JPS6260441A - Both sides-thick film fine coil for small-sized motor - Google Patents

Abstract

PURPOSE:To obtain a small sized printed coil having a high output and high reliability by using a through-hole having high reliability. CONSTITUTION:A resist is formed to a section except a pattern section first in a metallic sheet. Electric plating is executed from the upper section of the resist in order to form a conductor pattern, and the metallic plate is stuck to an insulating substrate while being positioned to an upper section. A through- hole is bored, pre-treatment is conducted by an activating liquid for electroless plating, and a double thick-film fine coil for a small-sized motor is manufactured through through-hole conduction by electrolytic plating. The fine coil is manufactured in such a manner that the thickness of a coil conductor is brought to 60-400mum, the width of the coil conductor to 10-300mum and a gap to 150mum or less and the conductor coating an insulating sheet in the through-hole section has substantially uniform thickness and is fast stuck to an insulating layer at that time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a printed coil for a small motor.

<Conventional technology and its problems> Conventionally, motor coils were made by winding enameled wire, formal wire, etc., but in recent years, printed coils using photosensitive resin and mainly etching have begun to be used. .

Although these printed coils can be made flat and thin, the etching factor during etching (etching is performed not only in the thickness direction but also in the direction parallel to the surface, and the wider the thick copper foil is etched, the wider the gap becomes. Therefore, if you try to make a pattern with a thick conductor and high line density, the gap will become wider and the proportion of copper in the cross section will decrease.As a result, the resulting motor will have a high coil resistance. Or the effective length of the coil becomes shorter,
Low torque and low efficiency. Therefore, JP-A-57-915
A method using plating as shown in No. 90 has made it possible to obtain a conductor pattern with high linear density (low resistance).

However, in order to use these motors, through holes are always required, and unlike through holes in general printed circuit boards, these through holes are subject to the reaction of the torque generated by the motor, so their reliability is particularly high. That was a problem.

Means and Effects for Solving Problems The present invention provides a printed coil for small motors with high output and high reliability by providing highly reliable through holes in a printed coil with high density and thick film. This is what we provide.

That is, the present invention has a plurality of substantially identical spiral coil conductors on both sides of an insulating sheet, and the opposing spiral coil conductors on both sides are electrically connected to each other by a through hole penetrating the above-mentioned insulating sheet. A double-sided thick film printed coil for small motors, which (i) has a coil conductor thickness of 60 to 400 μm and (ii)
) The coil conductor width is 10 to 300 μm (iii)
A double-sided device for a small motor, characterized in that the gap is 150 μm or less, and (iv) the conductor covering the insulating sheet in the through-hole portion has a substantially uniform thickness and is in close contact with the insulating layer. This provides a thick film fine coil.

If the thickness of the coil conductor is thinner than 60 μm, the resistance will be significantly high, and if you try to make it thicker than 400 μm,
Depending on the thickness, the width of the coil conductor must be increased, and it will come into contact with the adjacent conductor. Also, if the width of the coil conductor is less than 10 μm, the resistance will be high;
If it is 0 μm or more, the number of turns of the coil in such a small motor becomes too small, and the torque generated by the motor becomes weak. Furthermore, if the gap is 150 μm or more, the number of turns of the coil will also decrease.

In addition, in the through-hole land portion, the insulating layer protrudes convexly at the center of the through-hole, and the convex insulating layer is extended into a concave shape.
Preferably, it is closely covered with a conductor having a substantially uniform thickness. If the thickness of the conductor is not uniform and there are thin parts, even if the thickness is 20 to 30 μm, stress will be concentrated and the wire will be easily broken due to the reaction of the generated torque. Furthermore, if the insulating layer and the conductor are not in close contact with each other, the stress applied to the through hole acts only on the conductor of the through hole, making it easy to break the wire. When the conductor is in close contact with the insulating layer, the stress applied to the through hole has the effect of being dispersed to both the conductor and the insulating layer.

In particular, if the insulating layer at the through-hole land protrudes in a convex shape at the center of the through-hole land and is closely covered with a concave conductor, the insulating layer can sufficiently hold the through-hole land, resulting in the through-hole It has the effect of significantly reducing the stress applied to

In addition, by partially thickening the coil conductor, it is possible to lower the coil resistance and improve efficiency. For example, in a flat brushless morph, the radial conductor of the printed coil has a high linear density, and the circumferential By making the conductors thicker in each direction to lower the resistance, a motor with high torque and high efficiency can be obtained.

