Arrangement mask

Abstract

To provide a mask for arrangement capable of preventing defective mounting of solder balls.SOLUTION: With a mask for arrangement, solder balls 2 are mounted at prescribed positions on a work 3 by feeding the solder balls 2 into through holes 12 corresponding to a prescribed arrangement pattern. A mask body 10 is provided in which the through holes 12 are formed. A coating layer is provided on each of an inner surface of the through hole 12 and a surface of the mask body 10. A thickness of the coating layer provided on the inner surface of the through hole 12 is different from that of the coating layer provided on the surface of the mask body 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Solder bumps are formed through a printing process in which flux is applied to electrodes on workpieces such as wafers, flexible substrates, and rigid substrates; an arrangement process in which solder balls are arranged on the flux; and a heating process in which the solder balls are heated and melted. In the aforementioned arrangement process, the solder balls are arranged on the workpiece using a transfer method using a mask. In this method, solder balls are placed on the workpiece electrodes using an arrangement mask (hereinafter simply referred to as the "mask") with positioning holes through which the solder balls can be inserted, corresponding to the arrangement pattern of the workpiece's electrodes. Specifically, the mask is aligned with the workpiece so that the holes align with the electrodes. Then, solder balls are supplied onto the mask and swept with a squeegee or brush, placing one solder ball into each hole. The solder balls are then fixed to the flux, temporarily placing them in their designated positions on the workpiece.

[0003] Such a mask is disclosed in Patent Document 1. The mask described in Patent Document 1 has a number of support protrusions on the underside of a mask body having through holes, and the protrusions have the same protrusion dimension. As a result, when the mask is placed on a workpiece, the lower ends of all of the support protrusions abut against the upper surface of the workpiece, ensuring a gap between the mask body having through holes and the workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-287215 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, with the miniaturization of electronic devices, bumps have become increasingly smaller. In other words, as bumps become smaller, the spacing between through holes and between pattern areas in the mask becomes narrower, and the outer dimensions of the protrusions themselves arranged between through holes and between pattern areas (on the periphery of the pattern area) also tend to become smaller. This narrows the distance between the mask and the workpiece, making it easier for flux arranged on the workpiece's electrodes to adhere to the mask. If flux adheres to the surface of the mask, solder ball placement defects are likely to occur. An object of the present invention is to provide an array mask that can prevent solder ball placement defects. [Means for solving the problem]

[0006] The present invention Array mask for is an array mask that places solder balls 2 at predetermined positions on a workpiece 3 by inserting the solder balls 2 into through holes 12 that correspond to a predetermined array pattern, and the through holes 12 was formed Mask body 10 of Preparation, A coating layer is provided on each of the inner surface of the through hole 12 and the surface of the mask body 10, and the thickness of the coating layer provided on the inner surface of the through hole 12 and the thickness of the coating layer provided on the surface of the mask body 10 are different. It is characterized by The mask body 10 has protrusions 15 on its underside, i.e., on the side facing the workpiece 3, and the protrusions 15 have coating layers on their surfaces, with the thickness of the coating layer on the surface of the mask body 10 and the thickness of the coating layer on the surface of the protrusions 15 set to the same dimension.

[0007] When the thickness of the coating layer on the inner surface of the through hole 12 is T1 and the thickness of the coating layer on the lower surface of the mask body 10, that is, the surface facing the workpiece 3, is T2, T1>T2. When the thickness of the coating layer on the inner surface of the through hole 12 is T1 and the thickness of the coating layer on the lower surface of the mask body 10, i.e., the surface facing the workpiece 3, is T2, T1 <T2である。 When the thickness of the coating layer on the inner surface of the through-hole 12 is T1 and the thickness of the coating layer on the squeegee surface, which is the upper surface of the mask body 10, is T2, T1>T2. When the thickness of the coating layer on the inner surface of the through hole 12 is T1 and the thickness of the coating layer on the squeegee surface, which is the upper surface of the mask body 10, is T2, T1 <T2である。 [Effects of the Invention]

