JP7438116B2 - Solder paste application method and mask - Google Patents

Description

The present invention relates to a solder paste application method and a mask.
This application claims priority based on Japanese Patent Application No. 2018-166395 filed in Japan on September 5, 2018, the contents of which are incorporated herein.

Conventionally, solder paste has been widely used in surface mounting technology (SMT) in which electronic components such as LGA (Land Grid Array) and BGA (Ball Grid Array) are mounted on the surface of a printed circuit board or the like. Solder paste is made by mixing solder powder with flux. In surface mounting, solder paste is first applied to the surface of a printed circuit board where pads (electrodes) are provided. At this time, the solder paste is applied to the pad, and the application area is equivalent to the area of the pad. Next, the electronic component is placed on the surface of the printed circuit board so that the pad of the printed circuit board and the land (electrode) of the electronic component face each other. At this time, the solder paste is located between the electrodes of the printed circuit board and the electronic component. Finally, the printed circuit board on which the electronic components are mounted is heated (reflowed) in a reflow oven, the solder powder of the solder paste is melted and bonded to each other, and then solidified again to electrically connect the two electrodes. , surface mounting is completed. In order to ensure proper electrical connection, the resistance value of the solder connecting both electrodes needs to be below a predetermined value. Further, even if a shock or the like is applied to the printed circuit board after surface mounting, the solder is required to have a predetermined strength in order to maintain proper electrical connection without being damaged.

In order to apply solder paste to the surface of a printed circuit board, for example, screen printing using a mask as shown in Patent Document 1 is used.

Japanese Patent Application Publication No. 2001-77521

The solder that connects both electrodes after the reflow process may contain so-called voids. A void is a gap formed in the solder, and this gap is filled with a gas produced by vaporizing the resin component of the flux, the solvent of the flux, and the like. When voids are formed, the electrical resistance between both electrodes increases, and there is a possibility that proper electrical connection cannot be secured. Further, voids cause a decrease in the strength of the solder, and there is a possibility that the electrical connection between both electrodes cannot be maintained when an impact or the like is applied. Note that relatively small voids may not cause such problems, and the voids that cause the above problems are relatively large voids, so in the field of surface mounting, it is necessary to suppress the size of the voids that occur. is required to do so.

The present invention has been made in view of the above circumstances, and provides a solder paste application method and mask that can suppress the size of voids even when voids are formed in solder during surface mounting. The purpose is to provide

In order to solve the above problems, the present invention employs the following means.
A first aspect of the present invention is to apply a solder paste to an object to be applied, which is used in a method of joining the object to be applied and the electronic component by performing reflow with a solder paste applied between the object to be applied and the electronic component. A method of applying solder paste according to the present invention, wherein the solder paste is applied to an application area at least partially located within the bonding area of the object to be applied, so as to form a non-applying area within the bonding area including the electrode. The application region includes a plurality of peripheral regions arranged at intervals in a circumferential direction around the center of the bonding region , and a central region located radially inside the plurality of peripheral regions. However, the ratio of the gap between the plurality of peripheral regions, which opens radially outward from the center of the joint region, to the entire circumference of the joint region is 11.5% or more and 80.6% or less (provided that , excluding 11.5% or more and 16.7% or less) .

In the first aspect of the present invention, the number of the plurality of peripheral regions may be from two to six.

In the first aspect of the present invention, the plurality of peripheral regions may be arranged at equal intervals in the circumferential direction.

In the first aspect of the present invention, the plurality of peripheral regions have a first region and a second region having different lengths in the circumferential direction, and the first region and the second region have different lengths in the circumferential direction. may be arranged alternately.

In the first aspect of the present invention, opposing sides of the plurality of circumferential regions adjacent to each other in the circumferential direction may be parallel to each other.

In the first aspect of the present invention, opposing sides of the central region and each peripheral region may be parallel to each other.

In the first aspect of the present invention, the area of the central region may be 44.4% or more and 278% or less of the area of each peripheral region.

In the first aspect of the present invention, an area where solder paste is applied within the bonding area may be 17.5% or more and 60.1% or less of the area of the bonding area .

In the first aspect of the present invention, the plurality of peripheral regions may be arranged to overlap an outer edge of the bonding region.

In the first aspect of the present invention, the plurality of peripheral regions may be arranged within the bonding region.

