JP2017193065A - Production method of metal mask for screen printing, and production method of led device using metal mask for screen printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a production method of a metal mask for screen printing, with which a conductive paste for mounting a small-sized LED is printed on a substrate.SOLUTION: A production method of a metal mask for screen printing includes: a step of forming a plurality of recesses by machining a surface of a planar base material; a step of forming a metal mask material on a section of which corresponding to the recesses of the base material a plurality of recesses having flat bottom faces are formed, and on a section of which corresponding to sections other than the recess a plurality of protrusions having flat upper faces are formed by conducting metal plating onto the base material; a step of peeling off and separate the metal mask material from the base material; a step of vertically inverting the metal mask material such that the recesses having the flat bottom faces of the separated metal mask material are positioned to the upper side and the protrusions having the flat upper faces are positioned to the lower side; and a step of forming a plurality of through holes by positioning laser processing sites of the flat bottom faces of the recesses positioned on the upper side of the inverted metal mask material and subsequently conducting the laser processing from the upper side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a metal mask for screen printing used for printing on a substrate a conductive paste for mounting a small light emitting diode (LED), and manufacturing of an LED device using the metal mask for screen printing. It is about the method.

Conventionally, when mounting a small LED used for a liquid crystal backlight or the like, an adhesive is dispensed on the substrate, and after mounting the LED element on the adhesive, the upper electrode of the LED element and the electrode of the substrate are connected by a wire. Although connected, due to demands for miniaturization of LEDs and cost reduction, both electrodes were taken from the upper surface (epitaxial growth surface) side of the LED element without using adhesives or wires, and the upper side was turned over. A so-called flip chip structure has been developed in which the electrode surface is directly mounted with a conductive paste. However, when the conductive paste is dispensed on the substrate, it is difficult to finely adjust the coating amount, which causes the productivity to deteriorate. Therefore, recently, it has been considered to print an appropriate amount of conductive paste on a substrate using a screen printing metal mask.
Further, as a conventional prior art, there is a screen disposed on a protrusion for printing a printing material on a printing target position on a member having a plurality of protrusions, and the printing material is covered by covering the protrusion. A flat portion for guiding a squeegee for printing, and a concave portion that is integral with the flat portion and guides the printing material to a printing target position between the plurality of projection portions, A screen having an opening at a portion corresponding to a print target position is known at the bottom (see, for example, Patent Document 1).

JP 2001-199177 A

  The substrate for fixing the LED element is provided with a reflector or a case so as to surround the periphery of the LED element in advance. Therefore, on the substrate in the cavity surrounded by the reflector or the case while avoiding the reflector or the case. A conductive paste is screen-printed on the electrodes of the LED, and the electrode side of the LED element is mounted on the printed conductive paste, and then an encapsulating resin in which a phosphor is dispersed in a cavity surrounded by a reflector or a case. Filled and completed. Therefore, a cavity mask having a recess that penetrates into the cavity is required as a metal mask for screen-printing the conductive paste on the substrate. However, in an LED that is becoming increasingly miniaturized, the design of the recess of the cavity mask varies depending on the type of substrate, the depth of the recess also varies, and the depth of the recess is 2 mm or less, for example, up to 0.45 mm. However, it is usually difficult to produce a cavity mask having a recess depth of 0.45 to 2 mm.

  The present invention has been made to solve the above-described problems, and is used for printing on a substrate a conductive paste for mounting a small light emitting diode (LED) used for a liquid crystal backlight or the like. The manufacturing method of the metal mask for screen printing manufactured and the manufacturing method of the LED device using the metal mask for screen printing are provided.

  In the method of manufacturing a metal mask for screen printing according to the present invention, a step of preparing a flat base material and machining with a tool on the surface of the base material to form a large number of recesses on the surface of the base material. By applying plating to the base material on which the process and a large number of recesses are formed, a part corresponding to the recess of the base material is formed with a number of recesses having a bottom flat surface, and a part corresponding to other than the recess Includes a step of forming a metal mask material having a large number of convex portions having an upper flat surface, a step of separating the metal mask material from the base material, and a step of separating the separated metal mask material on the bottom flat surface. A step of inverting the metal mask material up and down so that the convex portion having the upper flat surface is located on the lower side, and the concave portion located on the upper side of the inverted metal mask material. After aligning the laser machining site of the bottom flat surface, those having a step of forming a plurality of through-holes subjected to laser processing from above, the.

