JP2009094251A - Print mask for printed circuit board, and method for mounting printed circuit board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a print mask which is not affected by the height of a solder precoat portion, exerts no influence on an arrangement interval between a micro electronic component and a large-sized electronic component, and eliminates a leakage of solder paste when the solder paste is supplied to another land of a printed circuit board where the solder precoat portion is formed, and to provide a method for mounting the printed circuit board which is shortened in process by performing printing of the large-sized electronic component on a land and flux application onto the solder precoat simultaneously. <P>SOLUTION: Disclosed is the print mask 1 for printing the solder paste 15 on an other land 12b of the printed circuit board 11 having solidified solder 13 at a partial land 12a. The print mask 1 is formed by stacking an outside mask 3 made of a metal material and a mask 5 on a printed circuit board side which is made of a buffer material, which in tern is fixed and formed to be present corresponding to a periphery of an opening portion 2 of the mask 5 for printing at least the paste 1 and the solidified solder 13 of the printed circuit board 11 and its periphery. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a print mask used when a solder paste is printed on a printed board using a screen printer, and more particularly, a solder paste is further applied to a printed board on which solidified solder (hereinafter referred to as a solder precoat portion) is formed. The present invention is applied to a printing mask used for printing and a mounting method using the same.

  Conventionally, as a method of soldering various electronic components mounted on an electronic device to a circuit board, a surface mounting method by reflow or flow has been mainly used. A reflow soldering method by a screen printing method widely used as a surface mounting method for a printed circuit board will be described below.

  FIG. 13 is a diagram for explaining a process showing a reflow soldering method by a conventional screen printing method. 13A, 13B, and 13C, 101 corresponds to a printed circuit board, 102 corresponds to a print mask, and 103 corresponds to a land 103a of a large electronic component typified by a QFP (Quad Flat Package) or 2012 chip component. Through holes formed in the printing mask 102, 104 are through holes formed in the printing mask 102 corresponding to the lands 104 a of small electronic components typified by 0603 chip components, and 105 is solder placed on the printing mask 102. The paste 106 is a squeegee, 107 is a large electronic component mounted on the printed circuit board 101, and 108 is a small electronic component mounted on the printed circuit board 101.

  First, as shown in FIG. 13A, the solder paste 105 is placed on a printing mask 102 provided with through holes 103 and 104 having the same shape as the soldering land on the printed circuit board 101. Next, the solder paste 105 is filled in the through holes 103 and 104 of the printing mask 102 by sliding the squeegee 106 in the direction of the arrow. Finally, by separating the printing mask 102 and the printed board 101, the solder paste 105 is supplied to the lands 103a and 104a on the printed board 101 as shown in FIG.

  Next, as shown in FIG. 13C, the large electronic component 107 and the small electronic component 108 are mounted on the printed circuit board 101 by a component mounting machine. Next, heating is performed by various heat sources in the atmosphere or nitrogen atmosphere, and the solder paste 105 supplied on the printed circuit board 101 is heated and melted so that the terminals of the large electronic component 107 and the small electronic component 108 are placed on the printed circuit board 101. Bonded to the lands 103a and 104a. This is a series of steps.

  Recently, however, there has been an increasing demand for higher functionality and downsizing in recent electronic devices typified by mobile phones. With these demands, electronic components mounted on electronic devices are also becoming narrower in pitch and smaller in size, and 0402 chip components that are smaller than 0603 chip components are now on the market. With the widespread use of this microelectronic component 0402 chip component, it has been strongly required to solder large electronic components and 0402 chip components on the same substrate with high quality.

  However, it has become difficult to solder large electronic components and 0402 chip components on the same substrate with high quality by the conventional screen printing method described above. That is, when the area of the through hole of the print mask is reduced in accordance with the micro land of the 0402 chip part, the solder paste 105 is applied to the print mask due to the aspect ratio (ratio between the width of the through hole 104 and the thickness of the print mask 102). Therefore, the solder paste amount 105 on the micro land of the 0402 chip component tends to be insufficient. Further, if the thickness of the printing mask 102 is reduced, the aspect ratio becomes smaller and this problem can be solved. However, the solder paste amount 105 on the land 103a of the large electronic component is insufficient, and the bonding strength with the large electronic component is ensured. The problem of being unable to do so has arisen.