[0008] According to the arrangement mask of the present invention, a coating layer is formed on the underside of the mask body, which prevents flux from remaining attached to the underside of the mask body. Furthermore, by forming the coating layer so as to cover the underside of the mask body and the surfaces of the protrusions, the coating layer functions as a protective layer for the protrusions, preventing them from falling off, deforming, or breaking. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the overall configuration of an arrangement mask and a workpiece according to the present invention; [Figure 2] 1 is a vertical cross-sectional side view of an array mask according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a plan view of an array mask according to a first embodiment of the present invention. [Figure 4] FIG. 10 is a vertical cross-sectional side view of another embodiment of the array mask according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a plan view of another embodiment of the array mask according to the first embodiment of the present invention. [Figure 6] FIG. 10 is a vertical cross-sectional side view of another embodiment of the array mask according to the first embodiment of the present invention. [Figure 7] 3A to 3C are explanatory diagrams of a method for manufacturing an array mask according to the first embodiment of the present invention. [Figure 8] 3A to 3C are explanatory diagrams of a method for manufacturing an array mask according to the first embodiment of the present invention. [Figure 9] FIG. 10 is a vertical cross-sectional side view of an array mask according to a second embodiment of the present invention. [Figure 10] 10A to 10C are explanatory diagrams of a method for manufacturing an array mask according to a second embodiment of the present invention. [Figure 11] 10A to 10C are explanatory diagrams of a method for manufacturing an array mask according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a partially enlarged plan view of an array mask according to another embodiment of the present invention. [Figure 13] FIG. 10 is a partially enlarged vertical cross-sectional side view of another embodiment of the array mask according to the second embodiment of the present invention. [Figure 14] 10A to 10C are explanatory diagrams of a method for manufacturing another embodiment of the array mask according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) 1 to 3 show a solder ball array mask according to a first embodiment of the present invention. This array mask (hereinafter simply referred to as the mask) 1 is used in the process of arranging solder balls 2 in the formation of solder bumps. In FIG. 2, reference numeral 3 denotes a workpiece on which the solder balls 2 are to be mounted using the mask 1. This workpiece 3 is, for example, formed by mounting multiple semiconductor chips 5 on a glass epoxy substrate base 4, wiring them with wire bonds, and then sealing them with a transfer mold. Electrodes 6, which are input / output terminals, are formed in a predetermined pattern on the top surface of the workpiece 3 so as to surround the semiconductor chips 5. After the bumps are formed, the workpiece 3 is cut into individual pieces to form individual LSI chips.

[0011] As shown in FIG. 1, the mask 1 comprises a mask body 10 made of nickel, nickel alloys such as nickel-cobalt, copper, or other metals, and a frame 11 can be attached to surround the mask body 10. A number of pattern areas are formed in the center of the mask body 10, each consisting of a number of independent through-holes 12 for inserting solder balls 2, corresponding to each semiconductor chip 5. As shown in FIG. 2, the through-holes 12 correspond to an arrangement pattern corresponding to the arrangement positions of the electrodes 6 of each semiconductor chip 5 on the workpiece 3. The solder balls 2 have a radius of 50 μm or less, and accordingly, each through-hole 12 is formed in a circular shape in plan view with an inner diameter slightly larger than the radius of the ball 2.

[0012] The frame 11 is a flat plate made of a material such as aluminum, 42 alloy, Invar, or SUS430, and has a square opening in the center of its surface corresponding to the mask body 10. In this embodiment, one mask body 10 is held by one frame 11. The frame 11 is a molded product that is thicker than the mask body 10 and is inseparably joined to the outer periphery of the mask body 10. Here, the thickness of the frame 11 is, for example, approximately 0.05 to 1.0 mm, and in this embodiment, it is set to 0.5 mm. The thickness of the mask body 10 is preferably 10 μm or more, and in this embodiment, it is set to 200 μm.

[0013] A downwardly projecting protrusion 15 may be provided on the underside of the mask body 10 (mask 1), i.e., the side facing the workpiece 3. Specifically, as shown in FIGS. 2 and 3, protrusions 15 (crosspieces 15a) may be provided between pattern areas (on the periphery of the pattern areas) so as to surround the pattern areas. These protrusions 15 (crosspieces 15a) do not need to be provided continuously as in FIG. 3, but may be provided piecemeal. Furthermore, as shown in FIG. 4, protrusions 15 (supports 15b) may be provided at positions within the pattern areas where no through-holes 12 are formed. Furthermore, the shape of the protrusions 15 provided between adjacent pattern areas (on the periphery of the pattern areas) so as to surround the pattern areas is not limited to crosspieces 15a, and may be supporters 15c, as shown in FIG. 5. Providing such protrusions 15 ensures a gap between the mask body 10 and the workpiece 3 by contacting the upper surface of the workpiece 3 during the alignment process. As shown in Figures 2 and 4, each protrusion 15 (crosspiece 15a, support 15b) is preferably formed so as to taper from the underside of the mask body 10 toward the tip of the protrusion 15, and has a truncated cone shape.