The double-sided thick film printed coil for small motors of the present invention is manufactured, for example, as follows.

First, a thin metal plate is prepared.The thin plate may be a conductor and can be etched, but it is preferable that the thin plate has etching characteristics different from those of electrolytic plated conductors.In this case, a thin metal plate is used. When removing the electroplated conductor by etching, the electrolytically plated conductor is not etched, allowing highly accurate etching of thin metal plates. Suitable materials include aluminum, tin, and zinc. The film thickness is 1 to 500 μm, especially 5 to 200 μm, and even 10 μm.
A preferable range is 100 μm. A film thickness of 1 μm or less is difficult to handle and tends to cause unevenness in the plating film thickness. Further, if the film thickness is 500 μm or more, it takes time to remove the film by etching, and productivity decreases.

Next, a resist is formed on the parts other than the pattern part, and the method thereof may be screen printing, gravure printing, etc., but it is preferable to use a photoresist that can easily form a fine pattern. As a forming method, it can be obtained through coating, exposure, and development processes. As photoresists, negative types such as Eastman Kodak's KPRlKOR, KPL, KTFR, KMER, Tokyo Ohka Co.'s TPR, 0MR81, Fuji Pharmaceutical's FSR, and Eastman Kodak's KADR,
There are positive types such as AZ-1350 manufactured by Shipley Co., Ltd., but those with excellent plating resistance are preferred, and negative types are particularly preferably used. A dry film resist can also be used. The thicker the resist film, the more useful it will be in preventing thickening of the plating, but if it is too thick, it will be impossible to obtain a fine pattern.
~10 μm is preferred. If the thickness is 0.1 μm or less, pinholes are likely to occur. Subsequently, electroplating is applied from above the resist to form a conductor pattern.

Any type of electrolytic plating may be used as long as it is a conductor, but silver, gold, copper, nickel, tin, etc. are preferred, and copper is particularly preferred from the standpoint of conductivity and economy. Examples of copper electrolytic plating include copper cyanide plating, copper pyrophosphate plating, copper sulfate plating, copper borofluoride plating, and copper pyrophosphate plating is particularly preferred. When electrolytically plating fine patterns, an important factor is the cathode current density. If the cathode current density is small, the film becomes thicker in the width direction than in the thickness direction, and the cathode current density is 3A/
d% or more, especially 5A/dnf or more, even 8A/dnf
The above is preferable, and increasing the cathode current density suppresses thickening in the width direction. The higher the cathode current density, the better.
Pulse meshing is also preferably used. The upper limit of the cathode current density is determined by burnout, and is preferably 50 A/d rrr or less.

Electrolytic plating is performed on a thin metal plate masked with a resist, and the thin metal plate is pasted on an insulating substrate with the thin metal plate facing up, or an adhesive is applied on the electrolytic plated layer without using a substrate, and after curing. Then apply adhesive and stick them together directly.

Adhesives include polyester-isocyanate-based, phenolic resin-butyral-based, phenolic resin-nitrile rubber-based, epoxy-nylon-based, and epoxy-nitrile rubber-based adhesives, which have excellent heat resistance, moisture resistance, and adhesive properties. Preferred are epoxy-nitrile rubber adhesives and phenolic resin-nitrile rubber adhesives. The film thickness of the adhesive is 1 to 200 μm for high density and adhesive properties.
A particularly preferred range is 2 to 100 μm.

Next, in order to form a through hole, first drill a hole for the through hole, then perform pretreatment with an activating solution for electroless plating, and then perform electroless metal thin plate removal and electrolytic plating, or , through-hole conduction is performed by removing the metal thin plate and electroless Metsky electrolytic plating. In this way, (i) the step of drilling for through holes;
(ii) a step of performing pretreatment with an activating solution for electroless plating, (iii) a step of performing electroless plating, (
iv) As long as it includes the process of making through holes conductive by electrolytic plating, there is no problem even if there is another process between each of these processes, or another process is included before or after all of these processes. do not have.

The through holes may be formed by any method as long as no particles or debris are generated and the conductor layer around the hole does not peel off from the insulating layer, for example, a drill or punch may be used.

