Squeegee

Abstract

To improve performance of a squeegee.SOLUTION: A squeegee 10 includes an extension part 1 extending in a first direction, a bent part 2A provided on one end of the extension part 1, and a bent part 2B provided on the other end of the extension part 1.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a squeegee, and more particularly to a technique that is effective when applied to a squeegee used to print, for example, a high-viscosity paste having a higher viscosity than solder paste or a high-adhesion paste having a higher adhesiveness than solder paste. [Background technology]

[0002] Japanese Utility Model Application Publication No. 4-2632 (Patent Document 1) describes a technology that prevents the paste from flowing out in the width direction of the squeegee by attaching protruding walls to both ends of the squeegee, thereby reducing the work of scraping back the paste.

[0003] Furthermore, Non-Patent Document 1 describes that the size of the rolling diameter of the paste affects the phenomenon of the paste being scraped off by the squeegee, and Non-Patent Document 2 describes a technique related to the shear rate applied to the paste. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 4-2632 [Non-patent literature]

[0005] [Non-Patent Document 1] "The Latest Screen Printing Utilization Technology for Print Optimization / High Quality - From Troubleshooting to Application Examples," by Information Organization, 2011 [Non-patent document 2] "Measurement of Solder Paste Viscosity and Adhesion" by Manabu Harada Summary of the Invention [Problem to be solved by the invention]

[0006] Printing is a common paste application process used in the manufacturing of electronic products. In this process, the paste is placed on a mask, and then transferred to the desired location by using a spatula-like tool called a squeegee to move the paste back and forth over the openings in the mask.

[0007] However, as printing is repeated, the paste spreads laterally in the width direction of the squeegee or creeps upward, resulting in less paste being embedded in the openings in the mask and effectively contributing to printing.

[0008] As a result, there is a concern that the printing performance will gradually deteriorate with the number of printings, resulting in defects in the printed pattern and a gradual decrease in the transferred weight of the paste. For this reason, a squeegee that can effectively suppress the lateral spreading and creeping up of the paste is desired. [Means for solving the problem]

[0009] In one embodiment, the squeegee includes an extending portion extending in a first direction, a first bent portion provided at one end of the extending portion, and a second bent portion provided at the other end of the extending portion, wherein a first angle formed between the extending direction of the first bent portion and the first direction is an obtuse angle, and a second angle formed between the extending direction of the second bent portion and the first direction is an obtuse angle.

[0010] Here, in a cross-sectional view perpendicular to the first direction, the extending portion has an inclined portion inclined from the vertical direction and a protruding portion connected to the inclined portion and protruding horizontally. Furthermore, in a cross-sectional view perpendicular to the extending direction of the first bent portion, the first bent portion has a first inclined portion inclined from the vertical direction and a first protruding portion connected to the first inclined portion and protruding horizontally. Furthermore, in a cross-sectional view perpendicular to the extending direction of the second bent portion, the second bent portion has a second inclined portion inclined from the vertical direction and a second protruding portion connected to the second inclined portion and protruding horizontally. [Effects of the Invention]

[0011] According to one embodiment, the performance of the squeegee can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 10 is a plan view illustrating a printing process using a flat squeegee. [Figure 2] FIG. 10 is a plan view illustrating a printing process using a flat squeegee. [Figure 3] FIG. 10 is a side view illustrating a printing process using a flat squeegee. [Figure 4] FIG. 10 is a side view illustrating a printing process using a flat squeegee. [Figure 5] 10A and 10B are diagrams illustrating a phenomenon that occurs in a paste due to repeated printing processes. [Figure 6] FIG. 10 is a diagram illustrating the rolling state of the paste. [Figure 7] 10A to 10C are diagrams illustrating an operation of filling paste into an opening pattern. [Figure 8] 1A and 1B are diagrams illustrating the phenomenon of scraping off paste with a flat squeegee. [Figure 9] FIG. 1 is a diagram schematically illustrating a squeegee according to a related art technique. [Figure 10] FIG. 2 is a diagram illustrating the configuration of a squeegee for reciprocating the paste. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] 12, (b) is a cross-sectional view taken along line BB in FIG. 12, and (c) is a cross-sectional view taken along line CC in FIG. [Figure 14] FIG. 10 is a diagram illustrating a first feature point. [Figure 15] 10A and 10B are diagrams illustrating structural innovations of a squeegee. [Figure 16] 10 is a graph showing the relationship between "T1" and the ratio E. [Figure 17] 1 is a table showing the shear rate when the squeegee speed and "T1" are changed. [Figure 18] 1 is a graph showing the relationship between viscosity and shear rate. [Figure 19] FIG. 10 is a diagram illustrating a second feature point. [Figure 20] 10A and 10B are diagrams illustrating the angle dependency of the lateral spread suppression force. [Figure 21] FIG. 10 is a plan view illustrating the operation of the squeegee. [Figure 22] FIG. 10 is a plan view illustrating the operation of the squeegee. [Figure 23] FIG. 10 is a side view illustrating the squeegee operation. [Figure 24] 10 is a table showing verification results of whether the number of sheets that can be continuously printed can be increased. [Figure 25] 10 is a graph showing the results of verification that the transfer weight can be stabilized. [Figure 26] FIG. 1 illustrates a related art. [Figure 27] FIG. 10 is a diagram illustrating that the size of the squeegee can be reduced. [Figure 28] FIG. 10 is a diagram showing an example of squeegee manufacturing using a 3D printer. DETAILED DESCRIPTION OF THE INVENTION

[0013] In all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations thereof will be omitted. In addition, hatching may be used even in plan views to make the drawings easier to understand.

[0014] <Examples of applicable items> A squeegee is a tool used in the paste printing process, which is one of the manufacturing processes for electronic products. The paste printing process is carried out, for example, in the manufacturing processes for printed circuit boards and power modules. In this printing process, printing masks such as metal masks and screen masks are used. The paste used as the printing material is solder paste or paste with dispersed metal particles on the nano to micron level, such as iron (Fe), silver (Ag), or copper (Cu).

