JP4773497B2 - Masking material, solder paste printing method using the masking material, and solder bump forming method - Google Patents

Description

  The present invention relates to a masking material used when printing a solder paste on an electrode formed on a substrate, and a solder paste printing method using the masking material, and in particular, a masking material containing a vehicle and nano silica, and The present invention relates to a solder paste printing method using the masking material.

  As electronic devices become smaller and more functional, there is a growing demand for smaller and higher density electronic components on the board. In order to meet such a demand, a flip chip mounting method in which solder bumps are formed on electrodes and a mounting substrate and an electronic component are connected using the solder bumps is widely used. In a conventional method for forming solder bumps, for example, a solder paste in which solder powder and a vehicle are mixed is printed and transferred using a printing metal mask having openings according to electrode patterns arranged on a substrate, There is a method of cleaning the vehicle residue after heating this in a reflow furnace to melt the solder paste. However, the printing method has a limitation in the ratio between the thickness of the metal mask and the opening, so that the amount of solder that can be supplied to the electrode is not sufficient, and there is a problem that the solder bump has a quantitative defect and connection reliability is low. is there. Further, when the solder paste is heated and melted, the solder paste oozes out to the outside of the electrode region, and there is a problem that the amount of solder of the electrode is further reduced and the connection reliability is further lowered.

  Therefore, a photosensitive resin is provided around the solder paste supply unit on the substrate to prevent the solder paste from oozing out from the electrode region, thereby suppressing the occurrence of solder bump defects. However, there is a problem that the operation of peeling the photosensitive resin from the substrate after forming the solder bumps is complicated. In addition, since it is easy to remove by washing instead of this photosensitive resin, it has been attempted to use a vehicle for solder paste. Therefore, there is a problem that the masking pattern accuracy of the vehicle is inferior.

For this reason, in Patent Document 1, first, a solder bump is formed on a dummy chip, the quality state of the solder bump is inspected, and then only the solder bump formed on the non-defective product is transferred to the actual chip. Is disclosed. However, the solder bump forming method of Patent Document 1 has many inspection processes, transfer processes, and inferior productivity.
Japanese Patent Application No. 10-99259

  In view of the above problems of the prior art, the present invention can prevent heating sagging to improve the accuracy of the masking pattern, increase the transfer amount of the solder paste, and is excellent in cleanability after heat curing. An object of the present invention is to provide a masking material, a solder paste printing method and a solder bump forming method using the masking material.

A first aspect of the present invention is a masking material used for printing a solder paste on an electrode formed on a substrate, the vehicle having the same main component as the vehicle used for the solder paste, and an inorganic powder And a masking material that can be cleaned and removed together with the vehicle residue of the solder paste . If a vehicle alone is used for the masking material, the mask shape is distorted in the heat curing step of the masking material and the step of heating and melting the solder powder, so that the mask becomes wider than before printing, so-called heating sagging occurs. By adding an inorganic powder to the vehicle, the sagging of the mask can be prevented. Here, the “masking material” means a material used for a mask for printing and transferring a solder paste in a predetermined pattern onto a substrate.

  According to a second aspect of the present invention, there is provided a masking material characterized in that the inorganic powder is hydrophilic nanosilica.

  A third aspect of the present invention is a masking material characterized in that the content of the inorganic powder is 2% by mass or more and 15% by mass or less.

  A fourth aspect of the present invention is a masking material having a viscosity of 5 Pa · s or more and 1000 Pa · s or less. This “viscosity” is the viscosity at room temperature.

According to a fifth aspect of the present invention, a region of the substrate on which no electrode is provided includes a vehicle having the same main component as the vehicle used for the solder paste, and an inorganic powder . A step of supplying a masking material which can be washed and removed together with a residue of the vehicle; a step of heat-curing the masking material; and a region where the electrode adjacent to the region where the electrode is not provided is provided with solder powder and the vehicle And a solder paste printing method using a masking material, characterized by comprising: The “region where no electrode is provided” is a region between the electrodes arranged on the substrate.