  Moreover, after forming a through-hole by laser processing, the process of obtaining a metal mask by cutting out a center part from a metal mask raw material is further added.

  Moreover, the shape of many recessed parts formed in the preform | base_material surface is a cup shape with a wide upper opening side and a lower bottom face side, and an inclination angle is the range of 5-10 degree | times.

  Moreover, the depth of many recessed parts formed in the preform | base_material surface is the range of 0.45-2.0 mm.

  Further, the plurality of through holes formed by laser processing on the bottom flat surface of the concave portion of the metal mask material are formed at a position 30 to 50 μm apart from the lower end portion of the peripheral side wall of the concave portion.

  In the LED device manufacturing method using the screen printing metal mask according to the present invention, electrodes are provided on the upper surface of the substrate constituting the LED device, and the reflector or the case protrudes so as to surround the upper surface of the substrate. LED device in which a cavity surrounded by a reflector or a case is formed on the upper surface of the substrate, and in the back side space of the convex portion of the metal mask so as to escape the reflector or the case protruding from the substrate The conductive paste is printed on the electrode of the substrate through a large number of through holes formed in the bottom flat surface of the concave portion by accommodating the concave portion of the metal mask in the cavity. The electrode on the lower side of the flip-chip LED element is mounted on a conductive paste on the substrate.

  Further, an electrode is provided on the upper surface of the substrate constituting the LED device, a reflection plate or case is projected so as to surround the periphery of the upper surface of the substrate, and a cavity surrounded by the reflection plate or case is formed on the upper surface of the substrate. The device is housed and arranged in the back side space of the convex part of the metal mask so as to escape the reflector or case protruding from the substrate, while the concave part of the metal mask is intruded into the cavity. The adhesive is printed on the substrate through a plurality of through holes formed in the bottom flat surface of the recess, and the LED element having the face-up chip structure is mounted on the adhesive, and then the upper part of the LED element is mounted. The electrode and the electrode of the substrate are connected by a wire.

  According to the present invention, screen printing can be performed much faster than dispensing a conductive paste or the like on the substrate of an LED device, and the amount of paste can be stabilized, so that productivity can be improved. In particular, there is an effect that it becomes possible to cope with the progress of miniaturization of LED devices.

It is sectional drawing which shows the manufacturing method of the metal mask for screen printing in Example 1 of this invention in order of a process. It is a top view which shows the whole structure before cutting out the metal mask raw material produced by the manufacturing method of the metal mask for screen printing in Example 1 of this invention. It is a top view which expands and shows only the recessed part of the metal mask which was produced with the manufacturing method of the metal mask for screen printing in Example 1 of this invention, and formed the through-hole by laser processing. It is sectional drawing which shows the process of manufacturing an LED device using the metal mask produced by the manufacturing method of the metal mask for screen printing in Example 1 of this invention.