[0015] Squeegee materials include, but are not limited to, metals such as stainless steel (SUS), urethane, engineering plastics such as nylon 6, nylon 66, POM, and PBT, and ONYX, which is used as a material for 3D printers.

[0016] <Consideration of improvements> For example, a typical squeegee has a three-dimensional shape that is approximately rectangular. In this specification, such a typical squeegee will be referred to as a "flat squeegee."

[0017] In the following, we will first explain the paste printing process using this "flat squeegee" and then explain the room for improvement inherent in the "flat squeegee."

[0018] 1 and 2 are diagrams illustrating a printing process using a flat squeegee 100. FIG.

[0019] As shown in Fig. 1, paste 130 is supplied onto a printing mask 110 and a flat squeegee 100 is placed on it. Then, as shown in Figs. 1 and 2, the flat squeegee 100 is moved to transfer the paste 130 to the opening pattern 120 provided in the printing mask 110. This allows the paste 130 to be applied to the substrate area (not shown) exposed from the opening pattern 120 of the printing mask 110. This process is the printing process.

[0020] Here, when the transfer of the paste 130 by moving the flat squeegee 100 is repeated, the paste 130 gradually spreads in the horizontal direction (x direction), as can be seen, for example, by comparing Figures 1 and 2. Furthermore, a phenomenon known as creeping up of the paste 130 is particularly noticeable when a paste with a higher viscosity or a higher adhesiveness than, for example, solder paste is used as the paste 130. The creeping up phenomenon is a phenomenon in which, as shown in Figures 3 and 4, when the transfer of the paste 130 by moving the flat squeegee 100 is repeated, the paste 130 creeps up in the upward direction (z direction) of the flat squeegee 100 and sticks to the flat squeegee 100, preventing it from falling onto the printing mask 110.

[0021] In general, the viscosity of pastes containing dispersed metal particles tends to increase rapidly as the proportion of metal particles increases, and the viscosity tends to increase even more in the case of small metal particles with nano to submicron diameters, such as those found in sintered materials. For example, sintered copper pastes containing dispersed copper particles often have a relatively high proportion of copper particles and small particle diameters, ranging from nano to submicron. These characteristics result in a high viscosity, which can make the creeping phenomenon described above more pronounced.

[0022] When such lateral spreading and creeping up phenomena of the paste 130 occur, less paste 130 contributes to filling the opening pattern 120 provided in the printing mask 110. In other words, by repeatedly performing the printing process, less paste 130 contributes to filling the opening pattern 120, resulting in a gradual deterioration in printability, which causes chipping of the printed pattern and a gradual decrease in the transfer weight.

[0023] This point will be explained in more detail below.

[0024] 5 is a diagram illustrating the phenomenon that occurs in the paste 130 as the printing process is repeated. As shown in FIG. 5, repeated printing processes cause the paste 130 to spread laterally and creep up, resulting in a decrease in the amount of paste 130 that contributes to filling the opening pattern 120. This decrease in the amount of paste 130 that contributes to filling the opening pattern 120 means the following: FIG. 6.

[0025] That is, as shown in Figure 6 (left side), in the early stages of the printing process, the paste 130 does not spread laterally or creep up, so there is a sufficient amount of paste 130 that contributes to filling the opening pattern 120. When the paste 130 is pressed by the flat squeegee 100, it moves over the printing mask 110 while rolling. Here, "rolling" as used in this specification refers to the rotational motion of the paste that occurs when the squeegee is moved, and the diameter of this rotational motion of the paste is the rolling diameter.

[0026] At the beginning of the printing process shown in Figure 6 (left), the paste 130 does not experience any lateral spreading or creeping-up phenomena, and there is sufficient paste 130 present to contribute to filling the opening pattern 120, so the rolling diameter of the paste 130 becomes large.

[0027] 6 (right part), when the printing process is repeated, the paste 130 undergoes lateral spreading and creeping-up phenomena, and therefore less paste 130 contributes to filling the opening pattern 120. As a result, as shown in FIG. 6 (right part), when the printing process is repeated, the rolling diameter of the paste 130 becomes smaller.

[0028] In this regard, the present inventor has found that a factor that causes chipping of the print pattern and a gradual decrease in the transfer weight is the influence of a smaller rolling diameter of the paste 130. Therefore, the mechanism by which a smaller rolling diameter of the paste 130 causes chipping of the print pattern and a gradual decrease in the transfer weight will be explained below.

[0029] FIG. 7 is a diagram illustrating the operation of filling the opening pattern 120 with paste 130. As shown in FIG.

[0030] 7, paste 130 being pressed and rolled by flat squeegee 100 hits the wall of opening pattern 120 provided in printing mask 110 on substrate 150, thereby filling the interior of opening pattern 120. Therefore, a smaller rolling diameter of paste 130 means a shorter time for filling opening pattern 120. As a result, when the rolling diameter of paste 130 becomes smaller, filling into opening pattern 120 becomes insufficient, resulting in chipping of the printing pattern.

[0031] 8 is a diagram illustrating the phenomenon of scraping off the paste 130 by the flat squeegee 100. As shown in Fig. 8, downward squeegee pressure is applied to the flat squeegee 100. As a result, as shown in Fig. 8 (left), a scraping phenomenon occurs on the surface of the paste 130 filled in the opening pattern 120 by the flat squeegee 100.

[0032] In this regard, as described in Non-Patent Document 1, for example, when the rolling diameter of the paste 130 is large, the internal pressure of the paste 130 increases, resulting in an increase in the reaction force against the squeegee pressure, and the scraping phenomenon is suppressed. In contrast, when the rolling diameter of the paste 130 is small, the internal pressure of the paste 130 decreases, which reduces the reaction force against the squeegee pressure and makes the scraping phenomenon more apparent (see the right part of FIG. 8). In other words, when the rolling diameter of the paste 130 is small, the amount of paste scraped off by the flat squeegee 100 increases, resulting in a gradual decrease in the transfer weight.

