JP3842606B2 - Coil holding pallet for screen printing and screen printing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screen printing coil holding pallet and a screen printing method used in a manufacturing process of a chip inductor functioning as an inductance element in an electronic circuit, and more particularly, to a coil main body in which a winding is applied to a core portion of a drum core. The present invention relates to a coil holding pallet for screen printing and a screen printing method used to fill and seal the outer periphery of the winding with resin by screen printing .
[0002]
[Prior art]
Conventionally, as a chip inductor, electrodes are formed by thick film or thin film technology on both end faces of a drum-shaped ferrite core, and a winding is wound around a core portion having a small diameter of the drum-shaped ferrite core. Solder the end to the electrode in advance, or connect with welding or conductive adhesive instead of soldering to configure the coil body, and further seal the outer periphery of the winding wound around the core with resin The structure to protect is adopted. The shape of the flange of the drum-shaped ferrite core is made square or circular, and the periphery of the core is resin-sealed, so that the overall shape is a chip part shape that can be easily mounted as a rectangular parallelepiped shape or a cylindrical shape.
[0003]
As a method of sealing the coil body with resin, for example, a method of forming a cavity into which resin is injected with the coil body sandwiched between upper and lower molds and injecting resin into the cavity through a runner communicating with the cavity is proposed. Has been. This is the same as the transfer resin sealing method used in the manufacture of resin-encapsulated electronic components such as transistors and ICs. The coil body includes electrodes formed on both end faces of the drum-shaped ferrite core as internal electrodes (base electrodes), and ends of windings are connected to the internal electrodes. An external electrode that is electrically covered by covering the internal electrode later is formed, and when the inductor component including the coil body is mounted on a printed circuit board or the like, the external electrode is electrically connected to the circuit pattern to be conductive. It becomes. Therefore, the cavity into which the resin is injected with the coil body sandwiched between the upper and lower molds is injected with the resin except for the portion where the internal electrode is electrically connected to the external electrode, and the portion where the resin is not injected is the coil body. It is necessary to make it a space that only accommodates.
[0004]
[Problems to be solved by the invention]
By the way, the coil body is mainly composed of a drum-like ferrite core that forms and fires ferrite powder, and the dimensional accuracy is poor and the shape varies compared to the case where the upper and lower mold cavities are manufactured by high-precision machining. Yes. The space that only accommodates the coil main body in the cavity has a margin within the range where the dimensional accuracy and shape of the coil main body can be tolerated, and a gap is easily formed between the cavity and the coil main body, and the cavity into which the resin is injected is formed. The resin is pushed out from the portion to the portion where the resin is not injected.
[0005]
In such a conventional manufacturing method, a coil body is formed by a gap between a portion that is not resin-sealed by internal electrodes due to dimensional variations of the ferrite core itself and a cavity of a molding die used for resin sealing including upper and lower dies. In this case, burrs are generated at the resin-sealed end. A post-treatment for removing the burrs is required, but the burrs are difficult to remove because they are generated on the internal electrode surface.
[0006]
Therefore, the present inventor considers that it is difficult to avoid unnecessary resin adhesion to the electrode surface or the like by resin sealing of the coil body using a mold, and only necessary portions of the coil body are utilized by using screen printing. The idea was to fill a resin paste (which would be an exterior coating after curing).
[0007]
In view of the above points, the present invention is for screen printing that can be suitably used for filling and sealing resin by screen printing on the outer circumference of a coil body in which a winding is applied to the core of a drum-shaped core. An object is to provide a coil holding pallet and a screen printing method .
[0008]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the coil holding pallet for screen printing according to the present invention has a flat plate shape by providing an elastic material on the upper and lower surfaces of a metal plate having a punched hole and the inner part of the punched hole. A coil holding pallet for screen printing in which a through-hole portion is formed by fitting and supporting a coil body with a winding wound around a core portion of a drum-shaped core to an elastic material of
The through-hole portion has a substantially rectangular opening, the opening width (W1) at both ends in the longitudinal direction is formed narrower than the opening width (W0) at the middle portion, and the opening width (W1) at both ends is It is characterized in that the flange portions on both sides of the drum core are sandwiched .
