Mask for array

Abstract

To provide a mask for arrangement that can prevent poor mounting of solder balls.SOLUTION: A mask for arrangement in which solder balls 2 are placed at a predetermined position on a workpiece 3 by placing the solder balls 2 into a through holes 12 corresponding to a predetermined arrangement pattern includes a mask body 10 in which the through hole 12 is formed. At least the squeegee surface of the mask body 10 is provided with a coating layer made of fluororesin, silicone resin, emulsion, resist, or acrylic resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an array mask used, for example, to form solder bumps.

Background Art

[0002] As a method for forming solder bumps, there are a printing step of applying flux to electrodes on a workpiece such as a wafer, a flexible substrate, or a rigid substrate, an array step of arranging solder balls on the flux, and a heating step of heating and melting the solder balls to form bumps. In the above-described array step, as a method of arranging solder balls on a workpiece, there is a transfer method using a mask. In the transfer method, an array mask (hereinafter, simply referred to as a "mask" as appropriate) having positioning through holes through which solder balls can be inserted corresponding to the array pattern of the electrodes of the workpiece is used to mount the solder balls on the electrodes of the workpiece. Specifically, after aligning the mask with the workpiece so that the through holes and the electrodes coincide, the solder balls supplied onto the mask are swept with a squeegee, a brush, or the like, and the solder balls are inserted into each through hole one by one. Then, by fixing the solder balls to the flux, the solder balls are temporarily mounted on predetermined positions on the workpiece.

[0003] As such a mask, there is one disclosed in Patent Document 1. The mask described in Patent Document 1 is provided with a plurality of supporting protrusions on the lower surface of a mask body having through holes, and the protruding dimensions of the protrusions are set to the same dimension. Thereby, when the mask is installed on the workpiece, the lower ends of all the supporting protrusions are brought into contact with the upper surface of the workpiece, and an opposing gap between the mask body having through holes and the workpiece is ensured.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in recent years, with the miniaturization of electronic devices, the miniaturization of bumps has been progressing. That is, with the miniaturization of bumps, the through-hole interval dimension and the pattern region interval dimension in the mask become narrower, and the outer dimension of the protrusion itself arranged between through-holes and between pattern regions (outer periphery of the pattern region) also tends to become smaller. Therefore, the facing interval between the mask and the work becomes narrower, and the flux arranged on the electrode of the work easily adheres to the mask. If the flux adheres to the surface of the mask, poor mounting of solder balls is likely to occur. An object of the present invention is to provide an array mask capable of preventing poor mounting of solder balls.

Means for Solving the Problems

[0006] The present invention is an array mask for mounting a solder ball 2 at a predetermined position on a work 3 by pouring the solder ball 2 into a through-hole 12 corresponding to a predetermined array pattern, comprising a mask body 10 in which a large number of pattern regions composed of through-holes 12 are formed, and a protrusion 15 provided on the facing surface side of the mask body 10 and the work 3, characterized in that a coating layer 50 is formed at least on the lower surface of the mask body 10. Further, the mask body 10 and the protrusion 15 are formed separately. Further, the coating layer 50 is formed so as to cover the lower surface of the mask body 10 and the surface of the protrusion 15. This coating layer 50 is preferably formed with a thickness of 1 μm or less.

[0007] The present invention also provides a method for manufacturing an alignment mask, which includes a mask body 10 having a large number of pattern regions formed by through holes 12, and a protrusion 15 provided on the surface of the mask body 10 facing the workpiece 3, and at least a coating layer 50 is formed on the lower surface of the mask body 10. First, a primary pattern resist 41 having a resist body 41a is formed on a master mold 40. Next, a primary electrodeposited layer 42 is formed on the master mold 40 using the resist body 41a. Next, a secondary pattern resist 44 having a resist body 44a is formed on the primary electrodeposited layer 42. Next, a coating layer 50 is formed on the surface of the primary electrodeposited layer 42. It is preferable to form this coating layer 50 on the surface of the primary electrodeposited layer 42 on the side having the secondary pattern resist 44 of the primary electrodeposited layer 42 and on the surface of the secondary pattern resist 44.

Advantages of the Invention

[0008] According to the alignment mask of the present invention, since a coating layer is formed on the lower surface of the mask body, it is possible to prevent the state where the flux adheres to the lower surface of the mask body. Further, by forming the coating layer so as to cover the lower surface of the mask body and the surface of the protrusion, the coating layer functions as a protective layer for the protrusion, and it is possible to prevent the protrusion from falling off, deforming, or being damaged.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 8

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Figure 10

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Figure 12

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Figure 14

Mode for Carrying Out the Invention

[0010] (First Embodiment) Figs. 1 to 3 show an array mask for solder balls according to a first embodiment of the present invention. This array mask (hereinafter simply referred to as a mask) 1 is used in the process of arranging solder balls 2 in the formation of solder bumps. In Fig. 2, reference numeral 3 indicates a work to which the solder balls 2 are to be mounted by the mask 1. This work 3 is formed, for example, by mounting a plurality of semiconductor chips 5 on a base 4 of a glass epoxy substrate, wiring them by wire bonding, and then performing transfer molding encapsulation. Electrodes 6, which are input / output terminals, are formed in a predetermined pattern on the upper surface of the work 3 so as to surround the semiconductor chips 5. Note that the work 3 is cut into individual pieces after the formation of the bumps and becomes individual LSI chips.