A second aspect of the present invention is a mask used in the solder paste coating method of the first aspect , in which an opening is formed at a position corresponding to the coating area.

According to the aspect of the present invention, even if a void is formed in the solder during surface mounting, the size of the void can be suppressed. For this reason, it is possible to ensure proper electrical connection between the object to be coated, such as a board, and both electrodes of electronic components, and it is also possible to prevent a decrease in the strength of the solder that connects both electrodes. etc. can be provided.

1 is a schematic diagram showing a solder printing device according to an embodiment of the present invention. FIG. 1 is a plan view of a substrate that is an object to be coated according to an embodiment of the present invention. FIG. 1 is a plan view of a mask used for screen printing according to an embodiment of the present invention. 1 is a schematic diagram showing each step of a solder paste application method according to an embodiment of the present invention. FIG. FIG. 3 is a schematic diagram showing the steps after the solder paste application step in surface mounting. 3 is a plan view showing a solder paste application area in Example 1. FIG. FIG. 7 is a plan view showing a solder paste application area in Example 2. FIG. 7 is a plan view showing a solder paste application area in Example 3. FIG. 7 is a plan view showing a solder paste application area in Example 4. FIG. 7 is a plan view showing a solder paste application area in Example 5. FIG. 7 is a plan view showing a solder paste application area in Example 6. 7 is a plan view showing a solder paste application area in Example 7. FIG. FIG. 7 is a plan view showing a solder paste application area in Example 8. FIG. 7 is a plan view showing a solder paste application area in Example 9. FIG. 7 is a plan view showing a solder paste application area in Example 10. FIG. 7 is a plan view showing a solder paste application area in Example 11. FIG. 7 is a plan view showing a solder paste application area in Example 12. FIG. 7 is a plan view showing a solder paste application area in Example 13. FIG. 7 is a plan view showing a solder paste application area in Example 14. FIG. 7 is a plan view showing a solder paste application area in Example 15. FIG. 7 is a plan view showing a solder paste application area in Example 16. FIG. 7 is a plan view showing a solder paste application area in Example 17. FIG. 7 is a plan view showing a solder paste application area in Example 18. FIG. 7 is a plan view showing a solder paste application area in Example 19. FIG. 7 is a plan view showing a solder paste application area in Example 20. FIG. 7 is a plan view showing a solder paste application area in Example 21. FIG. 7 is a plan view showing a solder paste application area in Example 22. FIG. 7 is a plan view showing a solder paste application area in Example 23. FIG. 7 is a plan view showing a solder paste application area in Example 24. FIG. 7 is a plan view showing a solder paste application area in Example 25. FIG. 7 is a plan view showing a solder paste application area in Example 26.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solder printing apparatus and a solder paste application method according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

The solder printing apparatus 1 of this embodiment is a screen printing apparatus using a mask M. As shown in FIG. 1, the solder printing apparatus 1 includes a substrate support section 2 that supports a substrate B to which solder paste S is applied, a printing section 3 disposed vertically above the substrate support section 2, and a substrate B. It includes a housing 4 that accommodates a support section 2 and a printing section 3. The mask M is held at a predetermined position within the housing 4 by a mask supporter (not shown) fixed to the housing 4 or the like.

The board support unit 2 includes a stage 21 that supports the board B from vertically below so that the mounting surface of the board B faces vertically upward, and a stage that is movable in the horizontal and vertical directions and rotatable around an axis extending in the vertical direction. A moving part 22 is provided. A clamp member 23 for holding the substrate B is provided on the stage 21. Further, the solder printing apparatus 1 is provided with a substrate transport section (not shown) that carries in and out the substrate B between the substrate support section 2 and the outside of the casing 4 .

The printing unit 3 includes a squeegee 31 for moving the solder paste S on the surface (upper surface) of the mask M, a vertical movement device 32 that can move the squeegee 31 up and down, and a horizontal movement device 33 that can move the vertical movement device 32 horizontally. It is equipped with The squeegee 31 is a member for spreading the solder paste S supplied onto the mask M by moving in the horizontal +X direction while contacting the surface of the mask M. The squeegee 31 is connected to a vertical movement device 32. The squeegee 31 may be a plate member made of a single material such as metal, resin, or rubber, or may be a plate member such as a metal plate whose portion that contacts the mask M is covered with resin or rubber. You can. The squeegee 31 is arranged so as to be inclined vertically downward as it goes in the -X direction, which is opposite to the +X direction. The inclination angle of this squeegee 31 may be adjustable manually or automatically.

