JP2002148002A - Displacement detector and its surface treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement detector which has a wiring-board structure capable of dealing with miniaturization. SOLUTION: A resin sheet 31a and a resin sheet 31b are arranged on, heated and pressurized to. Both faces of a readout head 2 are constituted by using a printed-wiring board 20 in which a transmitting electrode 22 and a signal interconnection 23 connected through a through hole 24 are formed on both faces. The through hole 24 is filled with a resin, and its surface is flattened at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detecting apparatus for detecting displacement by using electrical or magnetic coupling between two members which move relatively, and more particularly to a method for treating a surface of a member using a wiring board. About.

[0002]

2. Description of the Related Art FIG. 1 is an exploded perspective view of a capacitance type displacement detector. As shown in the figure, the displacement detector includes a scale 1 and a read head 2 which is disposed so as to be relatively movable with respect to the scale 1. Scale 1
Is formed by arranging transfer electrodes 11 on a scale member 10 at a predetermined pitch. The read head 2 is constituted by using a double-sided printed wiring board 20, and a transmission electrode group 22 which is capacitively coupled to the transfer electrode 11 on a surface facing the scale 1.
And the receiving electrode 21 are formed, and the signal wiring 2 is formed on the opposite surface.
3 is formed.

[0005] A transmission electrode 22 and a reception electrode 21 formed on one surface of a printed wiring board 20 are connected to signal wirings 23 formed on the other surface via through holes 24. FIG. 2 is a cross-sectional view showing how signals are transmitted between the read head 2 and the scale 1 and how the double-sided electrode wires of the read head 2 are connected through the through holes 24.

More specifically, the transmission electrode group 22 of the read head 2 has, for example, eight transmission signal terminals S1, S2,
.., And a plurality of sets of transmission electrodes to which transmission signals having different phases given from S8 are supplied. In this case, it is important that the coupling between the transmission electrode, the transfer electrode, and the reception electrode of each phase is uniform in order to obtain a displacement signal with a good S / N.

However, if the size of the displacement detecting device is reduced, the scale pitch is reduced, and the transmitting electrode group 22 is arranged with an extremely narrow electrode width, the existence of the through hole 24 will The effect on the bond cannot be ignored. As a countermeasure, conventionally, (1) the position of the through-hole is devised to balance the capacitive coupling between each transmission electrode and the transfer electrode. (2) The through-hole is plated with copper a plurality of times. A method of reducing the hole diameter has been adopted.

[0006]

However, the method (1) cannot be applied to a small displacement detecting device in which the width of the transmitting electrode is reduced to about the same as the diameter of the through hole.
Also, the method (2) cannot actually completely fill the through hole even if copper plating is performed a plurality of times,
There is also a problem that the production cost is increased. In addition, when copper plating is performed a plurality of times, a short circuit occurs between the electrode wirings having a narrow pitch, and the design rule of the wiring part is limited. A similar problem exists not only in a capacitance type displacement detection device but also in a displacement detection device using electromagnetic coupling.

The present invention has been made in view of the above circumstances, and provides a displacement detecting device having a wiring board structure capable of coping with miniaturization, and a method for treating the surface of such a wiring board. The purpose is.

[0008]

According to the present invention, there is provided a displacement detecting apparatus for detecting a displacement by a relative movement of a first member and a second member, wherein at least one of the first member and the second member includes: It is characterized by having a wiring substrate on which wiring is formed, and a resin sheet laminated by applying pressure so that at least one surface of the wiring substrate is filled with irregularities and the surface becomes flat.

The present invention also provides a displacement detection device for detecting a displacement by a relative movement between a first member and a second member, wherein at least one of the first member and the second member includes:
A wiring board on which wiring is formed on both sides, a wiring board having the wiring on both sides connected by through holes, and a resin laminated by applying pressure so as to fill the through holes on at least one surface of the wiring board and cover the wirings And a sheet. In this case, preferably, the resin sheet is laminated so as to fill the irregularities on the surface of the wiring board and to make the surface flat.

