Plate material cutting method, printed circuit board, and electronic device

Abstract

According to one embodiment, a plate material cutting method prepares a plate material including a joining member that joins a main body portion to a throw-out portion, sets the plate material on a die including an opening section, and pushes a punch against the joining member. The punch includes a first end portion corresponding to a first end of the joining member which is connected to the main body portion. The punch also includes a second end portion corresponding to a second end of the joining member which is connected to the throw-out portion. A gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. A gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

Description

BACKGROUND

1. Field

One embodiment of the invention relates to a plate material cutting method, a printed circuit board, and an electronic device. For example, one embodiment of the invention relates to (i) a plate material cutting method which is used for cutting a plate material to obtain a member, and (ii) a printed circuit board and an electronic device provided with a member which is cut out from the plate material.

2. Description of the Related Art

An electronic device such as a hard disk drive (hereinafter referred to as HDD) is provided with a printed circuit board. The printed circuit board can be prepared in a variety of methods. For example, a thin circuit board such as a flexible printed circuit board is made by press-working a sheet-like metal plate.

To make a printed circuit board, a sheet-like metal plate is cut out to have a predetermined product shape. By this working, the metal plate is divided into main body portion which is used as part of a product, and a throw-out portion which is later thrown out. A joining member is provided between the main body portion and the throw-out portion to connect these portions together. In other words, the main body portion is not completely cut off from the throw-out portion; it is supported by the throw-out portion, with the joining member located in between.

A circuit component is mounted on the main body portion in the state where the main body portion is supported by the throw-out portion. After the circuit component is mounted, the main body portion is separated from the joining member. In this manner, the main body portion is separated completely from the throw-out portion, and the printed circuit board can be mounted on an electronic device.

The main body portion is separated from the joining member by use of a die assembly including: a punch; a die having an opening section corresponding to the punch; and a blank holder. In the die assembly, the gap between the outer surface of the punch and the inner surface of the opening section is less than the thickness of a workpiece.

A metal plate is set on the die assembly in such a manner that the joining member is located above the opening section. With the metal plate secured to the die assembly, the punch is forcibly pushed against the joining member. By pushing the punch against the joining member, a shearing force is applied to the boundary between the main body portion and the joining member and to the boundary between the throw-out portion and the joining member. As a result, both the boundary between the main body portion and the joining member and the boundary between the throw-out portion and the joining member are cut.

A method for separating the main body portion from the throw-out portion, a cap manufacturing method is proposed, which separates a cap member from a throw-out member. An example of such a cap manufacturing method is described in Jpn. Pat. Appln. KOKAI Publication No. 11-114635, for example. The cap member described in this KOKAI Publication No. 11-114635 is supported by a throw-out portion by means of a joining member. By cutting the joining member by means of a blade cutter, the cap member is separated from the throw-out portion.

In the case of a small-sized HDD, a printed circuit board is very small. Therefore, a joining member which joints the main body portion of the printed circuit board to the throw-out portion is much smaller and lighter in weight.

The die assembly is so designed as to drop the cutoff joining member from the die assembly as a waste. In other words, the cutoff joining member does not impede the subsequent manufacturing process. However, if the joining member is too light in weight, it does not fall from the die assembly and may adhere to the surface of the punch, die or blank holder. If the press working is continued, with the joining member adhered to the surface of the punch, die or blank holder, the product may have an indentation resulting from the joining member.

In the manufacturing method described in Jpn. Pat. Appln. KOKAI Publication No. 11-114635, the joining member is cut off by means of a blade cutter. The blade cutter may be useful where portions to be cut is disposed in line, but is not advantageously applied to the case where a plurality of joining members extend in various directions.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.

