JP7712327B2 - Array Mask - Google Patents

Description

The present invention relates to an array mask that is used, for example, to form solder bumps.

The solder bumps are formed through a printing process in which flux is applied to the electrodes on the workpiece, such as a wafer, flexible board, or rigid board, a layout process in which solder balls are laid out on the flux, and a heating process in which the solder balls are heated and melted. In the above-mentioned layout process, the method of arranging the solder balls on the workpiece is a transfer method using a mask. In the transfer method, the solder balls are mounted on the electrodes of the workpiece using an array mask (hereinafter simply referred to as a "mask") that has positioning through-holes through which the solder balls can be inserted, corresponding to the layout pattern of the electrodes of the workpiece. Specifically, the mask is aligned with the workpiece so that the through-holes and the electrodes match, and the solder balls supplied onto the mask are swept with a squeegee or brush, and one solder ball is inserted into each through-hole. The solder balls are then fixed to the flux, and temporarily mounted in the designated positions on the workpiece.

One such mask is disclosed in Patent Document 1. The mask described in Patent Document 1 has a number of supporting protrusions on the underside of a mask body having through holes, and the protrusion dimensions of the protrusions are set to the same dimension. As a result, when the mask is placed on a workpiece, the lower ends of all of the supporting protrusions come into contact with the upper surface of the workpiece, ensuring a facing gap between the mask body having through holes and the workpiece.

JP 2006-287215 A

However, in recent years, bumps have become smaller as electronic devices become smaller. In other words, as bumps become smaller, the spacing between through holes and between pattern areas in the mask becomes narrower, and the external 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 work, making it easier for the flux arranged on the electrode of the work to adhere to the mask. If flux adheres to the surface of the mask, it becomes easier for solder balls to be mounted incorrectly. The object of the present invention is to provide an array mask that can prevent solder ball mounting errors.

The present invention is an array mask that places solder balls 2 at predetermined positions on a workpiece 3 by dropping solder balls 2 into through holes 12 that correspond to a predetermined array pattern, and is characterized in that it comprises a mask body 10 in which a large number of pattern areas consisting of through holes 12 are formed, and protrusions 15 provided on the side of the mask body 10 facing the workpiece 3, and a coating layer 50 is formed at least on the underside of the mask body 10. The mask body 10 and the protrusions 15 are formed separately. The coating layer 50 is formed so as to cover the underside of the mask body 10 and the surfaces of the protrusions 15. It is preferable that this coating layer 50 be formed to a thickness of 1 μm or less.

The present invention also provides a method for manufacturing an array mask that includes a mask body 10 in which a large number of pattern regions consisting of through holes 12 are formed, a protrusion 15 provided on the side of the mask body 10 facing the workpiece 3, and a coating layer 50 formed at least on the underside of the mask body 10. First, a primary pattern resist 41 having a resist body 41a is formed on a matrix 40. Next, a primary electrodeposition layer 42 is formed on the matrix 40 using the resist body 41a. Next, a secondary pattern resist 44 having a resist body 44a is formed on the primary electrodeposition layer 42. Next, a coating layer 50 is formed on the surface of the primary electrodeposition layer 42. This coating layer 50 is preferably formed on the surface of the primary electrodeposition layer 42 on the side having the secondary pattern resist 44 and on the surface of the secondary pattern resist 44.

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. In addition, by forming a coating layer to cover the underside of the mask body and the surface of the protrusions, the coating layer functions as a protective layer for the protrusions, preventing them from falling off, deforming, or breaking.

