Screen printing method, flux, and screen printing apparatus

Abstract

To provide a screen printing method capable of suppressing defective soldering. [Solution] The disclosed screen printing method is a screen printing method for disposing flux on multiple solder precoats 3 on a substrate 1. The method includes a mask position adjustment step for adjusting the relative position of a mask plate 421 having multiple through holes 421c and the substrate 1 so that the through holes 421c are positioned above the solder precoats 3 and so that the mask plate 421 does not come into contact with the solder precoats 3, and a squeegeeing step for applying flux F supplied to the upper surface of the mask plate 421 through the through holes 421c by moving the squeegee. In the squeegeeing step, the portion of the mask plate 421 pressed down toward the substrate 1 by the squeegee comes into contact with the solder precoats 3. The consistency of the flux F is 220 or more and 450 or less.

Description

[Technical Field]

[0001] The present disclosure relates to a screen printing method, a flux, and a screen printing apparatus. [Background technology]

[0002] Conventionally, a method for applying flux to a solder precoat on a substrate provided with the solder precoat has been proposed. Claim 1 of Patent Document 1 (WO 2022 / 054384) discloses "a mounting substrate manufacturing method for soldering terminals of electronic components to lands on a substrate, the method comprising: a paste placement step of placing solder paste on the lands; a melting and solidification step of melting and solidifying the solder paste to form a solder precoat on the lands; a destruction step of destroying residue covering the surface of the precoat by pressing a tool against the precoat; a flux placement step of placing flux on the precoat; a component mounting step of mounting the electronic component on the substrate with the terminals of the electronic component aligned with the precoat; and a reflow step of heating the substrate to melt the precoat and solder the terminals to the lands." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 054384 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, electronic components mounted on solder precoats have become increasingly smaller. Such small electronic components may unintentionally move on the flux applied to the solder precoat before being soldered. When electronic components move before soldering, soldering defects are more likely to occur. One of the objectives of the present disclosure is to provide a screen printing method capable of suppressing soldering defects. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a screen printing method for disposing flux on multiple solder precoats on a substrate, the method including: a mask position adjustment process for adjusting the relative position of a mask plate having multiple through holes and the substrate so that the through holes are located above the solder precoat and so that the mask plate does not come into contact with the solder precoat; and a squeegeeing process for applying the flux to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee, wherein in the squeegeeing process, a portion of the mask plate pressed down toward the substrate by the squeegee comes into contact with the solder precoat, and the consistency of the flux is 220 or more and 450 or less.

[0006] Another aspect of the present disclosure relates to a flux used in the screen printing method of the present disclosure, the flux having a consistency of 220 or more and 450 or less.

[0007] Another aspect of the present disclosure relates to a screen printing apparatus that places flux on multiple solder precoats on a substrate, the screen printing apparatus including: a mask plate having multiple through holes; a mask position adjustment mechanism that adjusts the relative position of the mask plate and the substrate so that the through holes are positioned above the solder precoats and so that the mask plate and the solder precoats do not come into contact; a flux supply mechanism that supplies the flux having a consistency of 220 or more and 450 or less to the upper surface of the mask plate; and a squeegeeing mechanism that applies the flux to the solder precoats through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee, wherein the squeegeeing mechanism presses down on the mask plate with the squeegee as the squeegee is moved, thereby bringing the mask plate into contact with the solder precoats in the areas where the squeegee is in contact. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to suppress soldering defects. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view schematically showing the configuration of an example of a mounting substrate manufacturing apparatus. [Figure 2] FIG. 2 is a diagram for explaining the manufacturing process of the mounting substrate. [Figure 3] FIG. 3 is a front view schematically illustrating the configuration of an example of a screen printing apparatus according to the present disclosure. [Figure 4] FIG. 4 is a side view schematically illustrating the configuration of an example of a screen printing apparatus according to the present disclosure. [Figure 5] FIG. 5 is a diagram schematically illustrating an example of a mask plate used in the screen printing method. [Figure 6] FIG. 6 is a diagram schematically showing an example of the positional relationship between the solder precoat and the through-holes of the mask plate. [Figure 7] FIG. 7 is a diagram schematically illustrating an example of the squeegeeing step. [Figure 8] FIG. 8 is a diagram schematically illustrating a part of an example of the squeegeeing process. [Figure 9] FIG. 9 is a diagram schematically illustrating a part of another example of the squeegeeing step. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0011] (Screen printing method) The screen printing method according to this embodiment may be referred to as the "screen printing method (M)" or "printing method (M)" below. The printing method (M) is a screen printing method for disposing flux (solder flux) on multiple solder precoats on a substrate. The printing method (M) includes a mask position adjustment process for adjusting the relative position of a mask plate having multiple through holes and the substrate so that the through holes are positioned above the solder precoats and so that the mask plate and the solder precoats do not come into contact with each other, and a squeegeeing process for applying flux to the solder precoats through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee. In the squeegeeing process, the portion of the mask plate pressed down toward the substrate by the squeegee comes into contact with the solder precoats. The consistency of the flux is 220 or more and 450 or less.

[0012] The substrate includes a plurality of lands to which electronic components are soldered, and a solder precoat is formed on the lands.

[0013] Currently, one method for soldering electronic components to lands on a board is to form a solder precoat on the lands. Flux (solder flux) is applied to the solder precoat. The electronic component is then placed on the solder precoat to which the flux has been applied. The board on which the electronic component is placed is then subjected to a reflow process to solder the electronic component to the lands.

[0014] In recent years, electronic components have become increasingly miniaturized. The present inventors have discovered that when soldering small electronic components, electronic components placed on flux tend to move before being soldered to the land. If electronic components move before being soldered to the land, soldering defects are more likely to occur. This problem is thought to be caused by the fact that small electronic components are light, which increases the influence of the surface tension of the flux. This problem rarely occurs when electronic components are relatively large. As a result of their investigation, the present inventors have newly discovered that by using the printing method (M), soldering defects can be suppressed even when soldering small electronic components. The present disclosure is based on this new finding.

[0015] A conventional flux application method involves placing a mask so that the mask and the solder precoat are in contact with each other and then applying the flux. However, this method tends to spread the flux between the underside of the mask and the solder precoat when the flux is applied, resulting in an excessive amount of flux being applied to the solder precoat. If an excessive amount of flux is applied to the solder precoat, electronic components placed on the flux are likely to move. Furthermore, if flux adheres to the underside of the mask, it will easily spread the flux the next time the flux is applied. To avoid this, frequent cleaning of the mask is required.