[0011] As shown in Fig. 1, the mask 1 is composed of a mask body 10 formed of a nickel alloy such as nickel or nickel cobalt, or copper or other metals, and a frame body 11 can be attached to the mask body 10 so as to surround it. In the central part of the board surface of the mask body 10, a large number of pattern regions each composed of a large number of independent through holes 12 for inserting solder balls 2 are formed corresponding to each semiconductor chip 5. As shown in Fig. 2, the through holes 12 correspond to an array pattern corresponding to the array positions of the electrodes 6 of each semiconductor chip 5 on the work 3. The solder balls 2 have a radius dimension of 50 μm or less, and accordingly, each through hole 12 is formed in a circular shape in plan view with an inner diameter dimension slightly larger than the radius dimension of the ball 2.

[0012] The frame body 11 is a flat plate made of a material such as aluminum, 42 alloy, invar material, SUS430, etc., and has a single rectangular opening corresponding to the mask body 10 at the center of its board surface. In this embodiment, one mask body 10 is held by one frame body 11. The frame body 11 is a molded product with a greater thickness than the mask body 10 and is joined to the outer peripheral edge of the mask body 10 in an inseparable and integral manner. Here, the thickness dimension of the frame body 11 is, for example, about 0.05 to 1.0 mm, and is set to 0.5 mm in this embodiment. Also, the thickness of the mask body 10 is preferably 10 μm or more, and is set to 200 μm in this embodiment.

[0013] On the lower surface side of the mask body 10 (mask 1), that is, on the side facing the workpiece 3, a downwardly protruding protrusion 15 can be provided. Specifically, as shown in FIGS. 2 and 3, the protrusion 15 (crossbar 15a) can be provided so as to surround the pattern region between the pattern regions (outer periphery of the pattern region). The protrusion 15 (crossbar 15a) does not have to be continuously provided as shown in FIG. 3, and may be provided fragmentarily. Also, as shown in FIG. 4, the protrusion 15 (support column 15b) can be provided at a position where the through hole 12 in the pattern region is not formed. Further, the shape of the protrusion 15 provided so as to surround the pattern region between adjacent pattern regions (outer periphery of the pattern region) is not limited to the crossbar 15a, and may be a support column 15c as shown in FIG. 5. If such a protrusion 15 is provided, during the alignment operation, it can contact the upper surface of the workpiece 3 to secure the opposing gap between the mask body 10 and the workpiece 3. In each of the protrusions 15 (crossbar 15a, support column 15b), as shown in FIGS. 2 and 4, it is preferably formed to taper from the lower surface of the mask body 10 toward the tip of the protrusion 15, presenting a frustum of a cone shape.

[0014] As the shape of the protruding portion 15, as shown in FIG. 6, in addition to this, it may be a shape that expands at the end where the base dimension of the protruding portion 15 increases as it approaches the lower surface of the mask body 10 (a shape that tapers from the base to the tip of the protruding portion 15), and the side surface is formed in an arc shape. Thereby, it is possible to prevent breakage caused by stress concentration particularly at the base portion 15” of the protruding portion 15. Also, when the mask 1 is placed on the workpiece 3, even if the flux 17 adheres to the protruding portion 15, since the side surface of the protruding portion 15 is an arc, it is possible to prevent the flux 17 from flowing into the through hole 12. Thus, it is possible to eliminate the risk of causing a mounting defect of the solder ball 2 due to the adhesion of the flux 17 to the through hole 12. Regarding the end position of the base portion 15” of the protruding portion 15, it is preferably located near the through hole 12 on the lower surface of the mask body 10, and forms that are located at the intersection of the lower surface 10a of the mask body and the inner surface 12a of the through hole, or that are located at a position where a gap is taken from the through hole 12 on the lower surface 10a of the mask body are conceivable. Also, the side surface of the protruding portion 15 may be either a convex arc or a concave arc. If it is a convex arc, it will have good strength, and if it is a concave arc, there will be no portion where the flux 17 adheres close to the electrode 6 at any position on the side surface of the protruding portion 15. That is, it may be in a state where a certain distance is maintained from the electrode 6 to which the flux 17 adheres. Furthermore, the tip portion 15’ and / or the base portion 15” of the protruding portion 15 may be formed in an arc shape, whereby the risk of the flux 17 adhering to the protruding portion 15 is reduced as much as possible.