  In order to solve such a problem, a method is known in which a micro land portion of a 0402 chip component is coated with solder in advance (hereinafter, this method is referred to as “solder precoat method”). As a means for forming this solder precoat method, for example, there are a method of performing plating with solder, a method of using a solder leveler, and a method of depositing on a land portion by a substitution reaction.

  Below, the mounting method of the electronic component with respect to the printed circuit board to which said various solder precoat method was applied is demonstrated.

  First, a flux is applied to the surface of each solder precoat portion on the printed circuit board, and an electronic component is mounted thereon. Thereafter, when the printed circuit board is heated, the oxide film of the solder is removed by the flux, the solder is melted, and the electronic component is soldered on the printed circuit board.

  However, this method is based on the premise that it is applied to a land of a narrow pitch portion and a micro land for a micro electronic component such as a 0402 chip component. Therefore, when applied to a printed circuit board in which micro electronic components and large electronic components are mixed, There is a problem that the amount of solder for a land of a large-sized electronic component having a large area is insufficient. That is, if the amount of solder is small, there is a high possibility that the large electronic component will be joined. For this reason, it is necessary to add solder to a land having a large area of a large electronic component in a separate process.

  Therefore, when microelectronic components and large electronic components are mixed on a single printed circuit board, usually solder is supplied to the land of the microelectronic components, the solder is solidified, and the solder precoat portion is formed first. After that, a solder paste by a screen printing method is supplied to the land portion of the large electronic component.

  However, when a solder paste is further printed on a solder precoated substrate, the problem shown in FIG. 14 occurs.

  In FIG. 14, 110 is a solder precoat portion, 113a is a land of a large electronic component near the land of the microelectronic component, 113b is a land of a large electronic component away from the land of the microelectronic component, 114a is a land of the microelectronic component, 105a Is a solder paste filled in the through hole of the printing mask 112 on the land 113a of the large electronic component near the land of the micro electronic component. 105b is a solder paste filled in the through hole of the printing mask 112 on the land 113b of the large electronic component that is separated from the land of the micro electronic component.

  As shown in FIG. 14, when the solder paste 105 is printed on the large electronic component land 113a on the printed circuit board 111 having the solder precoat portion 110 in the vicinity of the large electronic component land 113a, the lower surface of the print mask 112 is soldered. Since the precoat portion 110 is contacted, a gap is generated between the printed circuit board 111 and the print mask 112. That is, due to the height of the solder precoat portion 110, the adhesion between the print mask 112 and the printed board 111 is locally deteriorated.

  That is, an appropriate amount of solder paste is supplied to the land portion 113b of the large electronic component that is separated from the solder precoat portion 110, whereas the amount of solder supplied to the land 113a of the large electronic component in the vicinity of the solder precoat portion 110 is large. Therefore, there is a problem that the variation in the amount of solder becomes remarkable between the two.

  In addition, a part of the solder paste 105a filled in the through hole of the print mask 112 leaks to the lower surface of the print mask 112 from the gap, and the solder paste 105a easily adheres to the lower surface of the print mask 112. There was also. Thus, the solder paste 105a adhering to the lower surface of the printing mask 112 is transferred to the printed circuit board 111 when supplying the solder paste 105 to the next printed circuit board, and a bridge is generated between the lands of the printed circuit board. There is.

  As a method for solving these problems, as shown in FIG. 15, a printing method for adjusting the amount of solder supplied to each electronic component by changing the thickness of a printing mask used for screen printing and printing a plurality of times. Has been proposed (for example, Patent Document 1). This process will be briefly described below.

  As shown in FIGS. 15A and 15B, first, a solder paste 115 is supplied with a thin print mask 122 onto the land 114a of the microelectronic component. Next, as shown in FIG. 15C, the second and subsequent printings are thicker than the previously used printing mask 122, have through holes 113 corresponding to the lands 113a of the large electronic component, and have a printing mask. A printing mask 126 is used on the back surface side of which is formed into a concave shape by half-etching a range corresponding to the solder paste 115 portion before the previous printing stage. Finally, the solder paste 117 is filled on the large electronic component land 113a by a known screen printing method, and the printed circuit board 111 and the print mask 126 are separated to form the solder paste 117 on the large electronic component land 113a. . Through the above steps, the amount of solder supplied is adjusted according to each electronic component.