[0011]
Furthermore, the metal plate may be made of a magnetic material.
In the screen printing method according to the present invention, a coil body having a winding core wound around a core of a drum core is fitted into the through-hole portion of the coil holding pallet for screen printing, and both sides of the drum core are fitted. The coil portion is sandwiched and supported, and a resin paste is filled around the winding through a paste transmitting portion facing the core portion of the screen plate.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a screen printing coil holding pallet and a screen printing method according to the present invention will be described below with reference to the drawings.
[0013]
1 and 2 are embodiments of a coil holding pallet for screen printing according to the present invention and a manufacturing procedure of a chip inductor using the pallet, FIG. 3 is a coil body before and after forming an outer sheath with resin, and FIG. FIG. 5 and FIG. 6 show the paste filling process by screen printing, respectively.
[0014]
In this embodiment, the structure of the coil body to be held by the screen printing coil holding pallet will be described with reference to FIG. As shown in FIG. 3A, the chip-shaped coil body 1 before providing an outer sheath as a chip inductor has a drum-shaped ferrite core 2 having a winding core portion 4 between square rods 3 on both sides as a magnetic core. The winding 5 is wound around the core 4 (preferably a circular cross section). Both ends of the winding 5 are connected and fixed to the electrodes 6 formed on the end face of the square rod 3 and a part of the outer peripheral face by soldering or the like.
[0015]
The overall configuration of the screen printing coil holding pallet for holding a plurality of coil bodies 1 shown in FIG. 3A is shown in FIG. 4, and the partial cross section is shown in FIGS. As can be seen from these figures, the screen printing coil holding pallet (hereinafter referred to as a flat plate pallet) 10 is made of an elastic material 13 such as silicon rubber on the upper and lower surfaces of the metal plate 11 having the punched holes 12 and inside the punched holes 12. Is formed into a flat plate shape, and a through-hole portion 14 is formed to support the coil body 1 by fitting the elastic body 13 at the inner position of the punch hole 12. Such a structure is obtained by integrating the elastic material 13 with the metal plate 11 by insert molding or the like, and the through hole portion 14 is formed by the elastic material in the inner portion of the punched hole 12. That is, the periphery of the through-hole portion 14 is surrounded by the elastic material. The metal plate 11 is a magnetic metal (for example, stainless steel) so that it can be magnetically attracted by a permanent magnet or an electromagnet. Positioning holes 15 are formed at four corners of the flat pallet 10. The positioning hole 15 is formed in the metal plate 11, and the elastic member 13 is removed with a larger hole diameter. Here, in the flat pallet 10, the metal plate 11 is provided inside the elastic material 13 because the metal plate 11 having a small thermal expansion is provided so that the size of the elastic material 13 varies due to the thermal expansion. This is to prevent it at 11.
[0016]
The through-hole portion 14 has a shape that holds the coil body 1 so as not to easily fall off due to the elasticity of the elastic material 13, and as can be seen from the enlarged portions of FIG. 1A and FIG. The width W1 at both ends in the direction is narrower than the width W0 of other portions including the intermediate portion. For example, when the width and height of the coil body 1 is 0.8 mm and the length is 1.5 mm, the width W1 of the through hole 14 is 0.75 mm, W0 is 0.8 mm, and the length L is 1.45 mm. Yes, the depth is 0.8mm. Therefore, when the coil body 1 is inserted into the through-hole portion 14, the coil body 1 is mainly sandwiched between the four corners of the through-hole portion 14, in other words, the opening width (W1). (It is fitted and held on both sides of the square basket 3).