[0015] In this mask 1, it is preferable that the ratio of the height of the protrusion 15 to the thickness of the mask body 10 is 2:1 or more, and it is more preferable to satisfy this within the range where the thickness of the mask body 10 is 10 to 300 μm. Also, the protrusion 15 preferably has a large aspect ratio (the ratio of the height to the tip dimension in the protrusion 15), and in this embodiment, the aspect ratio is 3. Further, the base dimension L2 of the protrusion 15 is preferably 1.0 to 1.5 times the tip dimension L1 of the protrusion 15, and in this embodiment, it is set to 1.2 times. Furthermore, it is preferable that the ratio of the tip dimension L1 of the protrusion 15, the base dimension L2, and the width dimension L3 between the through holes 12 is 1:1.2:1.4 or more. Additionally, the dimension L4 from the pattern region to the base of the protrusion 15 (the crossbar 15a, the support column 15c) is preferably set to 0.01 mm or more, and in this embodiment, it is 0.02 mm. With such conditions, it is possible to prevent the adhesion of flux as much as possible. At this time, by satisfying the relationship of the ratio between the tip dimension L1 and the base dimension L2 of the protrusion 15 described above and the relationship of the dimension L4 from the pattern region to the base of the protrusion 15, it is possible to achieve both prevention of damage to the protrusion 15 and prevention of flux adhesion. Furthermore, when the dimension from the pattern region to the center of the tip of the protrusion 15 (the crossbar 15a, the support column 15c) is L5, by setting the ratio of L1, L2, and L5 to 1:3:2.5 or more, the above-mentioned dual effect can be maximally utilized.

[0016] Here, the mask 1 is formed by integrating the mask body 10 and the protrusion 15, but the mask body 10 and the protrusion 15 may be integrally formed as separate members. In the mask 1, if the mask body 10 is formed of a magnetic material and the protrusion 15 is formed of a non-magnetic material, when the mask 1 is fixed to the workpiece 3 by the magnetic attraction of the magnet, the magnetic force can act uniformly on the mask 1. Therefore, there is no risk of the mask 1 being accidentally bent, it can be well adhered to the workpiece, and the alignment accuracy of the through hole 12 with respect to the electrode 6 can be improved. Also, when removing the mask 1, since the workpiece 3 and the protrusion 15 are not directly magnetically coupled, the peeling can be improved. Such a mask 1 can be obtained, for example, by forming the mask body 10 of a magnetic metal (such as nickel, iron, etc.) and the protrusion 15 of a non-magnetic metal (such as copper, aluminum, etc.).

[0017] Also, in the case where the protrusion 15 is formed of a non-magnetic material, it is not limited to the above metals, and it may be formed of resin or resist. Thereby, in addition to the above effects, a cushioning effect derived from the elasticity of the resin is exhibited, and when the protrusion 15 abuts on the workpiece 3, the risk of the workpiece 3 being damaged is reduced. In order to significantly exhibit such an effect, in the mask 1, it is preferable to form not only the protrusion 15 but also all of the portions in contact with the workpiece 3 of resin. Also, when the protrusion 15 is formed of resin, if the same resist as that used when forming the mask body 10 by electroforming is used, it can be formed with high production efficiency.

[0018] Also, in this mask 1, as shown in FIGS. 2, 4, and 6, a coating layer 50 is provided on the lower surface of the mask body 10 and the inner surface of the through holes 12. The coating layer 50 preferably has water repellency, and examples of its material include fluororesin, silicone resin, emulsion, resist (liquid), etc. By providing such a coating layer 50, even if flux adheres to the lower surface of the mask body 10 or the inner surface of the through holes 12, the flux can be repelled, and it is possible to prevent the state where the flux remains adhered to the lower surface of the mask body 10 or the inner surface of the through holes 12. Note that the coating layer 50 may be formed on the upper surface of the mask body 10, and it does not need to be formed between the pattern regions and on the lower surface of the mask body 10 between the protruding portions 15 (crossbars 15a, support columns 15c). In short, it is desirable to form it in a portion where poor mounting of solder balls is likely to occur when flux adheres, and it is desirable to form it on the surfaces of the mask body 10 and the protruding portions 15 that face the flux 17 applied on the electrode 6 when the mask 1 is placed on the workpiece.

[0019] Note that each drawing does not show the actual state of the mask 1, but shows it schematically. Also, the opening dimensions of the through holes 12 and the thickness dimensions of the mask body 10, etc. in each drawing are shown in such dimensions for the convenience of drawing creation. Further, in FIGS. 3 and 5, the reference numeral 15 indicates the lower end surface (tip surface) of the protruding portion 15, and the base of the protruding portion 15 is not shown. Also, in FIGS. 3 and 5, the coating layer 50 is not shown.

