JPH07335440A - Electronic part having polyimide substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an electronic part having polyimide substrate in excellent productivity hardly imposing any residual strain inside the polyimide substrate. CONSTITUTION:A conductor for coil is formed on the surface of a polyimide substrate manufactured by coating, drying and setting in the screen printing step. The polyimide substrate 2 comprises polyimide base resin mixed with filler, As for the filler, high temperature conductive material, low linear expansion coefficient material, magnetic body material and dielectric material etc., are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component, particularly an electronic component having a polyimide substrate such as a laminated coil, a printed wiring board, a coaxial cable substrate and a stripline substrate, and a method for manufacturing the same.

[0002]

2. Description of the Related Art When manufacturing a polyimide substrate used for electronic components such as laminated coils and printed wiring boards, a polyimide resin containing no filler is applied to the surface of a metal foil by means of screen printing. The method is known.
However, the polyimide substrate formed by this method may have residual strain inside when it is cured and shrunk. Further, in order to make the polyimide resin liquid at room temperature, it is necessary to dissolve it in a solvent. However, since the polyimide-based resin is difficult to dissolve in a solvent, it has a low viscosity, and a bleeding defect is likely to occur during screen printing, and the coating thickness is likely to be thin. Therefore, the productivity of the polyimide substrate was poor.

Therefore, an object of the present invention is to provide an electronic component having a polyimide substrate which is less likely to have residual strain inside the polyimide substrate and has good productivity, and a method of manufacturing the same.

[0004]

In order to solve the above problems, an electronic component having a polyimide substrate according to the present invention is characterized in that the polyimide substrate is made of a polyimide resin mixed with a filler. As the polyimide resin, solvent-soluble imide group-containing polymers such as polyamide-imide resin, polyester-modified imide resin, and silicon-imide resin are used in addition to the polyamic acid resin.

The use of fine inorganic particles such as silica, calcium carbonate, and hydrous magnesium silicate, which are low linear expansion coefficient materials, as the filler increases the viscosity of the polyimide resin and increases the viscosity of the polyimide resin. Less shrinkage during curing and heat. Further, as the filler, by using high thermal conductive ceramics such as silicon carbide and aluminum nitride and metal powder such as copper, silver and aluminum, the viscosity of the polyimide resin is increased and the thermal conductivity of the formed polyimide substrate is improved. The rate is high.

Further, by using a magnetic powder such as manganese zinc or nickel zinc as the filler, the viscosity of the polyimide resin is increased and the permeability of the formed polyimide substrate is increased. Further, by using a dielectric powder such as titanium oxide or barium titanate as the filler, the viscosity of the polyimide resin is increased and the dielectric constant of the formed polyimide substrate is increased.

Further, the method of manufacturing an electronic component having a polyimide substrate according to the present invention is characterized in that a liquid polyimide resin mixed with a filler is vacuum-deaerated and then cured to obtain a polyimide substrate. By the method described above, even if the viscosity of the polyimide resin is increased by mixing the filler with the polyimide resin, the bubbles taken in the polyimide resin are scattered into the vacuum, and the defoaming treatment is completed.

[0008]

Embodiments of an electronic component having a polyimide substrate and a method of manufacturing the same according to the present invention will be described below with reference to the accompanying drawings. [First Embodiment, FIGS. 1 to 6] The first embodiment describes a laminated coil used as a transformer.

As shown in FIG. 1, the laminated coil comprises a coil portion 10, a terminal block 20 on which the coil portion 10 is mounted, cores 40 and 50, and resin covers 30a and 30b.
The coil portion 10 is configured by stacking a plurality of polyimide substrates having a coil conductor provided on the surface thereof. The polyimide substrate provided with the coil conductor on its surface is manufactured by the procedure described in detail below. That is, as shown in FIG. 2, a polyimide substrate 2 made of a polyimide resin mixed with a filler is provided on the upper surface of the metal foil 1. As the material of the metal foil 1, a material having excellent conductivity is used. Copper foil was used in the first embodiment. As a material of the polyimide substrate 2, a solvent-soluble imide group-containing polymer such as a polyamic acid resin, a polyamideimide resin, a polyester-modified imide resin, or a silicon imide resin mixed with a filler is used. In the case of the first embodiment, as the filler, silica having an average particle diameter of 80 nm and silica having an average particle diameter of 15 μm are added to the polyimide resin at 15 wt% and 5 wt, respectively.
% Mixed. Silica is a low linear expansion coefficient material.