1 is a perspective view showing an overall configuration of an arrangement mask and a work of the present invention; 1 is a vertical sectional side view of an array mask according to a first embodiment of the present invention; 1 is a plan view of an array mask according to a first embodiment of the present invention; FIG. 11 is a vertical sectional side view of another embodiment of the array mask according to the first embodiment of the present invention. FIG. 11 is a plan view of another embodiment of the array mask according to the first embodiment of the present invention. FIG. 11 is a vertical sectional side view of another embodiment of the array mask according to the first embodiment of the present invention. 3A to 3C are explanatory diagrams of a method for manufacturing an array mask according to the first embodiment of the present invention. 3A to 3C are explanatory diagrams of a method for manufacturing an array mask according to the first embodiment of the present invention. FIG. 11 is a vertical sectional side view of an array mask according to a second embodiment of the present invention. 6A to 6C are explanatory diagrams of a method for manufacturing an array mask according to a second embodiment of the present invention. 6A to 6C are explanatory diagrams of a method for manufacturing an array mask according to a second embodiment of the present invention. FIG. 13 is a partially enlarged plan view of an array mask according to another embodiment of the present invention. FIG. 11 is a partially enlarged vertical sectional side view of another embodiment of the array mask according to the second embodiment of the present invention. 10A to 10C are explanatory diagrams of a manufacturing method of another embodiment of the array mask according to the second embodiment of the present invention.

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 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 workpiece on which the solder balls 2 are to be mounted using the mask 1. This workpiece 3 is, for example, a glass epoxy substrate base 4 on which a plurality of semiconductor chips 5 are mounted, wired with wire bonds, and then sealed with transfer molding. Electrodes 6, which are input/output terminals, are formed in a predetermined pattern on the upper 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 be made into individual LSI chips.

As shown in FIG. 1, the mask 1 is made of 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 the mask body 10 so as to surround it. In the center of the surface of the mask body 10, a number of pattern areas are formed, each of which is made up 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 a plan view with an inner diameter dimension slightly larger than the radius dimension of the ball 2.

The frame 11 is a flat plate made of aluminum, 42 alloy, Invar, SUS430, or other material, and has a square opening in the center of its surface that corresponds 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, about 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.

A protrusion 15 that protrudes downward can be provided on the lower surface side of the mask body 10 (mask 1), that is, the surface side facing the workpiece 3. In detail, as shown in Figs. 2 and 3, a protrusion 15 (crosspiece 15a) can be provided between the pattern areas (periphery of the pattern area) so as to surround the pattern area. This protrusion 15 (crosspiece 15a) does not have to be provided continuously as in Fig. 3, but may be provided piecemeal. Also, as shown in Fig. 4, a protrusion 15 (support 15b) can be provided at a position in the pattern area where the through hole 12 is not formed. Also, the shape of the protrusion 15 provided between adjacent pattern areas (periphery of the pattern area) so as to surround the pattern area is not limited to the crosspiece 15a, but may be a support 15c as shown in Fig. 5. If such a protrusion 15 is provided, it can abut against the upper surface of the workpiece 3 during the arrangement work to ensure a facing gap between the mask body 10 and the workpiece 3. As shown in Figures 2 and 4, each protrusion 15 (crosspiece 15a, support 15b) is preferably tapered from the underside of the mask body 10 toward the tip of the protrusion 15, and has a truncated cone shape.

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 of the protrusion 15 toward the tip) 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 damage caused by stress concentration on the protrusion 15, particularly on the base portion 15", and even if flux 17 adheres to the protrusion 15 when the mask 1 is placed on the work 3, the arc-shaped side of the protrusion 15 prevents the flux 17 from flowing around the through hole 12, eliminating the risk of poor mounting of the solder ball 2 due to flux 17 adhering to the through hole 12. It is preferable that the terminal position of the base portion 15" of the protrusion 15 is located in the vicinity of the through hole 12 on the underside of the mask body 10, and possible configurations include a configuration in which it is located at the intersection of the mask body underside 10a and the through hole inner surface 12a, or a configuration in which it is located at a gap from the through hole 12 on the mask body underside 10a. In addition, the side of the protrusion 15 may be either a convex arc or a concave arc. A convex arc provides good strength, while a concave arc provides no part of the side of the protrusion 15 that approaches the electrode 6 to which the flux 17 is attached, that is, a constant distance is maintained from the electrode 6 to which the flux 17 is attached. Furthermore, the tip 15' and/or base 15" of the protrusion 15 may be formed in an arc shape, which reduces the risk of the flux 17 adhering to the protrusion 15 as much as possible.