[0033] As described above, it can be seen that a reduction in the rolling diameter of the paste 130 causes chipping of the print pattern and a gradual decrease in the transfer weight. From this, it can be seen that in order to improve printing stability by suppressing chipping of the print pattern and a gradual decrease in the transfer weight, it is important to suppress a reduction in the rolling diameter. Furthermore, since a reduction in the rolling diameter is caused by the lateral spreading and creeping-up phenomena of the paste 130, it can be seen that in order to improve printing stability by suppressing chipping of the print pattern and a gradual decrease in the transfer weight, it is important to suppress the lateral spreading and creeping-up phenomena of the paste 130.

[0034] In this regard, the flat squeegee 100 does not take measures to suppress the lateral spreading or creeping up of the paste 130. For this reason, with the flat squeegee 100, as the number of prints increases, chipping of the print pattern and a gradual decrease in transfer weight become apparent at an early stage of the print run, making it difficult to increase the number of sheets printed continuously, and there is room for improvement.

[0035] In particular, when a paste 130 having a higher viscosity or a higher adhesiveness than solder paste is used, the flat squeegee 100 causes the paste to creep up, resulting in a significant decrease in the number of sheets that can be continuously printed. Therefore, in order to increase the number of sheets that can be continuously printed, even when a high-viscosity paste is used, some innovation in the squeegee is required. The following describes related technologies related to squeegees.

[0036] <Squeegee-related technologies> As mentioned above, there are two main factors that can impair continuous printability in the printing process. One is the phenomenon of the paste spreading laterally in the width direction of the squeegee, which reduces the amount of paste that contributes to filling the opening pattern. The other is a phenomenon that becomes particularly apparent when using a paste with higher viscosity or adhesiveness than solder paste. With each printing, the paste gradually creeps up to the top of the squeegee and sticks there, reducing the amount of paste that contributes to filling the opening pattern.

[0037] In this regard, there are related techniques as shown below.

[0038] Here, the term "related art" as used in this specification refers to art that is not a known art, but has a problem that the inventor has discovered, and is a technology that is a premise for the present invention.

[0039] FIG. 9 is a diagram schematically showing a squeegee 200 in the related art.

[0040] 9, squeegee 200 is provided with protrusions 210 for suppressing the creeping up phenomenon of paste 130, and is also provided with shielding plates 220 for suppressing the lateral spreading phenomenon of paste 130. From this, it is believed that squeegee 200 can suppress the creeping up phenomenon and the lateral spreading phenomenon.

[0041] However, with the configuration of the protrusions 210 provided on the squeegee 200, for example, when a highly viscous and highly adhesive paste is used, the high viscosity and adhesiveness make it difficult for the paste to fall under its own weight, and it climbs over the protrusions 210 and further upward, as shown in the left part of FIG. 9. For this reason, it is believed that the squeegee 200 cannot effectively suppress the creeping up phenomenon of the paste 130. Furthermore, the shielding plate 220 provided to suppress the lateral spreading phenomenon of the paste 130 does not apply a force to push back the paste 130, and therefore its effect of suppressing the lateral spreading phenomenon is thought to be limited. In addition, it is thought that the paste 130 will stick to the shielding plate 220 itself, resulting in less paste contributing to filling the opening pattern.

[0042] In particular, as shown in Figure 10, since squeegees 200 are usually used in pairs to move the paste 130 back and forth, a considerable amount of paste 130 ends up sticking to the shielding plates 220 provided on each of the squeegees 200.

[0043] Therefore, when a highly viscous and highly adhesive paste is used, the squeegee 200 in the related art is thought to be unable to sufficiently suppress the creeping up and lateral spreading of the paste 130, and as a result, there is room for improvement in terms of improving the continuous printability in the printing process. Therefore, in this embodiment, an ingenuity has been implemented to address the room for improvement that exists in the related art. The technical concept of this ingenious embodiment will be described below.

[0044] <Configuration of the squeegee in the embodiment> FIG. 11 is an external view of the squeegee 10, and FIG. 12 is a plan view of the squeegee 10. As shown in FIG.

[0045] 11 and 12, squeegee 10 includes an extending portion 1 extending in a predetermined direction (first direction), a bent portion 2A provided at one end of extending portion 1, and a bent portion 2B provided at the other end of extending portion 1. In this case, the angle (first angle) formed between the extending direction of bent portion 2A and the first direction is an obtuse angle, and the angle (second angle) formed between the extending direction of bent portion 2B and the first direction is also an obtuse angle. In this manner, the external appearance of squeegee 10 is configured.

[0046] Fig. 13(a) is a cross-sectional view taken along line AA in Fig. 12. In other words, Fig. 13(a) is a cross-sectional view taken along a plane perpendicular to the x-direction, which is the first direction. As shown in Fig. 13(a), the extension 1 has an inclined portion 3A inclined from the vertical direction (z-direction) and a protruding portion 3B connected to the inclined portion 3A and protruding in the horizontal direction.

[0047] Next, Fig. 13(b) is a cross-sectional view taken along line BB in Fig. 12. In other words, Fig. 13(b) is a cross-sectional view taken along a plane perpendicular to the extending direction of bent portion 2A. As shown in Fig. 13(b), bent portion 2A has inclined portion 4A having a surface inclined from the vertical direction, and protruding portion 4B connected to inclined portion 4A and protruding in the horizontal direction.

[0048] Furthermore, Fig. 13(c) is a cross-sectional view taken along line CC in Fig. 12. In other words, Fig. 13(c) is a cross-sectional view taken along a plane perpendicular to the extending direction of bent portion 2B. As shown in Fig. 13(c), bent portion 2B has inclined portion 5A having a surface inclined from the vertical direction, and protruding portion 5B connected to inclined portion 5A and protruding in the horizontal direction.