FIG. 1 is an exemplary perspective view of a cellular phone according to a first embodiment of the invention;

FIG. 2 is an exemplary perspective view of an HDD according to the first embodiment;

FIG. 3 is an exemplary exploded perspective view of the HDD of the first embodiment;

FIG. 4 is an exemplary plan view of a metallic plate used in the first embodiment;

FIG. 5 is an exemplary sectional view of a press working apparatus according to the first embodiment;

FIG. 6 is an exemplary perspective view showing how a punch and a die are related in the first embodiment;

FIG. 7 is an exemplary plan view showing how the punch and the die are related in the first embodiment;

FIG. 8 is an exemplary sectional view showing how the metallic plate of the first embodiment is before it is punched;

FIG. 9 is an exemplary sectional view showing how the metallic plate of the first embodiment is when it is being punched;

FIG. 10 is an exemplary sectional view showing how the metallic plate of the first embodiment is after it is punched;

FIG. 11 is an exemplary perspective view showing how the punch and die of a press working apparatus according to the second embodiment of the present invention are related;

FIG. 12 is an exemplary plan view showing how the punch and die of the second embodiment are related; and

FIG. 13 is an exemplary sectional view of a die according to another embodiment of the invention.

DETAILED DESCRIPTION

Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, a plate material cutting method according to one aspect of the present invention prepares a plate material including a main body portion, a throw-out portion and a joining member that joins the main body portion to the throw-out portion. The plate material is set on a die including an opening section in such a manner that the joining member is opposed to the opening section. In this state, a punch opposing the opening section is pushed against the joining member. The punch includes a first end portion corresponding to that end of the joining member which is connected to the main body portion, and a gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. The punch also includes a second end portion corresponding to that end of the joining member which is connected to the throw-out portion, and a gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

In general, according to one embodiment of the invention, a printed circuit board according to another aspect of the present invention provided with a main body portion and a circuit component mounted on the main body portion. The main body portion is prepared from a plate material by use of a punch and a die including an opening section corresponding to the punch. The plate material includes the main body portion, a throw-out portion and a flexible joining member that joins the main body portion to the throw-out portion. The punch includes a first end portion and a second end portion. When the plate material is set on the die, the first end portion of the punch corresponds to that end of the joining member which is connected to the main body portion, and the second end portion of the punch corresponds to that end of the joining member which is connected to the throw-out portion. A gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. A gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

In general, according to one embodiment of the invention, an electronic device according to a further aspect of the invention provided with a casing and a printed circuit board received in the casing. The printed circuit board includes a main body portion and a circuit component mounted on the main body portion. The main body portion is prepared from a plate material by use of a punch and a die including an opening section corresponding to the punch. The plate material includes the main body portion, a throw-out portion and a flexible joining member that joins the main body portion to the throw-out portion. The punch includes a first end portion and a second end portion. When the plate material is set on the die, the first end portion of the punch corresponds to that end of the joining member which is connected to the main body portion, and the second end portion of the punch corresponds to that end of the joining member which is connected to the throw-out portion. A gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. A gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

An embodiment of the present invention will now be described, referring to the case where the present invention is applied to a cellular phone.

FIGS. 1-10 show a cellular phone, which is an example of an electronic device according to the first embodiment of the present invention. As shown in FIG. 1, the cellular phone 1 includes a main body 2, a display unit 3 and a hinge portion 4.

The main body 2 includes a box-like casing 5. The casing has an upper wall on which a plurality of push-type operation keys 6 are arranged. The casing 5 contains a main board 7 and an HDD 8. The display unit 3 includes a display housing 9 and a liquid crystal display module 10 received inside the display housing 9. The liquid crystal display module 10 has a display screen 10a. The display screen 10a is exposed to the outside of the display housing 9 though an opening section 9a of the display housing 9. The display unit 3 is supported by the rear end portion of the main body 2 by means of the hinge portion 4.

The HDD 8 received in the casing 5 of the main body 2 is an example of a disk drive, which is one type of electronic device. As shown in FIG. 2, the HDD 8 includes an HDD main body 11 and a circuit board unit 12. For example, the length L of the HDD main body 11 is 32 mm and the width W thereof is 24 mm. The total thickness T of the HDD main body 11 and the circuit board unit 12 combined is in the range of 3 mm to 6 mm.