According to a sixth aspect of the present invention, a vehicle having the same main component as the vehicle used for the solder paste and an inorganic powder around the electrode array region formed in a predetermined portion on the substrate , A step of supplying a masking material that can be cleaned and removed together with a vehicle residue of the solder paste, a step of heat-curing the masking material, and a step of supplying a solder paste containing solder powder and the vehicle to the electrode array region; And a solder paste printing method using a masking material. Here, the “predetermined portion on the substrate” means an outer edge portion of the substrate surface after dicing, a center portion of the substrate surface, or the like. The “electrode arrangement region” refers to a region where a plurality of electrodes are arranged at a predetermined interval.

According to a seventh aspect of the present invention, the alignment mark portion formed on the substrate contains a vehicle having the same main component as the vehicle used for the solder paste, and an inorganic powder, and the vehicle of the solder paste Supplying a masking material that can be cleaned and removed together with the residue , heating and curing the masking material, and supplying a solder paste containing the solder powder and the vehicle to an electrode array region formed at a predetermined position on the substrate And a solder paste printing method using a masking material. The alignment mark is a mark for alignment with a semiconductor element mounted on a substrate.

  The eighth aspect of the present invention is the solder paste printing method using the masking material according to claim 6, wherein the masking material is further supplied to an alignment mark portion formed on the substrate. .

  A ninth aspect of the present invention is a solder paste printing method using a masking material, wherein the inorganic powder is hydrophilic nanosilica.

  A tenth aspect of the present invention is a solder paste printing method using a masking material, wherein the content of the inorganic powder is 2% by mass or more and 15% by mass or less.

  An eleventh aspect of the present invention is a solder paste printing method using a masking material, wherein the masking material has a viscosity of 5 Pa · s or more and 1000 Pa · s or less. This “viscosity” is the viscosity at room temperature.

  A twelfth aspect of the present invention is a solder paste printing method using a masking material, wherein the substrate is a resin substrate or a semiconductor wafer.

  According to a thirteenth aspect of the present invention, the masking material containing the vehicle according to any one of claims 1 to 4 is supplied to a predetermined portion other than an electrode formed on a substrate, and the masking material is supplied. A step of heating and curing; a step of supplying and melting a solder paste containing a vehicle on the electrode; and a step of washing the masking material together with a vehicle residue of the solder paste. This is a solder bump forming method.

  According to the first, fifth, sixth, and seventh aspects of the present invention, since the vehicle is used as the masking material, the masking material is also used in the cleaning step of the vehicle residue performed after the heating and melting step of the solder powder. It can be removed and production efficiency is improved. When inorganic powder is contained in the masking material vehicle, the mask pattern can be prevented from sagging in the masking material heat curing process and solder powder heating and melting process, improving mask patterning accuracy. To do. Furthermore, by overprinting the masking material on the substrate, it is possible to increase the transfer amount of the masking material and increase the film thickness of the mask, so that it is possible to increase the supply amount of solder paste on the electrode rather than the metal mask. Connection reliability is improved.

  According to the first and sixth aspects of the present invention, since the mask shape can be prevented from sagging in the heat curing step of the masking material and the heat melting step of the solder powder, the mask is in contact with the electrode disposed on the substrate. Can be prevented. Furthermore, since the mask thickness can be prevented from being reduced due to heat sagging of the mask, it is possible to prevent the solder paste from flowing beyond the mask to the excess part, and to prevent the solder amount of the electrode near the mask from being reduced. Can do.

  According to the seventh and eighth aspects of the present invention, since the masking material is supplied to the alignment mark portion made of the same material as the electrode, the diffusion of the solder paste to the alignment mark portion during subsequent heat melting of the solder powder. This prevents the phenomenon that the solder of the electrode adjacent to the alignment mark portion is insufficient.

  According to the second and ninth aspects of the present invention, by using hydrophilic nanosilica, the effect of preventing the mask from sagging in the masking material heating and curing step and the solder powder heating and melting step is particularly improved. In addition, hydrophilic nanosilica is commercially available and can be used without any special treatment such as surface treatment of nanosilica particles, so that the masking material can be easily produced.