[0049] Here, the inclined portion 3A, the inclined portion 4A, and the inclined portion 5A are connected, and the protruding portion 3B, the protruding portion 4B, and the protruding portion 5B are connected. For example, the inclined portion 3A, the inclined portion 4A, and the inclined portion 5A are integrally formed so as to be smoothly connected. Similarly, the protruding portion 3B, the protruding portion 4B, and the protruding portion 5B are integrally formed so as to be smoothly connected.

[0050] In this manner, the squeegee 10 in this embodiment is configured.

[0051] <Features of the embodiment> Next, the features of this embodiment will be described.

[0052] The present embodiment is characterized in that, in the squeegee width direction, an angled bent portion 2A is provided at one end of the extending portion 1, an angled bent portion 2B is provided at the other end of the extending portion 1, and protrusions (3B, 4B, 5B) are provided as "returns" parallel to the printing mask 110 as shown in FIGS. 13(a) to 13(c). This prevents the paste 130 from creeping up toward the top of the squeegee 10 and prevents the paste 130 from spreading sideways without limit, even when a high-viscosity paste is used as the paste 130. In particular, the protrusion 3B provided on the extending portion 1, the protrusion 4B provided on the bent portion 2A, and the protrusion 5B provided on the bent portion 2B are smoothly connected, thereby preventing the paste from creeping up along the entire length of the squeegee 10.

[0053] Furthermore, due to the features of this embodiment, a rolling state close to that at the center can be achieved at both ends of the squeegee 10, ensuring uniform printability across the entire squeegee 10. This makes it possible, for example, to set the squeegee width shorter than the aperture pattern. This means that the paste 130 applied to the printing mask 110 can be quickly brought to a steady state where the rolling state is stable, thereby improving uniform continuous printability.

[0054] The following specifically describes the features of this embodiment.

[0055] The first feature of this embodiment is a device for suppressing the creeping up of paste 130, for example, by adopting a cross-sectional shape of extension portion 1 as shown in FIG. 14. That is, extension portion 1 has an inclined portion 3A having a surface inclined from the vertical direction, and a protruding portion 3B connected to inclined portion 3A and protruding in the horizontal direction parallel to printing mask 110, and is designed on the premise that the terminal angle F of protruding portion 3B is 90° or less. That is, the terminal angle F of each of protruding portions 3B, 4B, and 5B is designed to be 90° or less. This is the first feature for suppressing the creeping up of paste 130.

[0056] Here, the dimensions of the inclined portion 3A and the protruding portion 3B can be appropriately designed based on the amount and physical properties of the paste 130 supplied onto the printing mask 110.

[0057] In this way, according to the shape shown in FIG. 14, the inclined portion 3A and the protruding portion 3B guide the flow of the paste 130 horizontally during the extrusion operation (squeegee operation) of the squeegee 10 against the paste 130. When the terminal angle F of the protruding portion 3B is 90 degrees or less, the paste 130 guided horizontally does not undergo any further creeping up because no force is applied in the direction along the wall. As a result, according to the first characteristic point of the present first embodiment, the creeping up phenomenon of the paste 130 can be effectively suppressed, particularly even when a high-viscosity paste is used as the paste 130. As a result, according to this embodiment, the rolling diameter of the paste 130 can be stabilized.

[0058] The configuration of the extension portion 1 of the squeegee 10 has been described above, but the same configuration as the extension portion 1 is also adopted for the bending portion 2A of the squeegee 10 and the bending portion 2B of the squeegee 10. As a result, the state shown in FIG. 14 is also realized for the bending portion 2A and the bending portion 2B. As a result, the creeping up phenomenon of the paste 130 is suppressed also for the bending portion 2A and the bending portion 2B, and the rolling diameter of the paste 130 can be stabilized. In particular, in the squeegee 10 of the present embodiment, the extension portion 1, the bending portion 2A, and the bending portion 2B, each having a cross-sectional shape shown in FIG. 14, are smoothly connected, and therefore the creeping up phenomenon of the paste 130 is suppressed throughout the entire squeegee 10, and the rolling diameter of the paste 130 is stabilized.

[0059] As described above, protrusions 3B, 4B, and 5B function to guide the flow of paste 130 horizontally and prevent the paste 130 from creeping up. However, if the lengths (T2) of protrusions 3B, 4B, and 5B are unnecessarily long, the contact area between the paste 130 and the squeegee 10 increases. This means, for example, that if the paste 130 is highly viscous, the paste 130 may stick to the squeegee 10, increasing the risk that the paste 130 on the printing mask 110 will lift up along with the squeegee 10 when the squeegee 10 is removed from the printing mask 110 after the printing process is completed. For example, in a printing process using a pair of squeegees 10, i.e., an outward squeegee 10 and a return squeegee 10, if the paste 130 lifts up due to the outward squeegee 10, the printing process using the return squeegee 10 will be unable to be performed.

[0060] Therefore, from the viewpoint of suppressing the rising of paste 130, it is desirable that the length (T2) of each of protrusions 3B, 4B, and 5B is not unnecessarily long, but within a range that can suppress the creeping up phenomenon of paste 130. For example, it is desirable that the length (T2) of each of protrusions 3B, 4B, and 5B is equal to or less than the height (T1) of each of inclined portions 3A, 4A, and 5A.

[0061] Here, we will further discuss the following structural innovations regarding the lifting of the paste 130. Various combinations of the sizes of "T1" and "T2" and the attack angle of "T1" are possible. For simplicity's sake, consider a configuration in which "T1" and "T2" are the same size, the attack angle is 60 degrees, and the paste 130 fits snugly within the squeegee 10, as shown in Figure 15. The actual adhesive strength of the paste 130 to the squeegee 10 and the weight of the paste 130, which affect lifting, vary depending on the density of the paste 130, the type of paste 130, and the combination of the materials selected for the squeegee 10 and the printing mask 110. However, structurally, it is believed that the smaller the contact area, the weaker the adhesive strength, and the larger the volume of the paste 130, the greater the weight. Furthermore, it is believed that the greater the sum of the weight of the paste 130 and the adhesive strength between the paste 130 and the printing mask 110, relative to the adhesive strength between the paste 130 and the squeegee 10, the less likely lifting will occur. Therefore, the smaller the contact area between the paste 130 and the squeegee 10 is relative to the volume of the paste 130 and the contact area between the paste 130 and the printing mask 110, the less likely lifting will occur, which is advantageous.