Example 1.
FIG. 1 is a cross-sectional view showing a method of manufacturing a screen printing metal mask according to Embodiment 1 of the present invention in the order of steps.
First, a flat base material 1 made of a SUS material having a plate thickness of, for example, about 2 mm is prepared, and machining is performed using a drill 2 as a tool at a machining center, whereby a large number of surfaces are formed on the surface of the flat base material 1. Concave processing is performed (see FIG. 1A). The recesses 11 that are processed in large numbers on the surface of the base material 1 by the drill 2 have a depth d that is relatively deep in a range of about 0.45 to 2 mm (preferably, a range of about 0.6 to 1 mm). The shape of is a cup shape with a wide upper opening side and a narrow bottom bottom side, and is processed with an angle so that the inclination angle is in the range of about 5 to 10 degrees (opening angle is about 10 to 20 degrees) ( (Refer FIG.1 (b)). If the recess 11 is provided with an inclination angle, it is easy to peel off after plating, and there is an advantage that the conductive paste can easily enter. Thus, when forming the recessed part 11 with comparatively deep depth in the base material 1, the etching process is unsuitable, and the machining by the drill 2 is the most preferable processing method. Next, a metal mask material 3 having a thickness of about 50 to 200 μm is formed by plating from the base material 1 on which a large number of recesses 11 are formed (see FIG. 1C). In the metal mask material 3, a large number of concave portions 32 having a bottom flat surface 31 are formed in a portion corresponding to the concave portion 11 of the base material 1, and an upper flat portion is provided in a portion corresponding to other than the concave portion 11 of the base material 1. A large number of convex portions 33 having a surface are formed. Then, the plated metal mask material 3 is separated from the base material 1 and separated (see FIG. 1D). Here, when the metal mask material 3 is peeled from the base material 1, it is inevitable that the metal mask material 3 extends to some extent. Next, the separated metal mask material 3 is placed so that the concave portion 32 having the bottom flat surface 31 is located on the upper side and the convex portion 33 having the upper flat surface is located on the lower side (the state in which the top and the bottom are turned upside down) ), The metal mask material 3 is turned upside down. And after aligning the laser processing site | part of the bottom flat surface 31 of the recessed part 32 located in the upper side of the reversed metal mask raw material 3, the laser processing 4 is given from upper direction, and the several through-hole 34 is formed (FIG. 1). (See (e)). In the formation processing of the through hole 34 by the laser processing 4, since the distance w between the formation position of the through hole 34 and the lower end of the peripheral side wall of the recess 32 is as small as about 30 to 50 μm, the depth of the recess 32 is reduced. In connection with this, the method of forming a through hole using a resist in advance during plating is impossible, and the processing method of forming the through hole 34 in the bottom flat surface 31 of the recess 32 by laser processing 4 is the only optimum means. Become. When the through hole 34 is formed by the laser processing 4, the metal mask material 3 extends to some extent at the time of peeling, so that the data for laser processing is based on a reference point mark (described later) of the metal mask material 3. It is necessary to adjust so that the laser processing portion of the bottom flat surface 31 of the recess 32 is matched. Actually, alignment with the concave portion 32 is performed by a camera (not shown) of a laser processing machine, but it is necessary to design in consideration of a deviation of about ± 20 μm.

FIG. 2 is a plan view showing the entire structure before cutting out a metal mask material produced by the method for producing a screen printing metal mask according to Embodiment 1 of the present invention.
In FIG. 2, the inner portion surrounded by the dotted line 5 of the metal mask material 3 is the metal mask 3A, which is obtained by cutting out after forming the through hole 34 by the laser processing 4, and is used for, for example, a liquid crystal backlight or the like. The metal mask 3A for screen printing used for printing on the board | substrate the electrically conductive paste for mounting the small light emitting diode (LED) used. In the metal mask 3A, three pattern formation regions 6 are formed in parallel at the center, and a large number of recesses 32 are formed in each pattern formation region 6. A portion between the outer peripheral edge of the metal mask material 3 before being cut out and a dotted line 5 that is cut out to become the metal mask 3A is indicated by a dashed line 7 in an imaginary line. Reference point marks 8 for alignment at the time of forming the through holes 34 by the laser processing 4 are formed at two locations in the center. Therefore, at the time of forming the through hole 34 by the laser processing 4, the laser processing data is corrected using the reference point mark 8 as a base point so as to adjust the laser processing portion of the bottom flat surface 31 of the recess 32.

FIG. 3 is an enlarged plan view showing only the concave portion of the metal mask produced by the method for producing a screen printing metal mask in Example 1 of the present invention and having through holes formed by laser processing.
In FIG. 3, a screen printing metal mask 3A used for printing on a substrate a conductive paste for mounting a small light emitting diode (LED) used for, for example, a liquid crystal backlight or the like obtained by cutting. The shape of the concave portion 32 is a square shape with rounded corners in plan view, and rounded square-shaped through holes 34 are formed at the four corners of the bottom flat surface 31 of the concave portion 32. Note that the number, shape, and size of the recesses 32 change depending on the type of LED, and the number, shape, and size of the through holes 34 also change. Since the peripheral side wall of the recess 32 is angled, there is an advantage that the conductive paste can easily enter.