In the activation process for electroless plating, a normal activator for electroless plating is used, but when the metal sheet is aluminum, zinc, or tin, a normal activator cannot be used and The bath should be kept in a neutral region with a pH of 4 to 1 to prevent the metal thin plate from eluting and significantly deteriorating the bath, or from eluting all the metal thin plates and activating parts other than the conductor of the circuit.
0, especially those that can be controlled at pH=5 to 9.5 are used. Examples of things that can be used for this include organic palladium complexes; for example, the activating liquid is Schering's Activator Neo-Gantt 834, and the reducing liquid is Schering's Glueducer Neo-Gantt WA with sulfuric acid and oxalic acid, respectively. It can be used after adjusting the pH. In addition, pre-treatment for activation treatment includes a degreasing process using a surface activator to remove dirt from the thin metal plate or the inner wall of the through hole, and a process on the rough surface to improve the adhesion of metal deposited by electroless plating. Therefore, it is better to provide a soft etching process consisting of an aqueous ammonium persulfate solution.

As for the type of electroless plating, copper is preferable from the point of view of conductivity and economy, but any nickel, silver, or ring conductor may be used. If the metal sheet is aluminum, zinc, or tin,
Metal thin plate removal - If you use the electroless plating process, you can use a normal electroless plating solution, but in the case of the electroless meso-key metal plate removal process, use an electroless plating solution in the neutral range, pH = 4 to 10. There is a need to. For example, in the case of nickel, Schumer S-
680 etc.

To remove the metal thin plate, it is possible to directly peel it off, but in the case of fine patterns, it is preferable to use acid, alkali, or the like to etch it. In this case, it is preferable that the etching solution dissolves substantially only the thin metal plate.

In the second electrolytic plating, the conductive part on the inner wall of the long hole is plated to a thick and uniform thickness. The type and method of electrolytic plating are the same as the first electrolytic plating described above, and although different metals may be used for the first and second times, it is preferable that they be the same metal.

The product obtained as described above may be coated with a resin to prevent oxidation and maintain insulation on the surface. In this case, the resin used is epoxy, once, etc.

Furthermore, by widening the conductor width of a portion of the coil, it is possible to reduce the coil resistance or to concentrate the portion of the coil pattern that makes a large contribution to the motor torque in a certain area without increasing the coil resistance.

Particularly in flat brushless motors, the narrower the lines in the direction parallel to the radius of the coil of each pole are concentrated, the larger the l*lux becomes, but the thinner the lines are, the higher the coil resistance becomes. Therefore, the lines parallel to the radius are concentrated in a narrow width, and the lines in the circumferential direction are made as wide as space allows to keep the resistance low. As a result, a motor with large torque and high efficiency can be manufactured as a motor coil.

(Example 1) A negative resist "Microresist 747-" manufactured by Eastman Co., Ltd. was coated on a thin aluminum plate with a film thickness of 60 μm.
After drying 110cStJ, apply it to a film thickness of 5 μm, pre-bake it, expose it to a high-pressure mercury lamp through a coil pattern mask (line pitch is 340 μm), develop it using a special developer and rinse solution, Post-baking was performed to form a resist with a pitch of 340 μm, leaving a width of 18 μm.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Murata Co., Ltd., a thin aluminum plate was used as a cathode, and the current density was initially 0.5.
After copper plating with an average film thickness of 2 μm at A/dm, the current density was increased to 6 A/dn and plating was performed for 135 minutes to form a total of 180 μm thick copper on the circuit section.
From both sides of an insulating substrate, phenol resin-nitrile rubber adhesive rXA564-4J manufactured by Bostik was applied to both sides of DuPont's polyimide film "Kapton" (film thickness 25 μm) so that the film thickness after drying was 5 μm. ,
The electrolytically plated product was attached by thermocompression bonding at 150° C. for 30 minutes with the aluminum thin plate on the outside, and then a hole with a diameter of 0.70 mm was drilled in the through hole forming portion. Immediately after that, activation treatment was performed using Schering's pH-adjusted activation liquid activator Neogant 834 and reducing liquid reducer Neogant WA, and then the aluminum thin plate was diluted with 36% by weight hydrochloric acid in water. It was removed by etching with a diluted solution. After that, electroless copper plating (MK-430 manufactured by Muromachi Kagaku Co., Ltd.) was performed, and then copper plating was performed to a film thickness of 180 μm at a current density of 6 A/dry using a birophosphate copper plating solution manufactured by Versho Murata Co., Ltd.

The average conductor thickness of the completed printed coil is 360 μm.
The average conductor width was 295 μm, and the average gap was 45 μm. Further, when the through hole was cut and a cross-sectional photograph was taken, the inner wall of the through hole was 245 μm thick and flat, and it was found that it closely covered the concave and convex insulating layer. 250 printed coils with 8 through holes were connected in series, and one cycle consisted of processing at 120℃ for 60 minutes and then -60℃ for 60 minutes while flowing a constant current of 1mA. When the resistance was measured, there was no change greater than the change in resistance due to the temperature coefficient of copper (approximately 0.4%/deg).