JP 2001-60763 A

  However, according to the method described in the patent document, it is possible to change the amount of solder supplied to the lands of each electronic component. However, since the solder paste 115 printed earlier is in a paste state, half etching is performed. If the printing mask 126 processed into a concave shape is displaced even a little, the shape of the solder paste 115 printed at the corner is broken, and the solder paste 115 is bridged before mounting the electronic component. In addition, the concave part formed by half-etching has a thin printing mask, so if the half-etched part is formed in a wide range, the concave part is pressed and deformed by squeegee movement during printing. In this case as well, there is a problem that the shape of the solder paste 115 collapses.

  For these problems, in order to maintain the shape of the printed solder paste 115, the previously printed solder paste 115 is once heated and melted to form a solid state, and a printing mask 126 having a concave portion is used. It is conceivable to supply solder to the lands of large electronic components.

  However, when using the printing mask 126 having the concave shape portion, the through hole 113 of the printing mask 126 cannot be provided unless a distance of at least about 100 μm is provided from the end of the concave shape portion. Therefore, it is difficult to supply the solder with the printing mask to the land in the vicinity of the solder precoat portion, and the land of the large electronic component cannot be disposed substantially in the vicinity of the solder precoat portion. As a result, there is a problem that design flexibility is poor.

  As described above, although it is possible to realize a substrate in which microelectronic components and large electronic components are mixed, the distance between the microelectronic components and large electronic components is limited, and the realization of downsizing of the printed circuit board is realized. It was difficult.

  An object of the present invention is to provide a printing mask that is not affected by the height of a solder precoat portion when supplying a solder paste to another land of a printed circuit board on which a solder precoat portion is formed. Another object is to provide a print mask that does not affect the arrangement interval between the microelectronic component and the large electronic component. Another object is to provide a printing mask that eliminates solder paste leakage. Furthermore, another object is to provide a method of mounting a printed circuit board with a reduced process by simultaneously printing a large electronic component on a land and applying a flux on a solder precoat.

  The present invention relates to a printing mask for printing a solder paste on another land of a printed circuit board having a solidified solder on a part of the lands, the mask comprising an outer metal material and a buffer on the printed circuit board side. A mask made of a material is laminated, and the buffer material is fixed so as to exist at least in the vicinity of the opening of the mask for printing the paste and the solidified solder on the printed circuit board and the vicinity thereof. It is a printing mask characterized by being formed.

  Furthermore, the printing mask of the present invention is characterized in that the buffer material has a thickness exceeding the thickness of the solidified solder.

  Furthermore, in the printing mask of the present invention, a groove is formed at a location including a position corresponding to the solidified solder on the surface opposite to the surface in contact with the metal mask, and the groove is formed on the metal mask. Is not yet achieved.

  Furthermore, the printing mask of the present invention is characterized in that the buffer material is made of a silicone rubber material.

  Furthermore, the printing mask of the present invention is characterized in that the buffer material contains a flux.

Further, the present invention is a method of mounting a solder paste on a printed circuit board by printing a solder paste on another land of the printed circuit board having solder solidified on some lands.
Aligning the other lands of the printed circuit board with the openings of the print mask for printing the paste;
A step of contacting the printing mask and the printed circuit board after the alignment step, sinking the solidified solder, and applying a flux to the solder;
Filling the solder paste placed on the printing mask into the opening of the printing mask and supplying the solder paste onto the other lands of the printed circuit board;
A step of mounting electronic components on the solidified solder to which the flux is applied and on the solder paste of other lands on the printed printed board, and by heating the printed board, the solidified solder and the solder paste are removed. A method of mounting a printed circuit board using a printing mask, comprising: melting and fixing an electronic component to the printed circuit board.