[0014] As another shape of the protrusion 15, as shown in FIG. 6, the base dimension of the protrusion 15 may be a flared shape (a tapered shape that narrows from the base to the tip of the protrusion 15) in which the base dimension increases toward the underside of the mask body 10, and the side surface may be formed in an arc shape. This makes it possible to prevent breakage caused by stress concentration on the protrusions 15, particularly on the base portions 15'', and even if flux 17 adheres to the protrusions 15 when the mask 1 is placed on the workpiece 3, the arc-shaped side surfaces of the protrusions 15 prevent the flux 17 from flowing around the through holes 12, thereby eliminating the risk of the solder balls 2 being poorly mounted due to flux 17 adhering to the through holes 12. It is preferable that the terminal position of the base portions 15'' of the protrusions 15 be located near the through holes 12 on the underside of the mask body 10, and possible positions include a position at the intersection of the underside 10a of the mask body and the inner surface 12a of the through holes, or a position spaced apart from the through holes 12 on the underside 10a of the mask body. Furthermore, the side surface of protrusion 15 may be either a convex arc or a concave arc; a convex arc provides good strength, while a concave arc ensures that no part of the side surface of protrusion 15 approaches electrode 6 to which flux 17 is attached, i.e., a constant distance is maintained from electrode 6 to which flux 17 is attached. Furthermore, tip 15' and / or base 15" of protrusion 15 may be formed in an arc shape, thereby minimizing the risk of flux 17 attaching to protrusion 15.

[0015] In the present mask 1, the ratio of the height of the protrusions 15 to the thickness of the mask body 10 is preferably 2:1 or greater, and more preferably, the thickness of the mask body 10 satisfies this requirement within the range of 10 to 300 μm. Furthermore, the protrusions 15 preferably have a large aspect ratio (the ratio of the height to the tip dimension of the protrusions 15). In this embodiment, the aspect ratio is 3. Furthermore, the base dimension L2 of the protrusions 15 is preferably 1.0 to 1.5 times the tip dimension L1 of the protrusions 15, and is set to 1.2 times in this embodiment. Furthermore, the ratio of the tip dimension L1, the base dimension L2, and the width dimension L3 between the through holes 12 of the protrusions 15 is preferably 1:1.2:1.4 or greater. Furthermore, the dimension L4 from the pattern region to the base of the protrusions 15 (crosspieces 15a, supports 15c) is preferably set to 0.01 mm or greater, and is set to 0.02 mm in this embodiment. These conditions can minimize flux adhesion. At this time, it is possible to prevent both damage to the protrusions 15 and adhesion of flux by satisfying the relationship of the ratio between the tip dimension L1 and the base dimension L2 of the protrusions 15 and the relationship of the dimension L4 from the pattern area to the base of the protrusions 15. Furthermore, when the dimension from the pattern area to the tip center of the protrusions 15 (crosspieces 15a, supports 15c) is L5, the above-mentioned compatibility effect can be maximized by setting the ratio of L1 to L2 to L5 to 1:3:2.5 or more.

[0016] Here, the mask 1 is configured such that the mask body 10 and the protrusions 15 are integrated. However, the mask body 10 and the protrusions 15 may be integrally formed as separate members. In this case, if the mask body 10 is formed of a magnetic material and the protrusions 15 are formed of a non-magnetic material, when the mask 1 is fixed to the workpiece 3 by magnetic attraction of a magnet, a uniform magnetic force can be applied to the mask 1. This prevents the mask 1 from unintentionally bending, allows the mask 1 to be securely attached to the workpiece, and improves the accuracy of aligning the through-holes 12 with the electrode 6. Furthermore, when the mask 1 is removed, the workpiece 3 and the protrusions 15 are not directly magnetically coupled, allowing for smooth removal. Such a mask 1 can be obtained, for example, by forming the mask body 10 from a magnetic metal (nickel, iron, etc.) and the protrusions 15 from a non-magnetic metal (copper, aluminum, etc.).

[0017] Furthermore, when the protrusions 15 are formed from a non-magnetic material, they are not limited to the metals described above, but may also be formed from resin or resist. This not only provides the above-mentioned effect, but also provides a cushioning effect due to the elasticity of the resin, reducing the risk of damage to the workpiece 3 when the protrusions 15 come into contact with the workpiece 3. To achieve this effect more significantly, it is preferable to form not only the protrusions 15 but also the entire portion of the mask 1 that comes into contact with the workpiece 3 from resin. Furthermore, when the protrusions 15 are formed from resin, using the same resist as that used to form the mask body 10 by electroforming can improve production efficiency.