[0010] In the present invention, the first member and the second member are, specifically, a scale and a read head for outputting a displacement signal by electric or magnetic coupling with the scale.

The present invention also has a scale, and a read head which is disposed so as to be relatively movable with respect to the scale and outputs a displacement signal by electric or magnetic coupling with the scale. One is a surface treatment method in a displacement detection device configured with a wiring substrate in which wiring is formed on both surfaces and the wiring on both surfaces is connected by through holes, and a resin sheet is formed on at least one surface of the wiring substrate. By laminating under pressure, the through holes are filled and the surface is flattened.

According to the present invention, for example, a read head constituted by a wiring board is flattened by press lamination of a resin sheet, and in the case of a double-sided wiring board, a through hole is filled with a resin. In the case of a fine electrode width such that the diameter of the through hole cannot be ignored, the effect of reducing the disturbance of the electric field in the through hole by embedding the through hole with a resin is great. This allows
Variations due to through holes in capacitive coupling between the fine pitch electrode wiring and the opposing electrode can be reduced, and a good displacement signal can be obtained. Moreover, the surface treatment process is simple, and the increase in manufacturing cost does not matter.

In the present invention, preferably, a resin sheet in which glass fibers woven in a lattice are embedded. By pressing such a resin sheet containing glass fibers and laminating it on a wiring board, the unevenness on the surface is filled, and the through holes are filled and flattened. Also, by bonding the flattened surface to the glass plate so as to be tightly contacted, the warpage of the wiring board is corrected. Therefore, not only the balance of signal transmission from a large number of transmission electrodes is improved, but also the vacuum suction operation of the read head at the time of assembling the displacement detection device is ensured. In particular, when the resin sheet is laminated on both sides of the wiring board by pressing, both sides can be flattened and the warpage of the wiring board can be corrected. Further, the through holes can be more reliably embedded. In the present invention, the flatness can be further improved by further applying a resist on the surface of the resin sheet laminated on the wiring board.

The present invention further comprises a scale, and a read head which is disposed so as to be relatively movable with respect to the scale and outputs a displacement signal due to electrical or magnetic coupling with the scale, wherein at least one of the skate read heads is provided. One is a surface treatment method in a displacement detection device configured by a wiring substrate in which wiring is formed on both surfaces and the wiring on both surfaces is connected by through holes, and a plurality of times is formed on at least one surface of the wiring substrate. It is characterized in that the surface is flattened by applying a resist.

Although the step of the through-hole cannot be filled by a single application of the resist, the end of the through-hole can be embedded and the surface of the wiring substrate can be flattened by repeating the resist application a plurality of times. According to this method as well, it is possible to reduce the variation caused by the through holes in the fine pitch electrode wiring and obtain a good displacement signal. In addition, the surface treatment process is simpler than the case where copper plating is repeated, and the increase in manufacturing cost is not a problem, and there is no danger of wiring short-circuiting unlike copper plating. Does not disturb.

In this case, preferably, the resist application is performed a plurality of times so that the viscosity of the resist is increased in each application step. As a result, the resist can be buried in the through holes as much as possible in the first resist application, and the surface can be finally made flat. If you need more,
After applying resist several times, by polishing the surface,
Further flatness can be obtained.

In this specification, "wiring" of a wiring board is used in a broad sense including "electrode".

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 3A to 3D show a surface treatment step of the read head 2 of the capacitance type displacement detection device described with reference to FIG. The read head 2 is constituted by the double-sided printed wiring board 20 as described above,
The transmission electrode 22 on one side and the signal wiring 23 on the other side are connected via a through hole 24.

On both sides of such a wiring board 20, FIG.
As shown in (a), the resin sheets 31a and 31b are overlaid. The resin sheets 31a and 31b are so-called prepregs usually used as interior materials of a multilayer printed circuit board, and are made by impregnating a resin into glass fibers 30 woven in a lattice shape. An epoxy resin is typically used as the resin material.