  According to the present invention, since the solder precoat portion is solidified, the solder precoat portion is not deformed even if it is pressed by the buffer material provided on the printing mask. The solder precoat portion is concealed by the buffer material, and the land other than the solder precoat portion is covered. A good solder paste shape can be secured. In addition, the metal mask has no concave part and is formed with almost the same thickness, and the mask opening (hereinafter referred to as a through-hole) can be freely drilled, so the spacing between the microelectronic component and the large electronic component Will not be affected. In addition, the cushioning material may be provided on the entire surface, but it is formed so as to correspond to at least the vicinity of the through hole and the solidified solder of the printed circuit board and the vicinity thereof, so the deformation load of the cushioning material is small, Can be easily deformed. Therefore, the printing mask and the substrate can be securely adhered to each other, so that a stable printing state can be ensured. Further, since the leakage of the solder paste from the gap between the print mask and the land is prevented by the buffer material, the solder paste does not adhere to the lower surface of the print mask.

  Furthermore, according to the present invention, since the cushioning material has a thickness exceeding the thickness of the solder precoat portion, the height of the solder precoat portion can be reliably absorbed, so that the land other than the solder precoat portion is further improved. Solder paste printing is possible. That is, even if the height and shape of the solidified solder are different, the cushioning material is easily deformed to absorb these changes and the next solder paste printing can be performed without any problem. The thickness of the solder precoat portion refers to the thickness of the solder precoat portion having the highest thickness.

  Further, according to the present invention, since the buffer material has the groove only in the place including the solder precoat portion, the deformation load of the buffer material is further reduced and can be more easily deformed. Therefore, since it becomes possible to make a printing mask and a board | substrate adhere more reliably, the stable printing state is securable. Further, the flux described later can be more uniformly applied to the solder precoat portion.

  Furthermore, according to the present invention, since the cushioning material formed from a silicone rubber-based material is easily deformed and closely adheres to the solder precoat portion, and also has adhesiveness on the substrate surface, a stable printing mask that does not move during operation and can do.

  Furthermore, according to the present invention, since the adhesiveness of the buffer material to the solder precoat portion is good, the flux contained in the buffer material can be evenly applied to the solder precoat portion.

  In addition, according to the printing method of the present invention, printing on a land of a large electronic component and flux application on a solder precoat can be performed at the same time. It is possible to eliminate the flux supplying process to the solder pre-coating portion, and to reduce the tact time of the mounting process, which contributes to the improvement of productivity. Moreover, a flux supply apparatus becomes unnecessary and equipment cost can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a print mask in the embodiment, and FIGS. 2 and 3 are schematic cross-sectional views of the masks configured in the print mask of FIG. 1 in the embodiment. FIG. 2 is a schematic cross-sectional view of a metal mask made of a SUS member, and FIG. 3 is a schematic cross-sectional view of a buffer material mask made of a buffer material.

  As shown in FIG. 1, a printing mask 1 according to this embodiment includes two metal masks 3 of SUS members having through holes for solder paste printing and buffer masks 5 having through holes for solder paste printing. It is a laminated body composed of masks, and the positions and sizes of the through holes are the same.

  As shown in FIG. 2, the metal mask 3 is composed of a SUS member having a thickness of 60 μm in which a rectangular through hole 4 corresponding to a land on which a chip component is mounted is opened by laser processing. SUS304 is preferably used as the material for the metal mask. As an example of the size of the through hole, for example, the through hole size for a large electronic component (for example, 2012 chip component) is 1100 μm × 1500 μm, and the through hole size for a micro electronic component (1608 chip component) is 700 μm × 800 μm. It is done.

  On the other hand, as shown in FIG. 3, the buffer material mask 5 has the same outer dimensions as the metal mask 3, and the through hole 6 is also made of a buffer material provided at the same position as the metal mask 3 with the same size. .

  Since the thickness of the buffer mask 5 needs to absorb the thickness of the solder precoat portion, the thickness exceeding the thickness of the solder precoat portion is preferable. As an example of the thickness, the thickness of the metal mask is 60 μm, the thickness of the buffer mask is 60 μm, and the total is 120 μm. In FIG. 3, the thickness of the solder precoat portion is assumed to be 40 μm, and the thickness is set to 60 μm.

