JP2014048634A - Manufacturing method of leaf spring, leaf spring, camera module provided with leaf spring, and electronic terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a leaf spring that can prevent slight deformation of a leaf spring caused by gradual releasing of residual stress, even in a case where an impact of falling or the like is added.SOLUTION: An upper leaf spring 5 and a lower leaf spring 11 are used for a drive mechanism 1 of a camera module. When manufacturing the upper leaf spring 5 and the lower leaf spring 11, a rolled leaf spring material 40 made of copper alloy is prepared, the leaf spring material 40 is processed in a predetermined shape by etching, and then a leaf spring is formed. The leaf spring is annealed and the stress of the leaf spring in the case of 0.05% distortion is adjusted to 1,000 MPa or more, and thereby the upper leaf spring 5 and the lower leaf spring 11 are obtained.

Description

  The present invention relates to a leaf spring manufacturing method, a leaf spring, a camera module including the leaf spring, and an electronic terminal device.

  Interaction between the current flowing in the coil and the magnetic field of the magnetic circuit composed of the yoke and magnet for the purpose of autofocusing and zooming in small electronic devices with cameras such as mobile phones, smartphones, tablet terminals, notebook PCs, etc. A camera module drive mechanism (voice coil motor (VCM)) that can displace the lens unit in the optical axis direction is known.

  A plate spring for supporting the holder holding the lens unit so as to be displaceable in the optical axis direction of the lens unit is used in such a camera module drive mechanism.

JP 2009-122360 A

  Incidentally, in recent years, with the progress of thinning of small electronic devices, it is required that the camera module is also thinned. For this reason, the leaf spring incorporated in the camera module is also required to be as thin as possible. On the other hand, the spring strength required for the leaf spring differs depending on the weight of the camera lens. Specifically, when mounting a heavy lens, it is necessary to increase the thickness of the leaf spring in order to increase the spring strength of the leaf spring, and when mounting a light lens, the thickness of the leaf spring must be reduced. Required. Under such a background, in general, a leaf spring is manufactured using a thin copper alloy high-strength material of about 20 μm to 100 μm.

  By the way, in order to separate the boundary between elastic deformation and plastic deformation of the material for convenience, a metal material such as a leaf spring defines a stress corresponding to a yield stress as a yield strength. The 0.2% proof stress, which is a stress, is used as one index of the mechanical properties of the material.

  The leaf spring incorporated in the camera module also uses 0.2% proof stress as an indicator of the mechanical properties of the material, and is shown with 0.2% proof strength even when an impact is applied to the leaf spring due to, for example, dropping. The leaf spring material is selected so as not to exceed the stress.

  However, even when the material of the leaf spring is selected and the leaf spring is created as described above, there is a problem that the leaf spring is deformed. In this case, there is a possibility that a current for moving the lens by a desired amount of displacement becomes large, or a problem that the lens cannot be displaced by a desired amount of displacement may occur.

  As a result of various studies conducted by the inventor of the present invention, particularly in a leaf spring material that has been rolled after annealing, there is a residual stress on the surface of the leaf spring material. It has been found that this is because of a slight deformation.

  The present invention has been made in consideration of such points, and even when an impact such as dropping is applied, it is possible to prevent a problem that the leaf spring is slightly deformed by gradually releasing the residual stress. An object of the present invention is to provide a leaf spring manufacturing method, a leaf spring, a camera module including the leaf spring, and an electronic terminal device.

  The present invention relates to a method for manufacturing a leaf spring used in a camera module drive mechanism, in which a rolled copper alloy leaf spring material is prepared, and the leaf spring material is annealed, so A method for manufacturing a leaf spring, comprising: a step of adjusting a stress at the time of 05% strain to 1000 MPa or more; and a step of processing a leaf spring material into a predetermined planar shape to form a leaf spring.

  The present invention is the method for manufacturing a leaf spring, wherein the leaf spring material includes beryllium copper, nickel tin copper, or titanium copper.

  The present invention is a method for manufacturing a leaf spring, wherein the step of annealing the leaf spring material is performed in a hydrogen atmosphere.

  The present invention is a leaf spring produced by a leaf spring manufacturing method.