[0062] In the case of the cross-sectional view shown in FIG. 15, the contact length Ca between the paste 130 and the squeegee 10 is expressed by the following formula (1).

[0063]

number

[0064] The paste area A is expressed by the following formula (2).

[0065]

number

[0066] The contact length Cb between the paste 130 and the printing mask 110 is expressed by the following formula (3).

[0067]

number

[0068] When "T1" is changed from 1 mm to 15 mm, the ratio E of the contact length Ca between the paste 130 and the squeegee 10 to the sum of the paste area A and the contact length Cb between the paste 130 and the printing mask 110 varies as shown in Figure 16. From this, it can be seen that the larger "T1" is, the smaller the value of the ratio E becomes, and qualitatively, lifting is less likely to occur. On the other hand, when "T1" is around 6 mm, even if "T1" is increased, the rate of decrease in ratio E levels off, and the effect is limited.

[0069] Up to this point, we have been discussing the matter based on assumptions about specific dimensions, but even when considering the general state shown in Figure 14, the contact length Ca between the paste 130 and the squeegee 10, the area A of the paste, the contact length Cb between the paste 130 and the printing mask 110, and the ratio E of the contact length Ca between the paste 130 and the squeegee 10 to the sum of the paste area A and the contact length Cb between the paste 130 and the printing mask 110 can be approximately considered to satisfy the relationships shown in the following equations (4) to (7).

[0070]

number

[0071]

number

[0072]

number

[0073]

number

[0074] Therefore, in this case as well, a larger "T1" reduces the ratio E, which is advantageous from the viewpoint of suppressing lifting of the paste 130. Furthermore, compared to the reduction rate of the ratio E when "T1" is in the range of about 1 mm to 3 mm, the reduction rate of the ratio E when "T1" becomes about 6 mm becomes smaller, and it is estimated that the effect will gradually become limited.

[0075] Next, in the state shown in FIG. 15, the shear rate D acting on the paste 130 when the rolling diameter of the paste 130 is approximated by "T1" is approximated by the following mathematical formula (8), as described in Non-Patent Document 2, for example.

[0076]

number

[0077] Here, "V" represents the squeegee speed. Fig. 17 shows the shear rate D when "T1" is varied from 1 mm to 15 mm and "V" is varied from 10 mm / s to 100 mm / s. Fig. 17 shows that the shear rate D applied to the paste 130 decreases when "T1" is large.

[0078] Next, Figure 18 shows the relationship between paste viscosity and shear rate for two types of paste. It can be seen that for both types of paste, the viscosity tends to decrease as the shear rate increases. This tendency is called thixotropy, and many pastes used industrially exhibit this thixotropic property.

[0079] Here, a relatively low viscosity is desirable for the paste to roll stably during printing. In other words, it is necessary to apply a certain level of shear rate to the paste. In this regard, as shown in Figure 17, increasing "T1" reduces the shear rate applied to the paste 130. While it is possible to compensate for the reduced shear rate by increasing the squeegee speed, it is desirable to have as wide a range of selectable squeegee speeds as possible.

[0080] Therefore, as mentioned above, while a larger "T1" can suppress lifting, if it is made too large, the problem of the shear rate becoming too small will arise. Here, since the viscosity of the two types of pastes shown as examples decreases sufficiently at a shear rate of about 2.5 [1 / s], it can be seen that if "T1" is up to about 8 mm, the squeegee speed condition can be selected from a wide range of 10 mm / s to 100 mm / s.

[0081] From the above, it is of course possible to calibrate the dimensions of the squeegee 10 on a case-by-case basis, taking into account the properties of the paste 130 material being used at that time, but it is believed that if "T1" is set in the range of 6 mm or more and 8 mm or less, a squeegee 10 can be provided that can be used stably under a wide range of conditions.

[0082] The ingenuity to prevent lifting of the paste 130 will be further described below. When printing a highly viscous or highly adhesive paste, there were cases where the paste did not lift on one printing machine, but did lift on another printing machine.

[0083] When the discrepancy was examined, the following cause was identified. In a typical printing press, although this depends on the specifications, after the squeegee has completed a printing operation, it typically rests for a few seconds before slowly rising and moving on to the next printing operation. Here, the next printing operation refers to the return printing if the most recently completed printing operation was the outbound printing, and to the return printing if the most recently completed printing operation was the outbound printing. On the other hand, in the printing press where the lifting occurred, the squeegee momentarily jumped up slightly after the printing operation was completed, without any time to rest. This is thought to be because after the printing operation is completed, a pressure called printing pressure is applied to the squeegee to ensure close contact with the mask, and the slight lift was caused by the reaction to the action of releasing this pressure.

[0084] The effect of this phenomenon on paste lifting is roughly as follows: As mentioned above, the paste is rolling during printing, so shear is applied to the paste, which is thought to lower the viscosity of the paste overall. After that, when it stops, shear is no longer applied to the paste, so the viscosity returns to its original high state. The squeegee then rises, and as a result, shear is again applied to the area where the paste and squeegee are in contact, causing the viscosity to decrease. On the other hand, the viscosity remains high in other areas, so the area near the squeegee is low viscosity and the rest of the area is high viscosity, making it unlikely for lifting to occur.

[0085] On the other hand, if the squeegee is lifted instantly without stopping after the printing operation is completed, the overall viscosity remains lowered due to the rolling, and the difference in viscosity between the area where the paste is in contact with the squeegee and the other areas is small, which is thought to cause lifting.