[0018] Furthermore, in the present mask 1, as shown in FIGS. 2, 4, and 6, a coating layer 50 is provided on the underside of the mask body 10 and the inner surfaces of the through-holes 12. The coating layer 50 is preferably water-repellent, and examples of such materials include fluororesin, silicone resin, emulsion, and liquid resist. By providing such a coating layer 50, even if flux adheres to the underside of the mask body 10 or the inner surfaces of the through-holes 12, the coating layer 50 can repel the flux, preventing the flux from remaining on the underside of the mask body 10 or the inner surfaces of the through-holes 12. The coating layer 50 may be formed on the upper surface of the mask body 10, or it need not be formed on the underside of the mask body 10 between the pattern regions and the protrusions 15 (the crosspieces 15a and the support posts 15c). In short, it is desirable to form the coating layer 50 in areas where flux adhesion is likely to cause solder ball placement defects. It is desirable to form the coating layer 50 on the surfaces of the mask body 10 and the protrusions 15 that face the flux 17 applied to the electrode 6 when the mask 1 is placed on the workpiece.

[0019] It should be noted that each drawing does not show the actual appearance 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 as such for the convenience of drawing. Also, in Figs. 3 and 5, the reference numeral 15 indicates the lower end surface (tip surface) of the protrusion 15, and the base of the protrusion 15 is not shown. Also, in Figs. 3 and 5, the coating layer 50 is not shown.

[0020] The arrangement of solder balls 2 using the mask 1 is performed as follows. This arrangement is performed using a dedicated arrangement device (see, for example, Figures 1 and 5 of Patent Document 1). First, flux 17 (see Figure 2) is printed onto the electrodes 6 of the workpiece 3. Next, the mask 1 is aligned on the workpiece 3 so that the through holes 12 and the electrodes 6 are aligned, and then the mask 1 is fixed. This alignment is actually performed by aligning the outer edges of the frame 11 and the workpiece 3. After the alignment is complete, in this fixed state, the lower end surfaces of the protrusions 15 abut against the surface of the workpiece 3, thereby maintaining the mask body 10 in a spaced-apart position with a gap maintained between the mask body 10 and the workpiece 3, as shown in Figures 2, 4, and 6. At this time, a magnet can be placed below the workpiece 3, and the mask 1 can be attracted to the workpiece 3 by the magnetic force 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 one by one into the through-holes 12. In this way, the solder balls 2 are temporarily adhered and held on the electrodes 6 by the flux 17. In the insertion of the solder balls 2 using the squeegee brush, even if a large amount of squeegee brush pressure is applied to the mask 1, the protrusions 15 can prevent the mask 1 from bending, and the insertion work can be carried out efficiently and smoothly.

[0022] As described above, the mask 1 according to this embodiment is provided with the protrusions 15 that form a gap between the mask body 10 and the workpiece 3, and the protrusions 15 ensure a gap between the mask body 10 and the workpiece 3, thereby enabling the operation of inserting the solder balls 2 into the through holes 12 to proceed efficiently and without omissions.

[0023] A reinforcing frame 11 can be provided on the outer periphery of the mask body 10, and if the mask body 10 is formed under tension such that stress acts on it in a direction that causes it to contract inward, the expansion of the mask body 10 due to changes in ambient temperature can be absorbed by the tension in the contraction direction. This prevents the mask body 10 from shifting out of position relative to the workpiece 3. Furthermore, because uniform tension can be applied to the entire mask body 10, the solder balls 2 can be mounted on the workpiece 3 with good positional accuracy.

[0024] Next, a manufacturing method of the array mask 1 having such a configuration is shown in FIGS. 7 and 8. First, a photoresist layer 31 is formed on the surface of a matrix 30 made of, for example, conductive stainless steel or brass. This photoresist layer 31 is formed by laminating one or more sheets of negative-type photosensitive dry photoresist to a predetermined height and then thermocompression bonding. Next, as shown in FIG. 7(a), a pattern film (glass mask) 32 having light-transmitting holes 32a corresponding to the protrusions 15 is adhered to the photoresist layer 31. Then, as shown in FIG. 7(b), the photoresist is exposed to ultraviolet light from an ultraviolet lamp 33, and the unexposed portions are dissolved and removed by development and drying. As shown in FIG. 7(b), a primary pattern resist 34 having resist bodies 34a corresponding to the tapered protrusions 15 is formed on the matrix 30. It is preferable to tape the resist bodies 34a by using a photoresist that is less transparent to ultraviolet light or by reducing the exposure dose. Next, the matrix 30 was placed in an electroforming tank prepared under predetermined conditions, and as shown in FIG. 7(c), an electrodeposited metal such as nickel or copper was electroformed on the surface of the matrix 30 not covered by the resist layer 34a, within the height range of the resist layer 34a, to form a primary electroformed layer 35. Here, the primary electroformed layer 35 was formed over substantially the entire surface of the matrix 30 (first electroforming step). Next, as shown in FIG. 7(d), the primary pattern resist 34 was removed. At this point, it is advisable to polish the surface of the primary electroformed layer 35.