In this mask 1, the ratio of the height of the protrusion 15 to the thickness of the mask body 10 is preferably 2:1 or more, and it is more preferable that the thickness of the mask body 10 is in the range of 10 to 300 μm. In addition, the aspect ratio (ratio of the height to the tip dimension of the protrusion 15) of the protrusion 15 is preferably large, and in this embodiment, the aspect ratio is 3. In addition, the root 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 to the root dimension L2 and the width dimension L3 between the through holes 12 is 1:1.2:1.4 or more. Furthermore, the dimension L4 from the pattern area to the root of the protrusion 15 (crosspiece 15a, support 15c) is preferably set to 0.01 mm or more, and in this embodiment, it is set to 0.02 mm. Under these 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 area to the base of the protrusion 15, it is possible to prevent damage to the protrusion 15 and prevent the adhesion of flux at the same time. Furthermore, when the dimension from the pattern area to the tip center of the protrusion 15 (crosspiece 15a, support 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.

Here, the mask 1 is one in which the mask body 10 and the protrusions 15 are integrated, but the mask body 10 and the protrusions 15 may be one that are integrally formed of separate members. In the above mask 1, 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, the magnetic force can be uniformly applied to the mask 1, so that the mask 1 is not likely to bend inadvertently, can be well attached to the workpiece, and the alignment accuracy of the through holes 12 with respect to the electrode 6 can be improved. In addition, when removing the mask 1, the workpiece 3 and the protrusions 15 are not directly magnetically coupled, so that the plate can be easily removed. 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.).

In addition, when the protrusions 15 are formed from a non-magnetic material, they are not limited to the above metals, but may be formed from resin or resist. This provides the above-mentioned effect, as well as 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. In order to achieve this effect more significantly, it is preferable that not only the protrusions 15 but all of the parts of the mask 1 that come into contact with the workpiece 3 are formed from resin. In addition, when the protrusions 15 are formed from resin, they can be formed efficiently if the same resist is used as that used to form the mask body 10 by electroforming.

In addition, in this mask 1, as shown in Figures 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 hole 12. The coating layer 50 is preferably water-repellent, and examples of the material include fluororesin, silicone resin, emulsion, and resist (liquid). 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 hole 12, the flux can be repelled, and the state in which the flux remains attached to the lower surface of the mask body 10 or the inner surface of the through hole 12 can be prevented. The coating layer 50 may be formed on the upper surface of the mask body 10, or it is not necessary to form it on the lower surface of the mask body 10 between the pattern areas and between the protrusions 15 (the crosspieces 15a and the supports 15c). In short, it is desirable to form it in a part where the solder ball is likely to be mounted poorly when flux adheres, and it is desirable to form it 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 work.

Note that each drawing does not show the actual appearance of the mask 1, but shows it as a schematic. 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.

The arrangement of the solder balls 2 using the mask 1 is performed in the following procedure. This arrangement is performed by a dedicated arrangement device (see, for example, Figs. 1 and 5 of Patent Document 1). First, flux 17 (see Fig. 2) is printed and applied onto the electrode 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 coincide with each other, and then the mask 1 is fixed. This alignment is actually performed by aligning the outer periphery of the frame 11 and the workpiece 3. When the alignment is completed, the lower end surface of the protrusion 15 abuts against the surface of the workpiece 3 in the fixed state, and the mask body 10 is held in a separated position in which a facing gap with the workpiece 3 is secured, as shown in Figs. 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.