[0020] The operation of arranging the solder balls 2 using the mask 1 is performed in the following procedure. Note that this arranging operation is performed by a dedicated arranging device (refer to FIGS. 1 and 5 of Patent Document 1, etc.). First, flux 17 (refer to FIG. 2) is printed and applied onto the electrode 6 of the work 3. Next, after aligning the mask 1 on the work 3 so that the through holes 12 and the electrode 6 coincide, the mask 1 is fixed. Such alignment work is actually performed by aligning the outer peripheral edges of the frame body 11 and the work 3. When the alignment work is completed, in the fixed state, the lower end surface of the protrusion 15 abuts on the surface of the work 3, so that the mask body 10 is held in a separated posture with a facing gap with the work 3 as shown in FIGS. 2, 4, and 6. At this time, a magnet can also be arranged below the work 3, and the mask 1 can be attracted to the work 3 side by the magnetic force action of this magnet.

[0021] Next, a large number of solder balls 2 are supplied onto the mask 1, and the solder balls 2 are dispersed on the mask 1 using a squeegee brush, and the solder balls 2 are inserted into the through holes 12 one by one. Thus, the solder balls 2 are adhesively held in a temporarily fixed state by the flux 17 on the electrode 6. In the operation of inserting the solder balls 2 using such a squeegee brush, even if a large squeegee brush pressure is applied to the mask 1, the mask 1 can be prevented from being deflected by the protrusion 15, and the insertion operation can proceed smoothly with high work efficiency.

[0022] As described above, according to the mask 1 according to the present embodiment, since the protrusion 15 that forms the facing gap between the mask body 10 and the work 3 is provided, the facing gap with the work 3 can be surely secured by the protrusion 15, and the operation of inserting the solder balls 2 into the through holes 12 can be efficiently and smoothly performed without leakage.

[0023] A reinforcing frame 11 can be provided on the outer peripheral edge of the mask body 10. If the mask body 10 is formed under a tension such that a stress acts in a direction of contracting inwardly by itself, the expansion of the mask body 10 due to a change in the ambient temperature can be absorbed by the tension in the contracting direction. Thus, the occurrence of misalignment of the mask body 10 with respect to the workpiece 3 can be prevented. Further, since a uniform tension can be applied to the entire mask body 10, the solder balls 2 can be mounted on the workpiece 3 with high positional accuracy.

[0024] Next, a method for manufacturing the array mask 1 having such a configuration is shown in FIGS. 7 and 8. First, for example, a photoresist layer 31 is formed on the surface of a master mold 30 made of conductive stainless steel or brass. This photoresist layer 31 is formed by laminating one or several sheets of negative-type photosensitive dry photoresist according to a predetermined height and performing thermocompression bonding. Next, as shown in FIG. 7(a), after a pattern film (glass mask) 32 having a light-transmitting hole 32a corresponding to the protrusion 15 is brought into close contact with the photoresist layer 31, ultraviolet light is irradiated with an ultraviolet lamp 33 for exposure, and each process of development and drying is performed to dissolve and remove the unexposed portion, whereby, as shown in FIG. 7(b), a primary pattern resist 34 having a resist body 34a corresponding to the tapered protrusion 15 is formed on the master mold 30. At this time, it is preferable to taper the resist body 34a by using a photoresist that is difficult for ultraviolet rays to penetrate or by reducing the exposure amount. Subsequently, the master mold 30 is placed in an electroforming bath set under predetermined conditions, and as shown in FIG. 7(c), within the range of the height of the previous resist body 34a, electroplated metal such as nickel or copper is electroformed on the surface of the master mold 30 not covered by the resist body 34a of the master mold 30 to form a primary electroplated layer 35. Here, the primary electroplated layer 35 is formed over substantially the entire surface of the master mold 30 (first electroforming step). Next, as shown in FIG. 7(d), the primary pattern resist 34 is removed. Here, it is preferable to perform a polishing treatment on the surface of the primary electroplated layer 35.