[0016] In the printing method (M), in the mask position adjustment step, a mask plate is positioned so as not to come into contact with the solder precoat. Then, in the squeegeeing step, flux is applied to the solder precoat while the mask plate is pressed toward the substrate with a squeegee. As a result, the periphery of the through-hole in the mask plate is pressed against the solder precoat as the squeegee passes over the through-hole, and then separated from the solder precoat after the squeegee has passed. The inventors of this application have discovered that in such printing methods, the consistency of the flux is important when the through-holes are minute. Specifically, by setting the consistency of the flux to be 220 or more and 450 or less, it is possible to suppress soldering defects.

[0017] If the consistency is less than 220, the flux will have difficulty entering the through-holes. Furthermore, if the consistency is less than 220, the flux applied to the solder precoat will likely adhere to the mask plate when the mask plate separates from the solder precoat. As a result, the amount of flux placed on the solder precoat will be insufficient, which is thought to make soldering defects more likely to occur. If the consistency is more than 450, the flux applied to the solder precoat will spread and overflow from the area on the solder precoat. When the flux spreads, electronic components placed on it will be more likely to move. As a result, it is thought to make soldering defects more likely to occur.

[0018] In the printing method (M), it is preferable that the following conditions (1) and / or (2) are satisfied. (1) At least some of the through holes of the mask plate have a shape that fits inside the outer edge of the corresponding solder precoat when viewed from the normal direction of the upper surface of the mask plate. (2) In the squeegeeing step, the flux is applied to the solder precoat in at least some of the through holes so that the flux does not protrude from the solder precoat.

[0019] When the condition (1) is satisfied, it is preferable that the following condition (1') is satisfied. (1') In the mask position adjusting step, the relative positions of the mask plate and the substrate are adjusted so that the outer edges of the through holes are positioned inside the outer edges of the solder precoat when viewed from the normal direction of the upper surface of the mask plate.

[0020] By satisfying conditions (1) and (1') and setting the consistency of the flux within the above range, it becomes easier to satisfy condition (2). Satisfying condition (2) particularly prevents fine electronic components from moving on the flux. The above-mentioned problem occurs when the consistency is less than 220, particularly when the through-holes of the mask plate are small. Similarly, the above-mentioned problem occurs when the consistency is greater than 450, particularly when the through-holes of the mask plate are small. Therefore, when conditions (1) and / or (2) are satisfied, it is particularly important to set the consistency to 220 or more and 450 or less.

[0021] The area of ​​the land (when viewed from above) is Sa. The area of ​​the through-hole in the mask plate (when viewed from above) is St. The ratio St / Sa may be 0.15 or more and 0.65 or less. For example, when the dimension of the land (the length of the long side of the land) is 0.08 mm or more and 0.10 mm or less, the ratio St / Sa may be 0.30 or more and 0.60 or less. When the dimension of the land is 0.10 mm or more and 0.20 mm or less, the ratio St / Sa may be 0.25 or more and 0.50 or less. Furthermore, when the dimension of the land is 0.15 mm or more and 0.30 mm or less, the ratio St / Sa may be 0.15 or more and 0.65 or less.

[0022] In this specification, the consistency of the flux refers to a value (worked consistency) measured according to the procedure of the worked consistency test specified in JIS (Japanese Industrial Standards) K2220:2013. The consistency measurements in the examples were performed using a 1 / 2 cone. The measured consistency was then converted to the consistency measured using a standard cone according to the JIS standard. The converted consistency was then used as the consistency of the flux.

[0023] The consistency of the flux is 220 or more, and may be 275 or more, 290 or more, 320 or more, 380 or more, 415 or more, or 430 or more. The consistency of the flux is 450 or less, and may be 430 or less, 415 or less, 380 or less, 320 or less, 290 or less, or 275 or less. The consistency of the flux is in the range of 220 to 450, and may be in the range of 275 to 450, 290 to 450, 320 to 450, 380 to 450, 415 to 450, or 430 to 450. Within these ranges, the upper limit may be 430, 415, 380, 320, 290, or 275, as long as the lower limit is not equal to or greater than the upper limit.

[0024] The consistency of the flux can be adjusted by changing the components and the ratio of the components of the flux, examples of which are described below.

[0025] In the printing method (M), the following condition (3) may be satisfied. In a preferred example of the printing method (M), the condition (1) (or the conditions (1) and (1')) and the condition (3) are satisfied. For example, the condition (1) (or the conditions (1) and (1')), the condition (2), and the condition (3) are satisfied. (3) The thickness of the mask is 15 μm or more and 50 μm or less.

[0026] If the mask is too thick, the flux will not easily enter the through holes. Furthermore, if the mask is too thick, the flux applied to the solder precoat will easily adhere to the mask when it separates from the solder precoat. Therefore, the thickness of the mask is preferably 50 μm or less. The thickness of the mask may be 40 μm or less, 30 μm or less, or 25 μm or less. Conventionally, masks with a thickness of 50 μm or less have been considered prone to tearing and unsuitable as screen printing masks. However, after extensive investigation, the inventors have found that it is possible to apply flux using a mask with a thickness of 50 μm or less. On the other hand, if the mask is too thin, the durability of the mask decreases. Therefore, the thickness of the mask is preferably 15 μm or more. The thickness of the mask may be 20 μm or more, or 30 μm or more. The thickness of the mask may be in the range of 15 to 50 μm. The lower and / or upper limits of this range may be changed to the values ​​described above.

[0027] The material of the mask plate is not particularly limited. The mask plate may be a metal mask. From the viewpoint of durability, a stainless steel sheet may be used for the mask plate. The method for forming the through holes in the mask plate is not particularly limited, and they may be formed by a known method. For example, the through holes may be formed by laser processing or an additive method.

[0028] The mask plate is usually held by a frame. The mask used in the printing method (M) may include a frame, a mask plate placed in the frame, and a stretchable sheet connecting the frame and the mask plate. The stretchable sheet is stretchable. Use of the stretchable sheet makes it easier for the mask plate to be displaced by the squeegee. Furthermore, use of the stretchable sheet improves the durability of the mask plate. The frame and stretchable sheet are not particularly limited, and known frames and known stretchable sheets used in screen printing may be used. The stretchable sheet may be a sheet that can hold the mask plate with appropriate tension. The stretchable sheet may be a woven fabric. The woven fabric may be coated with an elastic material.

[0029] The substrate includes a plurality of lands to which a plurality of electronic components are soldered, and a plurality of solder precoats formed on the lands. A commercially available substrate may be used as the substrate. The manufacturing method (M) may include a step of forming a solder precoat on the substrate on which the lands are formed. The method of forming the solder precoat is not limited, and a known method may be used.