[0025] 8(a), a photoresist layer 36 was formed on the entire surface of the primary electroformed layer 35 and the matrix 30. A pattern film (glass mask) 37 having light-transmitting holes 37a corresponding to the through holes 12 was then attached to the surface of the photoresist layer 36. The photoresist layer 36 was then exposed to ultraviolet light from an ultraviolet lamp 33, and developed and dried to dissolve and remove the unexposed portions, forming a secondary pattern resist 38 having resist bodies 38a corresponding to the mask bodies 10 on the surface of the primary electroformed layer 35, as shown in FIG. 8(b). The electroformed layer 35 was then placed in an electroforming tank prepared under specified conditions. As shown in FIG. 8(c), an electrodeposited metal such as nickel or copper was electroformed on the surfaces of the primary electroformed layer 35 not covered by the resist bodies 38a within the height range of the resist bodies 38a, thereby forming a secondary electroformed layer 39 (second electroforming step). Next, the secondary pattern resist 38 is dissolved and removed, and the secondary electroformed layer 39 is peeled off from the matrix 30 and the primary electroformed layer 35. Finally, a coating layer 50 is formed on the matrix surface side of the secondary electroformed layer 39 corresponding to the underside of the mask body 10 and on the surface of the secondary electroformed layer 39 corresponding to the inner surface of the through hole 12 facing the secondary pattern resist 38, thereby obtaining the mask 1 shown in FIG. 8(e) and FIG. 2.

[0026] By attaching a frame 11 to the mask 1 obtained in this manner, an array mask 1 such as that shown in Fig. 1 is obtained. The mask 1 (secondary electroformed layer 39) can be held in the frame 11 under tension such that a stress acts on the mask 1 in a direction that causes it to contract inward. The application of such stress can be achieved, for example, by taking advantage of the difference in thermal expansion coefficients between the frame 11 and the mask 1, by attaching the frame 11 to the outer periphery of the mask 1 in a high-temperature environment, and then causing the mask 1 to contract inward at room temperature.

[0027] According to the above-described method for manufacturing the mask 1, an array mask can be produced with high precision using electroforming, allowing the solder balls 2 to be mounted on the workpiece 3 with high positional accuracy. Furthermore, by forming the mask 1 having the protrusions 15 integrally and inseparably through a single electroforming process (the second electroforming process), the mask 1 is less likely to suffer from problems such as breakage of the protrusions 15 than when the mask body 10 and the protrusions 15 are formed separately. This is advantageous in that a highly reliable mask 1 can be obtained with high precision. Furthermore, by forming the protrusions 15 in a tapered shape that increases in size toward the underside of the mask body 10, stress concentration, particularly at the base of the protrusions 15, can be avoided. This effectively reinforces the strength of the protrusions 15. Furthermore, the protrusions 15 can be brought into contact with the electrodes 6 while being spaced apart from the electrodes 6 to which the flux 17 is applied. This prevents the solder balls 2 from being poorly mounted due to the flux 17 applied to the electrodes 6 adhering to the mask body 10. In this case, it is more effective to set the ratio of the dimensions of tip 15' to the dimensions of base 15" of protrusion 15 to 1:3 or more, and to set the aspect ratio of protrusion 15 to 3 or more. Protrusion 15 having such desired dimensions and aspect ratio can be easily produced by adjusting the shape of resist pattern 35.

[0028] In the mask 1 having such a configuration, the through holes 12 and the protrusions 15 may be straight or tapered. Specifically, when the through holes 12 and the protrusions 15 are tapered, the through holes 12 can be tapered toward the surface of the mask body 10 facing the workpiece 3, making it easier to guide the solder balls 2 into the through holes 12. By tapering the through holes 12 toward the surface of the mask body 10 facing the workpiece 3, it is possible to prevent flux from adhering to the periphery of the through holes 12 on the surface of the mask body 10 facing the workpiece 3. Furthermore, by tapering the protrusions 15 toward the surface of the mask body 10 facing the workpiece 3, it is possible to securely place the mask on the workpiece 3. By tapering the protrusions 15 toward the surface of the mask body 10 facing the workpiece 3, it is possible to securely abut the protrusions 15 on the workpiece 3 while ensuring the strength of the protrusions 15, even when the electrodes 6 of the workpiece 3 are arranged at a narrow pitch. Such a shape can be easily obtained by changing the photosensitivity and exposure conditions of the photoresist layers 31 and 36.