  According to the third and tenth aspects of the present invention, by setting the content of the inorganic powder to 2 to 15% by mass, the viscosity of the masking material can be transferred onto the substrate while having the effect of suppressing heat sag. Therefore, the production efficiency can be improved. Further, since it is possible to prevent unevenness from occurring in the effect of suppressing the heating sag of the mask in the step of heating and curing the masking material and the step of heating and melting the solder powder, the accuracy of the masking pattern is improved.

  According to the fourth and eleventh aspects of the present invention, since the masking material has a viscosity of 5 Pa · s or more and 1000 Pa · s or less, the viscosity is suitable for printing transfer of the masking material onto the substrate, and the production efficiency is improved.

  According to the twelfth aspect of the present invention, since the substrate is a resin substrate or a semiconductor wafer, in the case of a resin substrate, it can be widely used as an interposer substrate (redistribution substrate). In the case of a semiconductor wafer, a semiconductor chip is used. Can be applied to a wafer mounted with high density, so the application range is wide.

  According to the thirteenth aspect of the present invention, since the masking material can be cleaned together with the vehicle residue of the solder paste, the efficiency of solder bump formation is improved.

  Next, a masking material according to an embodiment of the present invention will be described, and further, an embodiment of a solder paste printing method using this masking material will be described with reference to the drawings. FIG. 1 is a schematic view showing an aspect in which a masking material is supplied to a substrate using a printing mask in a solder printing method using a masking material according to a first embodiment of the present invention. FIG. 2 shows an aspect in which a solder paste is supplied to an electrode on a substrate using a printing mask after the masking material is supplied in the solder printing method using the masking material according to the first embodiment of the present invention. FIG. FIG. 3 is a schematic view of a substrate on which solder bumps are formed using a solder printing method using a masking material according to the first embodiment of the present invention. FIG. 4 is a schematic view of a second embodiment of a solder printing method using a masking material according to the present invention. FIG. 5 is a cross-sectional view taken along the line aa ′ of FIG. FIG. 6 is a schematic view of a third embodiment of a solder printing method using a masking material according to the present invention. FIG. 7 is a schematic view of a fourth embodiment of a solder printing method using a masking material according to the present invention. FIG. 8 is a flowchart of the solder bump forming method.

  First, a masking material according to an embodiment of the present invention will be described. The main components of the masking material are a solder paste vehicle and hydrophilic nanosilica.

  The solder paste vehicle constituting the masking material is for giving the solder paste an adhesive property, and a vehicle conventionally used as a solder paste vehicle may be used as it is. The vehicle for solder paste is mainly composed of rosin, its derivatives and resins, and if necessary, an organic acid, a thixotropic agent, an antioxidant, an activator such as halogen or amine, a solvent which is a viscosity modifier, etc. Can also be added.

  The embodiment of the present invention is a masking material characterized in that the solder paste vehicle contains an inorganic powder, for example, hydrophilic nanosilica. If a mask made of a masking material of a single vehicle is used, the mask shape will be distorted during the heating and curing process of the masking material and the heating and melting process of the solder powder. When created, the mask shape can be prevented from sagging.

  The particle diameter of the hydrophilic nanosilica is not particularly limited, but is preferably 5 nm or more from the viewpoint of dispersibility, and is preferably 500 nm or less from the viewpoint of suppressing heating sagging. From the viewpoint of availability, a particle diameter of 5 nm to 50 nm that is widely distributed as a commercial product is particularly preferable.

  The content of the hydrophilic nanosilica in the masking material is preferably 2% by mass or more from the viewpoint of exerting a heating sag suppressing effect, and particularly preferably 4% by mass or more from the viewpoint of surely producing a heating sag suppressing effect over the entire mask. . If it is less than 2% by mass, the effect of suppressing heating sag is uneven, and there are parts where heating sag occurs and parts where heating sag does not occur, so the mask patterning accuracy decreases. On the other hand, when the amount of hydrophilic nanosilica added increases, the viscosity of the masking material tends to increase. However, when the content of hydrophilic nanosilica exceeds 10% by mass, the viscosity of the masking material increases rapidly. For this reason, the content of hydrophilic nanosilica is preferably 15% by mass or less from the viewpoint of suppressing the viscosity of the masking material to such an extent that the mask can be printed and transferred onto the substrate. In particular, the viscosity of the masking material is rapidly increased. 10 mass% or less is preferable from the point to suppress.