[0086] To address this issue, the squeegee material was changed from metal to a more elastic engineering plastic such as POM. This allowed the squeegee, which would otherwise jump up instantly in reaction to the release of printing pressure, to use its own elastic deformation to mitigate this, effectively preventing the paste from lifting up. While various squeegee materials can be selected depending on the situation, using a more elastic engineering plastic rather than a metal one is more versatile. For example, the squeegee material can be made to contain any of the following: urethane, nylon 6, nylon 66, polyacetal, or polybutylene terephthalate.

[0087] 19 and 20, the angle θ1 between the extending portion 1 and the bending portion 2A and the angle θ2 between the extending portion 1 and the bending portion 2B are each greater than 180 degrees and equal to or less than 225 degrees. As a result, according to the present embodiment, even if the paste 130 is a high-viscosity paste, the lateral spreading phenomenon of the paste 130 can be effectively suppressed.

[0088] This point will be explained below.

[0089] In Figure 19, when a force "f1" is applied to the squeegee 10 in the "-y direction" and the squeegee 10 is moved, the lateral spread suppression force "f2" applied to the paste 130 pressed by the squeegee 10 depends on the magnitude of the angle θ1 and the angle θ2.

[0090] For example, when the angles θ1 and θ2 are each 270 degrees, the lateral spread suppression force "f2" does not work. Specifically, this configuration corresponds to the configuration of the shielding plate 220 provided in the squeegee 200 of the related art shown in FIG. 9. For this reason, in the shielding plate 220 of the related art, the lateral spread suppression force "f2" for pushing the paste 130 back to the center of the squeegee 200 is "0," and as shown in FIG. 9, the effect of the shielding plate 220 in suppressing the lateral spread phenomenon is considered to be limited, and the paste 130 ends up sticking to the shielding plate 220 itself.

[0091] In contrast, according to the second feature of the present embodiment, angles θ1 and θ2 are smaller than 270 degrees, and therefore a lateral spread suppression force "f2" acts on paste 130 from bent portion 2A and bent portion 2B. As a result, according to the present embodiment, this lateral spread suppression force "f2" acts on paste 130, thereby effectively suppressing the lateral spread phenomenon of paste 130.

[0092] In particular, as shown in Fig. 20, when the angle θ1 and the angle θ2 are 225 degrees, the magnitude of the lateral spread suppression force "f2" is maximized. Therefore, from the viewpoint of increasing the magnitude of the lateral spread suppression force "f2" and effectively suppressing the lateral spread phenomenon of the paste 130, it is desirable to set the magnitude of the angle θ1 and the angle θ2 to 225 degrees.

[0093] However, in the present embodiment, the squeegee 10 has a bent portion 2A and a bent portion 2B in the extension portion 1, so the squeegee 10 contacts the printing mask 110 with a surface. Therefore, the dimensional tolerance required for uniform contact with the printing mask 110 is stricter than that of a "flat squeegee" that contacts the printing mask 110 in a line. In particular, for a given length of the squeegee 10, the larger the angles θ1 and θ2, the stricter the dimensional tolerance required. Therefore, for example, if a paste that is not a high-viscosity paste is used as the paste 130, and the lateral spread phenomenon can be sufficiently suppressed even if the magnitude of the lateral spread suppression force "f2" is smaller than the maximum value, it is desirable to select appropriate values ​​for the angles θ1 and θ2 from a range greater than 180 degrees and equal to or less than 225 degrees, taking into account the balance between the suppression of the lateral spread phenomenon and the required dimensional tolerance.

[0094] From the above, in consideration of the first and second features of this embodiment, it can be said that bent portions 2A and 2B have the function of suppressing the lateral spreading phenomenon of paste 130 and suppressing the creeping up phenomenon of paste 130. In addition, it can be said that protruding portions 3B, 4B, and 5B have the function of suppressing the creeping up phenomenon of paste 130.

[0095] <Squeegee operation> The squeegee 10 in this embodiment is configured as described above, and the squeegee operation in which the printing process is carried out using the squeegee 10 will be described below.

[0096] 21 and 22 are plan views for explaining the squeegeeing operation of the squeegee 10. FIG.

[0097] As shown in FIG. 21, paste 130 is supplied onto printing mask 110, and squeegee 10 of this embodiment is placed thereon. This squeegee 10 has an extending portion 1, a bent portion 2A, and a bent portion 2B. Then, as shown in FIGS. 21 and 22, squeegee 10 is moved to transfer paste 130 to opening pattern 120 provided in printing mask 110. This allows paste 130 to be applied to substrate areas (not shown) exposed through opening pattern 120 of printing mask 110.

[0098] In the squeegee 10 of the present embodiment, a bent portion 2A is provided at one end of the extension portion 1, and a bent portion 2B is provided at the other end of the extension portion 1. As a result, a force to suppress lateral spread acts on the paste 130 from the bent portions 2A and 2B. As a result, as shown in FIGS. 21 and 22, even when the squeegee 10 performs a squeegeeing operation, the lateral spread of the paste 130 can be suppressed.

[0099] Furthermore, FIG. 23 is a side view for explaining the squeegee operation of the squeegee 10. As shown in FIG.

[0100] As shown in Figure 23, even when the squeegee operation of the squeegee 10 is performed, for example, as shown in Figures 12 and 13, a protrusion 3B is provided on the extension portion 1, a protrusion 4B is provided on the bending portion 2A, and a protrusion 5B is provided on the bending portion 2B, thereby suppressing the creeping up phenomenon of the paste 130.

[0101] From the above, by using the squeegee 10 of this embodiment, the lateral spreading and creeping up phenomena of the paste 130 during the printing process can be suppressed.

[0102] <Effects of the embodiment> (1) As described above, the squeegee 10 of this embodiment can suppress the lateral spreading and creeping up of the paste 130 during squeegee operation. This means that it is possible to prevent a decrease in the amount of paste 130 that contributes to filling the opening pattern 120. Furthermore, ensuring the amount of paste 130 that contributes to filling the opening pattern 120 means that the rolling diameter can be stabilized. As a result, this embodiment can suppress the occurrence of missing print patterns at an early stage of the printing cycle, thereby improving the number of sheets that can be continuously printed.