[0030] The area of ​​the multiple solder precoats (area when viewed from above) is 0.05 mm 2 The area Smin of the solder precoat having the smallest area among the plurality of solder precoats may be 0.03 mm 2 or less than 0.02 mm 2 The area of ​​the solder precoat varies depending on the area of ​​the electronic component to be soldered to the solder precoat. Typically, the smaller the electronic component, the smaller the area of ​​the solder precoat. Manufacturing method (M) is particularly suitable for mounting multiple electronic components, including electronic components that meet JIS (Japanese Industrial Standards) 0402 or smaller. JIS 0402 electronic components have a length of 0.4 mm and a width of 0.2 mm. In other words, manufacturing method (M) is particularly suitable for mounting multiple electronic components, including electronic components that are 0.4 mm or less in length and 0.2 mm or less in width.

[0031] The solder precoat may be composed of only a solder layer. Alternatively, the solder precoat may include a solder layer and another layer formed on the surface of the solder layer. For example, the solder precoat may include a solder layer and a coating layer (e.g., an organic layer) formed on the surface of the solder layer. Examples of the other layer include a layer of residue (flux residue) left when the solder layer is formed, an antioxidant film, etc. The organic layer is a layer whose main component is an organic material (content: 50% by mass). The flux residue layer is an organic layer. When the solder precoat includes a solder layer and another layer formed on the surface of the solder layer, the mask plate comes into contact with the other layer during the squeegeeing process.

[0032] (Mask position adjustment process) In the mask position adjustment process, the relative positions of the mask plate and the substrate are adjusted so that the through holes of the mask plate, which has multiple through holes, are positioned above the solder precoat and so that the mask plate and the solder precoat do not come into contact with each other. Furthermore, the mask plate is positioned at a height such that when the squeegee presses the mask plate toward the substrate, the portion of the mask plate pressed down by the squeegee toward the substrate is pressed against the solder precoat. The height of the mask plate can be adjusted, for example, by positioning a frame that holds the mask plate in a predetermined position. The gap G between the mask plate and the solder precoat can be selected depending on the elasticity of the mask plate, the presence or absence and area of ​​a stretchable sheet that holds the mask plate, etc. The gap G between the mask plate and the solder precoat may be 3 mm or less, or 2 mm or less.

[0033] (Squeegeeing process) The squeegeeing process is a process in which flux is applied to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee. The mask plate has a lower surface facing the substrate and an upper surface opposite the substrate. The flux may be supplied to the upper surface of the mask plate before the squeegee moves, or may be supplied to the upper surface of the mask plate while the squeegee moves. The flux may be supplied to the upper surface of the mask plate before the mask position adjustment process.

[0034] The squeegee moves while pushing the mask toward the substrate. During this process, the flux is applied onto the solder precoat through the through holes. During the squeegeeing process, the portion of the mask pressed down toward the substrate by the squeegee comes into contact with the solder precoat. The area to which the flux is applied is limited by the sidewalls of the through holes that come into contact with the solder precoat.

[0035] By ensuring that the consistency of the flux is within the above range, it is possible to apply an appropriate amount of flux to an appropriate area. As a result, it is possible to prevent electronic components from moving on the flux. When the consistency of the flux is within the above range and condition (1) is satisfied, condition (2) is also satisfied. As a result, it is possible to particularly prevent electronic components from moving on the flux.

[0036] The size of the electronic component may be, for example, 0.4 mm long x 0.2 mm wide, 0.3 mm long x 0.15 mm wide, 0.25 mm long x 0.125 mm wide, 0.2 mm long x 0.1 mm wide, or 0.1 mm long x 0.5 mm wide. The electronic components mounted on the substrate may include electronic components of various sizes and types. The multiple electronic components mounted on the substrate may include electronic components specified by JIS (Japanese Industrial Standards), such as 0402, 03015, 0201, and 01005. The smaller the size of the electronic component, the smaller its mass. Therefore, fine electronic components are more susceptible to bonding failure due to unintended movement. This tendency is particularly pronounced in extremely small components such as 03015, 0201, and 01005. On the other hand, the screen printing method according to the present disclosure can suppress unintended movement of electronic components, as described above, making it particularly suitable for use with such extremely small components.

[0037] As a result of our investigation, we found that when flux is applied by so-called contact printing, the underside of the mask (especially around the through-holes) becomes contaminated with flux. In contact printing, even after applying flux through the through-holes of the mask, the substrate and solder precoat remain in close proximity or contact with the underside of the mask. In this case, capillary action makes it easier for flux to penetrate into the tiny gaps between the substrate and solder precoat and the mask. Therefore, it is thought that the underside of the mask is more likely to become contaminated with flux during contact printing. If the underside of the mask becomes contaminated, it becomes necessary to clean the mask. This can reduce the efficiency of the flux application process.

[0038] In the squeegeeing process of manufacturing method (M), the periphery of the through hole is pressed against the solder precoat by the squeegee. Therefore, the sidewall of the through hole functions as a sealing surface that prevents the flux filled in the through hole from leaking between the underside of the mask plate and the solder precoat. The mask plate separates from the solder precoat after the squeegee passes through the solder precoat. Furthermore, printing method (M) uses flux with a predetermined consistency. Therefore, the squeegeeing process of printing method (M) can prevent the underside of the mask plate from being contaminated by the flux. As a result, the work efficiency of flux application can be improved.

[0039] The solder precoat (or solder layer) may have a flat top. Such a shape of the solder precoat may be formed by forming the solder precoat and then compressing the top. When the solder precoat has a flat top, the area around the through hole can more easily perform its sealing function, and the mask plate can be particularly prevented from being contaminated with flux.

[0040] (Screen printing equipment) The screen printing apparatus according to this embodiment may be referred to as a "screen printing apparatus (D)" or a "printing apparatus (D)." The screen printing apparatus (D) allows the screen printing method (M) to be easily implemented. However, the printing method (M) may also be implemented using an apparatus other than the printing apparatus (D). Since matters explained regarding the printing method (M) can also be applied to the printing apparatus (D), duplicate explanations may be omitted. Matters explained regarding the printing apparatus (D) may also be applied to the printing method (M).

[0041] The printing device (D) is a screen printing device that places flux on multiple solder precoats on a substrate. The printing device (D) includes a mask plate having multiple through holes, a mask position adjustment mechanism that adjusts the relative position of the mask plate and the substrate so that the through holes are located above the solder precoats and so that the mask plate and the solder precoats do not come into contact with each other, a flux supply mechanism that supplies flux having a consistency of 220 or more and 450 or less to the upper surface of the mask plate, and a squeegeeing mechanism that applies the flux to the solder precoats through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee. The squeegeeing mechanism presses down on the mask plate with the squeegee as it moves, bringing the mask plate into contact with the solder precoats at the portions where the squeegee is in contact.

[0042] The printing apparatus (D) achieves the effects described for the printing method (M). The mask and flux described above can be used. The mask position adjustment mechanism, flux supply mechanism, and squeegee mechanism are not limited, and known mechanisms used in off-contact printing apparatuses may be used. The squeegee may be made of a material with appropriate elasticity (such as rubber).