  The viscosity at room temperature of the masking material is not particularly limited as long as good printability can be ensured, but is preferably 50 Pa · s or more, and particularly preferably 90 Pa · s or more from the viewpoint of preventing the occurrence of printing bleeding. Further, it is preferably 1000 Pa · s or less from the viewpoint of preventing streaking in the printing direction, and particularly preferably 900 Pa · s or less from the viewpoint of preventing generation of mesh marks during screen printing. Moreover, when apply | coating a masking material using dispense, 5-200 Pa.s is preferable. Dispensing does not cause printing blur unlike screen printing, so the viscosity of the masking material at room temperature is suitably 5 Pa · s or more. The vehicle used for the masking material may have a viscosity at room temperature as long as the masking material is within the above viscosity range, and the composition of the vehicle may be appropriately selected according to the amount of hydrophilic nanosilica added.

  In the above embodiment, hydrophilic nanosilica is used for the inorganic powder, but it is not limited to hydrophilic nanosilica, and may be alumina powder, talc, inorganic acid salt, metal oxide, or the like. In particular, when the particle size is 5 to 50 nm, it can be produced by a dry / wet method and has a moderate degree of aggregation or nano metal particles.

  Next, a solder paste printing method using the masking material of the present invention will be specifically described with reference to the drawings.

  First, a first embodiment of a solder printing method using a masking material according to the present invention will be described with reference to FIGS. As shown in FIG. 1, on a resin substrate 1 having a solder resist 6 applied between the electrodes 3, using a mask for printing the masking material, the paste-like masking material 2 is, for example, 40 μm thick from the electrode surface. Print and transfer to The supply site of the masking material 2 is a gap between the electrodes 3 to which the solder resist 6 is applied.

  At this time, the masking material 2 is not particularly limited as long as it has the configuration as described above. In this embodiment, 5% by mass of hydrophilic nanosilica is added to the solder paste vehicle mainly composed of rosin. The masking material 2 having a viscosity of 331 Pa · s is used. Further, when it is desired to increase the amount of solder paste 5 to be supplied in the next step by increasing the mask formed in the gap between the electrodes 3, the masking material 2 may be appropriately overprinted. By increasing the supply amount of the solder paste 5 to the electrode 3, the connection reliability can be increased.

  The masking material 2 is cured by heating for several minutes after printing. Since hydrophilic nano silica is added to the masking material 2, it is possible to prevent the printed masking material 2 from being distorted. The heating temperature is 100 to 250 ° C, preferably 150 to 180 ° C.

  Next, as shown in FIG. 2, the solder paste 5 is printed and transferred onto the electrode 3 with a thickness of 60 μm from the electrode surface, for example. The solder paste 5 may be one generally used in the past, but the solder paste 5 of this embodiment example is composed of 30% by mass of solder powder and the remaining vehicle mainly composed of rosin. The main component is the same as that used in the masking material 2. Although the printing method is not particularly limited, a printing mask different from the mask for printing the masking material is used here.

  FIG. 3 shows a schematic view of the resin substrate 1 that has been subjected to vehicle cleaning after melting and heating the solder paste 5. As shown in FIG. 3, solder bumps 7 having substantially the same size are formed on each electrode 3. Even if the resin substrate 1 supplied with the masking material 2 and the solder paste 5 is subjected to heat treatment (for example, heat treatment using a reflow furnace) in order to form the solder bumps 7 on the electrode 3, the masking material 2 is hydrophilic. Since the functional nano silica is added, it is possible to prevent the heat-cured mask shape from sagging. Accordingly, it is possible to prevent the mask from coming into contact with the adjacent electrode 3, thereby improving the accuracy of the masking pattern. Further, since the solder paste 5 can be prevented from protruding from the electrodes 3, almost equal amounts of solder bumps 7 can be mounted on each electrode 3.

  Further, since the main components of the vehicle of the masking material 2 and the vehicle of the solder paste 5 are the same, when the residue of the vehicle contained in the solder paste 5 is washed with a solvent after the solder bump is formed, The mask can be cleaned and removed together.