[0103] FIG. 24 is a table showing the results of verification that the squeegee 10 of the present embodiment can increase the number of sheets that can be continuously printed. As shown in FIG. 24, when a printing process is performed using a "flat squeegee" as the squeegee, the number of sheets that can be continuously printed is approximately 20 when using a sintered copper paste, which is a high-viscosity paste. In contrast, when the printing process is performed using the squeegee 10 of the present embodiment as the squeegee, the number of sheets that can be continuously printed exceeds 100. As such, it can be seen that the squeegee 10 of the present embodiment is extremely useful in that it can significantly increase the number of sheets that can be continuously printed. Therefore, for example, the squeegee 10 of the present embodiment is excellent in that it can be used as a high-viscosity squeegee, which contributes to increasing the number of prints of high-viscosity paste, which has a higher viscosity than solder paste.

[0104] (2) As described above, being able to suppress the lateral spreading and creeping up phenomena of the paste 130 means being able to suppress the reduction in the rolling diameter. And being able to suppress the reduction in the rolling diameter means being able to suppress the scraping phenomenon as shown in Fig. 8, for example, and as a result, the squeegee 10 of this embodiment can stabilize the transfer weight.

[0105] FIG. 25 is a graph showing the results of verification that the squeegee 10 of this embodiment can stabilize the transfer weight. In FIG. 25, the horizontal axis indicates the number of printed sheets, while the vertical axis indicates the amount of reduction in the transferred weight of the sintered copper paste from the time of printing the first sheet. Also in FIG. 25, the "circles (black)" indicate the relationship between the number of printed sheets and the transfer weight when a flat squeegee is used, and the "triangles (gray)" indicate the relationship between the number of printed sheets and the transfer weight when a squeegee having only the extension portion 1 and no bent portions 2A and 2B is used, among the structures of the squeegee 10 of this embodiment. On the other hand, the "circles (gray)" indicate the relationship between the number of printed sheets and the transfer weight when the squeegee 10 of this embodiment is used.

[0106] As shown in Figure 25, when a flat squeegee is used, the slope of the graph showing the change in transfer weight with the number of prints is "-0.19 mg." Furthermore, when the bent portions 2A and 2B of the squeegee 10, indicated by the triangles, are removed, the slope is "-0.15 mg." In contrast, when the squeegee 10 of this embodiment is used, the slope of the graph showing the change in transfer weight with the number of prints is "-0.03 mg." This indicates that, according to this embodiment, the rate of decrease in transfer weight with the number of prints is smaller than when a flat squeegee is used. Furthermore, since the improvement in the amount of decrease in the data indicated by the triangles is only "-0.15 mg," this effect is quite limited when only the creeping phenomenon is suppressed. It is therefore essential to suppress both the creeping phenomenon and the lateral spreading phenomenon, as in this embodiment. In other words, the squeegee 10 of this embodiment is extremely superior in that it can maintain stable transfer weight even when the number of prints is increased. In particular, the squeegee of this embodiment is effective when applied to semiconductor manufacturing processes for power modules using sinter bonding. In other words, the squeegee of this embodiment is effective when applied to the manufacturing process of a power module using sintered copper paste.

[0107] (3) The fluidity of the paste 130 during squeegee operation is closely related to the success or failure of printing. For example, in the squeegee 200 of the related art shown in Fig. 26, puddles form at both ends, which can cause the fluidity of the paste 130 promoted by contact with the squeegee 200 to differ significantly from the fluidity of the paste 130 in the center. For this reason, in the related art shown in Fig. 26, both ends of the squeegee 200 must be spaced apart from the opening pattern 120 to a certain extent (distance L1) to prevent the fluidity of the paste 130 at both ends, which differs from the center, from adversely affecting the filling of the opening pattern 120 with the paste 130.

[0108] In contrast, the squeegee 10 of the present embodiment shown in FIG. 27 suppresses the lateral spreading and creeping of the paste 130 at both ends, resulting in a flow state at both ends that is relatively close to the center. This means that the flow state at both ends is less likely to adversely affect the filling of the paste 130 into the opening pattern 120 with the squeegee 10 of the present embodiment. Therefore, as shown in FIG. 27, the squeegee 10 of the present embodiment allows both ends of the squeegee 10 to be closer to the opening pattern 120 than the related art (distance L2<distance L1). That is, the squeegee 10 of the present embodiment allows the length of the extension portion 1 in the first direction (x direction) to be shorter than the related squeegee. As a result, the flow state of the paste 130 can be stabilized early after the start of printing. This ensures substantially consistent print quality from the initial to final stages of printing.

[0109] Furthermore, this means that printing can be performed with a small amount of paste 130 without waste, which also has the effect of reducing manufacturing costs in the printing process.

[0110] <Squeegee manufacturing method> The squeegee 10 in this embodiment can be manufactured using, for example, a 3D printer. Here, the internal structure of a shape created by a 3D printer is often not a completely filled structure but a hollow structure, such as a honeycomb structure. Therefore, in the squeegee 10 manufactured by a 3D printer, the extension portion 1 and the bent portion 2A and the bent portion 2B are configured with a hollow structure.

[0111] In this case, it is possible to utilize the above-described characteristics of the 3D printer to improve the internal structure of the squeegee 10, and this point will be described below.

[0112] For example, as shown in Figure 28, by adjusting the manufacturing conditions of the 3D printer, the hollow structure of the bending portion 2A is made sparser than the hollow structure of the extension portion 1, and the hollow structure of the bending portion 2B is made sparser than the hollow structure of the extension portion 1.

[0113] The technical significance of this configuration will be explained below.