Then, the wiring board 20 is attached to the resin sheet 31.
As shown in FIG. 3 (b), the material sandwiched between a and 31b is further sandwiched between press plates 32a and 32b, and heated and pressed in a vacuum. Thereby, the resin sheets 31a,
The resin 31b melts out and flows into the step portion and the through hole 24, and as shown in FIG.
The surface irregularities are flattened in a state where 4 is embedded in the resin. In addition, by laminating the resin sheets 31a and 31b while applying pressure while heating, the resin of the resin sheet melts out, acts like an adhesive, and the substrate and the resin sheet are firmly bonded.

As described above, the resin sheet 31 is vacuumed.
When a and 31b are bonded to the wiring board 20, no air remains inside the through hole 24 and the through hole 24
It becomes possible to pour the resin into the inside. If air remains in the through-hole, the air may expand and burst when the temperature rises later, causing breakage. However, such a danger is eliminated by processing in a vacuum. In the steps so far, the surface treatment of the read head 2 may be completed, but if necessary, as shown in FIG. 3D, a resist 33 is applied to both surfaces on which the resin sheets 31a and 31b are laminated.
a, 33b are applied.

According to such a process, it is possible to reduce variations in capacitive coupling caused by through holes in the transmission electrode. The surface treatment step is only one heating and pressing step, and is simpler than the case where copper plating is repeated. Further, unlike the case where copper plating is overlaid, it does not hinder the miniaturization of the wiring pitch. Further, the warping of the wiring board is not performed in the pressing step, which also contributes to the improvement of the signal transmission balance. As shown in FIG. 3D, if a resist is applied to the final surface, environmental resistance can be further improved.

The same technique can be applied to the case of manufacturing a multilayer printed wiring board. FIG. 4 shows an example in which two printed wiring boards 20a and 20b are stacked. In this case, as shown in FIG. 4A, the wiring boards 20a, 20b
Sheets 31a, 31b for flattening the surface on both sides
And a resin sheet 31c as an interior material between the wiring boards 20a and 20b.

The resin sheets 31a to 31c are assumed to have lattice-shaped glass fibers embedded therein as in the previous embodiment. Then, this is heated and pressed in a vacuum while being sandwiched between press plates, as in the previous embodiment. As a result, FIG.
As shown in (b), a read head composed of a multilayer printed wiring board whose surfaces are smoothed by filling the through holes 24 of the wiring boards 20a and 20b with resin is obtained.

FIGS. 5A to 5C show another surface treatment step for the same read head 2. FIG. FIG.
As shown in (a), a resist 41a is applied to both surfaces of the wiring board 20 by a spin coating method or the like. Resist 4
After lightly baking 1a, as shown in FIG. 5B, a second resist 41b is applied to both sides. Furthermore,
After light baking, a third resist 41c is applied to both sides as shown in FIG.

As described above, by repeating the resist application a plurality of times, it is possible to bury the steps and at least the ends of the through holes 24 and to planarize the surface.
In particular, by increasing the viscosity of the resist in the first coating step to be low and increasing in order, through hole filling and flattening are ensured. This surface treatment method also has a simpler process than the method of repeating copper plating, and does not limit the wiring pitch unlike copper plating.

However, unlike the method of applying a resin sheet in a vacuum, this resist coating method cannot embed resin inside the through hole. Therefore, even if it is once flattened, in the process of thermosetting, the expansion of the cavity formed between the resists of multiple layers and the cavity remaining in the through hole, etc.
As shown in FIG. 6A, there is a possibility that unevenness may be formed, or the cavity may be ruptured as shown in FIG. 6B.

On the other hand, by optimizing the thickness, the baking treatment, and the number of coating steps in each resist coating step, it is possible to prevent at least the cavity rupture as shown in FIG. Then, as shown in FIG. 7, the unevenness as shown in FIG. 6A is flattened by polishing the surface using an abrasive 51. As a result, the surface of the read head can be reliably flattened.