  In the first embodiment, the arrangement region of the electrodes 3 is not particularly limited, and may be anywhere such as an outer edge portion or a central portion on the surface of the resin substrate 1 or may be arranged on the entire surface of the resin substrate 1. In the first embodiment, the resin substrate is used, but another substrate such as a semiconductor wafer may be used.

  Next, a second embodiment of the solder printing method using the masking material according to the present invention will be described with reference to FIGS. FIG. 4 is a schematic view showing a second embodiment of the solder printing method using the masking material according to the present invention. As shown in FIG. 4, the outer peripheral portion of the rectangular peripheral chip 11 has an electrode array region 4 on each side, and the central portion is a region where the electrode 3 is not disposed. In addition, alignment marks 8 are provided at some of the four corners.

  First, using a mask for masking material printing, the paste-like masking material 2 is printed and transferred to a region surrounding the outer periphery of the electrode array region 4 of the peripheral chip 11 and the alignment mark 8. The masking material 2 is not particularly limited as long as it has the configuration as described above. In this embodiment, the viscosity is obtained by adding 5% by mass of hydrophilic nanosilica to a vehicle for solder paste mainly composed of rosin. A masking material 2 of 331 Pa · s is used. In addition, when the mask to be formed on the peripheral chip 11 is increased to increase the amount of solder paste supplied in the next process, the masking material 2 may be overprinted after the masking material 2 is heated and cured. By increasing the supply amount of the solder paste 5 to the electrode 3, the connection reliability can be increased.

  The printed masking material 2 is cured by heating for several minutes. Since hydrophilic nano silica is added to the masking material 2, it is possible to prevent the printed masking material 2 from being distorted. The heating temperature is 100 to 250 ° C, preferably 150 to 180 ° C.

  Next, the solder paste 5 is printed and transferred from the electrode to the electrode array region 4 with a thickness of 60 μm, for example. At this time, since the solder paste 5 is printed by placing the screen mask on the cured masking material, the supplied solder paste 5 is thicker than the masking material 2 by the thickness of the screen mask. The solder paste 5 may be one generally used in the past, but the solder paste 5 of this embodiment example is composed of 30% by mass of solder powder and the remaining vehicle mainly composed of rosin. The main component is the same as that used in the masking material 2. The printing method is not particularly limited, but screen printing using a silk mask is used here.

  FIG. 5 is a schematic view showing the second embodiment from the cross section. As shown in FIG. 5, the masking material 2 is disposed so as to surround the electrode array region 4, and the solder paste 5 is printed and transferred to the electrode array region 4. Since the masking material 2 surrounds the electrode array region 4, it is possible to prevent the solder paste 5 from protruding from the electrode array region 4 when the solder paste 5 is melted and heated. Therefore, the masking material 2 can suppress the shortage of the solder bump capacity of the electrode 3.

  Next, after the solder paste 5 is melted and heated, and the vehicle is cleaned, solder bumps 7 having substantially the same size are formed on each electrode 3 as in the first embodiment. Even if the peripheral chip 11 supplied with the masking material 2 and the solder paste 5 is subjected to heat treatment (for example, heat treatment using a reflow furnace) in order to form the solder bumps 7 on the electrode 3, the masking material 2 Since hydrophilic nanosilica is added to, it is possible to prevent the heat-cured mask shape from sagging. Therefore, it is possible to prevent the heat-cured mask from coming into contact with the adjacent electrode 3 or the solder paste 5 from exceeding the mask that has been deformed by heat-curing, so that the electrode 3 does not protrude from the electrode array region 4. An approximately equal amount of solder bumps 7 can be mounted.

  Further, since the main components of the vehicle of the masking material 2 and the vehicle of the solder paste 5 are the same, when the residue of the vehicle contained in the solder paste 5 is washed with a solvent after the solder bump is formed, The mask can be cleaned and removed together.