[0025] Next, as shown in Fig. 8(a), after forming a photoresist layer 36 on the entire surfaces of the primary electroformed layer 35 and the master mold 30, a pattern film (glass mask) 37 having a light-transmitting hole 37a corresponding to the through hole 12 was adhered to the surface of the photoresist layer 36. Then, ultraviolet light was irradiated with an ultraviolet lamp 33 for exposure, and each process of development and drying was performed to dissolve and remove the unexposed portions, thereby forming a secondary pattern resist 38 having a resist body 38a corresponding to the mask body 10 on the surface of the primary electroformed layer 35 as shown in Fig. 8(b). Subsequently, it was placed in an electroforming bath set under predetermined conditions, and as shown in Fig. 8(c), within the range of the height of the previous resist body 38a, electroplated metal such as nickel or copper was electroformed on the surface of the primary electroformed layer 35 not covered by the master mold 30 and the resist body 38a to form a secondary electroformed layer 39 (second electroforming step). Next, the secondary pattern resist 38 was dissolved and removed, and the secondary electroformed layer 39 was peeled off from the master mold 30 and the primary electroformed layer 35. Finally, a coating layer 50 was formed on the master mold surface side of the secondary electroformed layer 39 corresponding to the lower surface of the mask body 10 and the opposing surface of the secondary electroformed layer 39 corresponding to the inner surface of the through hole 12, thereby obtaining the mask 1 as shown in Figs. 8(e) and 2.

[0026] If the frame body 11 is attached to the mask 1 thus obtained, an array mask 1 as shown in Fig. 1 can be obtained. The mask 1 (secondary electroformed layer 39) can be held by the frame body 11 in a state where tension is applied thereto such that a stress in the direction of contracting inward acts on itself. The application of such stress can be realized, for example, by utilizing the difference in the thermal expansion coefficients between the frame body 11 and the mask 1, performing the attachment operation of the frame body 11 to the outer peripheral edge of the mask 1 in a high-temperature environment, and contracting the mask 1 inward at normal temperature.

[0027] According to the method for manufacturing the mask 1 as described above, since the array mask can be manufactured with high precision using the electroforming method, the solder balls 2 can be mounted on the workpiece 3 with high positional accuracy. Further, if the mask 1 having the protrusions 15 is formed such that the mask body 10 and the protrusions 15 are integrally formed inseparably by a single electroforming (the second electroforming step), compared with a mask in which the mask body 10 and the protrusions 15 are formed separately, there is less likelihood of problems such as breakage of the protrusions 15, and it is also excellent in that a mask 1 with excellent reliability can be obtained with high precision. Further, if the protrusions 15 are formed in a tapered shape so as to increase as they approach the lower surface of the mask body 10, stress concentration at the base of the protrusions 15 in particular is avoided, so that while the strength of the protrusions 15 can be firmly reinforced, the protrusions 15 can abut between the electrodes 6 in a state separated from the electrodes 6 coated with the flux 17. Therefore, it is possible to prevent defective mounting of the solder balls 2 due to the flux 17 applied to the electrodes 6 adhering to the mask body 10. At this time, it is more effective to set the ratio of the dimension of the tip portion 15' of the protrusion 15 to the dimension of the base portion 15" to 1 to 3 or more, and the aspect ratio of the protrusion 15 to 3 or more. The production of the protrusions 15 having such desired dimensions and aspect ratios can be easily obtained by adjusting the shape of the resist pattern 35.

[0028] In the mask 1 with such a configuration, the shapes of the through holes 12 and the protrusions 15 may be straight or tapered. Here, specifically explaining the case where the through holes 12 and the protrusions 15 are tapered, in the through holes 12, by providing a tapered shape that tapers toward the side facing the work 3 of the mask body 10, it becomes easier to guide the solder balls 2 into the through holes 12. By providing a tapered shape that expands toward the side facing the work 3 of the mask body 10, it is possible to prevent the flux from adhering to the periphery of the through holes 12 on the side facing the work 3 of the mask body 10. Also, in the protrusions 15, by providing a tapered shape that tapers toward the side facing the work 3 of the mask body 10, the mask can be firmly placed on the work 3. By providing a tapered shape that expands toward the side facing the work 3 of the mask body 10, even when the electrodes 6 of the work 3 are arranged in a narrow pitch, while ensuring the strength of the protrusions 15, the contact of the protrusions 15 with the work 3 can be firmly dealt with. Such a shape can be easily obtained by changing the photosensitivity of the photoresist layers 31 and 36 and the exposure conditions.

[0029] (Second Embodiment) Next, the array mask according to the second embodiment will be described. In this embodiment, as shown in FIG. 9, the coating layer 50 is formed not only on the lower surface of the mask body 10 but also on the surface of the protrusions 15.

[0030] According to the array mask of this embodiment, since the coating layer 50 is also formed on the surface of the protrusions 15, it is possible to prevent the flux from adhering to the protrusions 15. Also, by forming the coating layer 50 on the lower surface of the mask body 10, the inner surface of the through holes 12, and the surface of the protrusions 15, even if the flux adheres to the inner surface of the through holes 12, the flux can be bounced and flowed onto the work through the lower surface of the mask body 10 and the surface of the protrusions 15. Also, it is possible to more reliably prevent the flux 17 from entering the through holes 12.