[0043] The mask position adjustment mechanism may adjust the position of the mask, or may adjust the position of the substrate, or may adjust both. The examples described in the printing method (M) can be applied to examples of substrates processed by the printing device (D) and examples of electronic components mounted on the substrate.

[0044] The printing device (D) includes a control device for controlling each mechanism as needed. The control device may be the same as a control device used in a known printing device.

[0045] In the printing device (D), it is preferable that the above-mentioned condition (1) (or the conditions (1) and (1')) be satisfied. By satisfying the condition (1) (or the conditions (1) and (1')), the above-mentioned condition (2) is more likely to be satisfied.

[0046] The present disclosure further discloses a mounting substrate manufacturing method (M2). The manufacturing method (M2) includes the above-described screen printing method (M). The manufacturing method (M2) includes a flux application step of applying flux to multiple solder precoats using the printing method (M), an electronic component placement step of placing electronic components on the applied flux, and a reflow step of soldering the placed electronic components to lands. The electronic component placement step and the reflow step are not particularly limited. For example, the electronic component placement step and the reflow step may be performed using a known chip mounter and a known reflow oven, respectively. The mounting substrate manufacturing method (M2) may further include other steps. For example, the mounting substrate manufacturing method (M2) may further include a step of forming a solder precoat on multiple lands of the substrate before the flux application step.

[0047] The present disclosure further discloses a mounting substrate manufacturing system (S). The mounting substrate manufacturing system (S) includes the above-described screen printing apparatus (D). The manufacturing system (S) includes the printing apparatus (D), an electronic component placement apparatus that places electronic components on the multiple solder precoats onto which flux has been applied by the printing apparatus (D), and a reflow apparatus that solders the placed electronic components to lands. The electronic component placement apparatus and the reflow apparatus are not particularly limited. For example, a known chip mounter and a known reflow oven may be used as the electronic component placement apparatus and the reflow apparatus, respectively. The manufacturing system (S) may further include other apparatuses. For example, the manufacturing system (S) may further include an apparatus that forms a solder precoat on the multiple lands of the substrate before the flux application process.

[0048] (Flux) The flux according to this embodiment may be referred to as "flux (F)" below. The flux (F) is used in the printing method (M) and the printing device (D) and has a consistency of 220 or more and 450 or less. The matters explained about the flux in relation to the printing method (M) can also be applied to the flux (F).

[0049] Flux (F) contains rosin-based resin, thixotropic agent, activator, and solvent as essential components. The consistency of flux (F) can be adjusted by changing the type and ratio of the components. Increasing the ratio of rosin-based resin can lower the consistency (lower fluidity). Decreasing the ratio of rosin-based resin can increase the consistency (higher fluidity). Decreasing the ratio of solvent can lower the consistency, and increasing the ratio of solvent can increase the consistency. Flux (F) may contain other components in addition to the essential components listed above. Examples of other components include surfactants, silane coupling agents, antioxidants, colorants, etc. Flux (F) can be prepared by mixing its components.

[0050] The flux (F) may contain solder particles to facilitate subsequent reflow. The proportion of solder particles in the flux (F) may be 80% by mass or less (e.g., 70% by mass or less). However, the proportion of solder particles in the flux (F) is much smaller than the proportion of solder particles in a typical solder paste. If the flux (F) contains solder particles, the proportion of solder particles in the flux (F) is less than 50% by volume.

[0051] (rosin-based resin) Examples of rosin-based resins include natural rosins such as gum rosin and wood rosin, and derivatives thereof (polymerized rosin, hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, etc.).

[0052] The flux (F) may contain a resin other than a rosin-based resin, such as an organic fatty acid ester, a polyalkylene oxide-based resin, a propylene glycol fatty acid ester, or an acetylene glycol. Specific examples include organic fatty acid polyglycerol esters such as polyglycerol laurate, polyglycerol stearate, polyglycerol isostearate, polyglycerol sesquistearate, polyglycerol diisostearate, polyglycerol myristate, polyglycerol palmitate, polyglycerol oleate, polyglycerol behenate, and polyglycerol caprylate; polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyoxyethylene alkyl ester, polyoxyethylene tallow ester, polyglycerin, glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid esters; and acetylene glycols such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol-ethylene oxide adduct.

[0053] Other resins that can be used besides rosin-based resins include terpene resins, terpene phenolic resins, styrene resins, xylene resins, acrylic resins, polyester resins, polyolefin resins, polyamides, polyamines, phenolic resins, phenoxy resins, and epoxy resins. Examples of terpene resins include aromatic-modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic-modified terpene resins. Examples of terpene phenolic resins include hydrogenated terpene phenolic resins. Examples of styrene resins include styrene-acrylic acid copolymers and styrene-maleic acid copolymers. Examples of xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins. Examples of acrylic resins include acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and acrylic resins obtained by copolymerizing at least one monomer selected from vinyl chloride and vinyl acetate. Examples of polyolefin resins include polyethylene and polypropylene. Examples of epoxy resins include bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol AD ​​epoxy resin.

[0054] (thixotropic agent) The thixotropic agent imparts thixotropy to the flux. Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. Examples of the wax-based thixotropic agent include castor oil. Examples of the amide-based thixotropic agents include lauric amide, palmitic amide, stearic amide, behenic amide, hydroxystearic amide, saturated fatty acid amide, oleic amide, erucic amide, unsaturated fatty acid amide, p-toluenemethane amide, aromatic amides, methylene bisstearic amide, ethylene bislauric amide, ethylene bishydroxystearic amide, saturated fatty acid bisamide, methylene bisoleic amide, unsaturated fatty acid bisamide, m-xylylene bisstearic amide, aromatic bisamides, saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, substituted amides, methylolstearic amide, methylol amide, and fatty acid ester amide. Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, etc. One type of thixotropic agent may be used alone, or two or more types may be used in combination.

[0055] (activator) The activator is a compound that reduces the oxide film that covers the surface of solder used in soldering electronic components. Examples of such solder include solder pre-coat and solder applied to the terminals (component electrodes) of electronic components. Note that resins such as rosin-based resins may also have some activating properties. In this specification, the term "activator" refers to compounds other than rosin-based resins.

[0056] The activator reduces the oxide film and helps form a good bond. Examples of activators with a reducing effect include organic acids, amines, and halides. One activator may be used alone, or two or more activators may be used in combination.

[0057] Examples of organic acids used as activators include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, 2,2-bishydroxymethylpropionic acid, tartaric acid, malic acid, glycolic acid, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, and oleic acid.