FIG. 4 is a cross-sectional view showing a process for manufacturing an LED device using a metal mask manufactured by the method for manufacturing a screen printing metal mask in Example 1 of the present invention.
A process of manufacturing an LED device having a flip chip structure will be described with reference to FIG. The flip chip structure LED device is a type that takes both electrodes from the upper surface (epitaxial growth surface) side of the LED element and mounts it upside down. Compared to the LED device with the face up chip structure that is mounted by wire bonding Thus, the flip chip structure tends to be small in size and deep in the recess. In FIG. 4, the substrate 9 constituting the LED device having the flip chip structure is provided with an electrode 10 on the upper surface, and a reflecting plate or case 12 having a trapezoidal cross section is provided so as to surround the periphery of the upper surface of the substrate 9. A cavity 13 surrounded by a reflector or case 12 is formed on the upper surface of the substrate 9. Therefore, the screen printing metal mask 3A of the present invention is prepared, and the rear surface of the convex portion 33 of the metal mask 3A is escaped from the reflecting plate or the case 12 having a trapezoidal cross section protruding from the substrate 9. It is housed and arranged in the side space. At the same time, the concave portion 32 of the metal mask 3A is inserted and accommodated in the cavity 13, thereby bringing the bottom flat surface 31 of the concave portion 32 into contact with the electrode 10 of the substrate 9 (see FIG. 4A). At this time, a slight gap is formed between the upper end surface of the reflector or the case 12 and the back surface of the convex portion 33 of the metal mask 3A. However, they may be brought into contact without forming a gap. Next, in the state of FIG. 4A, when conductive printing such as solder is placed on the upper surface of the metal mask 3A and screen printing is performed, the conductive paste such as solder is filled in the recess 32 of the metal mask 3A. Then, the conductive paste 14 such as solder is printed on the electrode 10 of the substrate 9 through a large number of through holes 34 formed in the bottom flat surface 31 of the recess 32 (see FIG. 4B). Next, the LED element 15 having the flip chip structure in which both the electrodes 16 are taken from the upper surface (epitaxial growth) side of the LED element 15 is turned upside down (both electrodes 16 are on the lower surface). After the surface of the electrode 16 is placed on a conductive paste 14 such as solder on the electrode 10 of the substrate 9, it is reflowed and directly mounted (see FIG. 4C). Thereafter, a resin containing a phosphor is filled and sealed in the cavity 13 surrounded by the reflector on the upper surface of the substrate 9 or the case 12 so as to cover the entire LED element 15. Thereafter, the LED devices are cut one by one. In other words, unlike the face-up chip structure, it is not necessary to dispense an adhesive on the substrate and connect the upper electrode of the LED element and the electrode of the substrate by wire bonding, which enables further miniaturization of the LED device. Become.

Example 2
In the first embodiment, the case of manufacturing an LED device having a flip chip structure has been described. However, the metal mask for screen printing according to the present invention can also be applied to an LED device having a face-up chip structure mounted by wire bonding. .
That is, the LED device with the face-up chip structure mounted by wire bonding is the most general-purpose LED element structure having the light emitting surface on the upper surface. When the LED element is mounted, the metal mask for screen printing of the present invention is used for the substrate. After the adhesive is screen printed on the LED element, the LED element is mounted on the adhesive, and the upper electrode of the LED element and the electrode of the substrate are connected by a wire. Even if the LED device has a face-up chip structure, if there is a demand for further miniaturization, the screen-printing metal mask of the present invention can be applied when screen-printing the adhesive on the substrate. .