As shown in FIG. 3, the circuit board unit 12 is attached to the HDD main body 11 from below. The circuit board unit 12 includes a control circuit board 14 and an interface board 15. The control circuit board 14 is electrically connected to the HDD main body 11 and controls the same. The interface board 15 has one end portion electrically connected to the control circuit board 14, and the other end portion electrically connected to the main board 7 of the cellular phone 1.

The HDD main body 11 has a case 17. The case 17 is shaped like a box and has an upper wall 17a, a lower wall 17b and side walls 17c. As shown in FIG. 3, the case 17 contains a magnetic disk 21, a spindle motor 22, a magnetic head 23, a head actuator 24, a voice coil motor 25 and a signal processing section 26.

The magnetic disk 21 is an example of a disk-shaped information recording medium. The magnetic disk 21 has a diameter of 0.85 inches, for example. The spindle motor 22 is attached to the lower wall 17b. The spindle motor 22 includes a rotatably-supported hub 22a. The magnetic disk 21 is concentrically fitted around the hub 22a.

As shown in FIG. 3, the head actuator 24 includes a bearing portion 24a and an arm portion 24b horizontally extending from the bearing portion 24a. The tip end of the arm portion 24b supports the magnetic head 23. The magnetic head 23 writes information on the magnetic disk 21 and reads information from the magnetic disk 21. The bearing portion 24a rotatably supports the arm portion 24b. Thus, the magnetic head 23 is movable between an operating position where it is on the surface of the magnetic disk 21 and a retreat position where it is located away from the magnetic disk 21. The voice coil motor 25 rotates the head actuator 24.

As shown in FIG. 3, the signal processing section 26 includes a printed circuit board 28 and a connector 29. The connector 29 is attached to the lower surface of the printed circuit board 28. The connector 29 is fitted in a hole (not shown) formed in the lower wall 17b of the case 17 and exposed to the outside of the case 17. The connector 29 is electrically connected to the control circuit board 14 of the circuit board unit 12.

An example of the printed circuit bard is made of flexible printed circuit board (herein after referred to as an FPC). The printed circuit board 28 includes a printed wiring board 31 and a circuit component 32 mounted on the printed wiring board 31. The printed wiring board 31 is an example of the main body portion. The printed wiring board 31 includes a board main body 31a and a connection portion 31b.

The board main body 31a is secured to the lower wall 17b in the folded state. The connection portion 31b is integral with the board main body 31a. The connection portion 31b extends along the side surface of the board main body 31a. The distal end of the connection portion 31b is connected to the head actuator 24. To be more specific, the connection portion 31b is electrically connected to the magnetic head 23 by way of a cable (not shown) provided on the head actuator 24. With this configuration, the signal processing section 26 sends signals related to information processing to the magnetic head 23. An example of the circuit component 32 is a head IC, a head amplifier or the like.

FIG. 4 shows the printed circuit board 28 which is in the state of being fabricated. As shown in FIG. 4, a plurality of printed wiring boards 31 are formed in one metallic plate 34. In other words, the sheet-like metallic plate 34 is subject to press working in such a manner that outer shapes of desired printed wiring boards 31 are punched out.

The metallic plate 34 is an example of the plate material. The metallic plate 34 is a very thin plate of stainless steel and is flexible. As shown in FIG. 4, the metallic plate 34 includes printed wiring boards 31, a throw-out portion 36 and joining members 37. The throw-out portion 36 is an example of a throw-out member. The throw-out portion 36 is discarded after the manufacture. The throw-out portion 36 surrounds the printed wiring boards 31. The metallic plate 34 has a predetermined gap g between the printed wiring boards 31 and the throw-out portion 36.

As shown in FIG. 4, the joining members 37 are provided inside the gap g and are located between the throw-out portion 36 and the printed wiring boards 31. The number of joining members 37 provided is six, for example, and extend in various directions. Each joining member 37 has one end 37a (FIG. 6) connected to one of the printed wiring boards 31, and another end 37b (FIG. 6) connected to the throw-out portion 36. The joining members 37 permits the printed wiring boards 31 to remain connected to the throw-out portion 36. In other words, the printed wiring boards 31 are supported by the throw-out portion 36 through the use of the joining members 37.