[0058] Examples of amines used as activators include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-methylimidazole. Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')] ]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4, 5-Dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-Diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6 -(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

[0059] Examples of the halide used as an activator include amine hydrohalides, organic halogen compounds, etc. Examples of the amine constituting the amine hydrohalides include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylguanidine, methylimidazole, 2-ethyl-4-methylimidazole, etc. Examples of the hydrogen halides include hydrogen chloride, hydrogen bromide, hydrogen iodide, etc. Examples of organic halogen compounds include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, and 2,3-dibromo-2-butene-1,4-diol.

[0060] (solvent) Examples of the solvent include water, alcohol-based solvents, glycol-based solvents, ketone-based solvents, hydrocarbon-based solvents, ester-based solvents, glycol ether-based solvents, terpineols, etc. The solvents may be used alone or in combination of two or more.

[0061] Examples of alcohol-based solvents include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethoxymethyl)ethane, and 2,2'-oxybis(methylene)bis(2-ethoxymethyl)ethane. ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2-tris(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and the like.

[0062] Examples of glycol-based solvents include ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether (295°C), triethylene glycol monobutyl ether, diethylene glycol monohexyl ether (hexyl carbitol), diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monobenzyl ether, diethylene glycol dibutyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, propylene glycol monophenyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, 2-methylpentane-2,4-diol, and triethylene glycol monobutyl ether.

[0063] Examples of ketone solvents include methyl ethyl ketone, methyl-n-propyl ketone, diethyl ketone, and cyclohexanone.

[0064] Examples of hydrocarbon solvents include normal hexane, isohexane, cyclohexane, methylcyclohexane, ethylcyclohexane, normal heptane, isoheptane, normal octane, isooctane, limonene, 2-methyl-2-butene, 2-methyl-1-pentene, 2-methyl-2-pentene, 3-ethyl-2-butene, 2,3-dimethyl-2-butene, 2,4,4-trimethyl-1-pentene, and 2,4,4-trimethyl-2-pentene.

[0065] Examples of ester-based solvents include butyl stearate, 2-ethylhexyl stearate, isotridecyl stearate, methyl oleate, isobutyl oleate, coconut fatty acid methyl ester, methyl laurate, isopropyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, and octyldodecyl myristate.

[0066] Below, examples of a screen printing method (M), a screen printing apparatus (D), a mounting substrate manufacturing method (M2), and a mounting substrate manufacturing system (S) will be specifically described with reference to the drawings. The above-described examples can be applied to the components of the examples described below. The components of the examples described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Of the components of the examples described below, components that are not essential to the method, apparatus, and system according to this embodiment may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0067] (Embodiment 1) In the following example, an example of a screen printing apparatus incorporated into a mounting substrate manufacturing apparatus will be described. However, the screen printing apparatus can also be used independently. The mounting substrate manufacturing apparatus 10 (hereinafter sometimes referred to as "manufacturing apparatus 10") of embodiment 1 is an apparatus for manufacturing a mounting substrate on which a plurality of electronic components are mounted.

[0068] As shown in FIG. 1, the manufacturing apparatus 10 includes a substrate conveying line 11, an information processing device 20, a loader 50, a solder precoat forming device 90, a solder precoat inspection device 300, a screen printing device 400, electronic component mounting devices 501 and 502, a mounting state inspection device 600, a reflow device 700, a substrate inspection device 800, and an unloader 900. The components from the loader 50 to the unloader 900 are arranged in this order from upstream to downstream. A known configuration may be applied to configurations other than those specific to the present disclosure. Hereinafter, the electronic component mounting devices 501 and 502 may be collectively referred to as the electronic component mounting device 500.

[0069] (Substrate transfer line) The information processing device 20 is communicably connected to other devices included in the manufacturing apparatus 10 (such as the solder precoat forming device 90, the solder precoat inspection device 300, the screen printing device 400, the electronic component mounting device 500, and the reflow device 700) via a wired or wireless local area network 20N. The information processing device 20 exchanges data with these devices. In this way, the information processing device 20 manages the processes performed in the manufacturing apparatus 10.

[0070] The information processing device 20 has an arithmetic processing device and a storage device. The arithmetic processing device is configured with a CPU (Central Processing Unit) and the like. The storage device is configured with one or more RAMs (Random Access Memories), hard disks and the like. These may be configured as separate circuits or LSIs (Large Scale Integrated Circuits), or may be configured as an integrated unit. The storage device stores programs required for each device of the manufacturing apparatus 10 and the data required for them.

[0071] (loader and unloader) The loader 50 supplies substrates stored in a rack (not shown) to the solder precoat forming device 90. The unloader 900 retrieves completed mounted substrates into the rack. Each device from the solder precoat forming device 90 to the substrate inspection device 800 includes a conveyor (substrate transport line 11) for transporting substrates. Each conveyor is positioned so that it can receive substrates from a device on the upstream side (loader 50 side) and hand them over to a device on the downstream side (unloader 900 side).

[0072] (Solder pre-coating device) The solder precoat forming device 90 is a device that forms a solder precoat 3 (see FIG. 2) on the lands 2 (see FIG. 2) of the substrate 1. The solder precoat forming device 90 has a solder paste supply section 100, a heating section 210, and a cooling section 220. A part of the substrate conveying line 11 is arranged inside these sections.

[0073] The solder paste supply unit 100 supplies solder paste to the lands 2 of the substrate 1 by, for example, screen printing. The heating unit 210 heats the solder paste supplied to the lands 2 to melt the solder particles contained in the solder paste. The cooling unit 220 cools and solidifies the melted solder particles. As a result, a solder precoat 3 is formed on the lands 2 of the substrate 1. The substrate 1 with the solder precoat 3 formed thereon is transported by the substrate transport line 11 to the solder precoat inspection device 300.

[0074] (Solder pre-coat inspection device) The solder precoat inspection device 300 is a device that inspects whether the solder precoat 3 has been properly formed. The solder precoat inspection device 300 may, for example, detect the thickness of the solder precoat 3 and determine whether the solder precoat 3 has been properly formed based on the detected thickness. The substrate 1 that has been determined to have the solder precoat 3 properly formed is transported to the screen printing device 400 by the substrate transport line 11.

[0075] (Screen printing equipment) The screen printing apparatus 400 is the printing apparatus (D) described above. The screen printing apparatus 400 applies a flux (the flux (F) described above) for reflow soldering onto the solder precoat 3 using a screen printing method. The configuration of the screen printing apparatus 400 will be described in detail later. The substrate 1 to which the flux has been applied is transported to the electronic component mounting apparatus 500 by the substrate transport line 11.

[0076] (Electronic component mounting equipment) The electronic component mounting device 500 is a device that mounts electronic components 7 (see FIG. 2) on a solder precoat 3 covered with flux. The electronic component mounting device 500 may mount the electronic components on the solder precoat 3 using, for example, a suction nozzle (not shown) that sucks the electronic components. After the mounting of the electronic components is complete, the board 1 is transported to a mounting state inspection device 600 by a board transport line 11.