Silica having an average particle size of 80 nm is for increasing the viscosity of the polyimide resin. Also,
Silica having an average particle diameter of 15 μm is for adjusting the coating thickness of the polyimide resin, and the coating thickness can be increased as the mixing amount is increased. That is, the coating thickness can be easily adjusted by changing the particle size and mixing ratio of the filler mixed with the polyimide resin.

Thus, the viscosity was 50 Pa · sec (measurement condition: BH type viscometer was used and stirred at a rotation speed of 20 rpm), and thixo value (= viscosity at 4 rpm / 20 rp).
A polyimide resin having a viscosity (in m) of 1.05 had a viscosity of 120 Pa · sec and a thixo value of 1.47 after the filler was mixed. A polyimide resin mixed with this filler is applied to the upper surface of the metal foil 1 by means of screen printing. In the first embodiment, as the screen printing conditions, the hardness of the squeegee is 80 degrees and the squeegee speed is 50.
mm / sec, the printing pressure is 0.75 kgf / cm, the gap between the print mask surface and the print surface of the metal foil 1 is 1.5 mm, the mesh of the print mask is # 120, and the diameter of the mesh wire of the print mask is 9
The plate thickness of the print mask was 1 μm and 230 μm.

Next, the polyimide resin applied to the metal foil 1 is vacuum degassed to completely remove the air bubbles taken in the polyimide resin. The defoaming condition is, for example, 1 minute in an atmosphere having a vacuum degree of 1 mmHg or less. Next, the polyimide resin was dried and cured by using an oven or a dryer to obtain a polyimide substrate 2. The polyimide substrate 2 has a rectangular hole 3 in the center. In the case of the first embodiment,
The average plate thickness of the polyimide substrate 2 is 25 μm in one printing,
The amount of bleeding was 0.1 mm or less. For comparison, when a polyimide resin containing no filler was printed under the same printing conditions, the average thickness of the polyimide substrate was 15 μm,
The amount of bleeding was 0.3 mm or less. That is, by mixing the filler with the polyimide resin, the dimensional accuracy of the polyimide substrate 2 is improved and the polyimide substrate 2 has a predetermined thickness (usually 50
The number of times of printing for forming the polyimide substrate 2 having a thickness of about μm can also be reduced.

Next, as shown in FIGS. 3 and 4, a liquid etching resist is applied to the upper and lower surfaces of the metal foil 1 by means of screen printing and cured, whereby etching resist films 5a, 5c, 5d, 5e, 5g are formed. Next, as shown in FIGS. 5 and 6, after etching the metal foil 1 portion exposed from the etching resist films 5a to 5g, the etching resist films 5a to 5g are peeled off.
Thus, the coil conductor 6 and the dummy lead portions 8a and 8b
To form. The coil conductor 6 is spirally formed around the rectangular hole 3 of the polyimide substrate 2. One end 6a of the coil conductor 6 and the dummy lead portion 8a project from the edge of the polyimide substrate 2, and the other end 6b and the dummy lead portion 8b project from the edge of the hole 3. The dummy drawer portions 8a and 8b do not necessarily have to be provided.

The thus obtained polyimide substrate 2 having the coil conductor 6 provided on the surface thereof is not provided with the polyimide substrate 2 having a plurality of coil conductors similarly produced on the surface thereof or the surface thereof. The protective polyimide substrate 2 and the protective polyimide substrate 2 are stacked via an adhesive to form a coil portion 10. As shown in FIG. 1, the end portions 6a, 6 of the coil conductor 6 are
b and the dummy lead-out portions 8a and 8b are projected from the side surface of the coil portion 10 in an overlapped state. The vertically overlapping ends 6a, 6b and the dummy lead portions 8a, 8b are electrically connected by spot welding to form a lead electrode 16. The coil conductor 6 is electrically connected to the coil conductor 6 provided on another polyimide substrate 2 through the extraction electrode 16 to form an inductor. Then, each extraction electrode 16 is bent in the vertical direction.