1 Base material 11 Recess 2 Drill (tool)
3 Metal mask material 31 Bottom flat surface 32 Recess 33 Protrusion 34 Through hole 4 Laser processing 5 Dotted line 3A Metal mask 6 Pattern formation region 7 Dotted line 8 Reference point mark 9 Substrate 10 Electrode 12 Reflector or case 13 Cavity 14 Conductive paste 15 LED element 16 Both electrodes

Claims (7)

A step of preparing a flat base material;
Forming a large number of recesses on the surface of the base material by machining the surface of the base material with a tool;
By plating from above the base material on which a large number of recesses are formed, a number of recesses having a flat bottom surface are formed at the site corresponding to the recesses of the base material, and the site corresponding to other than the recesses Forming a metal mask material having a large number of convex portions having an upper flat surface, and
Peeling and separating the metal mask material from the base material;
Reversing the metal mask material so that the concave portion having the bottom flat surface is positioned on the upper side and the convex portion having the upper flat surface is positioned on the lower side,
After aligning the laser processing site of the bottom flat surface of the recess located on the upper side of the inverted metal mask material, forming a plurality of through holes by laser processing from above,
A method for producing a metal mask for screen printing, comprising: A step of preparing a flat base material;
Forming a large number of recesses on the surface of the base material by machining the surface of the base material with a tool;
By plating from above the base material on which a large number of recesses are formed, a number of recesses having a flat bottom surface are formed at the site corresponding to the recesses of the base material, and the site corresponding to other than the recesses Forming a metal mask material having a large number of convex portions having an upper flat surface, and
Peeling and separating the metal mask material from the base material;
Reversing the metal mask material so that the concave portion having the bottom flat surface is positioned on the upper side and the convex portion having the upper flat surface is positioned on the lower side,
After aligning the laser processing site of the bottom flat surface of the recess located on the upper side of the inverted metal mask material, forming a plurality of through holes by laser processing from above,
After forming a through hole by laser processing, obtaining a metal mask by cutting out the central portion from the metal mask material,
A method for producing a metal mask for screen printing, comprising:   3. The shape of a plurality of recesses formed on the surface of the base material is a cup shape having a wide upper opening side and a lower bottom surface side, and an inclination angle is in the range of 5 to 10 degrees. The manufacturing method of the metal mask for screen printing of description.   4. The metal mask for screen printing according to claim 1, wherein a depth of a plurality of recesses formed on the surface of the base material is in a range of 0.45 to 2.0 mm. 5. Manufacturing method.   The plurality of through holes formed by laser processing on the bottom flat surface of the concave portion of the metal mask material are formed at a position 30 to 50 μm apart from the lower end of the peripheral side wall of the concave portion. The manufacturing method of the metal mask for screen printing as described in any one of Claim 4. A method for producing an LED device having a flip chip structure using a metal mask for screen printing produced by the method for producing a metal mask for screen printing according to any one of claims 1 to 5,
An LED device in which an electrode is provided on the upper surface of a substrate constituting the LED device, a reflecting plate or case is projected so as to surround the periphery of the upper surface of the substrate, and a cavity surrounded by the reflecting plate or case is formed on the upper surface of the substrate. And disposed in the space on the back side of the convex portion of the metal mask so as to escape the reflecting plate or case protruding from the substrate, while accommodating the concave portion of the metal mask in the cavity. The conductive paste is printed on the electrode of the substrate through a plurality of through holes formed in the bottom flat surface of the recess, and the electrode on the lower side of the LED element of the flip chip structure is A method for manufacturing an LED device using a metal mask for screen printing, which is mounted on a conductive paste on a substrate. A method for producing an LED device having a face-up chip structure using a metal mask for screen printing produced by the method for producing a metal mask for screen printing according to any one of claims 1 to 5. ,
An LED device in which an electrode is provided on the upper surface of a substrate constituting the LED device, a reflecting plate or case is projected so as to surround the periphery of the upper surface of the substrate, and a cavity surrounded by the reflecting plate or case is formed on the upper surface of the substrate. And disposed in the space on the back side of the convex portion of the metal mask so as to escape the reflecting plate or case protruding from the substrate, while accommodating the concave portion of the metal mask in the cavity. After printing the adhesive on the substrate through a number of through holes formed on the bottom flat surface of the recess, and mounting the face-up chip structure LED element on the adhesive An LED device using a metal mask for screen printing, wherein the upper electrode of the LED element and the electrode of the substrate are connected by a wire Production method.

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