[0077] (Mounting status inspection device) The mounting state inspection device 600 is a device that inspects the mounting state of electronic components. The mounting state inspection device 600 may use an optical measuring device such as a camera or a three-dimensional measuring machine to recognize the mounting state of electronic components, such as their mounting position, posture, and presence or absence, and determine whether they meet predetermined standards. After inspection, the board 1 is transported to the reflow device 700 by the board transport line 11.

[0078] (reflow equipment) The reflow device 700 heats the board 1 on which electronic components are mounted to melt the solder precoat 3 and solder the electronic components 7 to the lands 2 (see FIG. 2). This produces a mounted board on which electronic components are mounted. After the soldering of the electronic components is complete, the board 1 is transported to the board inspection device 800 by the board transport line 11.

[0079] (Board inspection equipment) The board inspection device 800 is a device that inspects whether a mounted board is good or bad. After the board 1 has been inspected by the board inspection device 800, it is transported to the unloader 900 by the board transport line 11. The unloader 900 collects the completed mounted board into a rack.

[0080] (Manufacturing process of mounting board) The process for manufacturing a mounting board will be briefly described with reference to FIG. 2. First, a substrate 1 is prepared, which has lands 2 on which solder precoats 3 are formed (FIG. 2(a)). Next, a screen printing apparatus 400 applies flux to the solder precoats 3 (FIG. 2(b)). Next, an electronic component mounting apparatus 500 mounts electronic components 7 on the flux-applied solder precoats 3 (FIG. 2(c)). Next, a reflow apparatus 700 heats the substrate 1 on which the electronic components 7 are mounted, causing the solder precoats 3 to begin to melt (FIG. 2(d)). After that, the solder precoats 3 completely melt (FIG. 2(e)). Next, the substrate 1 is cooled, and the lands 2 and the electronic components 7 are connected at the connection portions 5 (connection portions 5 formed by solidifying the molten solder precoats 3). In this manner, a mounting board is manufactured (FIG. 2(f)).

[0081] (Screen printing equipment details) The screen printing apparatus 400 will be described with reference to Figures 3 to 6. In the following description, the transport direction of the substrate 1 is referred to as the X direction, the vertical direction as the Z direction, and the direction perpendicular to the X and Z directions as the Y direction. Also, axes extending along each direction are referred to as the X axis, Y axis, and Z axis, respectively.

[0082] 3 and 4, support frames 411 are erected on both ends in the X direction of the base 401. Between the pair of support frames 411, the components of the screen printing apparatus 400 are arranged.

[0083] A print stage movement mechanism 403 and a print stage 402 that moves thereby are provided on the upper surface of the base 401 between the pair of support frames 411. The print stage movement mechanism 403 includes a print stage table 403xyθ and a print stage lifting mechanism 403z that is arranged on the print stage table 403xyθ. The print stage table 403xyθ allows the print stage 402 to move horizontally along the X-axis and Y-axis, and to rotate the print stage 402 around the Z-axis. The print stage lifting mechanism 403z allows the print stage 402 to be raised and lowered. The print stage 402 holds the substrate 1 that is carried in from the upstream side. The print stage 402 has the function of adjusting the position of the substrate 1 relative to a mask plate 421. A through-hole (opening) 421c for printing (see FIG. 6) is formed in the mask plate 421.

[0084] The printing stage 402 includes a lifting table 404 connected to a printing stage lifting mechanism 403z. Support members 404a are erected on both ends of the upper surface of the lifting table 404. As shown in Figure 4, a holding block 404b extending in the X direction is connected to the upper end of the support member 404a. A printing stage conveyor 406b equipped with a drive belt for transporting the substrate 1 is provided on the inner surface of the holding block 404b.

[0085] The printing stage conveyor 406b can be connected to the loading conveyor 406a and the unloading conveyor 406c. The loading conveyor 406a and the unloading conveyor 406c are arranged to pass through through-holes provided in the upstream and downstream support frames 411, respectively. The substrate 1 loaded by the loading conveyor 406a is transferred to the printing stage conveyor 406b and held by the printing stage 402. After screen printing is completed on the printing stage 402, the substrate 1 is transferred from the printing stage conveyor 406b to the unloading conveyor 406c and unloaded. The printing stage conveyor 406b, loading conveyor 406a, and unloading conveyor 406c each constitute part of the substrate transport line 11.

[0086] A backup lifting mechanism 405a and a backup unit 405 that is lifted and lowered by the backup lifting mechanism 405a are provided on the upper surface of the lifting table 404. When the substrate 1 is loaded onto the printing stage conveyor 406b, the backup unit 405 is raised and supports the lower surface of the substrate 1 by driving the backup lifting mechanism 405a.

[0087] A side clamper 407 for gripping the side surfaces of the substrate 1 is provided on the upper surface of each of the pair of holding blocks 404b. These side clampers 407 can be opened and closed freely by a side clamper drive mechanism (not shown). When the side clampers 407 are closed while the backup unit 405 supports the lower surface of the substrate 1, both side surfaces of the substrate 1 are sandwiched between the side clampers 407. As a result, the substrate 1 is clamped.

[0088] In order to align the substrate 1 held by the printing stage 402 with the mask plate 421, the printing stage 402 holding the substrate 1 is moved relative to the mask plate 421. The printing stage table 403xyθ functions as an alignment mechanism that moves the printing stage 402 and the mask plate 421 relative to each other in order to align the substrate 1 with the mask plate 421.

[0089] A print head support beam 412 that supports the print head 413 is arranged at the upper ends of the pair of support frames 411. The print head support beam 412 is movable along the Y axis via a linear guide mechanism 412a. One end of the print head support beam 412 is connected to one of the support frames 411 via a print head movement mechanism 414 configured as shown in FIG. 4. In the print head movement mechanism 414, a nut portion 414c is connected to the print head support beam 412. A feed screw 414b is threadedly engaged with the nut portion 414c. The feed screw 414b is rotated by a print head motor 414a. By rotating the print head motor 414a, the print head 413 can be moved back and forth along the Y axis (squeegeeing operation).

[0090] As shown in FIG. 4, the print head 413 includes a rear squeegee 413b and a front squeegee 413c. A squeegee drive unit 413a is provided on the upper surface of the print head support beam 412. The squeegee drive unit 413a can lower either the rear squeegee 413b or the front squeegee 413c depending on the direction of the squeegeeing operation, so that the rear squeegee 413b or the front squeegee 413c comes into contact with the mask plate 421. Specifically, the rear squeegee 413b comes into contact with the mask plate 421 when the squeegeeing operation is performed to the left in FIG. 4. On the other hand, the front squeegee 413c comes into contact with the mask plate 421 when the squeegeeing operation is performed to the right in FIG. 4. The front squeegee 413c and the rear squeegee 413b are each an example of a squeegee 413.