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 to the electrodes 6 by the flux 17. In the insertion operation of the solder balls 2 using the squeegee brush, even if a large squeegee brush pressure is applied to the mask 1, the protrusions 15 prevent the mask 1 from bending, and the insertion operation can be carried out efficiently and smoothly.

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, so that the protrusions 15 can reliably secure a gap between the mask body 10 and the workpiece 3, and the solder balls 2 can be efficiently inserted into the through holes 12 without any omissions.

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 shrink inward, the expansion of the mask body 10 caused by changes in ambient temperature can be absorbed by the tension in the direction of shrinkage. This makes it possible to prevent the mask body 10 from shifting out of position relative to the workpiece 3. In addition, because uniform tension can be applied to the entire mask body 10, the solder balls 2 can be mounted with good positional precision on the workpiece 3.

Next, a manufacturing method of the array mask 1 having such a configuration is shown in Figures 7 and 8. First, a photoresist layer 31 is formed on the surface of a matrix 30 made of, for example, stainless steel or brass steel having electrical conductivity. This photoresist layer 31 is formed by laminating one or several sheets of negative-type photosensitive dry photoresist to a predetermined height and thermocompression bonding. Next, as shown in Figure 7(a), a pattern film (glass mask) 32 having a light-transmitting hole 32a corresponding to the protrusion 15 is adhered to the photoresist layer 31, and then, as shown in Figure 7(b), a primary pattern resist 34 having a resist body 34a corresponding to the tapered protrusion 15 is formed on the matrix 30 by irradiating ultraviolet light with an ultraviolet lamp 33, performing each process of development and drying, and dissolving and removing the unexposed portion. At this time, it is preferable to form a taper on the resist body 34a by using a photoresist that is difficult to transmit ultraviolet light or by weakening the exposure amount. Next, the above-mentioned mother mold 30 is placed in an electroforming tank prepared under specified conditions, and as shown in FIG. 7(c), within the range of the height of the previous resist body 34a, electroforming of an electrodeposited metal such as nickel or copper is performed on the surface of the mother mold 30 that is not covered by the resist body 34a, to form a primary electroforming layer 35. Here, the primary electroforming layer 35 is formed over almost the entire surface of the mother mold 30 (first electroforming process). Next, as shown in FIG. 7(d), the primary pattern resist 34 is removed. At this point, it is advisable to perform a polishing process on the surface of the primary electroforming layer 35.

Next, as shown in Fig. 8(a), a photoresist layer 36 was formed on the entire surface of the primary electroforming layer 35 and the matrix 30, and a pattern film (glass mask) 37 having a light-transmitting hole 37a corresponding to the through hole 12 was attached to the surface of the photoresist layer 36. After that, ultraviolet light was irradiated from an ultraviolet lamp 33 to perform exposure, and development and drying processes were performed to dissolve and remove the unexposed portion, thereby forming a secondary pattern resist 38 having a resist body 38a corresponding to the mask body 10 on the surface of the primary electroforming layer 35, as shown in Fig. 8(b). Next, the electroforming layer 35 was placed in an electroforming tank prepared under specified conditions, and as shown in Fig. 8(c), electroforming of electroplated metals such as nickel and copper was performed on the surface of the primary electroforming layer 35 not covered by the matrix 30 and the resist body 38a within the range of the height of the resist body 38a to form a secondary electroforming layer 39 (second electroforming process). Next, the secondary pattern resist 38 is dissolved and removed, and the secondary electroforming layer 39 is peeled off from the matrix 30 and the primary electroforming layer 35. Finally, a coating layer 50 is formed on the matrix surface side of the secondary electroforming layer 39 corresponding to the lower surface of the mask body 10 and on the surface of the secondary electroforming layer 39 corresponding to the inner surface of the through hole 12 facing the secondary pattern resist 38, thereby obtaining a mask 1 as shown in FIG. 8(e) and FIG. 2.