  In the second embodiment, the electrodes 3 are arranged on each side of the outer edge portion of the peripheral chip 11. However, the position of the electrode 3 is not limited to this, and the position of the peripheral chip 11 is any place. Also good. Also in this case, the masking material 2 is printed and transferred around the electrode array region 4. Further, when there is a region to be masked in a part of the electrode array region 4 as in the case where the array of the electrodes 3 is partially interrupted, the masking material 2 is also applied to the portion apart from the periphery of the solder paste supply unit 4. You may supply.

  In the second embodiment, the peripheral chip 11 is used, but another substrate such as a semiconductor wafer may be used. In the second embodiment, the peripheral chip 11 is square, but the shape is not particularly limited, and the shape of the electrode 3 may be rectangular, circular, or other shapes.

  Next, a third embodiment of the solder printing method using the masking material according to the present invention will be described with reference to FIG. The third embodiment is different from the second embodiment in the position of the electrode array region 4 and the supply position of the masking material 2. In the third embodiment, as shown in FIG. 6, instead of having an electrode array region 4 on each side and a region where the electrode 3 is not arranged in the center, a chip 21 in the form of a square area array is provided. Is substantially the electrode array region 4. In addition, alignment marks 8 are provided at some of the four corners.

  In the third embodiment, using a mask for printing a masking material, the paste-like masking material 2 is printed and transferred to the alignment mark 8 portion of the area array chip 21. The same masking material 2 as in the second embodiment is used. In addition, when the mask formed on the area array chip 21 is increased and the amount of solder paste supplied in the next process is increased, the masking material 2 may be overprinted after the masking material 2 is heat-cured. . By increasing the supply amount of the solder paste 5 to the electrode 3, the connection reliability can be increased.

  Next, the solder paste 5 is printed and transferred from the electrode to the electrode array region 4 with a thickness of 60 μm, for example. At this time, since the solder paste 5 is printed by placing the screen mask on the cured masking material, the supplied solder paste 5 is thicker than the masking material 2 by the thickness of the screen mask. The solder paste 5 is the same as that in the second embodiment. The printing method is not particularly limited, but screen printing using a silk mask is used here.

  Next, a fourth embodiment of the solder printing method using the masking material according to the present invention will be described with reference to FIG. In the fourth embodiment, the masking material 2 is supplied to each corner regardless of the presence or absence of the alignment mark 8 and the solder resist 6 is provided on the outer edge and the center of the resin substrate 1. This is different from the third embodiment. As shown in FIG. 7, in the fourth embodiment, an electrode array region 4 is provided on each side of the resin substrate 1. In addition, alignment marks 8 are provided at some of the four corners.

  In the fourth embodiment, the mask material for masking material printing is used to print and transfer the paste-like masking material 2 to each corner of the resin substrate 1. The masking material 2 is the same as in the second and third embodiments. If the mask to be formed on the resin substrate 1 is made high and the amount of solder paste supplied in the next process is increased, the masking material 2 may be overprinted after the masking material 2 is heat-cured. By increasing the supply amount of the solder paste 5 to the electrode 3, the connection reliability can be increased.

  Next, the solder paste 5 is printed and transferred from the electrode to the electrode array region 4 with a thickness of 60 μm, for example. At this time, since the solder paste 5 is printed by placing the screen mask on the cured masking material, the supplied solder paste 5 is thicker than the masking material 2 by the thickness of the screen mask. The solder paste 5 is the same as in the second and third embodiments. The printing method is not particularly limited, but screen printing using a silk mask is used here.

  Also in the third and fourth embodiment examples, as in the second embodiment example, the shape of the area array chip 21 and the resin substrate 1 and the position and shape of the electrode 3 are not particularly limited.

  Next, the solder bump forming method of the present invention will be described with reference to the flowchart of FIG. As shown in FIG. 8, the first step of the solder bump forming method is a masking material application process. This step is to supply a masking material to a predetermined region on the substrate where no electrode is provided, and is performed, for example, by screen printing or a dispenser. As described in detail above, the masking material contains a vehicle used for the solder paste and an inorganic powder, for example, hydrophilic nanosilica. The second step is a masking material heat curing process. This process cures the masking material supplied in the first step, and the heating conditions for curing are 100 to 250 ° C. for several minutes, preferably 150 ° C. for 3 minutes.