[0017]
FIGS. 5 and 6 show a configuration for screen printing in which a resin paste is filled in the through-hole portion 14 of the flat pallet 10 (which holds the coil body 1) shown in FIGS. . A screen plate 21 is stretched on the screen frame 20, and the flat pallet 10 (the one holding the coil body 1) is placed under the screen plate 21 as shown in FIGS. 1B and 1C. Positioned and arranged on 40. The filling roller 22 for applying and filling the resin paste 30 moves (rolls) while rotating on the screen plate. However, if the viscosity of the resin paste 30 is low, the filling roller 22 does not rotate and slips and causes a simple lateral movement, and the resin paste filling amount through the paste transmitting portion of the screen plate 21 is insufficient. For this reason, the self-propelled roller 23 that travels in a position opposite to the flat pallet 10 other than the region where the resin paste 30 is applied on the screen plate 21 is provided integrally on both sides of the filling roller 22. That is, the self-propelled roller 23 is fixed to the central shaft 24 to which the filling roller 22 is fixed. Since the self-propelled roller 23 travels in a region where the resin paste 30 is not applied, it moves while rotating without fail, and the filling roller 22 also moves while rotating integrally with this, The resin paste filling through the paste transmission part of the screen plate 21 is performed reliably. Although details are omitted, the center shaft 24 of the filling roller 22 and the self-running roller 23 is supported by the roller holding means 25 and driven in the front-rear direction as shown in FIG.
[0018]
As shown in FIGS. 1B and 1C, the paste transmitting portion 21 a (hole or mesh portion) of the screen plate 21 penetrates the flat pallet 10 positioned and mounted on the base 40. Although it is provided corresponding to the hole portion 14, it is preferably formed only in a portion facing the core portion 4 (winding 5) of the coil body 1 held in the through-hole portion 14.
[0019]
The resin paste 30 is preferably one in which magnetic powder is mixed in a thermosetting resin such as an epoxy resin. For example, as a magnetic powder, a ferrite spherical powder (particle size: 10 μm to 34 μm) mixed in an epoxy resin at a ratio of 50% by weight and an amorphous ferrite powder (particle size: 1 μm to 150 μm) at a ratio of 50% by weight is used. The mixing ratio of the magnetic powder to the thermosetting resin is such that the thermosetting resin is 20 to 50% by weight and the remainder is the magnetic powder. When the mixing ratio of the magnetic powder is less than 50%, the effect of mixing the magnetic powder is small, and when it exceeds 80%, the fluidity is deteriorated and filling failure is likely to occur.
[0020]
Next, a manufacturing procedure of the chip inductor using the flat pallet 10 will be described with reference to FIGS. First, as shown in FIG. 1A, in the pallet putting step, the coil main bodies 1 are respectively inserted into the through-hole portions 14 of the flat pallet 10 and are fitted and held.
[0021]
Then, the flat pallet 10 after the coil body 1 is provided in each through-hole portion 14 as shown in FIG. 1B is placed on the base 40. At this time, the flat pallet 10 is attached to the base 40 by fitting the positioning holes 15 of the flat pallet 10 of FIG. 4 to a taper pin (not shown) standing at a predetermined position of the base 40. Positioned. Although not shown, permanent magnets or electromagnets are embedded and integrated at a plurality of locations, for example, at equal intervals in the base 40, and magnetically attach the magnetic metal plate 11 in the flat pallet 10.
[0022]
In the first paste filling step of FIG. 1B, the resin paste 30 is applied to one surface (upper surface) of the flat pallet 10 positioned and fixed on the base 40 using the screen printing mechanism of FIGS. The through hole portion 14 is filled. That is, the screen plate 21 having the paste transmission part 21 a formed only in the part facing the core part 4 (winding 5) of the coil body 1 held in the through-hole part 14 is placed on the flat pallet 10. The resin paste 30 is filled in the outer periphery of the core portion 4 of the coil body 1, that is, the winding 5, through the paste transmission portion 21a by running while rotating the filling roller 22 on the screen plate while being aligned. To do. At this time, since the self-propelled roller 23 is integrated on both sides of the filling roller 22 and travels in the area of the screen plate 21 where there is no paste, the slip roller is prevented and the self-propelled roller 23 and The filling roller 22 connected integrally can be rotated, and the occurrence of filling failure can be prevented.
[0023]
In addition, an air vent hole 42 is formed at a position corresponding to the through hole portion 14 of the base 40 and serves to discharge air from the filling portion.