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

[0030] According to the array mask of this embodiment, the coating layer 50 is also formed on the surfaces of the protrusions 15, so that the adhesion of flux to the protrusions 15 can also be prevented. Furthermore, by forming the coating layer 50 on the lower surface of the mask body 10, the inner surfaces of the through holes 12, and the surfaces of the protrusions 15, even if flux adheres to the inner surfaces of the through holes 12, the flux can be repelled and flow onto the workpiece via the lower surface of the mask body 10 and the surfaces of the protrusions 15. Furthermore, the flux 17 can be more reliably prevented from getting around the through holes 12.

[0031] Furthermore, by forming the coating layer 50 so as to cover the entire underside of the mask body 10 and the surface of the protrusion 15, for example, if the mask body 10 and the protrusion 15 are formed from separate materials, the bonding strength between them will be weak (this is because as the bumps become finer, the spacing between the through holes and the spacing between the pattern areas becomes narrower and the external dimensions of the protrusion 15 itself arranged between the through holes and between the pattern areas (on the periphery of the pattern areas) tend to also become smaller, thereby reducing the bonding area between the protrusion 15 and the mask body 10), and there is a risk that the protrusion 15 will inadvertently fall off, deform, or break when the mask 1 is used. However, with this configuration, the coating layer 50 functions as a protective layer for the protrusion 15, which also contributes to preventing the protrusion 15 from falling off, deforming, or breaking. If you want to specifically prevent the protrusions 15 from falling off, deforming, or breaking, it is a good idea to provide a coating layer 50 by forming a metal layer (Ni, Cu, etc.) on the underside of the mask body 10 and the surface of the protrusions 15 by sputtering or electroless plating.

[0032] 10 and 11 illustrate the manufacturing method of the array mask of this embodiment. First, as shown in FIG. 10(a), a matrix 40 is prepared. Any conductive material can be used for the matrix 40; in this embodiment, stainless steel is used. Next, a photoresist layer is formed on the surface of the matrix 40. The unexposed portions are dissolved and removed by well-known exposure, development, and drying processes, forming a primary pattern resist 41 having a resist layer 41a on the matrix 40, as shown in FIG. 10(b). The photoresist layer was formed by laminating one or several negative-type photosensitive dry film resists to a predetermined height. Next, the matrix 40 was placed in an electroforming tank prepared under predetermined conditions, and a metal electrodeposited on the surface of the matrix 40 not covered by the resist layer 41a was electroformed to a height equivalent to that of the resist layer 41a, forming a primary electrodeposited layer 42, as shown in FIG. 10(c). In this embodiment, the primary electrodeposited layer 42 was formed by Ni-Co electroforming. After forming the primary electrodeposition layer 42, it is preferable to subject the surface of the primary electrodeposition layer 42 to mechanical polishing such as belt polishing and / or electrolytic polishing. Next, as shown in Fig. 10(d), the resist body 41a (resist pattern 41) was dissolved and removed.

[0033] Next, as shown in FIG. 11(a), a solder resist layer 43 was formed on the surface of the primary electrodeposition layer 42. This solder resist layer 43 was formed by laminating one or more layers to a predetermined height. Next, exposure, development, and drying processes were performed to dissolve and remove the unexposed portions, thereby forming a secondary pattern resist 44 having a resist body 44a integrally on the primary electrodeposition layer 42, as shown in FIG. 11(b). After forming the secondary pattern resist 44, it is preferable to perform a treatment such as baking to prevent its removal. This strengthens the adhesion between the secondary pattern resist 44 having the resist body 44a and the primary electrodeposition layer 42. Next, as shown in FIG. 11(c), the primary electrodeposition layer 42 and the secondary pattern resist 44 formed thereon were peeled from the matrix 40. Finally, a coating layer 50 was formed on the surface of the primary electrodeposition layer 42 on the side bearing the secondary pattern resist 44 and on the surface of the secondary pattern resist 44, thereby obtaining the array mask 1 shown in FIG. 11(d) and FIG. 9. The coating layer 50 may be formed before the primary electrodeposition layer 42 and the secondary pattern resist 44 are peeled off from the matrix 40. The coating layer 50 may be formed not only on the surface of the primary electrodeposition layer 42 on the side having the secondary pattern resist 44, but also on the entire surface of the primary electrodeposition layer 42. Of course, the coating layer 50 may also be formed on the inner surface of the through hole 12.