  The present invention includes a housing, a lens unit that constitutes an optical system, a holder that is disposed in the housing, accommodates the lens unit, and is movable in the optical axis direction of the lens unit, a coil provided in the holder, A camera module comprising a yoke and a magnet piece provided in a housing and providing a magnetic field to a coil, and a leaf spring interposed between the housing and a holder.

  The present invention is an electronic device terminal including a camera module.

  According to the present invention, since the leaf spring material is annealed after being rolled, the residual stress of the leaf spring material is removed and the stress (proof stress) at 0.05% strain of the leaf spring material is increased to 1000 MPa or more. It has been. As a result, even when an impact such as dropping is applied, or even when the residual stress is gradually released, it is possible to prevent a problem that the leaf spring is slightly deformed.

FIG. 1 is an exploded perspective view showing a drive mechanism of a camera module. FIG. 2 is a schematic side view showing the camera module. FIG. 3 is a plan view showing an upper leaf spring incorporated in the drive mechanism of the camera module. FIG. 4 is a plan view showing a lower leaf spring incorporated in the drive mechanism of the camera module. FIGS. 5A to 5G are schematic cross-sectional views showing a method for manufacturing a leaf spring.

  Embodiments of the present invention will be described below with reference to the drawings.

(Configuration of camera module drive mechanism)
As shown in FIGS. 1 and 2, the camera module drive mechanism 1 according to the present invention includes a housing 2A composed of a cover 2 and a base 13, a lens unit 26A composed of a plurality of lenses 26 constituting an optical system, A holder 9 which is disposed in the housing 2A and accommodates the lens unit 26A and is movable in the optical axis direction of the lens unit 26A, a coil 8 provided on the outer periphery of the holder 9, and a base 13 of the housing 2A. A yoke 6 and a magnet piece 7 for providing a magnetic field to the coil 8 are provided.

  An upper leaf spring 5 is interposed between the cover 2 of the housing 2A and the upper portion of the holder 9, and a lower leaf spring 11 is interposed between the base 13 of the housing 2A and the lower portion of the holder 9.

  Then, when an electric current is passed through the coil 8 via the lower leaf spring 11, an upward force acts on the holder 9, and the lens unit 26A moves upward as a whole against the forces of the upper leaf spring 5 and the lower leaf spring 11. Can be lifted (see FIG. 2).

  Also, by adjusting the amount of current to be input, the force that moves the holder 9 upward is changed, and the balance between the force of the upper leaf spring 5 and the lower leaf spring 11 allows the holder 9 to move up and down. Position adjustment can be performed.

  As shown in FIG. 2, the housing 2 </ b> A is fixed above the base 20 via the intermediate support 21, and a glass plate 24 that holds an infrared cut glass 22 is supported on the intermediate support 21. An image sensor 25 is disposed above.

  Thus, the camera module 1A is configured by the drive mechanism 1 of the camera module having the housing 2A, the intermediate support 21 that supports the infrared cut glass 22 and the glass plate 24, and the base body 20 on which the imaging element 25 is disposed. Has been.

  In the above configuration, as shown in FIG. 3, the upper leaf spring 5 includes an outer frame portion 5a on the housing 2A side, an inner frame portion 5b on the holder 9 side, an outer frame portion 5a, and an inner frame portion 5b. And a spring portion 5c having a spring property provided between them. As shown in FIG. 4, the lower leaf spring 11 is provided between the outer frame portion 11a on the housing 2A side, the inner frame portion 11b on the holder 9 side, and between the outer frame portion 11a and the inner frame portion 11b. And a spring portion 11c having a spring property.

  Next, each component of the camera module drive mechanism 1 will be further described.

  As described above, the holder 9 holding the lens unit 26A is accommodated in the space in the housing 2A composed of the cover 2 and the base 13 so as to be displaceable in the optical axis direction of the lens unit 26A.

  An inner frame portion 5b of the upper leaf spring 5 and an inner frame portion 11b of the lower leaf spring 11 are attached to the upper and lower cylindrical edge portions of the holder 9, respectively, and the outer frame portion 5a of the upper leaf spring 5 (FIG. 3). Is attached to the upper surface of the yoke 6 fixed to the base 13 of the housing 2A, and the outer frame portion 11a (see FIG. 4) of the lower leaf spring 11 is attached to the base 13 of the housing 2A.