It should be noted that the coil portion 10 may have only one inductor or a plurality of inductors. Further, by changing the connection method of the coil conductor 6 provided on each polyimide substrate 2, a plurality of inductors can be connected in series or in parallel. The terminal block 20 has a base portion 21.
Guide protrusions 22 are arranged at regular intervals on both sides of the upper surface. Lead terminals 26 are provided on both sides of the lower surface of the base portion 21.
One end portion is embedded at a constant interval, the other end portion extends along the side surface of the base portion 21 around the lower surface of the base portion 21, and is alternately arranged in a staggered pattern with the guide protrusions 22. Has been done. A hole 28 for allowing the middle leg portion 42 of the core 40 to penetrate is provided in the central portion. Further, grooves 23a and 23b are provided at the left and right end portions of both ends of the base portion 21.

The coil portion 10 has a guide protrusion 2 on the terminal block 20.
It is guided by 2 and placed. In this case, the holes 10a of the coil portion 10 and the holes 28 of the terminal block 20 are arranged so as to be aligned,
The extraction electrode 16 is electrically connected to the terminal 26 by means such as spot welding. The resin covers 30a and 30b have claws 32a and 32b at both ends, and partition plates 34a and 34b at the center. And this claw 32
The a and 32b are fitted into the grooves 23a and 23b of the base portion 21, and the covers 30a and 30b are assembled.

Furthermore, a core 40 having an E-shaped cross section and a cross section I
The letter-shaped core 50 is attached. The core 40 has a middle leg portion 42 at the center, outer leg portions 44a and 44b at both ends, and trapezoidal notches 45a and 45b at both sides. Cutout 45
a and 45b avoid the extraction electrode 16 of the coil portion 10. The middle leg portion 42 is inserted into the hole 10 a of the coil portion 10 and the hole 28 of the terminal block 20. The cores 40 and 50 are fixed to each other with an insulating tape or the like in an abutted state. The resin covers 30a and 30b are not always necessary, and the covers 30a and 30b can be omitted when the laminated coil is used in a place where there is little dust or the like. Similarly, the terminal block 20 is not always necessary, and the extraction electrode 1
When 6 is directly soldered to a printed wiring board or the like, the terminal block 20 can be omitted.

In the laminated coil thus obtained,
Since silica, which is a low linear expansion coefficient material, is mixed with the polyimide-based resin, it is possible to reduce shrinkage when curing the polyimide-based resin, suppress residual strain generated inside the polyimide substrate 2, and reduce the residual strain of the polyimide substrate 2. Warpage and deformation can be reduced, and the adhesive force between the polyimide resin and the conductor can be improved.

Further, since the amount of expensive polyimide resin used is reduced and the less expensive filler is used, the manufacturing cost of the polyimide substrate 2 can be reduced. Also,
Since the filler increases the viscosity of the polyimide resin, the coating thickness for one screen printing increases, and
Bleeding defects are reduced. Therefore, the productivity of the laminated coil is improved.

[Second Embodiment, FIGS. 7 to 12] A second embodiment will explain a high-frequency circuit board integrated with an inductor. As shown in FIGS. 7 and 8, a polyimide substrate 61
The circuit conductors 62 and 63 are provided in a part of the upper surface of the. One end 65a of the spiral coil conductor 65 is electrically connected to the circuit conductor 62, and the other end 65b is connected to the circuit conductor 63 via the lead conductors 66 and 67.
Electrically connected to. Around the coil conductor 65, a polyimide-based resin 68 (6) in which a magnetic powder such as manganese zinc or nickel zinc, which is a filler, is mixed.
8a, 68b, 68c). Although not shown, circuit conductors are also provided in the remaining area of the surface of the polyimide substrate 61.