(Example 2) A negative resist "Microresist 747-" manufactured by Eastman Co., Ltd. was coated on a thin aluminum plate with a film thickness of 60 μm.
After drying 110cStJ, apply it to a film thickness of 5 μm, brebake, and make a coil pattern mask (line pitch 2).
30 μm) with a high-pressure mercury lamp, developed using a special developer and rinse solution, and post-baked to form a resist with a pitch of 230 μm, leaving a width of 24 μm.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Murata Co., Ltd., a thin aluminum plate was used as a cathode, and the current density was initially 0.5.
After copper plating with an average thickness of 2 μm at A/drr, the current density was increased to 5A/drd and plating was performed for 36 minutes.
A copper film with a total thickness of 40 μm was formed on the circuit portion. After that, a polyimide film “Kapton” manufactured by DuPont (film thickness 25 μm) was applied.
m) phenolic resin-nitrile rubber adhesive rXA564-4J manufactured by Bostik Co., Ltd. after drying, the film thickness is 5μ
The electrolytically plated material was attached to both sides of the insulating substrate coated with a thickness of 0.0 m, with the aluminum thin plate facing outward, by thermocompression at 150°C for 30 minutes, and then drilled into the through-hole formation area. After drilling a hole of 70mm diameter, I activated it using Schering's activating liquid activator Neogant 834 and reducing liquid reducer Neogant WA, since the pH had already been adjusted, and then attached a thin aluminum plate. It was removed by etching with a solution prepared by diluting 36% by weight hydrochloric acid with water at a ratio of 2:3. After that, electroless copper plating (MK-430 manufactured by Muromachi Chemical Co., Ltd.) was performed, and then a current density of 5A was applied using a copper pyrophosphate plating solution manufactured by Versho Murata Co., Ltd.
The conductor thickness of the completed printed coil was 80 μm on average, the conductor width was 86 μm on average, and the gap was 144 μm on average. When the through-hole was cut and a cross-sectional photograph was taken, the inner wall of the through-hole was found to be 59 μm thick and flat, and closely covered the convex insulating layer in a concave manner. After 250 printed coils with 8 through holes are connected in series and treated at 120℃ for 60 minutes while flowing a constant current of 1mA =
One cycle was 60°C for 60 minutes, and the resistance was continuously measured during the process. There was no change.

(Example 3) A negative resist “Microresist 747-
110 c St" was dried, coated to a film thickness of 5 μm, prebaked, exposed to a high-pressure mercury lamp through a coil pattern mask (line pinch 120 μm), and developed using a special developer and rinse solution. Then, post-baking was performed to form a resist with a pitch of 170 μm, leaving a width of 20 μm.

Next, using a copper pyrophosphate solution manufactured by Barshaw Murata Co., Ltd., a thin tin plate was used as a cathode, and an initial current density of 0.1 A/dr was applied.
After copper plating with an average thickness of 0.5 μm using RF, the current density was increased to 5 A/d rrr and plating was performed for 36 minutes.
A total of 40 lm of copper with a thickness of 1 m was formed in the circuit portion.

After that, the conductive pattern surface was overcoated with an insulating face (WI-640 manufactured by Hitachi Chemical Co., Ltd.), and
PO, using BP-0081 boxy resin adhesive,
Attach the two sheets with the thin tin plate on the outside. Next, a hole of 0.70 mφ was drilled in the through-hole forming portion. After that, Schering's activation liquid activator Neogant 834, which had already adjusted its pH, and reducing liquid reducer.
・Activate using Neogun 1-WA, then-
The thin tin plate was removed by etching with a 5% by weight aqueous sodium hydroxide solution. Then electroless copper plating (M made by Muromachi Kagaku)
K-430), and then copper plating was performed to a film thickness of 40 μm at a current density of 5 A/drrr using a birophosphate copper plating solution manufactured by Versho Murata Co., Ltd.

The average conductor thickness of the completed printed coil was 80 μm, the average conductor width was 82 μm, and the average gap was 38 μm. Further, when the through hole was cut and a cross-sectional photograph was taken, the inner wall of the through hole was 58 μm thick and flat, and it was found that the convex insulating layer was closely covered in a concave shape. 250 printed coils with 8 through holes are arranged in series,
After treatment at 120℃ for 60 minutes while flowing a constant current of 1mA -6
300 cycles of treatment were performed, with 60 minutes at 0°C as one cycle, and the resistance was continuously measured during the process.
There was no change in resistance value greater than the change due to the temperature coefficient of copper (approximately 0.4%/deg).