  The third step is a solder paste material application process. This step is to supply a solder paste to the region where the electrodes are provided, and is performed by, for example, screen printing or a dispenser. The vehicle constituting the solder paste is the same as that used for the masking material. The fourth step is a solder paste material melting and heating step. In this step, the solder powder is melted with a heating profile suitable for various solder pastes. For example, with Sn-3Ag-0.5Cu solder, a 180 ° C. preheat-240 ° C. peak profile or the like is used.

  The fifth step is a cleaning process for the masking material and the vehicle residue. In this process, the masking material can be cleaned together with the vehicle residue of the solder paste. Through this cleaning process, solder bumps on the substrate are completed. The cleaning method in this step is not particularly limited, and may be any commonly used vehicle cleaning method. For example, spray cleaning using clean through is used.

  Below, an Example is shown and demonstrated about the heating sagging suppression effect of the masking material which concerns on this invention.

  The masking material was printed and transferred onto a 4 inch mirror wafer using a 325 mesh-φ18-emulsion thickness 18 μm printing mask, which was heated in an oven at 150 ° C. for 180 seconds. The heating sagging suppression effect of the masking material was evaluated by measuring the heating sagging of the masking material after heating.

The masking material was prepared by adding a predetermined amount of hydrophilic nanosilica Aerosil 200 (specific surface area: about 200 m ² / g, primary particle size: 12 nm) as an inorganic powder to a rosin-based vehicle and kneading in a mortar. . CWPrice is used for the printing machine. Masking material is used under printing conditions of squeegee speed: 15 mm / sec, push-in amount: 100 μm, printing pressure: 30 Psi, clearance: 1.2 mm, squeegee hardness: 80 degrees (square squeegee). Printing was performed on a mirror wafer with a width of 300 μm. The amount of sagging of the masking material was measured by measuring the difference between the width of the masking material immediately after printing and the width of the masking material after heat curing. Since the normal electrode pitch is 100 μm or more, when the amount of heating sag is 50 μm or less, it is considered that there is a heating sag suppressing effect.

  The vehicle viscosity was adjusted by changing the solvent content of the vehicle. The viscosity measuring device was a No. 4 rotor for small sample of HTB Brookfield viscometer, and the sample was stirred for 3 minutes at 5 rpm. The vehicle viscosity was then measured.

  Table 1 shows the relationship between the vehicle viscosity (Pa · s), the amount of hydrophilic nanosilica added (mass%), and the amount of heating sagging (μm) of the masking material. Materials that could not be measured due to uneven heating sagging and materials with poor printing were evaluated as NG.

  From the results in Table 1, it can be seen that heating sagging of the masking material is suppressed when the amount of hydrophilic nanosilica added increases regardless of the vehicle viscosity. In particular, when the content of hydrophilic nanosilica was 2 to 15% by mass, a good effect of suppressing heat sagging was observed. However, when the amount of hydrophilic nanosilica added is 20% by mass, the viscosity of the masking material becomes too high due to the excessive addition of hydrophilic nanosilica, so that it is not in the form of a paste. Further, when the amount of hydrophilic nanosilica added was 1% by mass, non-uniform heating sag occurred, and no significant heating sag suppressing effect was observed.

  Next, Table 2 shows the relationship between the viscosity of the masking material and the printability. The viscosity measurement method and the viscosity preparation method were the same as in Table 1 above, and the printability was evaluated by visual observation.

  From the results shown in Table 2, when the viscosity of the masking material to which hydrophilic nanosilica was added was 45 Pa · s, printing bleeding occurred and it was not suitable as a printed material to be printed. Further, when the viscosity of the masking material to which hydrophilic nanosilica was added was 1435 Pa · s, streaks were generated in the printing direction, which was unsuitable as a printed material to be printed.

  Next, a comparative test of the heat sagging suppression effect of hydrophilic nanosilica (Aerosil 200), hydrophobic nanosilica (Aerosil R974) and hydrophobic nanosilica (DM-20S: particle diameter of about 10 nm) was conducted. The test results are shown in Table 3. The amount of silica added was 4% by mass, and the viscosity of the masking material at this time was about 300 Pa · s. Other conditions were the same as in Tables 1 and 2 above.