[0034] Next, a description will be given of another embodiment of the array mask according to the second embodiment. Here, as shown in Fig. 13(a), the protrusions 15 are formed of resin, and a coating layer 70 is formed on the surface of the protrusions 15, and the coating layer 70 is made of a material different from the material of the protrusions 15.

[0035] As mentioned above, this mask is used to mount solder balls on the electrodes of the workpiece, but since dirt and other contaminants can adhere to the mask during the solder ball arrangement process (transfer mounting), the mask is washed as needed to remove this. When washing the mask, a solvent is used, and this solvent can have adverse effects such as causing stickiness on the surface of the material that makes up the protrusions, but the coating layer on the surface of the protrusions protects against such adverse effects.

[0036] Therefore, in the mask of this embodiment, in order to prevent adverse effects on the protrusions 15 formed from resin, a coating layer 70 is formed on the surface of the protrusions 15, and the coating layer 70 is formed from a material different from the material (resin) that constitutes the protrusions 15. In addition to the above materials, the coating layer 70 can also be formed from a photosensitive material whose main component is, for example, an acrylic resin.

[0037] The manufacturing method for this array mask is similar to the previously described process (see FIG. 10 ), from preparing the matrix to forming the primary electrodeposition layer and removing the resist. Next, a solder resist layer is formed on the surface of the primary electrodeposition layer 42, and then exposure, development, and drying processes are performed to form a secondary pattern resist 60 having a resist layer 60a integrally on the primary electrodeposition 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, primarily containing acrylic resin (55-65%), barium sulfate (15-25%), and silicon dioxide (15-25%). Finally, the primary electrodeposition layer 42 is peeled off from the matrix 40 together with the secondary pattern resist 60 and coating layer 70 formed on its surface, yielding the array mask 1 shown in FIG. 14(c) and FIG. 13. The coating layer 70 may also be formed on the surface of the primary electrodeposition layer 42 on the side bearing the secondary pattern resist 60. Alternatively, the secondary pattern resist 60 may be formed on the primary electrodeposition layer 42, and then peeled off from the matrix 40 before the coating layer 70 is formed. This allows the coating layer 70 to be easily formed not only on the surface of the primary electrodeposition layer 42 on the side bearing the secondary pattern resist 60, but also on the entire surface of the primary electrodeposition layer 42. The coating layer 70 may also be formed on the inner walls of the through holes 12. After forming the secondary pattern resist 60 and the coating layer 70, it is preferable to perform a fall-off prevention treatment such as baking. This strengthens the adhesion between the primary electrodeposition layer 42 and the secondary pattern resist 60, and between the secondary pattern resist 60 and the coating layer 70. Such a fall-off prevention treatment may be performed each time the secondary pattern resist 60 and the coating layer 70 are formed, or may be performed all at once after the coating layer 70 is formed on the surface of the secondary pattern resist 60.

[0038] The mask 1 obtained by this manufacturing method is resistant to cleaning (solvents) and can minimize stickiness on the protrusions 15. Furthermore, as shown in Fig. 13(b), if the coating layer 70 is formed so as to cover the entire surface of the protrusions 15, damage and chipping of the protrusions 15 can be prevented.

[0039] Here, since the protrusions 15 and the coating layer 70 are made of the same resin, the adhesion between the protrusions 15 and the coating layer 70 is strong, but after forming the protrusions 15 on the mask body 10 (before forming the coating layer 70 on the surface of the protrusions 15), the protrusions 15 can be washed to intentionally make the surface of the protrusions 15 sticky, and then the coating layer 70 can be formed on that surface, thereby making the adhesion between the protrusions 15 and the coating layer 70 even stronger.

[0040] Furthermore, as shown in FIG. 13(c), the protrusions 15 can be formed solely from the material forming the coating layer 70. The material forming the coating layer 70 is one that resists flux adhesion, specifically, a resin mixture containing acrylic resin and barium sulfate and / or silicon dioxide. This resin mixture has excellent solvent resistance. Specifically, masks made of this resin mixture and having protrusions measuring 0.2 to 3.0 mm in width (seven products: 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 2.0 mm, and 3.0 mm) on a nickel-cobalt alloy mask body were immersed in a cleaning agent (manufactured by Kaken Tech Co., Ltd.) for 6 to 24 hours (three times for 6, 12, and 24 hours), and it was confirmed that the protrusions did not peel off in any of the masks. Furthermore, this resin mixture is compatible with the mask body 10 and has good adhesion, allowing the width of the protrusions 15 to be narrowed. Since this resin mixture has a hardness (5H to 6H in the JIS scratch hardness test), if the width of the protrusions is greater than 5 mm when the thickness of the mask body is 100 μm or less, warping of the mask may occur, so it is preferable to set the width of the protrusions to 5 mm or less. As such, the coating layer 70 is formed mainly from materials such as fluororesin, silicone resin, and acrylic resin. The protrusions 15 can be formed mainly from such materials.