[0114] For example, referring to FIG. 6, the angle between the flat squeegee 100 and the printing mask 110 is called the "attack angle." Similarly, the angle between the squeegee 10 and the printing mask 110 is also called the "attack angle." In the case of a soft squeegee, the squeegee itself will bend due to pressure applied to it from above. In this case, the apparent "attack angle" will change. When this "attack angle" changes, the printability will change. For this reason, in order to stabilize printability, it is desirable to prevent the "attack angle" from changing.

[0115] In this regard, squeegee 10 in this embodiment has extending portion 1 and bending portion 2A and bending portion 2B, and if the entire internal structure of squeegee 10 is constructed from a similar hollow structure, bending portion 2A and bending portion 2B are shorter than extending portion 1 and are therefore considered to have high rigidity. In other words, bending portions 2A and 2B are considered to have a small amount of deformation in response to pressure applied to squeegee 10. As a result, the "angle of attack" changes due to the difference in the amount of deformation between extending portion 1 and bending portion 2A and bending portion 2B, which is considered to cause changes in printability.

[0116] Therefore, in this embodiment, as described above, the rigidity of bending portions 2A and 2B is reduced by "making the hollow structure of bending portion 2A less dense than the hollow structure of extending portion 1, and making the hollow structure of bending portion 2B less dense than the hollow structure of extending portion 1." As a result, the difference between the amount of deformation of extending portion 1 and the amount of deformation of bending portions 2A and 2B is reduced, making it possible to suppress unintended changes in the "angle of attack," thereby stabilizing printability.

[0117] Furthermore, based on a similar concept, it is also possible to configure the bending portions 2A and 2B so that they are less rigid and more easily deformed in order to accommodate the dimensional error required for uniform contact with the printing mask 110, thereby absorbing any minor dimensional error through deformation of the bending portions 2A and 2B.

[0118] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0119] 1 Extension 2A Bending part 2B Bending part 3A Slope 3B Protrusion 4A Slope 4B Protrusion 5A Slope 5B Protrusion 10 Squeegee 110 Print Mask 120 opening pattern 130 Paste

Claims

1. an extension portion extending in a first direction; a first bent portion provided at one end of the extending portion; a second bent portion provided at the other end of the extension portion; A squeegee comprising: a first angle formed between an extension direction of the first bent portion and the first direction is greater than 180 degrees and not greater than 225 degrees; a second angle formed between an extension direction of the second bent portion and the first direction is greater than 180 degrees and not greater than 225 degrees; The extension portion is In a cross-sectional view perpendicular to the first direction, an inclined portion having a surface inclined from a vertical direction; a protruding portion connected to the inclined portion and protruding in a horizontal direction; and The first bent portion is In a cross-sectional view perpendicular to the extending direction of the first bent portion, a first inclined portion having a surface inclined from the vertical direction; a first protrusion connected to the first inclined portion and protruding in the horizontal direction; and The second bent portion is In a cross-sectional view perpendicular to the extending direction of the second bent portion, a second inclined portion having a surface inclined from the vertical direction; a second protruding portion connected to the second inclined portion and protruding in the horizontal direction; and A squeegee, wherein the extension direction of the first bent portion, the extension direction of the second bent portion, and the inclination direction of an inclined portion having a surface inclined from the vertical direction are each on the side of the movement direction of the squeegee during printing.

2. 2. The squeegee according to claim 1, the inclined portion, the first inclined portion, and the second inclined portion are connected to each other, The protruding portion, the first protruding portion, and the second protruding portion are connected to each other.

3. 2. The squeegee according to claim 1, a protruding length of the protruding portion is equal to or less than a height of the inclined portion, a protruding length of the first protruding portion is equal to or less than a height of the first inclined portion, A squeegee, wherein the protruding length of the second protruding portion is equal to or less than the height of the second inclined portion.

4. 2. The squeegee according to claim 1, The squeegee, wherein the extending portion, the first bent portion, and the second bent portion have a hollow structure.

5. The squeegee according to claim 4, a hollow structure of the first bent portion is less dense than a hollow structure of the extension portion, A squeegee, wherein the hollow structure of the second bent portion is less dense than the hollow structure of the extension portion.

6. 2. The squeegee according to claim 1, The squeegee is a high-viscosity squeegee that contributes to increasing the number of printing times for high-viscosity paste that has a higher viscosity than solder paste.

7. 2. The squeegee according to claim 1, The first bent portion and the second bent portion have a function of suppressing the lateral spreading of the paste in the first direction and the creeping up of the paste.

8. 2. The squeegee according to claim 1, The protruding portion, the first protruding portion, and the second protruding portion have a function of suppressing creeping up of paste.

9. 2. The squeegee according to claim 1, the protrusion has a lower surface, an upper surface opposite to the lower surface, and a tip surface connected to the lower surface and the upper surface, the first protrusion has a first lower surface, a first upper surface opposite to the first lower surface, and a first tip surface connected to the first lower surface and the first upper surface, the second protrusion has a second lower surface, a second upper surface opposite to the second lower surface, and a second tip surface connected to the second lower surface and the second upper surface, The terminal angle of the protrusion is the angle between the lower surface and the tip surface, a first terminal angle of the first protrusion is an angle between the first lower surface and the first tip surface, a second terminal angle of the second protrusion is an angle between the second lower surface and the second tip surface, The terminal angle of the protrusion is 90 degrees or less, the first terminal angle of the first protrusion is less than or equal to 90 degrees; The second terminal angle of the second protrusion is less than or equal to 90 degrees.

10. 2. The squeegee according to claim 1, The height of the inclined portion is 6 mm or more and 8 mm or less, the height of the first inclined portion is equal to or greater than 6 mm and equal to or less than 8 mm; A squeegee, wherein the height of the second inclined portion is equal to or greater than 6 mm and equal to or less than 8 mm.

11. 2. The squeegee according to claim 1, The squeegee is made of a material containing any one of urethane, nylon 6, nylon 66, polyacetal, and polybutylene terephthalate.

12. 2. The squeegee according to claim 1, A squeegee used in the semiconductor manufacturing process for power modules that uses sinter bonding.

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