  Further, the material of the buffer material is not particularly limited as long as it can be easily deformed according to the shape and height of the solder precoat portion, but a rubber-like material rich in elasticity is preferable. Specifically, for example, rubbers such as silicone rubber, urethane rubber, and fluorine rubber can be used. Among these, the silicone rubber is more preferable because it has adhesiveness on the substrate surface and the solder precoat portion, so that the printing mask does not move easily during operation and stable printing can be performed. Further, it is preferable that the cushioning material is porous foamed rubber having fine pores because it can be satisfactorily impregnated with the flux described later and can be satisfactorily applied to the solder precoat portion. That is, porous silicone rubber is particularly preferable. In addition, the formation method of the through-hole 6 of the buffer material mask 5 can be easily processed by a water jet processing method.

  The integration of laminating and fixing the metal mask 3 and buffer material mask 5 subjected to the through-hole treatment is performed by, for example, applying a thermosetting epoxy resin or the like to the surface of any mask and aligning the through-holes 4 and 6 with each other. Then, the metal mask 3 and the buffer material mask 5 are bonded together by heating at 150 ° C. for 30 minutes in a curing furnace. Next, the side walls of the through-holes 2 of the integrated printing mask 1 are polished to remove the bonding resin and the like that have spread when bonded, and the surface roughness Ra of the through-holes 2 is about 3 μm. It is obtained by processing up to.

  FIG. 4 is a schematic plan view showing the state of the surface of the cushioning material mask on the surface facing the printed circuit board. As shown in FIG. 4, lattice-like cuts 7 having a width of about 50 μm are formed on the surface of the buffer mask 5 at intervals of 50 μm and a depth of 50 μm. A sandblasting method or the like can be applied as a method for processing the cut 7. The width of the cut 7 is preferably smaller than the solder precoat portion formed on the land size 0.1 mm × 0.2 mm of the 0402 chip component which is a minute electronic component. Since the buffer material mask 5 is easily deformed by providing the cut 7 in the buffer material mask 5, the height of the solder precoat portion can be reliably absorbed.

  Next, the flux is impregnated or applied to the cut 7 of the buffer mask 5 by dropping the flux with a dispenser or the like along the surface of the print mask 1 on the buffer mask 5 side, specifically along the cut 7. In addition, since only the solder precoat portion is sufficient for the portion requiring the flux, it is preferable to drop the flux only on the portion corresponding to the solder precoat portion and its vicinity. The amount of the flux to be dropped may be an amount that allows the flux to ooze out on the surface of the portion where the buffer material mask 5 is deformed. By doing so, the buffer material is deformed by sinking the solder precoat portion into the buffer material, and the flux filled in the cut 7 is applied to the surface of the solder precoat portion.

  By incorporating the flux into the buffer mask 5, the flux application process on the solder precoat portion that has been conventionally performed can be eliminated, and the productivity can be improved.

  5 and 6 are schematic views showing a second embodiment of the printing mask, and FIG. 5 is a schematic sectional view of the printing mask of the second embodiment. FIG. 6 is a schematic plan view seen from the buffer material mask side of the printing mask of the second embodiment.

  As shown in FIGS. 5 and 6, in the second embodiment, the cushioning material 5 is provided only in the portion corresponding to the solder precoat portion 8 formed on the substrate and in the vicinity thereof and in the vicinity of the through hole 2 of the printing mask. This is the structure of the printing mask 20. By adopting such a structure, the buffer material is disposed only in the solder precoat portion and the vicinity thereof, so that the deformation load of the buffer material is small and can be easily deformed. Therefore, since it becomes possible to make a printing mask and a board | substrate adhere firmly, it becomes possible to prevent bleeding of a solder paste, and can ensure the stable printing state also during operation. In addition, since the back surface of the metal mask 3 can be confirmed by appearance, it is easy to confirm the amount of flux contained in the buffer material mask 5. That is, whether or not the amount of flux is sufficient can be determined based on whether or not the flux oozes out from the surface of the metal mask 3 on the surface to which the buffer material mask 5 is bonded.

  Next, the thickness of the buffer material mask 5 with respect to the thickness of the solder precoat portion 8 (hereinafter simply referred to as “thickness”) is changed, and an electronic component is mounted via the flux applicability applied on the solder precoat portion 8 and the flux. The solder meltability after reflow bonding was examined.

  Specifically, 0402 chip components are mounted on the solder precoat portion 8 for three types of solder precoat portions 8 having a thickness of 20 μm, 40 μm, and 60 μm, and the meltability of the solder precoat portion 8 with respect to the 0402 chip components, and 2012 chips The printability of the parts land was evaluated. The number of samples evaluated is 10 samples for each condition.