[0031] Furthermore, by forming the coating layer 50 so as to cover the entire lower surface of the mask body 10 and the entire surface of the protrusion 15, for example, when the mask body 10 and the protrusion 15 are formed as separate members, the bonding strength between the two is weak (this is because as the bumps are miniaturized, the through-hole interval dimension and the pattern region interval dimension become narrower, and the outer shape dimension of the protrusion 15 itself arranged between the through-holes and between the pattern regions (outer periphery of the pattern region) also tends to become smaller, resulting in a smaller bonding area between the protrusion 15 and the mask body 10), and there is a risk that the protrusion 15 may accidentally fall off, deform, or break during the use of the mask 1. However, with such a configuration, since the coating layer 50 functions as a protective layer for the protrusion 15, it can also contribute to preventing the protrusion 15 from falling off, deforming, or breaking. In addition, when it is desired to specialize in preventing the protrusion 15 from falling off, deforming, or breaking, it is advisable to provide the coating layer 50 by forming a metal layer (such as Ni or Cu) on the lower surface of the mask body 10 and the surface of the protrusion 15 by sputtering or electroless plating.

[0032] Figures 10 and 11 show the manufacturing method of the alignment mask of the present embodiment. First, as shown in Fig. 10(a), a master mold 40 is prepared. The master mold 40 can be anything as long as it has conductivity, and stainless steel is used in this embodiment. Next, a photoresist layer is formed on the surface of the master mold 40, and each process of exposure, development, and drying is performed by a well-known method to dissolve and remove the unexposed portion, thereby forming a primary pattern resist 41 having a resist body 41a on the master mold 40 as shown in Fig. 10(b). The above photoresist layer is formed by laminating one or several negative-type photosensitive dry film resists to a predetermined height. Next, the master mold 40 is placed in an electroforming bath set under predetermined conditions, and as shown in Fig. 10(c), electroplated metal is electroformed on the surface of the master mold 40 not covered by the resist body 41a of the master mold 40 to the same extent as the height of the previous resist body 41a to form a primary electroplated layer 42. In this embodiment, the primary electroplated layer 42 is formed by Ni-Co electroforming. It is preferable to perform mechanical polishing such as belt polishing and / or electrolytic polishing on the surface of the primary electroplated layer 42 after forming the primary electroplated layer 42. Next, as shown in Fig. 10(d), the resist body 41a (resist pattern 41) is dissolved and removed.

[0033] Next, as shown in FIG. 11(a), a solder resist layer 43 was formed on the surface of the primary electrodeposited layer 42. This solder resist layer 43 was formed by laminating one or several sheets according to a predetermined height. Next, by performing exposure, development, and drying processes to dissolve and remove the unexposed portions, a secondary pattern resist 44 having a resist body 44a was integrally formed on the primary electrodeposited layer 42 as shown in FIG. 11(b). It is preferable to perform an anti-peeling process such as baking after forming the secondary pattern resist 44. Thereby, the adhesion between the secondary pattern resist 44 having the resist body 44a and the primary electrodeposited layer 42 can be made stronger. Next, as shown in FIG. 11(c), the primary electrodeposited layer 42 and the secondary pattern resist 44 formed on its surface are peeled off from the master mold 40. Finally, by forming a coating layer 50 on the surface of the primary electrodeposited layer 42 on the side having the secondary pattern resist 44 and the surface of the secondary pattern resist 44, the array mask 1 shown in FIGS. 11(d) and 9 can be obtained. Note that the coating layer 50 may be formed before peeling the primary electrodeposited layer 42 and the secondary pattern resist 44 from the master mold 40. Also, the coating layer 50 may be formed not only on the surface of the primary electrodeposited layer 42 on the side having the secondary pattern resist 44 but also on the entire surface of the primary electrodeposited layer 42. Of course, the coating layer 50 may also be formed on the inner surface of the through hole 12.

[0034] Next, another embodiment of the array mask according to the second embodiment will be described. Here, as shown in FIG. 13(a), the protrusion 15 is formed of resin, and a coating layer 70 is formed on the surface of such a protrusion 15, and the coating layer 70 is formed of a material different from the material of the protrusion 15.

[0035] As described above, this mask is used to mount solder balls on the electrodes of the workpiece. However, during the process of arranging the solder balls (transfer and mounting), dirt or the like may adhere to the mask. Therefore, in order to remove this, the mask is washed as necessary. When washing the mask, since it is performed using a solvent, there is a possibility that adverse effects such as stickiness may occur on the surface of the material constituting the protrusions. However, because there is a coating layer on the surface of the protrusions, it is protected from such adverse effects.

[0036] Therefore, in order to protect the protrusions 15 formed of resin from adverse effects, the mask of this embodiment has a coating layer 70 formed on the surface of the protrusions 15, and the coating layer 70 is formed of a material different from the material (resin) constituting the protrusions 15. As the coating layer 70, in addition to the above material, for example, it is also possible to form it with a photosensitive material mainly composed of an acrylic resin.