The polyimide substrate 61 having the above structure is manufactured by the procedure described in detail below. That is, a polyimide resin mixed with a filler such as silica is applied to the surface of the metal foil by means of screen printing. Since the filler is mixed in the polyimide resin, the viscosity of the polyimide resin is high. Therefore, bleeding defects at the time of printing are reduced, the dimensional accuracy of the polyimide substrate 61 is improved, and the number of times of printing for forming the polyimide substrate 61 having a predetermined thickness can be reduced. Next, after defoaming the polyimide resin applied to the metal foil in vacuum, the polyimide resin is dried and cured in an oven or the like. Next, after forming an etching resist on the surface of the metal foil by means of screen printing or the like, the metal foil portion exposed from the etching resist is etched. In this way, the polyimide substrate 61 having the circuit conductors 62 and 63 shown in FIG. 9 on the surface is formed.

Next, as shown in FIG. 10, a polyimide resin 68a mixed with magnetic powder is applied between the circuit conductors 62 and 63 on the upper surface of the polyimide substrate 61 by means of screen printing. Further, the polyimide resin 68a is degassed in vacuum and then cured in an oven or the like. Next, a conductive paste is applied by means of screen printing to form the coil conductor 65 and the lead conductor 67 on the surface of the polyimide substrate 61.

Next, as shown in FIG. 11, a polyimide resin 6 in which magnetic substance powder is mixed on the upper surface of the polyimide substrate 61.
8b is applied by means of screen printing. At this time,
Holes 7 are formed in the polyimide resin 68b at the end portions 65b of the coil conductor 65 and the lead conductor 67, respectively.
2 is formed. The polyimide resin 68b is degassed in a vacuum and cured in an oven or the like.

Next, as shown in FIG. 12, a conductive paste is applied by means of screen printing to form ends 65b of the coil conductor 65 exposed through the holes 71 and 72 of the polyimide resin 68b. The lead conductor 66 that electrically connects the ends of the lead conductor 67 is formed. Thereafter, a polyimide resin 68c mixed with magnetic powder is applied by means of screen printing, and then degassed in vacuum to cure (see FIG. 8).

In the thus obtained polyimide substrate 61, since the polyimide substrate 61 is made of a polyimide resin mixed with a filler such as silica, the polyimide substrate 61 has a small internal residual strain and a small warp or deformation,
The substrate has a large adhesive force between the conductor and the polyimide resin.
Further, since the viscosity of the polyimide-based resin is increased by the filler, bleeding defects are less likely to occur and the coating thickness for one screen printing is increased. As a result, the polyimide substrate 61
Productivity is improved.

Further, since the polyimide resin 68 provided around the coil conductor 65 is mixed with the filler of magnetic powder, the viscosity of the polyimide resin 68 is high. Therefore, bleeding defects during printing are reduced, the dimensional accuracy of the polyimide resin 68 is improved, and the number of times of printing for forming the polyimide resin 68 having a predetermined thickness can be reduced. Moreover, the magnetic powder of the filler can increase the magnetic permeability of the polyimide resin 68, and the inductance of the coil conductor 65 can be improved.

[Third Embodiment, FIGS. 13 to 18] In the third embodiment, a high-frequency module substrate having coaxial signal lines and strip lines built therein will be described. As shown in FIG. 13, the high frequency module substrate 81 has a structure in which a polyimide substrate 84 containing a coaxial signal line or a strip line is sandwiched between two polyimide substrates 82 and 83. The polyimide substrates 82 and 83 are multi-layer printed wiring boards and are manufactured by the following manufacturing method, for example. A polyimide resin mixed with a filler is applied by screen printing and dried to form a polyimide resin film. Next, a conductive paste is applied to the surface of the polyimide resin film by screen printing and dried to form a circuit conductor. By repeating this, a multilayer structure substrate is obtained.

The polyimide substrate 84 is made of a polyimide resin mixed with a dielectric powder such as titanium oxide or barium titanate which is a filler. Coaxial signal lines 86, strip lines 87, 88, and ground conductors 90, 91, 92, 93 are arranged inside the polyimide substrate 84.
The polyimide substrate 84 having the above structure is manufactured by the procedure described in detail below. That is, as shown in FIG. 14, a conductive paste is applied to the upper surface of the polyimide substrate 82 by means of screen printing to form part of the ground conductor 90 and the ground conductor 92.