  As shown in Table 1, when the solder precoat thickness and the buffer material thickness are the same, when the solder precoat thickness is 60 μm and the buffer material thickness is 60 μm, the printability on the lands of the terminals of some of the 2012 chip components is poor. Moreover, when the thickness of the buffer part exceeded the thickness of the solder precoat part, all the printability was good. If the buffer material has a thickness that exceeds the thickness of the solder precoat portion 8 even a little, the buffer material can absorb the thickness of the solder precoat portion, so that the printability is improved. The printability on the large-sized electronic component land is good because there is no gap between the print mask and the printed circuit board, and the solder paste does not wrap around the back surface of the print mask.

  Next, the flux application property (also called transfer property) on the solder precoat portion will be described. The material of the flux is not particularly limited, and a known flux can be used. Among them, an adhesive is preferable because it can remain on the solidified solder for a long time even after the mask is removed, and the effect of flux can be exhibited. As such a commercial product, for example, “Deltalux 529D-1” (trademark, manufactured by Senju Metal Co., Ltd.) having adhesiveness can be mentioned. Here, the flux covers the entire upper surface of the solder precoat, and when the 0402 chip component is mounted, it is determined that the 0402 chip component can be fixed (tucked) by the flux.

  As shown in Table 1, it was good with respect to the solder precoat part thickness of 20 μm, except for the case of the buffer material thickness of 60 μm. In the case where the thickness of the buffer material is 60 μm with respect to the thickness of the solder precoat portion of 20 μm, the solder precoat portion is only sunk to about 1/3 of the thickness of the buffer material. It was found that the amount of flux applied was insufficient for tacking parts.

  Regarding the meltability of the 0402 chip component mounted on the solder precoat, the combination of the solder precoat thickness in which the 0402 chip component was tacked on the solder precoat and the buffer material thickness had good meltability and had no problem.

  From the above, a buffer material having a thickness exceeding the solder precoat thickness is preferable because there are no problems such as printability and solder meltability. In particular, the thickness exceeds the thickness of the solder precoat portion, more preferably less than 3 times, and particularly preferably about 2 times.

  Next, a printed circuit board mounting method using a printing mask according to the present embodiment will be described with reference to FIGS.

  FIG. 7 shows a flowchart of a printing method using a printing mask in the present embodiment. 8 to 12 are schematic cross-sectional views of steps of a printed circuit board mounting method using the printing mask of the present invention.

  In the printed circuit board on which the micro land portion 12a and the large electronic component land 12b are formed, the solder pre-coated substrate 11 in which the solder film is applied only to the micro land portions such as the 0402 chip component and the narrow pitch IC by the solder pre-coating method. prepare. (Step 1 in FIG. 7, FIG. 8)

  The through holes 2 of the land on which the large electronic component on the prepared solder precoat substrate 11 is mounted and the printing mask 1 facing the land are aligned. After the alignment, the print mask 1 and the precoat substrate 11 are brought into contact, the solder paste 15 is placed on the print mask 1, and the squeegee 16 is slid in the direction of the arrow. (Step 2 in FIG. 7, FIG. 9)

  Due to the pressing force when the squeegee 16 slides on the printing mask 1, the precoat portion 13 sinks into the cushioning material 5 of the printing mask 1, and the solder paste 15 placed on the printing mask 1 is applied to the printing mask 1. The through hole 2 corresponding to the land portion 12b of the formed large electronic component is filled. At this time, since the buffer material 5 of the printing mask 1 is impregnated with the flux, the flux is applied to the surface of the solder precoat portion 13 submerged in the buffer material 5. At this point, the surface of the precoat substrate 11 and the surface of the cushioning material of the printing mask 1 are securely adhered. (Step 3 in FIG. 7, FIG. 10)

  Next, the printing mask 1 or the pre-coated substrate 11 is separated from the pre-coated substrate 11 by a constant acceleration mode or the like. By this separation, the solder paste 17 filled in the through hole of the printing mask 1 with the squeegee is applied to the land 12b of the large electronic component on the precoat substrate 11. (Step 4 in FIG. 7, FIG. 11)

  As described above, the flux 14 is applied to the surface of the solder precoat portion 13 on the precoat substrate 11 separated from the printing mask, and an appropriate amount of solder paste is applied to the land portion 12b of the large electronic component that is not precoated with solder. 17 is supplied.

