JPH04326579A - Bonding method for piezoelelctric vibrator - Google Patents

Abstract

PURPOSE:To prevent short circuits caused by the overflow of an adhesive agent and to enable the manufacture of thin-plate piezoelectric vibrators having an excellent insulating property without taking special measures, in the case of bonding flexible printed boards for the thin-plate piezoelectric vibrators having protrusions partially on the surfaces to be bonded. CONSTITUTION:A bonding method for piezoelectric vibrators; a nonprinting pattern section 8 is provided at the corresponding parts to the protrusions of a printing pattern for printing an adhesive agent by a screen printing method, the nonprinting pattern such as circles, etc., in the section 8 has a pattern pitch 15 which corresponds to a proper quantity of the adhesive agent for a protrusion, and the adhesive agent is applied by the screen printing method using this pattern. When a flexible printed board for a thin-plate piezoelectric vibrator is bonded, short circuits do not occur by the overflow of the adhesive agent, and an insulating property is secured even in a high-temperature state. Accordingly, high-reliability piezoelectric vibrators can be obtained.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a piezoelectric vibrator used in manufacturing a piezoelectric vibrator by bonding a film-like flexible printed circuit board having partially convex portions to both sides of a thin plate-like piezoelectric vibrator element. The present invention relates to an adhesion method.

0002

[Prior Art] Conventionally, the bonding method for this type of thin plate-shaped piezoelectric vibrator has been to use Tetron or stainless steel mesh screens on both sides of the piezoelectric vibrator element to achieve a uniform thickness over the entire surface, and to bond the piezoelectric vibrator element with heat-curing epoxy. An adhesive or the like was printed, a flexible printed circuit board having convex portions was bonded to this, and the adhesive was cured by heating while applying pressure. However, due to pressurization, the amount of adhesive protruding from the convex portion of the flexible printed circuit board becomes larger than the amount protruding from other than the convex portion, and the protruding adhesive shorts between the upper and lower electrodes of the piezoelectric vibrator element. If the adhesive is cured and used as it is, there is a problem in that the insulation resistance tends to deteriorate under high humidity conditions due to the water absorption of the adhesive, and if necessary, it is necessary to take moisture-resistant measures such as silicone resin. There was a problem of lack of reliability.

0003

[Problems to be Solved by the Invention] An object of the present invention is to eliminate these drawbacks and create a pattern on an adhesive printing screen that has a large number of non-printed portions at locations corresponding to the convex portions of a flexible printed circuit board. By creating a pattern, the amount of printed adhesive is reduced, the amount of protrusion due to pressure is uniformly controlled over the entire circumference, preventing short circuits caused by the adhesive between the upper and lower electrodes of the piezoelectric vibrator element, and providing moisture resistance. An object of the present invention is to provide a method for bonding a thin plate-shaped piezoelectric vibrator, which can prevent insulation deterioration.

0004

[Means for Solving the Problems] The present invention provides a thin piezoelectric vibrator element having electrode surfaces on both sides, or a flexible printed circuit board attached to the piezoelectric vibrator element, which is bonded to the adhesive surface by screen printing. When applying an agent and bonding them together, a non-printing pattern portion including a pattern such as a round pattern or a checkered pattern is provided in the screen printing pattern at a position corresponding to the convex portion on the adhesive surface of the flexible printed circuit board. This is a piezoelectric vibrator bonding method that uses an adhesive coating method that prints a pattern and adjusts the amount of adhesive so that the amount of adhesive can be reduced by the amount corresponding to the amount that protrudes from the convex portion. be.

That is, in the present invention, an adhesive is applied to both surfaces of a thin plate-shaped piezoelectric vibrator element or to the adhesive surface of a flexible printed circuit board having a partially convex portion on the adhesive surface, and the piezoelectric vibrator element is In the method for manufacturing a piezoelectric vibrator by bonding a flexible printed circuit board and a piezoelectric vibrator element, when printing an adhesive by screen printing on the adhesive surface of the piezoelectric vibrator element or the adhesive surface of the flexible printed circuit board, the adhesive surface of the flexible printed circuit board is This is a piezoelectric vibrator bonding method characterized by screen printing an adhesive in a pattern in which non-printed portions are provided at locations corresponding to convex portions.

[0006]

[Function] When applying adhesive to the adhesive surface, in order to adjust the amount of adhesive on the part corresponding to the convex part, a non-printing part is provided at the position corresponding to the convex part of the screen printing pattern. We applied a method that allows the amount of adhesive to be adjusted locally, and when the whole is pasted together and crimped together, we devised a way to prevent short-circuiting of the adhesive between the upper and lower electrodes due to too much adhesive protruding from the periphery. This is an adhesion method.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the bonding method according to the present invention will be explained with reference to the drawings while comparing it with a conventional method. Figure 2 shows a disk-shaped thin plate piezoelectric vibrator element on which adhesive is printed, and its outer diameter is approximately 50 mm.
mm, the thickness was approximately 3 mm, and electrodes of the same size were processed on both sides. FIG. 3 shows a flexible printed circuit board 14 having a partially convex portion, in which a copper foil 3 having approximately the same size as the piezoelectric vibrator element to be bonded and a lead wire extraction portion from the copper foil are integrally molded. A part of the bonded portion of the copper foil is covered with a coverlay 2 made of a polyimide resin film having a thickness of 50 μm. This lead wire extraction part corresponds to the stress concentration part in the vibration state when the piezoelectric vibrator is driven, and has a length of about 5 mm and serves as a reinforcing part to prevent damage to the flexible printed circuit board. The copper foil 3 is attached to a base film 4 of a polyimide resin film having a diameter of about 52 mm and a thickness of about 50 μm, which is slightly larger than the piezoelectric vibrator element 1. The base film 4 is slightly larger than the piezoelectric vibrator element 1 and is designed to protect the outer periphery of the piezoelectric vibrator and the copper foil leads.