The vertical movement device 32 is supported by the horizontal movement device 33, and includes, for example, a ball screw. The vertical movement device 32 can press the lower end of the squeegee 31 against the surface of the mask M with a predetermined force. The horizontal movement device 33 is fixed to the housing 4, and includes a linear motion guide 34 that guides the vertical movement device 32 in the horizontal direction, and a motor that rotates a ball screw (not shown) provided in parallel to the linear motion guide 34. It is equipped with 35. The horizontal movement device 33 can horizontally move the vertical movement device 32 connected to the ball screw via a nut member by driving the motor 35. In addition, the horizontal movement device 33 moves the vertical movement device 32 in the horizontal direction while the squeegee 31 is pressing the mask M downward by the vertical movement device 32, so that the squeegee 31 presses the mask M. It can be moved horizontally while The solder printing apparatus 1 is also provided with a dispenser (not shown) that supplies solder paste S onto the mask M.

The housing 4 has sufficient rigidity to support the mask support section and the printing section 3. The casing 4 may have a structure that allows its interior to be airtight. Further, when applying the solder paste S in a reduced pressure atmosphere, the housing 4 may be provided with an exhaust device such as a vacuum pump and an atmosphere release valve.

2A is a plan view of the substrate B, and FIG. 2B is a plan view of the mask M. Note that in this embodiment, a "plan view" refers to a view seen from a direction perpendicular to the mounting surface of the board B and the upper surface of the mask M.

As shown in FIG. 2A, the substrate B on which the solder paste S is applied in this embodiment is a printed circuit board made of a hard plate-like base material, and has a plurality of pads P (electrodes, bonding area) are located. This one board surface is a mounting surface on which an electronic component E, which will be described later, is mounted. Examples of the material of the pad P include copper, gold, and silver. On the mounting surface of the substrate B, a region other than the plurality of pads P is coated with a solder resist having a property of repelling molten solder.

As shown in FIG. 2B, the mask M used in this embodiment is made of a metal plate such as stainless steel, and has a plurality of openings H passing through it in the thickness direction. The thickness of the mask M is, for example, 30 μm to 200 μm, but may be changed as appropriate depending on how thick the solder paste S is applied onto the substrate B. In a conventional screen printing mask, an opening is formed at a position opposite to a pad on the substrate in an area equivalent to the pad, but the opening H in this embodiment is in a plane different from that of the pad P on the substrate B. It has a visual shape. That is, the mask M of this embodiment has an opening H for applying the solder paste S to an application area that is at least partially located within the pad P so as to form a non-application area within the pad P on the substrate B. It is formed. In other words, the opening H is formed in the same shape at a position corresponding to the application area. The shape of the opening H in the mask M of this embodiment, that is, the shape of the application area of the solder paste S applied to the substrate B, will be explained in detail in Examples 1 to 26 described later. In the mask M shown in FIG. 2B, two rectangular openings H are formed for one pad P, and these openings H are arranged to face each other with the center of the pad P in between.

The solder paste S used in this embodiment is not particularly limited, and may be appropriately selected depending on usage conditions such as coating atmosphere, temperature, and the opening size and shape of the mask M. As mentioned above, solder paste is made by mixing solder powder with flux. Copper, tin, silver, alloys thereof, and the like are used for the solder powder, and the shape of the solder powder may be either spherical or irregular. Flux includes, for example, a resin such as rosin, a solvent to adjust viscosity, an activator to clean the surface of the electrode, and a thixotropic agent to adjust viscosity, stickiness, thixotropy, etc. may be adjusted as appropriate depending on the mode of use.

Next, a method for applying solder paste S using the solder printing apparatus 1 of this embodiment will be described with reference to FIG. Note that in FIG. 3, the configuration of the solder printing apparatus 1 other than the squeegee 31 is omitted.