By attaching a frame 11 to the mask 1 obtained in this way, an array mask 1 as shown in Figure 1 is obtained. The mask 1 (secondary electroforming 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 shrink inward. Such stress can be applied, for example, by taking advantage of the difference in thermal expansion coefficients between the frame 11 and the mask 1, attaching the frame 11 to the outer periphery of the mask 1 in a high-temperature environment, and causing the mask 1 to shrink inward at room temperature.

According to the above-mentioned manufacturing method of the mask 1, since the array mask can be manufactured with high accuracy by electroforming, the solder balls 2 can be mounted on the workpiece 3 with good positional accuracy. In addition, if the mask 1 having the protrusions 15 is formed by electroforming the mask body 10 and the protrusions 15 in a single unit by a single electroforming (second electroforming process), there is less risk of problems such as damage to the protrusions 15 compared to a case in which the mask body 10 and the protrusions 15 are formed separately, and it is also superior in that a mask 1 with excellent reliability can be obtained with high accuracy. In addition, if the protrusions 15 are formed in a tapered shape so that they become larger as they approach the lower surface of the mask body 10, stress concentration, especially at the base of the protrusions 15, can be avoided, so that the strength of the protrusions 15 can be firmly reinforced, and the protrusions 15 can be abutted between the electrodes 6 in a state separated from the electrodes 6 to which the flux 17 is applied, and therefore poor mounting of the solder balls 2 due to the flux 17 applied to the electrodes 6 adhering to the mask body 10 can be prevented. In this case, it is more effective to set the ratio of the dimensions of the tip 15' of the protrusion 15 to the dimensions of the base 15" to 1:3 or more, and to set the aspect ratio of the protrusion 15 to 3 or more. Protrusions 15 having the desired dimensions and aspect ratio can be easily produced by adjusting the shape of the resist pattern 35.

In the mask 1 having such a configuration, the through holes 12 and the protrusions 15 may be straight or tapered. Here, to specifically explain the case where the through holes 12 and the protrusions 15 are tapered, the through holes 12 are 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, and the through holes 12 are tapered toward the surface of the mask body 10 facing the workpiece 3, making it 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. In addition, the projections 15 have a tapered shape that narrows toward the surface of the mask body 10 that faces the workpiece 3, allowing the mask to be securely placed on the workpiece 3, and a tapered shape that widens toward the surface of the mask body 10 that faces the workpiece 3, allowing the projections 15 to be securely attached to the workpiece 3 while ensuring the strength of the projections 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.

Second Embodiment
Next, an array mask according to a 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.

According to the array mask of this embodiment, the coating layer 50 is also formed on the surface 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 underside of the mask body 10, the inner surface of the through hole 12, and the surface of the protrusions 15, even if flux adheres to the inner surface of the through hole 12, the flux can be repelled and flow onto the workpiece via the underside of the mask body 10 and the surface of the protrusions 15. Furthermore, the flux 17 can be more reliably prevented from wrapping around the through hole 12.

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 members, the bonding strength between them is weak (this is due to the fact that as the bumps become finer, the through-hole spacing dimensions and pattern area spacing dimensions become narrower and the external dimensions of the protrusion 15 itself arranged between the through-holes and between the pattern areas (outer periphery of the pattern area) tend 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 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, you can 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.

10 and 11 show the manufacturing method of the array mask of this embodiment. First, as shown in FIG. 10(a), a mother mold 40 is prepared. The mother mold 40 may be any material as long as it is conductive, and in this embodiment, stainless steel is used. Next, a photoresist layer is formed on the surface of the mother mold 40, and the unexposed portion is dissolved and removed by performing exposure, development, and drying processes by a well-known method, thereby forming a primary pattern resist 41 having a resist body 41a on the mother mold 40, as shown in FIG. 10(b). The photoresist layer is formed by laminating one or several sheets of negative-type photosensitive dry film resist to a predetermined height. Next, the mother mold 40 is placed in an electroforming tank prepared under predetermined conditions, and as shown in FIG. 10(c), an electrodeposited metal is electroformed on the surface of the mother mold 40 that is not covered by the resist body 41a to the same height as the previous resist body 41a, forming a primary electrodeposition layer 42. In this embodiment, the primary electrodeposition layer 42 is formed by Ni-Co electroforming. After the primary electrodeposition layer 42 is formed, 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.