[0037] The manufacturing method of the mask for the array is the same as the above-described process (see Fig. 10) from the preparation of the master mold to the formation of the primary electrodeposited layer and the removal of the resist body. Next, a solder resist layer is formed on the surface of the primary electrodeposited layer 42, and by performing each process of exposure, development, and drying, a secondary pattern resist 60 having a resist body 60a is integrally formed on the primary electrodeposited layer 42 as shown in Fig. 14(a). Next, as shown in Fig. 14(b), a coating layer 70 is formed on the surface of the secondary pattern resist 60. The coating layer 70 is an alkali-developable photosensitive material, and the main components are acrylic resin (55 - 65%), barium sulfate (15 - 25%), and silicon dioxide (15 - 25%). Finally, the primary electrodeposited layer 42 is peeled off from the master mold 40 together with the secondary pattern resist 60 and the coating layer 70 formed on its surface, whereby the mask 1 for the array shown in Figs. 14(c) and 13 can be obtained. Note that the coating layer 70 may also be formed on the surface of the primary electrodeposited layer 42 on the side having the secondary pattern resist 60. Also, after forming the secondary pattern resist 60 on the primary electrodeposited layer 42, it may be peeled off from the master mold 40 and then the coating layer 70 may be formed. By doing so, the coating layer 70 can be easily formed not only on the surface of the primary electrodeposited layer 42 on the side having the secondary pattern resist 60 but also on the entire surface of the primary electrodeposited layer 42. The coating layer 70 may also be formed on the inner wall of the through hole 12. Also, after forming the secondary pattern resist 60 and the coating layer 70, it is preferable to perform an anti-drop-off treatment such as baking. Thereby, the adhesion between the primary electrodeposited layer 42 and the secondary pattern resist 60, and between the secondary pattern resist 60 and the coating layer 70 can be made stronger. Such an anti-drop-off treatment may be performed every time the secondary pattern resist 60 and the coating layer 70 are formed, or may be performed together after forming the coating layer 70 on the surface of the secondary pattern resist 60.

[0038] The mask 1 obtained by such a manufacturing method becomes resistant to cleaning (solvent), and it is possible to prevent stickiness from occurring on the protrusions 15 as much as possible. Also, as shown in Fig. 13(b), if the coating layer 70 is formed so as to cover the entire surface of the protrusions 15, breakage and loss of the protrusions 15 can be prevented.

[0039] Here, since the protruding portion 15 and the coating layer 70 are made of the same resin, the adhesion between the protruding portion 15 and the coating layer 70 is strong. However, after forming the protruding portion 15 on the mask body 10 (before forming the coating layer 70 on the surface of the protruding portion 15), the protruding portion 15 is washed to deliberately cause stickiness on the surface of the protruding portion 15, and by forming the coating layer 70 on the surface, the adhesion between the protruding portion 15 and the coating layer 70 can be made stronger.

[0040] Also, as shown in FIG. 13(c), the protruding portion 15 can be formed only with the material for forming the coating layer 70. The material for forming the coating layer 70 is one to which flux hardly adheres. Specifically, examples thereof include a resin mixture in which barium sulfate and / or silicon dioxide is contained in an acrylic resin. This resin mixture is excellent in solvent resistance. Specifically explaining this, each mask provided with protruding portions having a width dimension of 0.2 to 3.0 mm (a total of 7 products of 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 2.0 mm, and 3.0 mm) made of a nickel-cobalt alloy using such a resin mixture was immersed in a cleaning agent (manufactured by Kaken Tech Co., Ltd.) for 6 to 24 hours (a total of 3 times of 6 hours, 12 hours, and 24 hours), and it was confirmed that there was no peeling of the protruding portions in all the masks. Further, since such a resin mixture has good compatibility with the mask body 10 and good adhesion, it is possible to narrow the width dimension of the protruding portion 15. Incidentally, since such a resin mixture is hard (5H to 6H in the JIS standard scratch hardness test), when the width dimension of the protruding portion is made larger than 5 mm when the thickness of the mask body is 100 μm or less, the mask may be warped, so the width dimension of the protruding portion is preferably 5 mm or less. Thus, the coating layer 70 is formed mainly of materials such as fluororesin, silicone resin, and acrylic resin. And it is possible to configure the protruding portion 15 mainly with such materials.

[0041] The main component of the resin mixture forming the above-mentioned protrusion 15 is an acrylic resin, but it is not limited to this, and examples include polyethylene, polypropylene, polystyrene, polyurethane, polyvinyl chloride, polyvinyl acetate, ABS resin, AS resin, PET resin, EVA resin, fluororesin, polyamide, polyacetal, polycarbonate, polyphenylene ether, polyester, polyolefin, polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, polyetheretherketone, polyimide, polyamideimide, etc. (so-called thermoplastic resins). Also, phenolic resin, epoxy resin, melamine resin, urea resin, alkyd resin, polyurethane, etc. (so-called thermosetting resins) may be used.