In the above embodiments, the read head of the capacitance type displacement detecting device has been described. However, the present invention can be similarly applied to an inductive displacement detecting device. As shown in FIG. 8, the inductive type displacement detecting device includes a scale 1 and a read head 2 as in the case of the capacitance type.

A magnetic field modulator 74 is arranged on the scale 1 at a predetermined pitch.
And a receiving coil 72. When the read head 2 is configured using the double-sided printed wiring board 20,
The receiving coil 72 is configured by connecting a wiring 72 a indicated by a solid line formed on one surface of the wiring board 20 and a wiring 72 b indicated by a broken line formed on the other surface via a through hole 73. .

In the case of such an inductive read head as well, when the scale pitch is reduced and the wiring width and pitch of the coil are reduced, the presence of the through-hole 73 adversely affects the characteristics. Therefore, it is effective to apply the surface treatment method described above for the capacitance type read head. In particular, by performing pressure lamination of a resin sheet containing glass fibers, environmental resistance such as strength, abrasion resistance, and water resistance is greatly improved.

In the embodiments described above, the case where the wiring board is used on the read head side has been described. However, there is also a displacement detecting apparatus using the wiring board on the scale side. Fig. 9 shows such an example.
And FIG. This is a development of the inductive displacement detection device shown in FIG. 8, and includes a read head 220 and a scale 210 (Japanese Patent Laid-Open No. 10-31878).
No. 1). The read head 220 has a transmission winding 222 having a first transmission winding part 223A and a second transmission winding part 223B. Terminal 222 of transmission winding 222
A and 222B are connected to the excitation signal generator 150.
First and second reception windings 224 and 226 are provided between the two transmission winding units 223A and 223B. These receiving windings 224 and 226 are formed by conductor segments 228 and 229 formed on both surfaces of the wiring board. These conductor segments 228 and 229 are
30 to form a positive loop 232 and a negative loop 234.

The scale 210 receives the primary magnetic field from the transmission winding, generates an induced current, and generates coupling loops 212, 216 for generating a secondary magnetic field to be coupled to the reception winding.
214 and 218 are formed. This scale 210
Is made by bonding two wiring boards 410 shown in FIGS. 10A and 10B. That is, the conductor segments 409, 410, 40
6, 408 are formed and bonded together, and the corresponding segments are connected via through holes 407 to form coupling loops 212, 216, 214, 218.

In the case of such a displacement detecting device configuration, it is effective to apply the surface treatment described in each of the above embodiments not only to the read head 220 but also to the scale 210.

[0035]

As described above, according to the present invention, the surface of a read head or a scale formed by using a printed wiring board is flattened, and in the case of double-sided wiring, the through holes are filled and flattened. Thereby, the characteristics of the small displacement detection device can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a capacitance type displacement detection device.

FIG. 2 is a cross-sectional view showing a signal transmission state of the displacement detection device and a structure of a read head.

FIG. 3 is a diagram showing a surface treatment step of a read head according to an embodiment of the present invention.

FIG. 4 is a diagram showing a surface treatment step of a read head according to another embodiment of the present invention.

FIG. 5 is a view showing a surface treatment step of a read head according to another embodiment of the present invention.

FIG. 6 is a diagram for explaining a problem of resist coating of the embodiment.

FIG. 7 is a view showing a preferred final polishing step of the embodiment.

FIG. 8 is a diagram showing a configuration of an inductive displacement detection device.

FIG. 9 is a diagram showing another configuration of an inductive displacement detection device.