Next, as shown in FIG. 15, a polyimide resin 84a mixed with a dielectric powder is applied to the upper surface of the polyimide substrate 82 by means of screen printing. At this time, recesses 95 and 96 are formed at the position of the ground conductor 90 in the polyimide resin 84a. Polyimide resin 8
4a is degassed in vacuum and cured in an oven or the like. Next, as shown in FIG. 16, a conductive paste is applied to the surface of the polyimide resin 84a by means of screen printing, and the ground conductor 90 exposed from the recesses 95 and 96.
And the coaxial signal line 86 and the strip lines 87 and 88 are formed.

Next, as shown in FIG. 17, a polyimide resin 84b mixed with a dielectric powder is applied by means of screen printing, and then vacuum degassing is performed to cure. The polyimide resin 84b has a recess 97 at the position of the ground conductor 90,
98 is formed. Next, as shown in FIG. 18, a conductive paste is applied to the surface of the polyimide resin 84b by means of screen printing to extend the ground conductor 90 exposed from the recesses 97 and 98, and at the same time, to ground conductor. 91 and 93 are formed.

Next, a polyimide resin 84c mixed with a dielectric powder is applied by means of screen printing, and then vacuum degassing is performed to cure the polyimide resin 84c, whereby the polyimide resin 8 is formed.
A polyimide substrate 84 composed of 4a to 84c is manufactured (see FIG. 13). Then, the polyimide substrate 83 is laminated on the upper surface of the polyimide substrate 84 with an adhesive. In the high frequency module substrate thus obtained, since the polyimide substrates 82, 83, 84 are made of a polyimide resin mixed with a filler, the internal residual strain is small,
The warp and deformation are small, and the adhesive force between the conductor and the polyimide resin is large. Further, since the filler increases the viscosity of the polyimide resin, there are few bleeding defects, and
The coating thickness of the screen printing is increased. As a result, the productivity of the polyimide substrates 82 to 84 is improved.

Further, since the polyimide substrate 84 is made of a polyimide resin mixed with a dielectric powder filler, the polyimide substrate 84 has a high dielectric constant, and the distance between the coaxial signal line 86 and the outer conductor 90 is narrowed. Alternatively, the strip lines 87 and 88 can be made narrower to have the same characteristic impedance, and the high frequency module substrate can be miniaturized.

[Other Embodiments] The electronic component having the polyimide substrate according to the present invention and the method for manufacturing the same are not limited to the above embodiments, but can be variously modified within the scope of the invention. . In the first embodiment, a circuit conductor may be formed instead of the coil conductor 6 and the dummy lead portions 8a and 8b to manufacture a rigid or flexible printed wiring board. Further, a plurality of the printed wiring boards may be laminated with an adhesive to produce a multilayer printed wiring board.

The high frequency circuit board of the second embodiment may have the structure shown in FIGS. 19 and 20. The coil conductor 65 is provided on the upper surface of the polyimide substrate 61, and one end portion 65a is electrically connected to the circuit board 62, and the other end portion 65b is electrically connected to the circuit conductor 63. Around the coil conductor 65, a polyimide resin 68 (68a, 68a) mixed with magnetic powder is provided.
b) is provided.

The procedure for manufacturing the polyimide substrate 61 in this case will be described. After forming the coil conductor 65 on the upper surface of the polyimide substrate 61 by screen printing, a polyimide resin 68a mixed with magnetic powder is applied by screen printing. At this time, the polyimide resin 68a
Has holes formed at the positions of the ends 65a and 65b of the coil conductor 65, respectively. Next, a conductive paste is applied by means of screen printing to remove the polyimide resin 68a.
Circuit conductors 62, 63 electrically connected to the ends 65a, 65b of the coil conductor 65 exposed through the holes
To form. Then, the polyimide resin 68b mixed with the magnetic powder is formed by screen printing. Therefore, it is possible to reduce the number of times of printing, save material, and reduce the thickness of the polyimide substrate 61.

As the filler, castor oil-based organic fine powder can also be used. Further, as the filler, by using high thermal conductive ceramics such as silicon carbide and aluminum nitride, and metal powder such as copper, silver and aluminum, the viscosity of the polyimide resin is increased and the thermal conductivity of the formed polyimide substrate is improved. The rate can be increased.