Circuit components 32 are mounted on the printed wiring boards 31 in the state where the printed wiring boards 31 are supported by the throw-out portion 36. After the circuit components 32 are mounted, the joining members 37 are cut off from the printed wiring boards 31. As a result, the printed wiring boards 31 are separated from the metallic plate 34.

A press working apparatus 40 according to the first embodiment of the present invention will now be described, referring to FIGS. 5-7. The press working apparatus 40 is a working apparatus that separates the joining members 37 from the printed wiring boards 31.

FIG. 5 schematically shows the entire press working apparatus 40. The press working apparatus 40 includes a die assembly 41, a frame 42, a bed 43 and a slide 44. The die assembly 41 includes a die 45, a blank holder 46 and punches 47.

The bed 43 is fixed to the frame 42. The die 45 is provided on the upper surface of the bed 43. The die 45 is provided with an attachment surface 45a on which the metallic plate 34 is mounted. The die 45 has a plurality of opening sections 51 which are open in the attachment surface 45a. The opening sections 51 are equal in number to the joining members 37. When the metallic plate 34 is set on the die 45, the opening sections. 51 are located under the joining members 37.

The slide 44 and the blank holder 46 are attached to the frame 42 in such a manner that they are vertically movable. The slide 44 and the blank holder 46 can be advanced toward the bed 43 or retreated from the bed 43 by a driving source (not shown).

The blank holder 46 is located in correspondence to the die 45, and has a plurality of through holes 52 at positions corresponding to the opening sections 51 of the die 45. The punches 47 are fixed to the slide 44. The punches 47 are arranged at positions corresponding to the opening sections 51 of the die 45 and are inserted in the through holes 52 of the blank holder 46. In other words, the punches 47 are equal in number to the joining members 37, and are located above the joining members 37 when the metallic plate 34 is set on the die 45.

The relationships between the die 45 and the punches 47 will now be described in detail, referring to FIGS. 6 and 7.

As shown in FIGS. 6 and 7, an example of a punch 47 has a substantially square cross section if taken in the horizontal direction. That is, the punch 47 is a square pillar. The punch 47 has a first end portion 47a and a second end portion 47b. When the metallic plate 34 is set on the die 45, the first end portion 47a is located above that end 37a of the joining member 37 which is connected to the printed wiring board 31, and the second end portion 47b is located above that end 37b of the joining member 37 which is connected to the throw-out portion 36.

An example of an opening section 51 of the die 45 has a rectangular cross section if taken in the horizontal direction. That is, the opening section 51 is a rectangle The opening section 51 extends in the insertion direction of the punch 47 and has a depth greater than the longitudinal dimension of the joining member 37. The opening section 51 has an inner surface. The inner surface includes a first inner surface portion 51a and a second inner surface portion 51b.

When the punch 47 is inserted into the opening section 51, the first inner surface portion 51a is opposed to the first end portion 47a, and the second inner surface portion 51b is opposed to the second end portion 47b.

As shown in FIGS. 7 and 8, when the metallic plate 34 is set on the die 45, the boundary 55a between the printed wiring board 31 and the joining member 37 is located between the first end portion 47a of the punch 47 and the first inner surface portion 51a of the opening section 51. When the metallic plate 34 is set on the die 45, the boundary 55b between the throw-out portion 36 and the joining member 37 is located above the second inner surface portion 51b. In other words, the second inner surface portion 51b is located under the boundary 55b between the throw-out portion 36 and the joining member 37. Thus, the opening section 51 extends from boundary 55a (which is between the printed wiring board 31 and the joining member 37) to boundary 55b (which is between the throw-out portion 36 and the joining member 37).

At the edge 51c of the opening section 51, the attachment surface 45a of the die 45 is perpendicular to the first and second inner surface portions 51a and 51b. This means that the edge 51c of the opening section 51 is not chamfered.