FIG. 10 is a diagram showing a structure of a scale of the displacement detection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Scale, 2 ... Read head, 20 ... Printed wiring board, 21 ... Receiving electrode, 22 ... Transmitting electrode, 23 ... Signal wiring, 24 ... Through hole, 31a, 31b ... Resin sheet, 20 ... Glass fiber, 32a, 32b … Press plate,
33a, 33b ... resist, 41a, 41b, 41c ...
Resist.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01D 5/245 101 G01D 5/245 101Z

Claims (15)

[Claims] 1. A displacement detection device for detecting displacement by relative movement between a first member and a second member, wherein at least one of the first member and the second member is connected to a wiring board on which a wiring is formed. A resin sheet laminated by applying pressure so that at least one surface of the wiring board is filled with irregularities and the surface is flattened. 2. A displacement detection device for detecting displacement by relative movement of a first member and a second member, wherein at least one of the first member and the second member has wiring formed on both surfaces thereof. A wiring board having wiring on both sides connected by through holes, and a resin sheet laminated on at least one surface of the wiring board by filling the through holes and applying pressure so as to cover the wiring. And a displacement detection device. 3. A scale, and a read head which is disposed so as to be relatively movable with respect to the scale and outputs a displacement signal by electric or magnetic coupling with the scale, wherein at least one of the scale and the read head is provided. A wiring was formed on both sides, and the wiring on both sides was laminated by applying pressure to fill the through hole and cover the wiring on at least one surface of the wiring board, the wiring being connected by through holes. A displacement detection device comprising: a resin sheet. 4. The displacement according to claim 2, wherein the resin sheet is laminated by applying pressure to at least one surface of the wiring substrate so as to fill the unevenness of the surface so as to be flat. Detection device. 5. The displacement detecting device according to claim 1, wherein the resin sheet has a structure in which glass fibers woven in a lattice are embedded. 6. The displacement detecting device according to claim 1, wherein resin sheets are laminated under pressure on both surfaces of the wiring board. 7. The displacement detection device according to claim 1, wherein a resist is further applied on the resin sheet. 8. The scale has a scale substrate and transfer electrodes arranged and formed on the scale substrate at a predetermined pitch. The read head is formed on one surface of the wiring substrate, and the transfer electrode is formed on the scale substrate. A transmission electrode group and a reception electrode that are capacitively coupled to, and a signal wiring formed on the other surface of the wiring substrate and connected to the transmission electrode group and the reception electrode via a through hole; 4. The displacement detection device according to claim 3, wherein the readout head is pressurized and laminated on the surface on the transmission electrode group and the reception electrode side. 9. A scale comprising: a scale; and a read head which is disposed so as to be relatively movable with respect to the scale and outputs a displacement signal by electric or magnetic coupling with the scale, wherein at least one of the scale and the read head is provided. In a displacement detection device configured with a wiring board in which wiring is formed on both surfaces and the wiring on both surfaces is connected by through holes, by pressing and laminating a resin sheet on at least one surface of the wiring substrate, A surface treatment method for a displacement detecting device, wherein the through hole is filled and the surface is flattened. 10. The surface treatment method for a displacement detection device according to claim 9, wherein a resin sheet is pressed and laminated on both surfaces of the wiring board to fill the through holes and flatten the surface. . 11. The surface treatment method for a displacement detection device according to claim 9, wherein the resin sheet has a structure in which glass fibers woven in a lattice shape are embedded. 12. The surface treatment method for a displacement detection device according to claim 9, further comprising applying a resist to a surface of the resin sheet laminated on the wiring board. 13. A scale comprising: a scale; and a read head which is disposed so as to be relatively movable with respect to the scale and outputs a displacement signal due to electrical or magnetic coupling with the scale.
In at least one of the scale and the read head, an electrode wiring is formed on both surfaces, and in a displacement detection device configured by a wiring substrate in which the electrode wirings on both surfaces are connected by through holes, at least one surface of the wiring substrate A surface treatment method for a displacement detection device, wherein a surface is planarized by performing resist application a plurality of times. 14. The surface treatment method for a displacement detection device according to claim 13, wherein in the resist application in a plurality of times, the viscosity of the resist is increased in each application step. 15. The surface treatment method for a displacement detection device according to claim 13, wherein after the resist is applied a plurality of times, the surface is further polished and flattened.