The substrate B is placed on the stage 21 by the substrate transport section, and the substrate B is held on the stage 21 by the clamp member 23. Subsequently, by the operation of the stage moving section 22, the horizontal position and rotational position of the substrate B relative to the fixed mask M around the axis extending in the vertical direction are adjusted, and then the stage moving section 22 is moved from the state shown in FIG. 3(a). The stage 21 is raised to bring the upper surface (mounting surface) of the substrate B into close contact with the lower surface of the mask M, as shown in FIG. 3(b). At this time, the adjustment of the horizontal position and rotational position of the substrate B by the stage moving unit 22 has been completed, so the opening H of the mask M is placed at an appropriate position with respect to the pad P of the substrate B. That is, when the surface of the substrate B on which the pad P is provided comes into contact with the mask M, a portion of the mask M is located at a position corresponding to (opposed to) the area (application area) where the solder paste S is applied to the substrate B. , an opening H is formed.

Subsequently, as shown in FIG. 3C, the dispenser supplies the solder paste S onto the mask M where the squeegee 31 advances, that is, on the +X side of the squeegee 31. Further, the squeegee 31 is lowered by driving the vertical movement device 32, and presses the mask M downward with a predetermined force. In this state, the horizontal movement device 33 moves the vertical movement device 32 in the +X direction, so that the squeegee 31 moves in the +X direction while pressing the mask M. Since the solder paste S is supplied to the position where the squeegee 31 advances, it moves in the +X direction as the squeegee 31 moves. Further, since the squeegee 31 is inclined as described above, a force directed vertically downward is applied to the solder paste S as the squeegee 31 moves. Therefore, as shown in FIG. 3(d), the solder paste S is forced into and filled into the opening H of the mask M, and comes into contact with the upper surface (mounting surface) of the substrate B. Furthermore, since the squeegee 31 moves in the +X direction while pressing the mask M downward, it can move while scraping off the solder paste S from the upper surface of the mask M other than the openings H. Therefore, the solder paste S can be supplied only to the openings H. Can be done. When the horizontal movement of the squeegee 31 by the horizontal movement device 33 is completed, filling of the solder paste S into the plurality of openings H of the mask M is completed, as shown in FIG. 3(e).

Subsequently, as shown in FIG. 3F, the stage moving unit 22 lowers the stage 21, so that the substrate B is spaced downward from the lower surface of the mask M. At this time, since the solder paste S filled in the opening H is attached to the upper surface of the substrate B, this solder paste S is also separated from the mask M, and therefore the solder paste S is formed in a pattern corresponding to the opening H of the mask M. is printed on the mounting surface of the board B. Since the opening H of the mask M has a shape as shown in FIG. The solder paste S is applied to an application area where at least a portion of the solder paste S is located. When the substrate B is separated from the lower surface of the mask M and the solder paste S is printed on the substrate B, the solder paste application process of this embodiment is completed. The board B coated with the solder paste S is carried out from the solder printing apparatus 1 by the board transport section.

Next, steps after the solder paste application step of this embodiment in surface mounting will be described with reference to FIG. 4.
First, as shown in FIG. 4(a), an electronic component E is placed on the mounting surface of a substrate B coated with a solder paste S. The electronic component E may be LGA or BGA. A plurality of lands L (electrodes) are provided on the bottom surface (the surface facing the substrate B) of the electronic component E so as to correspond to the plurality of pads P on the substrate B. In the step shown in FIG. 4A, the electronic component E is placed on the substrate B so that the pad P of the substrate B and the land L of the electronic component E face each other. At this time, the solder paste S is located between the pad P of the substrate B and the land L of the electronic component E.

Subsequently, as shown in FIG. 4(b), the board B on which the electronic components E are mounted is heated in a reflow oven (not shown) to melt the solder powder in the solder paste S and bond them together. The molten solder contacts both electrodes of the board B and the electronic component E. At this time, due to the action of the flux contained in the solder paste S, the wettability of the molten solder to the pad P is improved, and the surface of the board B other than the pad P is coated with a solder resist that repels the molten solder. , the molten solder flows toward the inside of the pad P in the radial direction. That is, even when the solder paste S is applied to two regions as in the present embodiment, the solder contained in the two regions becomes integrated in the reflow process. Thereafter, the molten solder is cooled and solidified to electrically connect the electrodes of the board B and the electronic component E with the solder S1. As described above, the surface mounting of the electronic component E onto the substrate B is completed.