Gap S1 is formed between the first end portion 47a of the punch 47 and the first inner surface portion 51a of the opening section 51. Gap S1 is smaller than the thickness t of the metallic plate 34. Likewise, gap S2 is formed between the second end portion 47b of the punch 47 and the second inner surface portion 51b of the opening section 51. Gap S2 is larger than the thickness t of the metallic plate 34. In the case where the thickness t of the metallic plate 34 (which is a plate of stainless steel) is 0.050 mm, gap S1 is set at 0.005 mm and gap S2 is set at 0.100 mm, for example.

As shown in FIG. 8, the through holes 52 of the blank holder 46 are slightly larger than the punches 47.

A plate material cutting method according to the present embodiment will now be described, referring to FIGS. 6-10.

First of all, as shown in FIG. 6, the metallic plate 34 is placed on the attachment surface 45a of the die 45. In other words, the metallic plate 34 is set on the die 45 in such a manner that the joining member 37 of the metallic plate 34 is located above the opening section 51 of the die 45. To be more specific, as shown in FIG. 7, the boundary 55a between the printed wiring board 31 and the joining member 37 is located between the first end portion 47a of the punch 47 and the first inner surface portion 51a of the opening section 51. The boundary 55b between the throw-out portion 36 and the joining member 37 is located above the second inner surface portion 51b of the opening section 51.

As shown in FIG. 8, after the metallic plate 34 is set on the die 45, the blank holder 46 is set at the intended position. In other words, the blank holder 46 is brought into contact with the metallic plate 34 from above, and the metallic plate 34 is applied with a load acting downward. Thus, the metallic plate 34 is sandwiched between the blank holder 46 and the die 45, and is therefore fixed in position.

As shown in FIG. 9, after the metallic plate 34 is fixed in position, the punch 47 is forcibly pushed against the joining member 37. The metallic plate 34 is located between the punch 47 and the die 45. When the punch 47 touches the metallic plate 34, a shearing force is applied to that portion of the metallic plate 34 which is sandwiched between the first end portion 47a of the punch 47 and the first inner surface portion 51a of the opening section 51. As a result, the shearing force is exerted on the boundary 55a between the printed wiring board 31 and the joining member 37, and the printed wiring board 31 and the joining member 37 separate from each other.

Of the portions of the metallic plate 34, the portion between the second end portion 47b of the punch 47 and the second inner surface portion 51b of the opening section 51 is not applied with a shearing force sufficiently strong for cutting. In general, a shearing force is generated when the gap between two blades is smaller than the thickness of a workpiece. In the present embodiment, the second end portion 47b of the punch 47 corresponds to one blade, and the second inner surface portion 51b of the opening section 51 corresponds to the other. Gap S2 between them is larger than thickness t of the metallic plate 34. As can be seen from this, the boundary 55b between the throw-out portion 36 and the joining member 37 is not cut. In other words, the joining member 37 is not separated from the throw-out portion 36.

The metallic plate 34 is flexible. As shown in FIG. 9, when the punch 47 is inserted into the opening section 51, the joining member 37 is bent with its end 37b supported by the throw-out portion 36.

After being inserted into the opening section 51, the punch 47 is retreated to the original position, which is located above the metallic plate 34. As shown in FIG. 10, when the punch 47 is retreated to the original position, the joining member 37 is cut off from the printed wiring board 31 but remains connected to the throw-out portion 36.

After the joining member 37 is cut off from the printed wiring board 31, the blank holder 46 is moved away from the die 45. Thus, the printed wiring board 31, which has been fixed by the die 45 until then, can be taken out. In addition, the joining member 37 and the throw-out portion 36 can be taken out of the die 45 as one piece. In this way, the printed wiring board 31 can be separated from the throw-out portion 36.

The above-mentioned plate material cutting method and the die assembly 41 are advantageous in that the printed wiring board 31 can be separated from the throw-out portion 36 without producing cutting chips. To be specific, a shearing force sufficiently strong for cutting is not applied to the boundary 55b between the throw-out portion 36 and the joining member 37 because gap S2 between the second end portion 47b of the punch 47 and the second inner surface portion 51b of the opening section 51 is greater than thickness t of the metallic plate 34.