(Example 4) On a thin aluminum plate with a film thickness of 60 μm, a negative resist “Microresist 747-
After drying 110cStJ, apply it to a film thickness of 5 μm, pre-bake, and make a pattern mask (line pitch 320
micrometer) with a high-pressure mercury lamp, developed using a special developer and rinse solution, and post-baked.
A resist was formed with a pitch of 320 μm, leaving a width of 218 μm.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Gyoda Co., Ltd., a thin tin plate was used as a cathode, and the current density was initially 0, IA/dr.
After plating with an average film thickness of 0.5 μmw4 at rr, the current density was increased to 5 A/drrr and plating was carried out for 36 minutes to form a total of 40 μm thick copper on the circuit portion. After that, the conductive pattern surface was overcoated with an insulating face (Wl-640 manufactured by Hitachi Chemical Co., Ltd.), and SC-do PO1EP-00 manufactured by Cemedine Co., Ltd.
Using an 8-layer poxy resin adhesive, a hole of 0.701φ was drilled in the 0th order through-hole formation area where the two sheets were pasted together with the thin tin plate on the outside. Thereafter, activation treatment was carried out using Schering's pH-adjusted activation liquid activator Neogant 834 and reducing liquid reducer Neogant WA, and then the thin tin plate was removed by etching with a 5% by weight aqueous sodium hydroxide solution. . After that, electroless copper plating (MK-430 manufactured by Muromachi Kagaku Co., Ltd.) was performed, and then copper plating with a film thickness of 40 um was performed at a current density of 5 A/drrr using a birophosphate copper plating solution manufactured by Versho Murata Co., Ltd.

The completed printed coil had an average conductor thickness of 80 μm, an average conductor width of 2801 Jm, and an average gap of 40 μm. Further, when the through hole was cut and a cross-sectional photograph was taken, the inner wall of the through hole was 60 μm thick and flat, and it was found that the convex insulating layer was closely covered with a concave shape. 250 printed coils with 8 through holes were connected in series, and 300 cycles were performed with a constant current of 1 mA flowing at 120°C for 60 minutes, followed by -60°C for 60 minutes. When the resistance was measured, there was no change greater than the change in resistance due to the temperature coefficient of copper (approximately 0.4%/deg).

(Example 5) A negative resist "Microresist 747-" manufactured by Eastman Co., Ltd. was coated on a thin aluminum plate with a film thickness of 60 μm.
After drying 110cStJ, apply it to a film thickness of 5μm, brebake, and make a pattern mask (line pitch 190μm).
m) with a high-pressure mercury lamp, - developed using a special developer and rinse solution, and post-baked.
A resist was formed with a pitch of 90 μm, leaving a width of 29 μm.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Gyoda Co., Ltd., a thin tin plate was used as a cathode, and an initial current density of 0.1 A/dn was applied.
? After copper plating with an average film thickness of 0.5 μm, the current density was set to 5 μm.
Increase A/d rd and plating for 71 minutes.
Copper with a total thickness of 80 μm was formed in the circuit portion.

After that, the conductive pattern surface was overcoated with an insulating face (WI-640 manufactured by Hitachi Chemical), and 5G-E manufactured by Cemedine was applied.
Using POlEP-008 poxy resin adhesive, stick the two sheets together with the thin tin plate facing outside. Next, a hole of 0.70 mφ was drilled in the through-hole forming portion. After that, Schering's activating liquid activator Neogant 834, which had already been adjusted to pH, and reducing liquid reducer.
Neogan) WA was used for activation treatment, and then the thin tin plate was removed by etching with a 5% by weight aqueous sodium hydroxide solution. After that, electroless copper plating (MK-4 manufactured by Kuai Kagaku Co., Ltd.)
30), and then using a copper pyrophosphate plating solution manufactured by Vershaw Gyoda Co., Ltd., a film thickness of 80 mm was applied at a current density of 5 A/drn'.
μm copper plating was performed.