[0091] As shown in FIGS. 5 and 6, the mask 420 includes a mask plate 421, a frame 422 surrounding the mask plate 421, and a stretchable elastic sheet 423. The mask plate 421 has an upper surface 421a, a lower surface 421b, and a printing through-hole 421c that penetrates from the upper surface 421a to the lower surface 421b. The through-hole 421c is formed at a position where flux is to be applied. When viewed from the normal direction of the upper surface 421a of the mask plate 421, the through-hole 421c has a shape that fits within the outer edge of the corresponding solder precoat 3. That is, when aligned with the corresponding solder precoat 3, the through-hole 421c of the mask plate 421 has a dimension A that is smaller than the dimension B of the solder precoat 3 in any cross section, an example of which is shown in FIG. 6. The stretchable sheet 423 connects the mask plate 421 and the frame 422 while applying outward tension to the mask plate 421. In FIG. 5, the through-hole 421c is not shown.

[0092] A camera movement mechanism 416 is provided between the upper surface of the printing stage 402 and the lower surface 421b of the mask plate 421. The camera movement mechanism 416 moves a camera mounting base 417, to which a first camera 418 and a second camera 419 are attached, along the X and Y axes. The camera movement mechanism 416 includes a camera X-axis movement mechanism 416X that moves the camera mounting base 417 in the X direction along the camera X-axis beam 415, and a camera Y-axis movement mechanism 416Y that moves the camera X-axis beam 415 in the Y direction. The movement of the camera X-axis beam 415 is guided by a linear guide mechanism 412a arranged on the inner surface of the support frame 411.

[0093] The camera X-axis movement mechanism 416X includes a camera X-axis motor 415a and a feed screw 415b shown in FIG. 3, and a nut portion 415d shown in FIG. 4. By driving the camera X-axis motor 415a, the camera mounting base 417 coupled to the nut portion 415d moves along the X-axis. As shown in FIG. 4, the camera Y-axis movement mechanism 416Y includes a camera Y-axis motor 416a, a feed screw 416b, and a nut portion 416c. The camera X-axis beam 415 coupled to the nut portion 416c can be moved along the Y-axis by the camera Y-axis motor 416a.

[0094] Here, the functions of the first camera 418 and the second camera 419 will be explained. The first camera 418 is positioned so that it can take pictures downward. The first camera 418 takes pictures of the board 1 held on the printing stage 402. By image processing the results of the image taken by the first camera 418, the position of the board 1 and the position of the solder precoat on the board 1 are detected. The second camera 419 is positioned so that it can take pictures upward. The second camera 419 takes pictures of a mask recognition mark (not shown) formed on the mask 420. By image processing the results of the image taken by the second camera 419, the center of the mask plate 421 and the position of the through-hole 421c in the mask plate 421 are recognized.

[0095] Next, application of flux using the screen printing apparatus 400 will be described with reference to Figures 7 and 8. Note that Figure 7 only illustrates the backup unit 405, the substrate 1 supported by the backup unit 405, the mask 420, and the front squeegee 413c.

[0096] First, as shown in FIG. 7(a), flux F (the above-described flux (F)) is supplied to the upper surface 421a of the mask plate 421. Furthermore, the mask plate 421 is placed above the substrate 1 supported by the backup unit 405. That is, the mask plate 421 and the substrate 1 are not in contact with each other. The mask 420 is positioned so that the through-hole 421c of the mask plate 421 is located above the solder precoat 3 formed on the substrate 1 (mask position adjustment process). Although the solder precoat 3 shown in FIG. 7(a) has a flat top, the shape of the solder precoat 3 is not limited to the shape shown in FIG. 7(a). The flat top may be formed by crushing the solder precoat 3 from above. A crushing mechanism for crushing the solder precoat 3 may be provided within the screen printing apparatus 400 or may be provided separately from the screen printing apparatus 400.

[0097] Next, as shown in Fig. 7(b), the flux F supplied to the upper surface 421a of the mask plate 421 is moved by the front squeegee 413c, thereby applying the flux F to the solder precoat 3 through the through holes 421c of the mask plate 421 (squeegeeing process). Fig. 8(a) is an enlarged view of region G in Fig. 7(b) (i.e., the region where the front squeegee 413c is located). Fig. 8(b) is an enlarged view of region H in Fig. 7(b) (i.e., the region after the front squeegee 413c has passed).

[0098] As shown in FIG. 8(a), in the region where the front squeegee 413c performing the squeegeeing operation is located, the mask plate 421 is pressed down toward the substrate 1 by the front squeegee 413c. As a result, the peripheral portion of the through hole 421c on the lower surface 421b of the mask plate 421 is pressed against the solder precoat 3. The sidewall of the through hole 421c prevents the flux F filled in the through hole 421c from leaking between the lower surface 421b of the mask plate 421 and the solder precoat 3. As shown in FIG. 8(b), after the front squeegee 413c passes over the solder precoat 3, the peripheral portion of the through hole 421c separates from the solder precoat 3 due to the tension applied to the mask plate 421 by the elastic sheet 423.

[0099] 9, the solder precoat 3 may include a solder layer 3a and an organic layer 3b (e.g., an antioxidant film) formed on the surface of the solder layer 3a. The organic layer 3b may be a layer made of a residue of solder paste (residue of flux components in the solder paste) formed when the solder precoat 3 is formed.