[0024]
With only the first paste filling step, it is difficult to wrap the resin paste 30 to the back side of the flat pallet 10. For this reason, the flat pallet 10 that has finished the first paste filling step is inverted as shown in FIG. 1C in the second paste filling step, and is screen-printed from the other surface of the flat pallet 10. The resin paste 30 is filled in the outer periphery of the core 4 (winding 5) in the same manner as in the first paste filling step. Thereby, the space in the through-hole part 14, ie, the outer periphery of the core part 4 of the coil main body 1, is completely filled with the resin paste 30, and the rectangular parallelepiped by the coil main body 1 and filling resin is formed.
[0025]
When the first and second paste filling steps are finished, in other words, after the screen printing from both surfaces of the flat pallet 10 is finished, the coil body 1 is fitted as shown in FIG. A paste curing step is performed in which the resin paste 30 in the through-hole portion 14 is heated to a predetermined temperature and cured while the flat plates 50 are stacked on the upper and lower surfaces of the flat pallet 10. The flat plate 50 used here is obtained by providing an elastic material 53 of the same material as that of the elastic material 13 of the flat pallet 10 above and below the metal plate 51 of the same material as that of the metal plate 11 of the flat pallet 10. Has a hole 52 of the same shape at the same position as the hole 12 of the metal plate 11. However, a portion corresponding to the through-hole portion 14 of the flat pallet 10 is formed on the flat surface by the elastic material 53. The flat plate 50 made of the same material as that of the flat plate pallet 10 is used so that when the resin paste 30 is heated and cured, the flat pallet 10 and the flat plate 50 are aligned so that the thermal expansion of the flat plate pallet 10 and the flat plate 50 is uniform. It is for doing so.
[0026]
If the flat plate 50 is not used, the surface of the resin paste filled in the core portion 4 of the coil body 1 is not preferable because the surface tension is rounded.
[0027]
The resin paste around the core portion 4 (winding 5) of the coil body 1 is cured by the paste curing step of FIG. A chip inductor is produced in each through hole 14.
[0028]
The chip inductor 1A is taken out from each through hole portion 14 of the flat pallet 10 by sandwiching the upper and lower sides of the flat pallet 10 with a perforated metal plate 60 as shown in FIG. This is executed by simultaneously pressing down the chip inductor 1A in the hole 14. The metal plate 60 is formed with a hole 61 that is slightly larger than the vertical and horizontal dimensions of the chip inductor 1A (for example, 0.1 mm in both vertical and horizontal directions (0.05 mm on one side)). When taking out from 10, even if there is a burr on the outer sheath 7, it is cut off at the edge of the punched hole 61 of the metal plate 60.
[0029]
An external electrode that covers the electrode 6 of the chip inductor 1A shown in FIGS. 3B and 3C taken out from the flat pallet 10 and is electrically conductive is formed to a predetermined film thickness by plating or the like. Completed product.
[0030]
In addition, it is preferable to perform barrel polishing for deburring the exterior coating 7 before forming the external electrode.
[0031]
According to this embodiment, the following effects can be obtained.
[0032]
(1) Since the coil body 1 is fitted and held in the through-hole portion 14 surrounded by the elastic material 13 of the flat pallet 10 and the resin paste 30 is filled by screen printing, the drum-shaped ferrite core 2 of the coil body 1 Even if there is a variation in dimensions, it can be absorbed by the elastic material 13, and the outer covering 7 can be formed around the core portion 4 without the resin paste 30 wrapping around the electrode 6 side of the coil body 1. The deburring work becomes easy.
[0033]
(2) A large number of through-hole portions 14 can be formed in the flat pallet 10, and the resin paste 30 can be filled into each through-hole portion 14 at a time by screen printing, so that mass productivity is good and expensive. Since no mold is used, production facilities are inexpensive and manufacturing costs can be reduced compared to injection molding or transfer molding.
[0034]
(3) In the injection molding or transfer molding, the resin is consumed in the runner part other than the product, and the material efficiency is poor. However, the resin paste 30 can be filled only in the necessary portions by screen printing using the flat pallet 10, and the material The efficiency is extremely high.
[0035]
(4) After the coil body 1 is provided in the through-hole portion 14 of the flat pallet 10, the core portion 4 is coated with the resin paste 30 on one side of the flat pallet 10 by screen printing and then reversed. However, since the air holes are not generated in the filled resin paste and the resin paste is filled from both sides of the flat pallet, the resin into the through hole 14 is filled. Paste filling is ensured.