Next, a plurality of specific examples of the solder paste application method of this embodiment will be described with reference to the drawings. Furthermore, in order to compare with these examples, comparative examples corresponding to conventional coating methods were also studied.
In Examples 1 to 26 below, the application area of the solder paste is explained using FIGS. 5 to 30, which show plan views of the mounting surface of the board B. This is an enlarged view of one pad P. In each example, the shape of the pad P in plan view was a circle with a diameter of 1.0 mm. In the following description, a direction passing through the center of the pad P and intersecting an axis perpendicular to the mounting surface of the board B will be referred to as a radial direction, and a direction around the axis will be referred to as a circumferential direction. Furthermore, for convenience, the vertical direction of each drawing may be simply referred to as the "vertical direction" and the horizontal direction of the drawing may simply be referred to as the "horizontal direction."
In these Examples and Comparative Examples, the gap ratio GR, coating area ratio AR, and maximum void area ratio VR, which will be described below, were confirmed.
Note that among Examples 1 to 26 below, Examples 1 to 5, 15, 16, and 23 to 26 are reference examples.

The gap ratio GR refers to the ratio of gaps between a plurality of peripheral areas A1, which will be described later, that open radially outward from the center of the pad P to the entire circumference of the pad P. In other words, if two straight lines can be drawn that extend radially outward from the center of the pad P and do not include any of the peripheral area A1 between them, then calculate the ratio of the angle between these two straight lines to 360°. The gap ratio is GR. If a plurality of pairs of two straight lines that do not include the peripheral area A1 can be drawn, the ratio of the sum of the angles between the two straight lines of each pair to 360° is defined as the gap ratio GR. Note that in calculating the gap ratio GR, the existence of the central region A2, which will be described later, is not taken into account.

The coating area ratio AR refers to the ratio of the total coating area of solder paste applied to one pad P to the area of the pad P. In addition, pi was set to 3.14.

When confirming the maximum void area ratio VR, two test boards with 36 pads P lined up were prepared for each example, and each was soldered to an electronic component having the same number of lands. A total of 72 solder connection samples of pads P were obtained. For this solder connection, the surface mounting method shown in FIGS. 3 and 4 was used. The ratio of the area of the generated void (area in plan view) to the area of one pad P (hereinafter referred to as void area ratio) is calculated for each of the 72 pads P, and the largest void area ratio among them is calculated. was defined as the "maximum void area ratio" of each example. The land of the electronic component had the same shape as the pad P in plan view.

(Comparative example)
The comparative example had a conventional configuration in which solder paste was applied to a pad P having a diameter of 1.0 mm in the same area as the pad P. This comparative example is indicated by "Ref" in Table 1 shown later. In this comparative example, since there are no plurality of peripheral areas, the gap ratio GR cannot be calculated, and the coating area ratio AR is 100%. Further, the maximum void area ratio VR was 43.5%.

(Example 1)
The application area of the solder paste in Example 1 will be explained with reference to FIG.
In Example 1, solder paste is applied to a coating area T that is at least partially located within the pad P on the substrate B so as to form a non-coating area N within the pad P. In FIG. 5, the area where the solder paste is applied is shaded (the same applies to other FIGS. 6 to 30). The application area T has a plurality of (two) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P. Each peripheral area A1 has a rectangular shape extending in one direction, the length in the longitudinal direction is 0.7 mm, and the width in the transverse direction orthogonal to the longitudinal direction is 0.35 mm.
The plurality of peripheral regions A1 are arranged to face each other with the center O of the pad P interposed therebetween.
The plurality of peripheral regions A1 are arranged to extend in a direction perpendicular to the direction in which the plurality of peripheral regions A1 face each other (vertical direction in the paper of FIG. 5). That is, each peripheral area A1 extends in the left-right direction in the drawing. Note that the plurality of peripheral areas A1 may be arranged to extend in a direction intersecting the facing direction.
The size of the gap between the plurality of peripheral areas A1 (the gap in the opposing direction) is 0.7 mm. Therefore, the gap between the plurality of peripheral regions A1 is 70% of the maximum diameter (1.0 mm) of the pad P, and is 200% of the width of each peripheral region A1 in the opposing direction.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
Opposing sides a and b of the plurality of peripheral areas A1 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.
The plurality of peripheral regions A1 are arranged to overlap the outer edge of the pad P. That is, a portion of each peripheral region A1 is located on the outside of the pad P in the radial direction. Note that the plurality of peripheral regions A1 may all be arranged within the pad P.