[0100] (Addendum) The above description of the embodiments discloses the following techniques. (Technology 1) 1. A screen printing method for depositing flux onto a plurality of solder precoats on a substrate, comprising: a mask position adjustment step of adjusting the relative position of a mask plate having a plurality of through holes and the substrate so that the through holes are positioned above the solder precoat and so that the mask plate and the solder precoat do not come into contact with each other; a squeegeeing step of applying the flux to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee, In the squeegeeing step, a portion of the mask plate that is pressed down toward the substrate by the squeegee comes into contact with the solder precoat, The screen printing method, wherein the consistency of the flux is 220 or more and 450 or less. (Technology 2) at least some of the through holes have a shape that fits within an outer edge of the corresponding solder precoat when viewed from a normal direction of the upper surface of the mask plate; The screen printing method according to Technology 1, wherein in the squeegeeing step, the flux is applied to the solder precoat in at least some of the through holes so as not to overflow from the solder precoat. (Technology 3) 3. The screen printing method according to claim 1, wherein the thickness of the mask plate is 15 μm or more and 50 μm or less. (Technology 4) 4. The screen printing method according to any one of techniques 1 to 3, wherein the solder precoat includes a solder layer and an organic layer formed on the surface of the solder layer. (Technology 5) A flux used in the screen printing method according to any one of techniques 1 to 4, Flux with a consistency of 220 or more and 450 or less. (Technology 6) 1. A screen printing apparatus for depositing flux onto a plurality of solder precoats on a substrate, the apparatus comprising: a mask plate having a plurality of through holes; a mask position adjustment mechanism that adjusts the relative position of the mask plate and the substrate so that the through holes are positioned above the solder precoat and so that the mask plate and the solder precoat do not come into contact with each other; a flux supply mechanism that supplies the flux having a consistency of 220 or more and 450 or less to the upper surface of the mask plate; a squeegeeing mechanism that applies the flux to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee; The squeegee mechanism presses down on the mask plate with the squeegee when moving the squeegee, thereby bringing the mask plate into contact with the solder precoat at the portion where the squeegee is in contact. (Technology 7) A screen printing apparatus described in Technology 6, wherein at least some of the plurality of through holes have a shape that fits within the outer edge of the corresponding solder precoat when viewed from the normal direction of the top surface of the mask plate. (Technology 8) 8. The screen printing apparatus according to claim 6, wherein the thickness of the mask plate is 15 μm or more and 50 μm or less. (Technology 9) 9. The screen printing apparatus according to any one of techniques 6 to 8, wherein the solder precoat includes a solder layer and an organic layer formed on the surface of the solder layer. [Example]

[0101] This embodiment will be described in more detail with reference to an example. In this example, flux was applied to a solder precoat formed on a substrate by screen printing. The consistency of the flux was changed and the state of the applied flux was evaluated.

[0102] The length of the land was 0.2 mm and the width was 0.1 mm. This land corresponds to a JIS 0402 size electronic component. The planar shape of the solder precoat was the same as that of the land. A stainless steel metal mask (thickness: 30 μm) was used as the mask plate. The area of ​​the through-hole (area when viewed from above) was 50% of the area of ​​the solder precoat (area when viewed from above). In the mask position adjustment process, the relative position of the mask plate and the substrate was adjusted so that the outer edge of the through-hole was located inside the outer edge of the solder precoat when viewed from the normal direction of the top surface of the mask plate.

[0103] In this example, the consistency of the flux was changed to evaluate the printing results by screen printing. Specifically, the state of the flux placed on the solder precoat was observed using a digital microscope (Keyence Corporation: VHX-7000), and the printing results were evaluated based on the observation results. The consistency of the flux was changed by changing the ratio of the components that make up the flux. The consistency was measured using the method described above.

[0104] The flux was prepared by mixing a rosin resin, an activator, a thixotropic agent, and a solvent. Polymerized rosin was used as the rosin resin, an organic acid was used as the activator, hydrogenated castor oil was used as the thixotropic agent, and a glycol ether-based solvent was used. The flux preparation conditions and the screen printing evaluation results are shown in Table 1.

[0105] The evaluation of print defects in Table 1 shows the following results. A: The volume of the applied flux is 80% or more of the volume of the through-hole. B: The volume of the applied flux is 60% or more and less than 80% of the volume of the through hole. C: The volume of the applied flux is less than 60% of the volume of the through-hole.

[0106] The evaluation results of print bleeding in Table 1 show the following results. A: The thickness of the applied flux is 60% or more of the thickness of the metal mask. B: The thickness of the applied flux is 50% or more and less than 60% of the thickness of the metal mask. C: The thickness of the applied flux is less than 50% of the thickness of the metal mask.

[0107] [Table 1]

[0108] Printing using fluxes A1 to A8 is an example of the screen printing method (M). Printing using fluxes C1 and C2 is a comparative example. As shown in Table 1, when printing method (M) was used, an appropriate amount of flux was applied to the solder precoat. Therefore, printing method (M) can suppress the movement of electronic components placed on the flux. [Industrial Applicability]

[0109] The present disclosure can be used for a screen printing method, a screen printing apparatus, and a flux. [Explanation of symbols]

[0110] 1: Circuit board 2: Land 3: Solder precoat 3a: solder layer 3b:Organic layer 7: Electronic components 400: Screen printing equipment 413c: Front squeegee (squeegee) 413b: Rear squeegee (squeegee) 420: Mask 421: Mask version 421c: Through hole 423: Stretch sheet F: Flux

Claims

1. 1. A screen printing method for depositing flux onto a plurality of solder precoats on a substrate, comprising: a mask position adjustment step of adjusting the relative position of a mask plate having a plurality of through holes and the substrate so that the through holes are positioned above the solder precoat and so that the mask plate and the solder precoat do not come into contact with each other; a squeegeeing step of applying the flux to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee, In the squeegeeing step, a portion of the mask plate that is pressed down toward the substrate by the squeegee comes into contact with the solder precoat, The screen printing method, wherein the consistency of the flux is 220 or more and 450 or less.

2. at least some of the through holes have a shape that fits within an outer edge of the corresponding solder precoat when viewed from a normal direction of the upper surface of the mask plate; The screen printing method according to claim 1 , wherein in the squeegeeing step, the flux is applied to the solder precoat in such a manner that the flux does not protrude from the solder precoat in at least some of the through holes.

3. 3. The screen printing method according to claim 1, wherein the mask has a thickness of 15 [mu]m or more and 50 [mu]m or less.

4. The screen printing method according to claim 1 or 2, wherein the solder precoat includes a solder layer and an organic layer formed on a surface of the solder layer.

5. A flux used in the screen printing method according to claim 1 or 2, A flux having a consistency of 220 or more and 450 or less.

6. 1. A screen printing apparatus for depositing flux onto a plurality of solder precoats on a substrate, the apparatus comprising: a mask plate having a plurality of through holes; a mask position adjustment mechanism that adjusts the relative position of the mask plate and the substrate so that the through holes are positioned above the solder precoat and so that the mask plate and the solder precoat do not come into contact with each other; a flux supply mechanism that supplies the flux having a consistency of 220 or more and 450 or less to the upper surface of the mask plate; a squeegeeing mechanism that applies the flux to the solder precoat through the through holes by moving the flux supplied to the upper surface of the mask plate with a squeegee; The squeegee mechanism presses down on the mask plate with the squeegee when moving the squeegee, thereby bringing the mask plate into contact with the solder precoat at the portion where the squeegee is in contact.

7. The screen printing apparatus according to claim 6 , wherein at least some of the plurality of through holes have a shape that fits within the inner periphery of the corresponding solder precoat when viewed from the normal direction of the top surface of the mask plate.

8. 8. The screen printing apparatus according to claim 6, wherein the mask plate has a thickness of 15 [mu]m or more and 50 [mu]m or less.

9. 8. The screen printing apparatus according to claim 6, wherein the solder precoat includes a solder layer and an organic layer formed on a surface of the solder layer.

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