[0036]
(5) The flat pallet 10 has a configuration in which the elastic material 13 is provided on the upper and lower surfaces of the metal plate 11 having the punching hole 12 larger than the through-hole portion 14 and the inner portion of the punching hole 12. By providing, thermal expansion of the flat pallet 10 can be suppressed, and highly accurate resin paste filling is possible.
[0037]
(6) The metal plate 11 of the flat pallet 10 is a magnetic body, and the flat pallet 10 is magnetically adsorbed on a base 40 integrated with permanent magnets or electromagnets to execute the first and second paste filling steps. Therefore, the screen pallet 10 is not displaced during screen printing, and high-precision screen printing is possible.
[0038]
Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.
[0039]
【The invention's effect】
In the resin sealing of the coil body using the conventional mold, a gap is generated between the mold cavity and the coil body due to the dimensional variation of the drum-shaped core to avoid unnecessary resin adhesion to the electrode surface or the like. However, according to the chip inductor manufacturing method using the screen-printing coil holding pallet according to the present invention, only the necessary portions of the coil main body are made of resin paste (after-curing exterior coating and coating) by using screen printing. Filling) is possible. The screen-printing coil holding pallet has a through-hole portion made of an elastic material, so that a resin paste is unnecessary for screen printing by fitting and holding the coil body in the through-hole portion. It is possible to eliminate or reduce unnecessary resin removal work after forming the exterior coating by curing the resin so that it does not leak to any region. Furthermore, the use of the screen printing method has the advantage that the manufacturing equipment is cheaper than that of injection molding and transfer molding, the consumption of the resin paste is not wasted, and the material efficiency is high.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a screen printing coil holding pallet according to the present invention, which is a main part configuration of a screen printing coil holding pallet and a pallet placing step in a manufacturing procedure of a chip inductor using the pallet; It is explanatory drawing which shows the 1st and 2nd paste filling process.
FIG. 2 is an explanatory diagram showing a step after a second paste filling step in the manufacturing procedure of the chip inductor using the screen printing coil holding pallet;
FIG. 3 is a perspective view showing an example of a coil body to be held by the screen-printing coil holding pallet and a chip inductor provided with an exterior coating.
FIG. 4 is a plan view of the overall configuration of the screen printing coil holding pallet;
FIG. 5 is a front view showing a mechanism for executing screen printing using the coil holding pallet for screen printing.
FIG. 6 is a schematic perspective view showing a mechanism for screen printing in the same manner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Coil main body 1A Chip inductor 2 Drum-like ferrite core 3 Square iron 4 Winding core part 5 Winding 6 Electrode 7 Exterior coating 10 Flat pallet 11, 51 Metal plate 12, 52 Punch hole 13, 53 Elastic material 14 Through-hole part 15 Positioning hole 20 Screen frame 21 Screen plate 21a Paste transmission part 22 Filling roller 23 Self-propelled roller 24 Center shaft 30 Resin paste 40 Base 42 Air vent hole 50 Flat plate 60 Perforated metal plate 61 Perforation hole 65 Push-down pin

Claims (3)

An elastic material is provided on the upper and lower surfaces of the metal plate having the punched hole and the inner part of the punched hole to form a flat plate, and winding is applied to the core part of the drum core on the elastic material at the inner position of the punched hole. A coil holding pallet for screen printing in which a through-hole portion for supporting the coil body by fitting is formed ,
The through-hole portion has a substantially rectangular opening, the opening width (W1) at both ends in the longitudinal direction is formed narrower than the opening width (W0) at the middle portion, and the opening width (W1) at both ends is A coil holding pallet for screen printing, wherein the flange portions on both sides of the drum-shaped core are sandwiched . The metal plate is a screen printing coil holding pallet of claim 1 wherein the magnetic body. A hook body on both sides of the drum-shaped core is fitted into the through-hole portion of the coil holding pallet for screen printing according to claim 1 or 2 by fitting a coil main body with a winding on the core portion of the drum-shaped core. A screen printing method characterized in that a resin paste is filled around the windings through a paste transmission part facing the winding core part of the screen plate.

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