[0041] The resin mixture forming the protrusions 15 is mainly composed of acrylic resin, but is not limited to this. Examples of the resin mixture 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). Furthermore, phenolic resin, epoxy resin, melamine resin, urea resin, alkyd resin, polyurethane, etc. (so-called thermosetting resins) may also be used.

[0042] In each of the above embodiments, the protrusions 15 (supports 15b) and the through holes 12 may be arranged such that the protrusions 15 (supports 15b) surround one through hole 12, or such that one protrusion 15 is surrounded by one through hole 12. When the protrusions 15 are arranged to surround one through hole 12, the shape of the protrusions 15 is not limited to being provided partially like a support, but may be provided in an endless frame shape. Furthermore, the shape of the protrusions 15 is not limited to being a crosspiece 15a or a cylinder, but may also be a polygon such as a rhombus or hexagon, or an ellipse. Furthermore, as shown in FIG. 12 , these shapes are preferably elongated and / or have rounded corners. By aligning the longitudinal and major axis directions of these shapes in a fixed direction, for example, when cleaning the back surface of the mask 1, it is possible to minimize the risk of the cleaning means (such as a cloth or sponge) getting caught on the protrusions 15 and damaging the cleaning means or the protrusions 15, and to achieve smooth cleaning. Therefore, it is desirable to align the longitudinal and major axis directions of all of the protrusions 15 in one direction. Note that the elongated shape is only at the lower end surface (tip surface) of the protrusions 15, and the surface of the base portion 15b of the protrusions 15 does not necessarily need to be elongated in terms of strength, etc.

[0043] Also, in each of the above embodiments, the thickness 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 solder balls. Further, if the coating layer 50 is formed of a material that is slippery (has low friction), a slippery region 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 will be. Therefore, when the solder ball 2 is wiped 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 an immersion method and a spray 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 thick, it can be achieved by locally spraying the portion to be thickened or by varying the immersion direction of the mask 1 (for example, when it is desired to thicken on the lower surface of the mask body 10, it is advisable to immerse it with the lower surface of the mask body 10 parallel to the immersion surface, and when it is desired to thicken on the inner surface of the through hole 12, it is advisable to immerse it with the lower surface of the mask body 10 perpendicular to the immersion 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" base 30, 40 master mold 31, 36, 43 Photoresist layer (solder resist layer) 34, 41 Primary pattern resist 34a, 41a Resist body 35, 42 Primary electrodeposition layer 38, 44, 60 Secondary pattern resist 38a, 44a Resist body 39 Secondary electrodeposition layer 50, 70 coating layers

Claims

1. An array mask for mounting solder balls (2) at predetermined positions on a workpiece (3) by dropping the solder balls (2) into through holes (12) corresponding to a predetermined array pattern, The mask includes a mask body (10) having the through hole (12) formed therein, A coating layer is provided on each of the inner surface of the through hole (12) and the surface of the mask body (10), The arrangement mask is characterized in that the thickness of the coating layer provided on the inner surface of the through hole (12) is different from the thickness of the coating layer provided on the surface of the mask body (10).

2. A protrusion (15) is provided on the underside of the mask body (10), i.e., on the side facing the workpiece (3), and a coating layer is provided on the surface of the protrusion (15); 2. The array mask according to claim 1, wherein the thickness of the coating layer provided on the surface of the mask body (10) and the thickness of the coating layer provided on the surface of the protrusions (15) are set to the same dimension.

3. An array mask as described in claim 1, wherein when the thickness of the coating layer on the inner surface of the through hole (12) is T1 and the thickness of the coating layer on the underside of the mask body (10), i.e., the surface facing the workpiece (3), is T2, T1 > T2.

4. An array mask as described in claim 1, wherein when the thickness of the coating layer on the inner surface of the through hole (12) is T1 and the thickness of the coating layer on the underside of the mask body (10), i.e., the surface facing the workpiece (3), is T2, T1 < T2.

5. An array mask as described in claim 1, wherein when the thickness of the coating layer on the inner surface of the through hole (12) is T1 and the thickness of the coating layer on the squeegee surface, which is the upper surface of the mask body (10), is T2, T1 > T2.

6. An array mask as described in claim 1, wherein when the thickness of the coating layer on the inner surface of the through hole (12) is T1 and the thickness of the coating layer on the squeegee surface, which is the upper surface of the mask body (10), is T2, T1 < T2.

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