[0042] In each of the above embodiments, the protrusion 15 (support column 15b) and the through hole 12 may be arranged such that the protrusion 15 (support column 15b) surrounds one through hole 12, or one protrusion 15 may be arranged to be surrounded by the through hole 12. When arranging the protrusion 15 to surround one through hole 12, the shape of the protrusion 15 is not limited to being partially provided like a support column, and it may be provided in an endless frame shape. Also, the shape of the protrusion 15 is not limited to the crossbar 15a or a cylinder, and may be a polygon such as a rhombus or a hexagon, or an ellipse. Furthermore, in these shapes, as shown in FIG. 12, an elongated shape and / or a shape with rounded corners is preferable. By aligning the longitudinal direction and / or the major axis direction of these shapes in a certain direction, for example, when cleaning the back surface of the mask 1, the possibility of the cleaning means (such as a cloth or a sponge) being caught by the protrusion 15 and causing damage to the cleaning means or the protrusion 15 can be minimized as much as possible, and smooth cleaning can be achieved. Therefore, it is desirable to align the longitudinal direction and the major axis direction of all the protrusions 15 in one direction. Note that the elongated shape is only for the lower end surface (tip surface) of the protrusion 15, and it is not necessarily required to be an elongated shape in terms of strength and other aspects on the surface of the base portion 15b of the protrusion 15.

[0043] Also, in each of the above embodiments, the thicknesses of the coating layers 50 and 70 may be made different between the inner surface of the through hole 12 and the surfaces of the mask body 10 and the protrusions 15. Specifically, when the thickness of the coating layer 50 on the inner surface of the through hole 12 is T1 and the thickness of the coating layer 50 on the surfaces of the mask body 10 and the protrusions 15 is T2 (see FIG. 9), if T1 > T2, it is possible to more reliably prevent the adhesion of flux to the inner surface of the through hole 12 that causes poor mounting of the solder balls. Further, if the coating layer 50 is formed of a material that is easy to slide (low friction), a region that is easy to slide will appear at the boundary between the upper surface of the mask body 10 and the inner surface of the through hole 12 by the thickness of T1. The thicker T1 is, the larger this region becomes. Therefore, when the solder ball 2 is scraped with a squeegee brush, the squeegee brush and the solder ball 2 can be moved smoothly, and an improvement in productivity and work efficiency can be expected. And if T1 < T2, when the protrusions 15 are separately formed on the lower surface of the mask body 10, it is possible to more reliably prevent the protrusions 15 from falling off, deforming, or being damaged. Note that, as a method for forming the coating layer 50, there are various methods such as a dipping method and a spraying method. When forming the coating layer 50, it is advisable to cover the portions other than the desired formation locations with a protective sheet. Also, when it is desired to form the coating layer 50 thickly, it can be realized by locally spraying the locations where thickening is desired or by varying the dipping direction of the mask 1 (for example, when thickening is desired on the lower surface of the mask body 10, it is advisable to dip it with the lower surface of the mask body 10 parallel to the dipping surface, and when thickening is desired on the inner surface of the through hole 12, it is advisable to dip it with the lower surface of the mask body 10 perpendicular to the dipping surface).

Explanation of Reference Numerals

[0044] 1 Mask 2 Solder Ball 3 Workpiece 6 Electrode 10 Mask Body 12 Through Hole 15 Protrusion 15a Crossbar 15b Support Pillar 15c Support Pillar 15’ Tip 15” Root part 30 and 40 mother types 31, 36, 43 Photoresist layer (solder resist layer) 34, 41 Primary pattern resist 34a, 41a Resist body 35, 42 Primary electroplating layer 38, 44, 60 Secondary pattern resist 38a, 44a Resist body 39 Secondary electroplating layer 50, 70 Coating layer

Claims

【Claim 1】 An array mask for mounting the solder balls (2) at predetermined positions on a workpiece (3) by pouring the solder balls (2) into through holes (12) corresponding to a predetermined array pattern, wherein: The array mask includes a mask body (10) in which the through holes (12) are formed, and protrusions (15) provided on the lower surface side of the mask body (10), i.e., the surface side facing the workpiece (3). A coating layer formed of a silicone resin, an emulsion, a resist, or an acrylic resin is provided on at least the squeegee surface which is the upper surface of the mask body (10), and a coating layer formed of a silicone resin, an emulsion, a resist, or an acrylic resin that can prevent the adhesion of flux is provided on the surface of the mask body (10) facing the workpiece (3).

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