  A plurality of magnet pieces 7 are bonded to the yoke 6 to constitute a magnetic circuit of the drive mechanism 1 of the camera module. A coil 8 is disposed in the magnetic field formed by this magnetic circuit. The coil 8 is wound around the outer periphery of the holder 9, and the holder 9 can be displaced in the optical axis direction of the lens unit 26 </ b> A by supplying a current to the coil 8. In FIG. 2, a member indicated by reference numeral 12 is a conductor (flexible printed circuit board or the like) for supplying a current from an external power source to the coil 8, and a member indicated by reference numeral 4 is attached to the upper surface of the upper leaf spring 5. It is an adjustment plate.

  Such a camera module 1A is incorporated into an electronic device terminal such as a small electronic device with a camera such as a mobile phone, a smartphone, a tablet terminal, or a notebook PC. In the present embodiment, such an electronic device terminal is also provided.

(Configuration of leaf spring)
Next, the upper leaf spring 5 and the lower leaf spring 11 will be further described with reference to FIGS.

  The upper leaf spring 5 and the lower leaf spring 11 are each produced using a leaf spring material 40 made of a copper alloy (FIGS. 5A to 5G), as will be described later.

  As shown in FIG. 3, the upper leaf spring 5 includes a rectangular outer frame portion 5a, a ring-shaped inner frame portion 5b disposed on the holder 9 side and inside the outer frame portion 5a, an outer frame portion 5a, A spring portion 5c is provided between the inner frame portion 5b and has a spring property that expands and contracts the outer frame portion 5a and the inner frame portion 5b in the normal direction of the upper leaf spring 5.

  Positioning holes 17 for attaching the upper leaf springs 5 to the upper surface of the yoke 6 fixed to the base 13 of the housing 2A are provided in three of the four corners of the outer frame portion 5a. The positioning hole 17 is engaged with a positioning protrusion (not shown) provided on the upper surface side of the yoke 6 to accurately position the upper leaf spring 5 on the upper surface side of the yoke 6.

  Further, the outer frame portion 5a is provided with an adhesive portion 30A for attaching the upper leaf spring 5 to the housing 2A. The adhesive portions 30A are provided at the four corners of the outer frame portion 5a and in the vicinity of the connecting portion between the outer frame portion 5a and each spring portion 5c. A plurality (four) of the bonding portions 30A are provided at predetermined intervals in the circumferential direction of the outer frame portion 5a.

  On the other hand, the inner frame portion 5 b is provided with an adhesive portion 30 </ b> B for attaching the upper leaf spring 5 to the holder 9. The adhesive portions 30B are provided at the four corners of the inner frame portion 5b and in the vicinity of the connecting portion between the inner frame portion 5b and each spring portion 5c. A plurality (four) of the bonding portions 30B are provided at predetermined intervals in the circumferential direction of the inner frame portion 5b.

  Next, the lower leaf spring 11 will be described with reference to FIG. In the lower leaf spring 11 shown in FIG. 4, the same parts as those of the upper leaf spring 5 shown in FIG.

  As shown in FIG. 4, the lower leaf spring 11 includes a rectangular outer frame portion 11a, a ring-shaped inner frame portion 11b disposed on the holder 9 side and inside the outer frame portion 11a, and an outer frame portion 11a. A spring portion 11c is provided between the inner frame portion 11b and has a spring property that expands and contracts the outer frame portion 11a and the inner frame portion 11b in the normal direction of the lower leaf spring 11.

  Among these, the outer frame portion 11a is provided with an adhesive portion 30A for attaching the lower leaf spring 11 to the base 13 of the housing 2A. The adhesive portions 30A are provided at the four corners of the outer frame portion 11a and in the vicinity of the connecting portion between the outer frame portion 11a and the spring portion 11c. A plurality (four) of the bonding portions 30A are provided at predetermined intervals in the circumferential direction of the outer frame portion 11a.

