injected to form the casing 211. Finally, the battery 241 is attached to the casing 211, and the lid 211a is covered to complete.

  According to the portable medical diagnostic apparatus 200 according to the present embodiment, even when the number of electronic components 240 mounted on the flexible substrate 230 is increased, the number of conductive layers in the unit substrates 231 and 232 is a predetermined number. Since there is no increase, the flexibility of the flexible substrate 230 can be maintained. In addition, it is possible to increase the functionality of the portable medical diagnostic apparatus 200 while maintaining manufacturing restrictions.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  For example, in the present invention, an ultrasonic probe is exemplified as a small medical diagnostic apparatus, but any apparatus using a flexible substrate on which electronic components are mounted is applicable.

  DESCRIPTION OF SYMBOLS 100 ... Ultrasonic probe, 110 ... Flexible substrate, 120 ... Unit substrate, 121 ... Substrate body, 122 ... Front electrode, 123 ... Back electrode, 124 ... Conductive layer, 125 ... Terminal, 130 ... Expansion unit substrate, 131 ... Substrate body , 132 ... front auxiliary electrode, 133 ... back auxiliary electrode, 134 ... conductive layer, 135 ... auxiliary terminal, 140 ... anisotropic conductive film, 150 ... laminated piezoelectric vibrator (electronic component), 200 ... portable medical diagnostic device, DESCRIPTION OF SYMBOLS 211 ... Case, 220 ... Electrical equipment part, 230 ... Flexible substrate, 231, 232 ... Unit substrate, 300 ... Pulse heat type thermocompression bonding apparatus, 320 ... Thermocompression bonding tool, 321 ... Heater tool, 322 ... Smooth plate material.

Claims (3)

A plurality of front surface electrodes for mounting electronic components provided on the front surface, a back surface electrode provided on the back surface and connected to any one of the front surface electrodes, and provided on the inside, the front surface electrode and a terminal provided on the end surface A unit substrate on which a plurality of conductive layers to be connected are formed;
A surface auxiliary electrode disposed on the back side of the unit substrate via an anisotropic conductive film and provided at a position facing the back electrode, and provided inside, and a terminal provided on the surface auxiliary electrode and the end face And an extension unit board on which a plurality of conductive layers are connected.
The flexible printed circuit board, wherein the unit board and the extension unit board have a bent portion. A plurality of front surface electrodes for mounting electronic components provided on the front surface, a back surface electrode provided on the back surface and connected to any one of the front surface electrodes, and provided on the inside, the front surface electrode and a terminal provided on the end surface A unit substrate on which a plurality of conductive layers to be connected are formed;
A back surface auxiliary electrode disposed on the back surface side of this unit substrate via an anisotropic conductive film and provided at a position facing the back surface electrode, a back surface auxiliary electrode provided on the back surface and connected to any of the front surface auxiliary electrodes, And provided with an extension unit board formed with a plurality of conductive layers connecting the surface auxiliary electrode and the terminal provided on the end face,
The flexible printed circuit board, wherein the unit board and the extension unit board have a bent portion. In the method for manufacturing a flexible substrate configured by laminating and arranging at least the first and second unit substrates,
Placing the first unit substrate on a substrate stage;
An anisotropic conductive film is temporarily attached to the surface of the first unit substrate,
Positioning the second unit substrate on the first unit substrate together with corresponding electrodes;
A thermocompression bonding tool having a convex portion is brought into contact with the second unit substrate side, and the anisotropic conductive film is heated while forming bent portions in the first unit substrate and the second unit substrate. A method of manufacturing a flexible substrate, wherein the electrode of the first unit substrate and the electrode of the second unit substrate are electrically connected by pressure bonding.

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