  From the results of Table 3, it can be seen that hydrophilic nanosilica has a heating sag suppressing effect although hydrophobic nano silica did not have a heating sag suppressing effect.

  The masking material and the solder printing method of the present invention suppress heating sag at the time of heat curing, and the mask can be cleaned and removed together in the cleaning process of the vehicle residue. Is expensive.

It is the schematic which shows the aspect which supplied the masking material to the board | substrate among the solder printing methods which concern on the example of 1st Embodiment. It is the schematic which shows the aspect which supplied the solder paste to the electrode on a board | substrate among the solder printing methods which concern on the example of 1st Embodiment. It is the schematic of the board | substrate with which the bump produced by the solder printing method which is the example of 1st Embodiment was formed. It is the schematic of 2nd Embodiment of the solder printing method using a masking material. It is the sectional view on the aa 'line of FIG. It is the schematic of the 3rd embodiment of the solder printing method using a masking material. It is the schematic of the example of 4th Embodiment of the solder printing method using a masking material. It is a flowchart of a solder bump formation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin board 2 Masking material 3 Electrode 4 Electrode arrangement area 5 Solder paste 6 Solder resist 7 Solder bump 8 Alignment mark

Claims (13)

A masking material used for printing a solder paste on an electrode formed on a substrate,
A masking material containing a vehicle having the same main component as that of the vehicle used for the solder paste and an inorganic powder, and capable of being cleaned and removed together with a residue of the vehicle of the solder paste .   The masking material according to claim 1, wherein the inorganic powder is hydrophilic nanosilica.   The masking material according to claim 1 or 2, wherein the content of the inorganic powder is 2% by mass or more and 15% by mass or less.   The masking material according to any one of claims 1 to 3, wherein the viscosity is 5 Pa · s or more and 1000 Pa · s or less. A masking material which contains a vehicle having the same main component as the vehicle used for the solder paste and an inorganic powder in a region where no electrode is provided on the substrate, and can be cleaned and removed together with the residue of the vehicle of the solder paste. A process of supplying
Heat-curing the masking material;
Supplying a solder paste containing solder powder and the vehicle to a region where an electrode adjacent to a region where the electrode is not provided is provided, and a solder using a masking material How to print the paste. Around the electrode arrangement region formed in a predetermined part on the substrate, a vehicle having the same main component as the vehicle used for the solder paste and an inorganic powder are washed together with the residue of the vehicle of the solder paste. Supplying a masking material that can be removed ;
Heat-curing the masking material;
And a step of supplying a solder paste containing solder powder and the vehicle to the electrode array region. A method of printing a solder paste using a masking material. A masking material containing an alignment mark formed on the substrate and a vehicle having the same main component as the vehicle used for the solder paste and an inorganic powder, which can be cleaned and removed together with the residue of the vehicle of the solder paste. Supplying, and
Heat-curing the masking material;
A method of printing a solder paste using a masking material, comprising: supplying a solder paste containing solder powder and the vehicle to an electrode array region formed at a predetermined portion on a substrate.   The method of printing a solder paste using a masking material according to claim 6, wherein the masking material is further supplied to an alignment mark portion formed on the substrate.   The solder paste printing method using a masking material according to any one of claims 5 to 7, wherein the inorganic powder is hydrophilic nano silica.   The method for printing a solder paste using a masking material according to any one of claims 5 to 7, wherein the content of the inorganic powder is 2% by mass or more and 15% by mass or less.   The solder paste printing method using a masking material according to any one of claims 5 to 8, wherein the viscosity of the masking material is 5 Pa · s or more and 1000 Pa · s or less.   9. The method for printing solder paste using a masking material according to claim 5, wherein the substrate is a resin substrate or a semiconductor wafer. Supplying a masking material containing the vehicle according to any one of claims 1 to 4 to a predetermined portion other than on an electrode formed on a substrate, and heating and curing the masking material;
Supplying a solder paste containing a vehicle on the electrode and heating and melting;
And a step of cleaning the masking material together with a vehicle residue of the solder paste.

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