  Next, on the solder precoat portion 13 formed on the land 12a of the minute electronic component and the solder paste 17 transferred onto the land 12b of the large electronic component, the corresponding electronic components 10a and 10b are respectively mounted on the component mounting machine. By mounting at a predetermined position and heating the substrate, 13 parts of the solder precoat and the solder paste 17 are melted and each electronic component is fixed onto the substrate. (Step 5 in FIG. 7, FIG. 12)

  As described above, the flux can be supplied to the solder precoat portion simultaneously with the solder supply to the land portion of the large electronic component. Accordingly, it is possible to eliminate the flux supply process that has been conventionally performed after supplying the solder to the large-sized electronic component land, and thus it is possible to reduce the production process.

It is typical sectional drawing of the printing mask of this invention. It is typical sectional drawing of the metal mask which comprises the printing mask of this invention. It is typical sectional drawing of the buffer material mask which comprises the printing mask of this invention. It is a typical top view of the buffer material mask which comprises the printing mask of this invention. It is typical sectional drawing which shows 2nd Embodiment of the printing mask of this invention. It is a schematic plan view which shows 2nd Embodiment of the printing mask of this invention. It is a flowchart of the process which shows the mounting method of the printed circuit board using the printing mask of this invention. It is typical sectional drawing of the precoat board | substrate in the mounting method of this invention. In the mounting method of this invention, it is typical sectional drawing which shows the process made to contact a printing mask printed circuit board. In the mounting method of this invention, it is typical sectional drawing of the state which made the printing mask contact the printed circuit board. In the mounting method of this invention, it is typical sectional drawing of the printed circuit board after releasing the printing mask. In the mounting method of this invention, it is typical sectional drawing of the printed circuit board of the state which mounted the electronic component on the solder coat part and the solder paste. It is a figure explaining the process which shows the reflow soldering method by the conventional screen printing method. It is a figure explaining the process which shows the reflow soldering method by the conventional screen printing method. It is a figure explaining the process which shows the reflow soldering method by the conventional screen printing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 Print mask 2,4,6 Through-hole 3 Metal mask 5 Buffer mask 5a Silicone rubber type material 7 Cut 8,13 Solder precoat part 10a Large electronic component 10b Microelectronic component 11 Solder precoat substrate 12a Microelectronic component land 12b Land of large electronic component 14 Flux 15 Solder paste 16 Squeegee 17 Transferred solder paste

Claims (6)

  A print mask for printing a solder paste on another land of a printed circuit board having solder solidified on a part of the lands, wherein the print mask is composed of an outer metal material mask and a printed circuit board side buffer material. And the buffer material is fixed so as to be present at least in the vicinity of the opening of the mask for printing the paste and the solidified solder on the printed circuit board and the vicinity thereof. A printing mask characterized by comprising   The printing mask according to claim 1, wherein the buffer material has a thickness that exceeds a thickness of the solidified solder.   The buffer material is characterized in that a groove is formed in a location including a position corresponding to the solidified solder on a surface opposite to the surface in contact with the metal mask, and the groove does not reach the metal mask. The printing mask according to claim 1 or 2.   The printing mask according to claim 1, wherein the cushioning material is made of a silicone rubber material.   The printing mask according to claim 1, wherein the cushioning material contains a flux. In a method of printing a solder paste on another land of a printed circuit board having solder solidified on some lands and mounting the printed circuit board on the printed circuit board,
Aligning the other lands of the printed circuit board with the openings of the print mask for printing the paste;
A step of contacting the printing mask and the printed circuit board after the alignment step, sinking the solidified solder, and applying a flux to the solder;
Filling the solder paste placed on the printing mask into the opening of the printing mask and supplying the solder paste onto the other lands of the printed circuit board;
A step of mounting electronic components on the solidified solder to which the flux is applied and on the solder paste of other lands on the printed printed board, and by heating the printed board, the solidified solder and the solder paste are removed. A method of mounting a printed circuit board using a printing mask, comprising: melting and fixing an electronic component to the printed circuit board.

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