The average conductor thickness of the completed printed coil is 160 μm.
The average conductor width was 152 μm, and the average gap was 38 μm. When the through-hole was cut and a cross-sectional photograph was taken, the inner wall of the through-hole was found to be 105 μm thick and flat, and closely covered the convex insulating layer in a concave manner. 250 printed coils with 8 through holes were connected in series, and 300 cycles were performed with a constant current of 1 mA flowing at 120°C for 60 minutes, followed by -60°C for 60 minutes. When the resistance was measured, there was no change greater than the change in resistance due to the temperature coefficient of copper (approximately 0.4%/deg).

(Example 6) On a thin aluminum plate with a film thickness of 60 μm, a negative resist “Marikroresist 7” manufactured by Eastman Co., Ltd. was applied.
After drying 47-110cStJ, apply it to a film thickness of 5 μm, bake it, expose it to a high-pressure mercury lamp through a pattern mask, develop it using a special developer and rinse solution, post-bake, and carry out. Compared to the coil of Example 5, the outer diameter is 0.86 m larger and the inner diameter is 1.29 m smaller, and the coil has a long radial component effective for motor torque, and the line pitch is 190 μm in the radial direction, and the outer circumferential side is 2.
A resist pattern was formed with a pitch of 38 μm and a pitch of 261 μm on the inner peripheral side.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Gyoda Co., Ltd., a thin tin plate was used as a cathode, and an initial current density of 0.1 A/dr was applied.
Average film thickness at RL: 0.5. After um copper plating, the current density was increased to 5A/dnf and plating was performed for 71 minutes, totaling 8
Copper with a thickness of 0 μm was formed on the circuit portion.

After that, the conductive pattern surface was overcoated with an insulating face (Wl-640 manufactured by Hitachi Chemical Co., Ltd.), and 5G-E manufactured by Cemedine Co., Ltd.
Using PO, EP-008 poxy resin adhesive, stick the two sheets together with the thin tin plate on the outside. Next, a hole of 0.701 mφ was drilled in the through-hole forming part. After that, Schering's activation liquid activator Neogant 834, which had already been pH adjusted, and the reducing liquid reducer.
- Activation treatment was performed using Neogant WA, and then the thin tin plate was removed by etching with a 5% by weight aqueous sodium hydroxide solution. After that, electroless copper plating (MK-
430), and then using a birophosphate copper plating solution manufactured by Versho Murata Co., Ltd., a film thickness of 80 μm was applied at a current density of 5 A/dm.
Copper plating was performed.

The average conductor thickness of the completed printed coil is 160 μm.
The average conductor width is 198μm at the outer periphery and 40μm per gap.
, an average of 224 μm and a gap of 37 μm in the inner circumference, and an average of 153 μm and a gap of 37 μm in the radial direction.

Furthermore, compared to the printed coil of Example 5, the coil wire length was improved by 9% and the torque was improved by 8%, but the increase in coil resistance remained at 1%. Also, when the through hole was cut and a cross-sectional photograph was taken, the inner wall of the through hole was 105 μm.
It was thick and flat, and closely covered the convex insulating layer in a concave shape. 250 printed coils with 8 through-holes are connected in series, and 1 mA of constant current is applied.
The treatment was carried out for 300 cycles, with 60 minutes of treatment at 20°C followed by 60 minutes of treatment at -60°C.The resistance was continuously measured during the process, and the temperature coefficient of copper (approximately 0.4%
/deg) did not change more than the change in resistance value.

<Effects of the Invention> The double-sided thick film fine print coil for a small motor obtained as described above has high fine density and low resistance, so the resulting motor has large torque and high efficiency. Furthermore, since the through holes are highly reliable, the resulting motor is also highly reliable.

Claims (3)

[Claims] (1) A small motor that has a plurality of substantially identical spiral coil conductors on both sides of an insulating sheet, and the opposing spiral coil conductors on both sides are electrically connected to each other by a through hole penetrating the above insulating sheet. A double-sided thick-film fine coil for use with (i) coil conductor thickness of 60 to 400μ
m, (ii) the coil conductor width is 10 to 300 μm, (iii) the gap is 150 μm or less, and (iv) the conductor covering the insulating layer in the through-hole portion has a substantially uniform thickness, A double-sided thick-film fine coil for a small motor, characterized in that the coil is in close contact with the insulating layer. (2) A patent claim in which, in the through-hole land portion, an insulating layer protrudes convexly at the center of the through-hole, and the convex insulating layer is tightly covered with a concave conductor having a substantially uniform thickness. A double-sided thick-film fine coil for small motors as described in item 1. (3) A double-sided thick-film fine coil for a small motor according to claim 1, in which the width of the conductor pattern is partially wide.