If the application area T of this embodiment is divided into four by two straight lines passing through the center O and extending in the vertical and horizontal directions, for example, a straight line L1 extending from the center O to the right side of the paper and a straight line L1 extending from the center O to the upper side of the paper. Since the section between the straight line L2 and the other three sections is the same or a mirror image, the ratio of the angle θ _G to 90° between the straight lines L1 and L2 was defined as the gap ratio GR in this example. Further, the angle θ _G is an angle between the straight line L1 and a straight line L3 extending radially outward from the center O and touching the lower right vertex of the peripheral area A1 on the upper side of the paper. The peripheral area A1 is not arranged between the straight lines L1 and L3. Therefore, the gap ratio GR in this embodiment is (arctan (0.35/0.35)/90°)=50%.
The coating area ratio AR of this example is (0.7×0.35×2)/(0.5 ² ×π)=62.4%.
The maximum void area ratio in this example was 2.3%.

(Example 2)
The solder paste application area in Example 2 will be explained with reference to FIG. 6. In the second embodiment, only the configurations that are different from the first embodiment will be explained below, and the explanation of the other configurations will be omitted.
The size of the gap between the plurality of peripheral areas A1 (the gap in the opposing direction) is 0.3 mm. Therefore, the gap between the plurality of peripheral regions A1 is 30% of the maximum diameter (1.0 mm) of the pad P, and is 85.7% of the width of each peripheral region A1 in the opposing direction.

The gap ratio GR in this embodiment is (arctan (0.15/0.35)/90°)=25.8%.
The maximum void area ratio in this example was 13.8%.

(Example 3)
The solder paste application area in Example 3 will be explained with reference to FIG. 7. In the third embodiment, only the configurations that are different from the first embodiment will be explained below, and the explanation of the other configurations will be omitted.
The size of the gap between the plurality of peripheral areas A1 (the gap in the opposing direction) is 0.4 mm. Therefore, the gap between the plurality of peripheral regions A1 is 40% of the maximum diameter (1.0 mm) of the pad P, and is 114% of the width of each peripheral region A1 in the opposing direction.

The gap ratio GR in this example is (arctan (0.2/0.35)/90°)=33%.
The maximum void area ratio in this example was 11.7%.

(Example 4)
The solder paste application area in Example 4 will be described with reference to FIG. 8. In the fourth embodiment, only the configurations that are different from the first embodiment will be explained below, and the explanation of the other configurations will be omitted.
The size of the gap between the plurality of peripheral areas A1 (the gap in the opposing direction) is 0.5 mm. Therefore, the gap between the plurality of peripheral regions A1 is 50% of the maximum diameter (1.0 mm) of the pad P, and is 143% of the width of each peripheral region A1 in the opposing direction.

The gap ratio GR in this example is (arctan (0.25/0.35)/90°)=39.5%.
The maximum void area ratio in this example was 7.0%.

(Example 5)
The solder paste application area in Example 5 will be explained with reference to FIG. 9. In the fifth embodiment, only the configurations that are different from the first embodiment will be explained below, and the explanation of the other configurations will be omitted.
The size of the gap between the plurality of peripheral areas A1 (the gap in the opposing direction) is 0.6 mm. Therefore, the gap between the plurality of peripheral regions A1 is 60% of the maximum diameter (1.0 mm) of the pad P, and is 171% of the width of each peripheral region A1 in the opposing direction.

The gap ratio GR in this example is (arctan (0.3/0.35)/90°)=45.1%.
The maximum void area ratio in this example was 4.2%.

(Study of Examples 1 to 5)
The maximum void area ratio VR of Examples 1 to 5 was all lower than that of the comparative example. Therefore, it can be seen that in all of Examples 1 to 5, the size of the generated voids could be suppressed.
The reason why the void size was suppressed will be discussed below. When melted solder powders are bonded to each other in the reflow process, the resin components of flux, etc. located between the solder powders before melting are pushed outward by the bonding of the molten solder. However, when the solder paste is applied over a large area, the solder cools and solidifies before the resin component is expelled from the solder, which may cause the resin component to remain in the solder (i.e., voids). It will be done. On the other hand, in Examples 1 to 5, the width of each peripheral area A1 is 0.35 mm, which is significantly smaller than the maximum diameter of pad P (1.0 mm). Therefore, if the resin components of the flux move in the lateral direction of the peripheral area A1, they are discharged from the molten solder relatively quickly, so the size of voids is suppressed in each peripheral area A1 compared to the comparative example. It is thought that
Further, as shown in FIG. 4, the solder powder in the solder paste applied to the two regions is also integrated in the reflow process. That is, the solder powder melted in the two peripheral regions A1 flows toward the center O of the pad P, and comes into contact with each other near the center of the pad P. Since the flow of molten solder radially inward is maintained, the connection location of the molten solder flowing from the two regions expands radially outward. Since this connection point expands toward the outside in the radial direction, a force is generated that directs the resin components of the flux toward the outside in the radial direction, and it is thought that this force can also discharge the resin components toward the outside of the solder.