  On the other hand, the inner frame portion 11 b is provided with an adhesive portion 30 </ b> B for attaching the lower leaf spring 11 to the holder 9. The adhesive portion 30B is provided in the vicinity of the connecting portion with the spring portion 11c in the inner frame portion 11b. A plurality (four) of the bonding portions 30B are provided at predetermined intervals in the circumferential direction of the inner frame portion 11b.

  In addition, a pair of connection terminals 11 e and 11 e connected to an external power source are provided on the outer frame portion 11 a of the lower leaf spring 11. The connection terminals 11e, 11e and an external flexible printed circuit board (FIG. 2) are soldered, for example, so that the connection terminals 11e, 11e and the external power supply are electrically connected.

  Further, the inner frame portion 11b is provided with a pair of electrical connection terminals 11d and 11d connected to the coil 8 side. The connection terminals 11d and 11d and the coil 8 (FIG. 2) are soldered, for example, so that the connection terminals 11d and 11d and the coil 8 are electrically connected. In this way, a current can flow from the external power source to the coil 8 side via the lower leaf spring 11.

Further, as shown in FIG. 4, the outer frame portion 11a is composed of a pair of outer frame members 11a ₁ and 11a ₂ that are separated from each other, so that the connection terminals 11e and 11e are not short-circuited. The inner frame portion 11b is composed of a pair of inner frame members 11b ₁ and 11b ₂ that are spaced apart from each other, so that the connection terminals 11d and 11d are not short-circuited.

  Next, materials for the upper leaf spring 5 and the lower leaf spring 11 will be described. Both the upper leaf spring 5 and the lower leaf spring 11 are produced by etching or punching a metal plate made of a copper alloy. Examples of such a copper alloy include beryllium copper (Cu—Be), nickel tin copper (Cu—Ni—Sn), titanium copper (Cu—Ti), and the like.

(Method for manufacturing leaf spring)
Next, a method of manufacturing the upper leaf spring 5 and the lower leaf spring 11 will be described with reference to FIGS.

  The upper leaf spring 5 and the lower leaf spring 11 are produced by processing a leaf spring material 40 including a copper alloy (beryllium copper, nickel tin copper, titanium copper, etc.).

  Specifically, first, a leaf spring material 40 is prepared as shown in FIG.

  Next, as shown in FIG. 5B, the leaf spring material 40 is rolled along a predetermined rolling direction D. In this case, the leaf spring material 40 is passed between the pair of rollers 45 and 45 and rolled to have a predetermined thickness. The rolling method may be hot rolling, cold rolling, or both.

  Subsequently, the leaf spring material 40 rolled in this manner is wound into a roll shape, and then annealed in, for example, a batch-type hydrogen atmosphere bell-type annealing furnace 46 (FIG. 5C). In this case, the leaf spring material 40 is heated and removed in the annealing furnace 46 at a maximum temperature of 250 ° C. to 350 ° C. for 20 to 28 hours, for example. Specifically, the leaf spring material 40 is heated to the maximum temperature in the annealing furnace 46 over 8 hours to 14 hours, then maintained at this temperature for 1 hour to 3 hours, and then removed over 8 hours to 14 hours. It is preferable to cool. By heating the leaf spring material 40 under the above conditions, in particular, the maximum temperature for heating the leaf spring material 40 is not so high as to change its crystal structure, and the time for heating the leaf spring material 40 is lengthened. Therefore, the residual stress can be sufficiently removed without changing the crystal structure.

  As described above, the step of annealing the leaf spring material 40 is preferably performed in a hydrogen atmosphere. Thus, by performing an annealing process in a hydrogen atmosphere, hydrogen and oxygen are combined to generate water. That is, the copper alloy constituting the leaf spring material 40 is not oxidized. In addition, since the reaction for reducing the copper oxide present on the surface of the leaf spring material 40 occurs, the quality of the leaf springs 5 and 11 can be improved. This is different from an inert gas such as nitrogen gas used for normal annealing.

  Thus, since the leaf spring material 40 is annealed after being rolled, residual stress generated particularly on the outermost surface of the leaf spring material 40 can be removed. Thereby, the stress (0.05% yield strength) at the time of 0.05% strain of the leaf spring material 40 can be adjusted to 1000 MPa or more. In addition, 0.05% proof stress means that in the relationship curve between strain and stress, a tangent line is drawn at a point where the strain is 0%, and a straight line is drawn at a point where the strain is 0.05% parallel to the tangent line. It is the stress at the point where the straight line and the curve intersect.