Even when the punch 47 is pushed into the die 45, the joining member 37 is not cut off from the throw-out portion 36, and they are integral with each other. When the throw-out portion 36 is taken out, the joining member 37 is also taken out together with the throw-out portion 36. Therefore, the joining member 37 does not produce cutting chips.

Since the joining member 37 does not produce cutting chips, it does not adhere to the surface of the punch 47, blank holder 46 or die 45, and the product does not have an indentation resulting from the joining member 37. In addition, the die assembly 41 need not be cleaned after the joining member 37 is cut off. The elimination of the need to perform the cleaning operation contributes to improvement of the manufacturing process of the printed circuit board 28. That is, the printed circuit board 28 can be manufactured in a short time and at low cost.

In the case where the second inner surface portion 51b of the opening section 51 is under the boundary 55b between the throw-out portion 36 and the joining member 37, the joining member 37 can be bent satisfactorily in appearance. Even if the opening section 51 is formed in such a manner that the second inner surface portion 51b is located under the throw-out portion 36, the joining member 37 can be bent by the pushing of the punch 47.

When the joining member 37 is bent, part of the throw-out portion 36 is also subject to the bending force, and in some cases, part of the throw-out portion 36 may crack or have another type of damage.

In the case where the second inner surface portion 51b is under the boundary 55b between the throw-out portion 36 and the joining member 37, the throw-out portion 36 is not subject to a bending force when the joining member 37 is bent. Therefore, the throw-out portion 36 is not damaged.

In the case where the boundary 55a between the printed wiring board 31 and the joining member 37 is between the first end portion 47a and the first inner surface portion 51a, the cut surface is limited to the boundary 55a between the printed wiring board 31 and the joining member 37. In other words, after the cutting process, part of the joining member 37 does not remain attached to the printed wiring board 31.

In the case where the depth of the opening section 51 is greater than the longitudinal dimension of the joining member 37, the joining member 37 can be freely bent in accordance with the movement of the punch 47.

In the die assembly 41, the attachment surface 45a of the die 45 are perpendicular to the inner surface portions 51a and 51b. This means that the edge 51c of the opening section 51 is not chamfered. Gap S2 is provided between the second end portion 47b of the punch 47 and the second inner surface portion 51b of the opening section 51. With this structure, no special measure has to be taken for the edge 51c of the opening section 51, and yet cutting chips are not produced. The die 41 can be manufactured at low cost with no need to chamfer the opening edge 51c or take another special measure.

The printed circuit board 28 of the above structure is advantageous in that it can be manufactured in a short time and at low cost. Where the printed circuit board 28 is incorporated in the HDD 8 or the cellular phone 1, the HDD 8 or the cellular phone 1 can be manufactured in a short time and at low cost.

A die assembly 61 and a plate material cutting method according to the second embodiment of the present invention will now be described with reference to FIGS. 11 and 12. The structural components that have the same function as the die assembly 41 and printed circuit board 28 of the first embodiment are denoted by the same reference numerals, and reference to such structural components will be omitted herein.

As shown in FIGS. 11 and 12, the die 45 of the die assembly 61 has an opening section 62. An example of this opening section has an ellipse cross section if taken in the horizontal direction. The elliptic opening section 62 has a long axis extending from the first inner surface portion 51a to the second inner surface portion 51b. The opening section 62 extends from the boundary 55a between the printed wiring board 31 and the joining member 37 to the boundary 55b between the throw-out portion 36 and the joining member 37. Another example of opening section 62 is a circle.

The die assembly 61 has a punch 63. An example of this punch has a circular cross section if taken in the horizontal direction. That is, the punch 63 is cylindrical. Gap S1 is formed between the first end portion 47a of the punch 63 and the first inner surface portion 51a of the opening section 62. Gap S1 is smaller than the thickness t of the metallic plate 34. Likewise, Gap S2 is formed between the second end portion 47b of the punch 63 and the second inner surface portion 51b of the opening section 62. Gap S2 is larger than the thickness t of the metallic plate 34.