[0037]

As is apparent from the above description, according to the present invention, since the polyimide substrate is made of a polyimide resin mixed with a filler, it is possible to reduce shrinkage when curing the polyimide resin, It is possible to suppress the residual strain generated inside the polyimide substrate, reduce the warpage and deformation of the polyimide substrate, and increase the adhesive force between the conductor and the polyimide resin. In addition, since the amount of expensive polyimide resin used is reduced and less expensive filler is used,
The manufacturing cost of the polyimide substrate can be reduced.

Further, since the viscosity of the polyimide resin is increased by the filler, the coating thickness at the time of screen printing becomes thicker and the bleeding defect is reduced. Therefore, the productivity of the polyimide substrate and further of the electronic component is improved. And by changing the particle size and mixing ratio of the filler,
The coating thickness can be easily adjusted. Further, by using a high thermal conductive material, a low linear expansion coefficient material, a magnetic material, or a dielectric material as the filler, the characteristics of each material can be added to the polyimide substrate to form a high value-added substrate.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an electronic component having a polyimide substrate according to the present invention and a first embodiment of a manufacturing method thereof.

FIG. 2 is a perspective view showing a procedure for manufacturing a polyimide substrate used for the laminated coil shown in FIG.

FIG. 3 is a perspective view showing a manufacturing procedure following that of FIG. 2;

FIG. 4 is a perspective view of the polyimide substrate shown in FIG. 3 viewed from the back side.

FIG. 5 is a perspective view showing a manufacturing procedure following that of FIG. 3;

6 is a perspective view of the polyimide substrate shown in FIG. 5 viewed from the back side.

FIG. 7 is a plan view showing a second embodiment of an electronic component having a polyimide substrate according to the present invention and a manufacturing method thereof.

8 is a sectional view taken along line VIII-VIII of FIG.

9 is a cross-sectional view showing the procedure for manufacturing the polyimide substrate shown in FIG.

FIG. 10 is a cross-sectional view showing the manufacturing procedure following FIG. 9;

FIG. 11 is a cross-sectional view showing the manufacturing procedure following FIG. 10;

FIG. 12 is a cross-sectional view showing the manufacturing procedure following FIG. 11.

FIG. 13 is a sectional view showing an electronic component having a polyimide substrate according to the present invention and a third embodiment of a method for manufacturing the same.

FIG. 14 is a cross-sectional view showing the manufacturing procedure of the high-frequency module substrate shown in FIG.

FIG. 15 is a cross-sectional view showing the manufacturing procedure following FIG. 14;

16 is a cross-sectional view showing the manufacturing procedure following FIG.

FIG. 17 is a cross-sectional view showing the manufacturing procedure following FIG. 16;

FIG. 18 is a cross-sectional view showing the manufacturing procedure following FIG. 17;

FIG. 19 is a plan view showing a modification of the second embodiment.

20 is a sectional view taken along line XX-XX of FIG.

[Explanation of symbols]

2 ... Polyimide substrate 10 ... Coil part 61 ... Polyimide substrate 68 (68a, 68b, 68c) ... Polyimide resin 82, 83, 84 mixed with magnetic substance powder ... Polyimide substrate 84a, 84b, 84c ... Dielectric powder mixed Polyimide resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01F 41/04 C H05K 1/03 E 7511-4E

Claims (6)

[Claims] 1. An electronic component having a polyimide substrate, wherein the polyimide substrate is made of a polyimide resin mixed with a filler. 2. The electronic component having a polyimide substrate according to claim 1, wherein the filler mixed with the polyimide resin is a high thermal conductive material. 3. The electronic component having a polyimide substrate according to claim 1, wherein the filler mixed with the polyimide resin is a low linear expansion coefficient material. 4. The electronic component having a polyimide substrate according to claim 1, wherein the filler mixed with the polyimide resin is a magnetic material. 5. The electronic component having a polyimide substrate according to claim 1, wherein the filler mixed with the polyimide resin is a dielectric material. 6. A method for producing an electronic component having a polyimide substrate, which comprises degassing a liquid polyimide resin mixed with a filler in a vacuum and then curing it to obtain a polyimide substrate.