  This prevents the upper leaf spring 5 and the lower leaf spring 11 from being slightly deformed even when an impact such as a drop is applied after the upper leaf spring 5 and the lower leaf spring 11 are incorporated into the module. Therefore, the current value for displacing the lens 26 by a desired amount of displacement can always be made constant. As a result, it is possible to provide the camera module drive mechanism 1 in which the focusing function does not deteriorate over a long period of time.

  On the other hand, when the leaf spring material 40 is rolled after being annealed as a comparative example, the residual stress remains on the surface of the leaf spring material 40, and thus the 0.05% yield strength is reduced. In this case, when an impact such as dropping is applied to the camera module, the residual stress is gradually released and the upper leaf spring 5 and the lower leaf spring 11 may be slightly deformed.

  Next, the leaf spring material 40 thus annealed is processed into a predetermined planar shape without being rolled again.

  That is, as shown in FIG. 5D, a casein resist (resist) 41 is applied on the leaf spring material 40 and dried.

  Next, a glass pattern is placed on the resist 41 and exposed for a predetermined time with an ultrahigh pressure mercury lamp. Next, after developing the resist 41, post baking is performed to form a resist 41 having a predetermined pattern on the leaf spring material 40 (see FIG. 5E).

  Thereafter, the leaf spring material 40 to which the resist 41 is applied is etched using an etching solution such as an aqueous ferric chloride solution so that the leaf spring material 40 has a predetermined planar shape (FIG. 5). (Refer to (f)). Thus, the outer frame portions 5a and 11a, the inner frame portions 5b and 11b, and the spring portions 5c and 11c are formed in the leaf spring material 40.

  Next, the resist 41 is stripped from the leaf spring material 40 using a resist stripping solution such as a sodium hydroxide solution, and then the leaf spring material 40 is washed with water and dried (see FIG. 5G).

  Thereafter, the leaf spring material 40 is cut and separated into a spring shape, and thus the upper leaf spring 5 and the lower leaf spring 11 are obtained from the leaf spring material 40 (see FIG. 5G).

  Thus, according to the present embodiment, the leaf spring material 40 is annealed after being rolled. Thereby, the residual stress of the leaf spring material 40 can be removed and the 0.05% proof stress of the leaf spring material 40 can be increased. As a result, even when an impact such as dropping is applied, the upper leaf spring 5 and the lower leaf spring 11 are not slightly deformed, so that the focusing function of the drive mechanism 1 of the camera module is not deteriorated over a long period of time. be able to.

  In the present embodiment, the rolled leaf spring material 40 is annealed, and then the leaf spring material 40 is processed into a predetermined shape by etching. However, the present invention is not limited to this, and the rolled leaf spring material 40 may be processed into a predetermined shape by etching, and then the leaf spring material 40 may be annealed. In this case, since the leaf spring material 40 has already been etched, there is an advantage that a small annealing furnace can be used.

(Operation of camera module drive mechanism)
Next, the operation of the camera module drive mechanism will be described with reference to FIG.

  First, a current is passed through the coil 8 through the lower leaf spring 11. As a result, an interaction occurs between the current and the magnetic field of the magnet piece 7, and an upward force acts on the holder 9, so that the lens unit 26 </ b> A moves upward as a whole against the forces of the upper leaf spring 5 and the lower leaf spring 11. (See FIG. 2).

  Further, by adjusting the amount of current flowing through the coil 8, the force that moves the holder 9 upward is changed, and the balance between the force of the upper leaf spring 5 and the lower leaf spring 11 is made, so that the holder 9 moves up and down. And its position can be adjusted.

  In this case, an adhesive portion 30A is provided in the vicinity of the connecting portion with the spring portions 5c and 11c of the outer frame portions 5a and 11a of the upper plate spring 5 and the lower plate spring 11, and the spring portions 5c and 11b of the inner frame portions 5b and 11b. An adhesive portion 30B is provided in the vicinity of the connecting portion with 11c.