The elliptic opening section 62 has the long axis extending in a direction from the first end portion 47a to the second end portion 47b. As shown in FIG. 12 when the metallic plate 34 is set on the die 45, the boundary 55a between the printed wiring board 31 and the joining member 37 is located between the first end portion 47a of the punch 47 and the first inner surface portion 51a of the opening section 51. When the metallic plate 34 is set on the die 45, the boundary 55b between the throw-out portion 36 and the joining member 37 is located above the second inner surface portion 51b.

The opening section 62 extends in the insertion direction of the punch 63 and has a depth greater than the longitudinal dimension of the joining member 37. At the edge 51c of the opening section 62, the attachment surface 45a of the die 45 is perpendicular to the first and second inner surface portions 51a and 51b.

The printed wiring board 31 obtained by the die assembly 61 and plate material cutting method according to the second embodiment of the present invention is incorporated in the cellular phone 1 or HDD 8.

The above-mentioned plate material cutting method and the die assembly 61 are advantageous in that the printed wiring board 31 can be separated from the throw-out portion 36 without producing cutting chips. For the same reason as stated in connection with the first embodiment, when the punch 63 is pushed against the throw-out portion 36, the joining member 37 is cut off from the printed wiring board 31 but remains connected to the throw-out portion 36. Therefore, the joining member 37 does not produce any cutting chips.

The punch 63 of the second embodiment has a circular cross section. The joining member 37 of the metallic plate 34 is very small, and its longitudinal dimension is several mm or less. Therefore, the punch 63 is also very small in size and cannot be made with ease unless it is cylindrical. Compared to a rectangular cylinder, a circular cylinder is easy to make. This holds true for the punch 63 of the second embodiment.

Since the punch 63 is cylindrical, the metallic plate 34 is cut in such a manner as to leave an arcuate cut section. With this structure, the length by which a edge of the punch 63 comes into contact with the plate material 34 is large. Compared to the case where the cutting section is flat, the cutting line of the arcuate cutting section is sufficiently long. As a result, a reliable cutting operation is ensured.

A description was given above of the plate material cutting methods and die assemblies of the first and second embodiments of the present invention, along with printed circuit board 28 and cellular phone 1. Needless to say, the embodiments of the present invention are not limited to these. For example, the opening sections 51, 62 may have cross sections other than rectangular and oval ones. In addition, the opening sections 51, 62 need not extend from the boundary 55a between the printed wiring board 31 and the joining member 37 to the boundary 55b between the throw-out portion 36 and the joining member 37.

For example, the second inner surface portion 51b of the opening section 51 may be at any position as long as it is located under the joining member 37. In other words, the opening section 51 is formed in such a manner that the first inner surface portion 51a is at a position corresponding to the plate material portion to be cut. As long as the first inner surface portion 51a is located at such a position, the second inner surface portion 51b does not have to be at a specific position. As in the opening sections 51 and 62 of the first and second embodiments, however, it is effective that the second inner surface portion 51b be located close to the throw-out portion 36. Where the second inner surface portion 51b is close to the throw-out portion 36, the opening sections 51 and 62 can have a wide cross section, and the opening sections 51 and 62 can be formed with ease. As shown in FIG. 13, the opening edge 51c of the opening section 51 may be chamfered so that the joining member 37 can be easily bent.

The printed circuit board to which an embodiment of the present invention is applied is not limited to that adapted for use in the HDD 8, and is applicable to any type of electronic apparatus. Moreover, the embodiments of the present invention are not limited to the printed circuit board 28. For example, the embodiments of the present invention are applicable to the case where a plate made of a material other than a metal (such as resin or rubber) is cut. The embodiments of the present invention are applicable to any type of plate material on condition that the plate material does not break when it is bent.