Next, as shown in FIG. 11(a), a solder resist layer 43 was formed on the surface of the primary electrodeposition layer 42. The solder resist layer 43 was formed by laminating one or several sheets according to a predetermined height. Next, the processes of exposure, development, and drying were performed to dissolve and remove the unexposed parts, and a secondary pattern resist 44 having a resist body 44a was integrally formed on the primary electrodeposition layer 42 as shown in FIG. 11(b). It is preferable to perform a fall-off prevention process such as baking after forming the secondary pattern resist 44. This makes it possible to further strengthen 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 on its surface are peeled off from the mother mold 40. Finally, a coating layer 50 is formed on the surface of the primary electrodeposition layer 42 on the side having the secondary pattern resist 44 and 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 on the entire surface of the primary electrodeposition layer 42, not just on the surface of the primary electrodeposition layer 42 on which the secondary pattern resist 44 is formed. Of course, the coating layer 50 may also be formed on the inner surface of the through hole 12.

Next, another embodiment of the array mask according to the second embodiment will be described. Here, as shown in FIG. 13(a), the protrusions 15 are made 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.

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

Therefore, in order to prevent adverse effects on the protrusions 15 formed from resin, the mask of this embodiment forms a coating layer 70 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.

The manufacturing method of the array mask is the same as the above-mentioned process (see FIG. 10) from preparation of the matrix to forming the primary electrodeposition layer and removing the resist body. Next, a solder resist layer is formed on the surface of the primary electrodeposition layer 42, and the processes of exposure, development, and drying are performed to integrally form a secondary pattern resist 60 having a resist body 60a 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 development type photosensitive material, and its main components are 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 the coating layer 70 formed on its surface, to obtain 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 having the secondary pattern resist 60. The coating layer 70 may also be formed after the secondary pattern resist 60 is formed on the primary electrodeposition layer 42 and then peeled off from the matrix 40. In this way, the coating layer 70 can be easily formed not only on the surface of the primary electrodeposition layer 42 on the side having 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 wall of the through hole 12. In addition, after the secondary pattern resist 60 and the coating layer 70 are formed, it is preferable to perform a fall-off prevention treatment such as baking. This makes it possible to make 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 stronger. The 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 together after the coating layer 70 is formed on the surface of the secondary pattern resist 60.

The mask 1 obtained by this manufacturing method is resistant to cleaning (solvents) and can prevent the protrusions 15 from becoming sticky. In addition, as shown in FIG. 13(b), if the coating layer 70 is formed to cover the entire surface of the protrusions 15, damage or chipping of the protrusions 15 can be prevented.

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 are washed to intentionally make the surface of the protrusions 15 sticky, and then the coating layer 70 is formed on that surface, thereby making the adhesion between the protrusions 15 and the coating layer 70 even stronger.

As shown in FIG. 13(c), the protrusions 15 can be formed only from the material that forms the coating layer 70. The material that forms the coating layer 70 is one to which flux does not easily adhere, and specifically, a resin mixture containing barium sulfate and/or silicon dioxide in an acrylic resin can be mentioned. This resin mixture has excellent solvent resistance. To explain this in detail, each mask made of the resin mixture and having a protrusion with a width of 0.2 to 3.0 mm (a total of 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 mask body made of a nickel-cobalt alloy was immersed in a cleaning agent (manufactured by Kaken Tech Co., Ltd.) for 6 to 24 hours (a total of three times for 6 hours, 12 hours, and 24 hours), and it was confirmed that the protrusions did not peel off in all masks. Furthermore, since the resin mixture has good compatibility with the mask body 10 and good adhesion, it is possible to narrow the width of the protrusions 15. In addition, since the resin mixture has a hardness (5H to 6H in the JIS scratch hardness test), if the width of the protrusion is greater than 5 mm when the thickness of the mask body is 100 μm or less, there is a risk of the mask warping, so it is preferable to set the width of the protrusion to 5 mm or less. In this way, the coating layer 70 is formed mainly from materials such as fluororesin, silicone resin, and acrylic resin. It is possible to form the protrusion 15 mainly from such materials.