As described above, when the flexible printed circuit board 14 shown in FIG. 3 is bonded to the piezoelectric vibrator element 1 shown in FIG. It is tall and has a convex shape over the entire adhesive surface.

FIG. 4 shows a printing pattern of a Tetron mesh screen conventionally used for printing adhesives. The size is set to be approximately the same as the outer diameter of the piezoelectric vibrator element 1 shown in FIG. The thickness of the adhesive printed with the screen is:
In order to satisfy the required reliability, a coating of approximately 200 μm is applied to the area 1 where the entire printing pattern is coated.
It is designed to be 3.

FIG. 6 shows a state in which the piezoelectric vibrator element 1 and the flexible printed circuit board are bonded together when an adhesive is printed using the printing pattern shown in FIG. 4 using a conventional method. Since the adhesive 5 on the adhesive surface is cured under pressure from above and below with a force of approximately 30 kgf, the adhesive 9 that spills out at that time accumulates around the adhesive surface, but the adhesive 9 on the adhesive surface hardens. In the vicinity of the coverlay 2 corresponding to the convex portion, a short circuit occurs due to the adhesive 9 protruding from both sides of the piezoelectric vibrator element 1, and the insulation resistance in high humidity conditions decreases from 104 MΩ to 1 due to water absorption of the adhesive.
It deteriorates to 0.2 MΩ.

Next, FIG. 1 shows a printing pattern of an adhesive printing screen in an embodiment of the present invention, in which a circular non-printing pattern 7 with a diameter of 0.5 mm is arranged in a chidori pattern on an arc-shaped part corresponding to a convex part. A non-print pattern portion 7 is provided, and the other portions are formed into a print pattern of a portion 13 to be coated on the entire surface. The size of the non-printing pattern 7 in the non-printing pattern portion 8 and the pitch 15 of the non-printing pattern are adjusted depending on the height of the convex portion and the processing conditions during adhesion, but the overflowing adhesive may be slightly around the piezoelectric vibrator element. It is preferable that the amount of water accumulates.

FIG. 5 shows a state in which the flexible printed circuit board shown in FIG. 3 is bonded to the piezoelectric vibrator element 1 printed with an adhesive using the screen printing printing pattern according to the method of the present invention shown in FIG. Approximately 30 kg, same as the conventional method
The adhesive 9 that protrudes when pressure is applied with a force of f does not short-circuit between the upper and lower electrodes as seen in the conventional method, and the adhesive 9 slightly protrudes from the edge of the piezoelectric vibrator element 1 and hardens as a bond. did it. There was almost no deterioration in insulation resistance under high temperature conditions in humidity resistance, and a value of 104 MΩ could be secured.

[0013]

As described above, by bonding thin plate piezoelectric vibrators using the method of the present invention, piezoelectric vibrators with good moisture resistance can be manufactured without taking any moisture resistance measures.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a screen printing pattern used in the method of the present invention.

[Fig. 2] Fig. 2 shows a thin disc-shaped piezoelectric vibrator element;
2(a) is a top view, and FIG. 2(b) is a front view.

3 shows a flexible printed circuit board partially having a convex portion, FIG. 3(a) is a top view seen from the adhesive surface side, and FIG. 3(b) is a front view.

FIG. 4 is a diagram showing an example of a screen printing pattern used in a conventional method.

FIG. 5 shows a piezoelectric vibrator that has been properly bonded using the method of the present invention, with FIG. 5(a) being a front sectional view and FIG. 5(b) being a top view.

FIG. 6 shows a piezoelectric vibrator bonded by a conventional method in which a short circuit has occurred in the adhesive; FIG. 6(a) is a front sectional view, and FIG. 6(b) is an external perspective view.

[Explanation of symbols]

1 Piezoelectric vibrator element 2 Coverlay 3 Copper foil 4 Base film 5 Adhesive 6 Adhesive short circuit part 7 Non-printing pattern 8 Non-print pattern section 9. Adhesive sticking out 10 Electrode 11 Piezoelectric ceramics 12 Part corresponding to the convex part 13. Area to be completely coated 14 Flexible printed circuit board 15 Pitch of non-printing pattern

Claims (1)

[Claims] 1. The piezoelectric vibrator element and the flexible printed circuit board are bonded by applying an adhesive to both surfaces of a thin plate-like piezoelectric vibrator element or to the adhesive surface of a flexible printed circuit board having a partially convex portion on the adhesive surface. In the manufacturing method of a piezoelectric vibrator made by gluing a A method for bonding a piezoelectric vibrator, the method comprising screen printing an adhesive in a pattern with non-printed areas.