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. A plate material cutting method comprising: preparing a plate material including a main body portion, a throw-out portion and a joining member that joins the main body portion to the throw-out portion; setting the plate material on a die including an opening section such that the joining member is opposed to the opening section; and pushing a punch opposing the opening section against the joining member, the punch including a first end portion corresponding to a first end of the joining member which is connected to the main body portion, a gap smaller than thickness of the plate material being defined between the first end portion of the punch and an inner surface of the opening section, the punch also including a second end portion corresponding to a second end of the joining member which is connected to the throw-out portion, a gap larger than the thickness of the plate material being defined between the second end portion of the punch and the inner surface of the opening section.

2. The plate material cutting method according to claim 1, wherein the punch is cylindrical, and the opening section of the die is ellipse having a long axis extending in a direction from the first end portion to the second end portion.

3. The plate material cutting method according to claim 1, wherein the inner surface of the opening section includes a first inner surface portion corresponding to the first end portion of the punch and a second inner surface portion corresponding to the second end portion of the punch, and the second inner surface portion is located under a boundary between the throw-out portion and the joining member when the plate material is set on the die.

4. The plate material cutting method according to claim 3, wherein a boundary between the main body portion and the joining member is located between the first end portion of the punch and the first inner surface portion of the opening section when the plate material is set on the die.

5. The plate material cutting method according to claim 4, wherein the punch is cylindrical, and the opening section of the die is ellipse having a long axis extending in a direction from the first end portion to the second end portion.

6. The plate material cutting method according to claim 4, wherein the opening section of the die extends in a direction in which the punch is inserted, and has a depth greater than a longitudinal dimension of the joining member.

7. The plate material cutting method according to claim 6, wherein the die includes an attachment surface on which the plate material is placed, and the attachment surface is perpendicular to the first and second inner surface portions of the opening section at an opening edge of the opening section.

8. A printed circuit board comprising: a main body portion prepared from a plate material by use of a punch and a die including an opening section corresponding to the punch, the plate material including the main body portion, a throw-out portion and a joining member that joins the main body portion to the throw-out portion; and a circuit component mounted on the main body portion, wherein the punch includes a first end portion and a second end portion, when the plate material is set on the die, the first end portion of the punch corresponds to a first end of the joining member which is connected to the main body portion, the second end portion of the punch corresponds to a second end of the joining member which is connected to the throw-out portion, a gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section, and a gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

9. The printed circuit board according to claim 8, wherein the punch is cylindrical, and the opening section of the die is ellipse having a long axis extending in a direction from the first end portion to the second end portion.

10. The printed circuit board according to claim 8, wherein the inner surface of the opening section includes a first inner surface portion corresponding to the first end portion of the punch and a second inner surface portion corresponding to the second end portion of the punch, and the second inner surface portion is to be located under a boundary between the throw-out portion and the joining member.

11. The printed circuit board according to claim 10, wherein a boundary between the main body portion and the joining member is to be located between the first end portion of the punch and the first inner surface portion of the opening section.

12. An electronic device comprising: a casing; and a printed circuit board received in the casing, the printed circuit board including a main body portion and a circuit component mounted on the main body portion, wherein the main body portion is prepared from a plate material by use of a punch and a die including an opening section corresponding to the punch, the plate material includes the main body portion, a throw-out portion and a joining member that joins the main body portion to the throw-out portion, the punch includes a first end portion and a second end portion, when the plate material is set on the die, the first end portion of the punch corresponds to a first end of the joining member which is connected to the main body portion, and the second end portion of the punch corresponds to a second end of the joining member which is connected to the throw-out portion, a gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section, a gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section.

13. The electronic device according to claim 12, wherein the punch is cylindrical, and the opening section of the die is ellipse having a long axis extending in a direction from the first end portion to the second end portion.

14. The electronic device according to claim 12, wherein the inner surface of the opening section includes a first inner surface portion corresponding to the first end portion of the punch and a second inner surface portion corresponding to the second end portion of the punch, and the second inner surface portion is to be located under a boundary between the throw-out portion and the joining member.

15. The electronic device according to claim 14, wherein a boundary between the main body portion and the joining member is to be located between the first end portion of the punch and the first inner surface portion of the opening section.