  Thus, by firmly fixing both ends of the spring portions 5c and 11c of the upper leaf spring 5 and the lower leaf spring 11 to each of the yoke 6, the base 13 and the holder 9 fixed to the base 13 of the housing 2A, The spring constant of the spring parts 5c and 11c can be stabilized.

  Thus, a camera module drive mechanism having stable spring characteristics can be obtained.

  Next, specific examples in the present embodiment will be described.

Example 1
An upper leaf spring 5 having the configuration shown in FIG. 3 and a lower leaf spring 11 (Example 1) having the configuration shown in FIG. 4 were produced. In this case, the leaf spring material 40 of nickel tin copper (including 15% nickel, 8% tin and 77% copper) was rolled, and then the rolled leaf spring material 40 was annealed. At this time, the leaf spring material 40 was heated to 300 ° C. in an annealing furnace 46 over 9 hours and then held for 3 hours. After holding, it was cooled for 12 hours. Subsequently, when the 0.05% yield strength of the leaf spring material 40 was measured, it was 1200 MPa. The 0.05% proof stress of the leaf spring material 40 was measured using a tensile tester after cutting the leaf spring material 40 into a test piece having a width of 4 mm. Thereafter, the leaf spring material 40 was etched to obtain the upper leaf spring 5 and the lower leaf spring 11. In addition, the thickness of the upper leaf | plate spring 5 and the lower leaf | plate spring 11 was 30 micrometers.

(Comparative Example 1)
An upper leaf spring and a lower leaf spring (Comparative Example 1) having the same shape as in Example 1 were produced in the same manner as in Example 1 except that the leaf spring material was annealed and then rolled. The 0.05% yield strength of the leaf spring material was 700 MPa.

  The above-mentioned two types of upper and lower leaf springs (Example 1 and Comparative Example 1) were each incorporated in a camera module and subjected to a drop test. The drop test was carried out by applying a strictness (height) of 750 mm based on the natural drop test method of JIS standard “JISC 60068-2-32.” Thereafter, for the upper leaf springs and the lower leaf springs in each camera module, the number of deformations among all the camera modules (100) was measured (Table 1).

  As a result, the upper plate spring 5 and the lower plate spring 11 of Example 1 were not deformed at all. On the other hand, the upper leaf spring and the lower leaf spring of Comparative Example 1 were deformed.

DESCRIPTION OF SYMBOLS 1 Camera module drive mechanism 1A Camera module 2 Cover 2A Housing | casing 4 Adjustment board 5 Upper leaf | plate spring 5a Outer frame part 5b Inner frame part 5c Spring part 6 Yoke 7 Magnet piece 8 Coil 9 Holder 11 Lower leaf | plate spring 11a Outer frame part 11b Inner frame portion 11c Spring portion 11d Connection terminal 11e Connection terminal 12 Flexible printed circuit board 13 Base 17 Positioning hole 20 Base body 21 Intermediate support body 22 Infrared cut glass 24 Glass plate 25 Imaging element 26 Lens 26A Lens unit 30A, 30B Bonding portion 40 Plate spring Material 46 annealing furnace

Claims (6)

In the manufacturing method of the leaf spring used for the drive mechanism of the camera module,
Preparing a rolled copper alloy leaf spring material;
Adjusting the stress at the time of 0.05% strain of the leaf spring material to 1000 MPa or more by annealing the leaf spring material;
A method of manufacturing a leaf spring, comprising: processing a leaf spring material into a predetermined planar shape to form a leaf spring.   2. The method for manufacturing a leaf spring according to claim 1, wherein the leaf spring material includes beryllium copper, nickel tin copper, or titanium copper.   The method of manufacturing a leaf spring according to claim 1 or 2, wherein the step of annealing the leaf spring material is performed in a hydrogen atmosphere.   A leaf spring produced by the method for producing a leaf spring according to any one of claims 1 to 3. A housing,
A lens unit constituting an optical system;
A holder that is disposed in the housing, accommodates the lens unit, and is movable in the optical axis direction of the lens unit;
A coil provided in the holder;
A yoke and a magnet piece provided in the housing and providing a magnetic field to the coil;
A camera module comprising the leaf spring according to claim 4 interposed between the housing and the holder.   An electronic device terminal comprising the camera module according to claim 5.

Images