The main component of the resin mixture forming the protrusion 15 is 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). Phenol resin, epoxy resin, melamine resin, urea resin, alkyd resin, polyurethane, etc. (so-called thermosetting resins) may also be used.

In each of the above embodiments, the arrangement of the protrusions 15 (supports 15b) and the through holes 12 may be such that the protrusions 15 (supports 15b) surround one through hole 12, or one protrusion 15 may be surrounded by the 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 a partial arrangement like a support, but may be an endless frame. The shape of the protrusions 15 is not limited to a crosspiece 15a or a cylinder, but may be a polygon such as a rhombus or hexagon, or an ellipse. Furthermore, among these shapes, as shown in FIG. 12, an elongated shape and/or a rounded corner are preferable. In this way, by aligning the longitudinal direction and major axis direction of these shapes in a certain direction, for example, when cleaning the back surface of the mask 1, 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 can be eliminated as much as possible, and cleaning can be performed smoothly. Therefore, it is desirable to align the longitudinal direction and major axis direction of all of the protrusions 15 in one direction. Note that the elongated shape is only on 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.

In addition, in each of the above embodiments, the thickness of the coating layer 50/70 may be different between the inner surface of the through hole 12 and the surface of the mask body 10 and the protrusion 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 surface of the mask body 10 and the protrusion 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, which causes a solder ball mounting failure. In addition, if the coating layer 50 is formed of a material that is slippery (has low friction), a slippery area 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, and the thicker the thickness of T1, the larger the area will be, so that when the solder ball 2 is brushed with the squeegee brush, the squeegee brush and the solder ball 2 can be moved smoothly, which is expected to improve productivity and work efficiency. If T1<T2, the protrusions 15 can be more reliably prevented from falling off, deforming, or breaking when the protrusions 15 are formed separately on the underside of the mask body 10. There are various methods for forming the coating layer 50, such as immersion and spraying, but when forming the coating layer 50, it is recommended to cover the parts other than the desired formation part with a protective sheet. In addition, if you want to form a thick coating layer 50, you can achieve this by locally spraying the parts you want to make thicker or by changing the direction in which the mask 1 is immersed (for example, if you want to make the bottom of the mask body 10 thicker, you can immerse the mask body 10 with the bottom of the mask body 10 parallel to the immersion surface, and if you want to make the inner surface of the through hole 12 thicker, you can immerse the mask body 10 with the bottom of the mask body 10 perpendicular to the immersion surface).

REFERENCE SIGNS LIST 1 mask 2 solder ball 3 work 6 electrode 10 mask body 12 through hole 15 protrusion 15a crosspiece 15b support 15c support 15' tip 15" base 30, 40 matrix 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 layer

Claims (1)

An array mask for mounting solder balls (2) at predetermined positions on a workpiece (3) by inserting the solder balls (2) into through holes (12) corresponding to a predetermined array pattern,
The mask includes a mask body (10) in which the through hole (12) is formed, and a protrusion (15) provided on the lower surface side of the mask body (10), i.e., on the surface side facing the work (3),
An array mask characterized in that at least the squeegee surface , which is the upper surface of the mask body (10) , is provided with a coating layer formed of silicone resin, emulsion, resist, or acrylic resin, and that the surface of the mask body (10) facing the workpiece (3) is provided with a coating layer formed of silicone resin, emulsion, resist, or acrylic resin that can prevent flux from adhering .