In Examples 1 to 5, the gap between the plurality of peripheral areas A1 was 30% or more and 70% or less of the maximum diameter (1.0 mm) of the pad P.
Further, the gap between the plurality of peripheral regions A1 was 85.7% or more and 200% or less of the width of each peripheral region A1 in the opposing direction of the plurality of peripheral regions A1.

(Modifications of Examples 1 to 5)
The following modifications can be considered for Examples 1 to 5.
Each peripheral area A1 has a rectangular shape in plan view, but may have an elliptical or elliptical shape in plan view. Although the opposing sides a and b of the plurality of peripheral areas A1 are formed in a straight line, these opposing sides may have a shape that bulges radially inward, or radially outward. It may also have a concave shape. Similarly, the radially outer side of the peripheral region A1 may be depressed radially inward or radially outward.

(Example 6)
The solder paste application area in Example 6 will be explained with reference to FIG. 10.
In Example 6, solder paste is applied to an application area T that is at least partially located within the pad P on the substrate B so as to form a non-application area N within the pad P. The application area T includes a plurality of (six) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Each of the peripheral areas A1 and the central area A2 has a square shape with each side having a length of 0.3 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 10.
The plurality of peripheral areas A1 are arranged at approximately equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
Opposing sides a and b of the plurality of circumferential regions A1 adjacent to each other in the circumferential direction are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.
Opposing sides c and d of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides c and d may be non-parallel to each other.
The area of the central region A2 is the same (100%) as the area of each peripheral region A1.
The plurality of peripheral regions A1 are arranged to overlap the outer edge of the pad P. That is, a portion of each peripheral region A1 is located on the outside of the pad P in the radial direction. Note that the plurality of peripheral regions A1 may all be arranged within the pad P.

If the application area T of this embodiment is divided into four by two straight lines passing through the center O and extending in the vertical and horizontal directions, for example, a straight line L1 extending from the center O to the right side of the paper and a straight line L1 extending from the center O to the upper side of the paper. Since the section between the straight line L2 and the other three sections is the same or a mirror image, the ratio of the sum of the angle θ _G1 and the angle θ _G2 with respect to 90° between the straight lines L1 and L2 is calculated as the gap in this embodiment. The ratio was expressed as GR. The angle θ _G1 is the angle between the straight line L1 and the straight line L3 extending radially outward from the center O and touching the lower right vertex of the peripheral area A1 at the upper right of the page, and is equal to arctan(0.1/0 .65). The angle θ _G2 is between a straight line L4 that extends radially outward from the center O and touches the upper left vertex of the peripheral area A1 on the upper right side of the paper, and a straight line L4 that extends radially outward from the center O and touches the lower right vertex of the peripheral area A1 on the upper right side of the paper. The angle between the straight line L5 that is in contact with , and is expressed as (arctan (0.35/0.15) - arctan (0.4/0.35)). Therefore, the gap ratio GR in this example is (θ _G1 +θ _G2 )/90°=29.7%.
The coating area ratio AR of this example is (0.3 ² ×7)/(0.5 ² ×π)=80.3%.
The maximum void area ratio in this example was 4.8%.

(Example 7)
The solder paste application area in Example 7 will be described with reference to FIG. 11. In the seventh embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The central area A2 has a square shape with a side length of 0.4 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 11.
The area of the central region A2 is 178% (=0.4 ² /0.3 ² ) of the area of each peripheral region A1.

The gap ratio GR in this example is 29.7%, the same as in Example 6.
The coating area ratio AR of this example is (0.3 ² ×6+0.4 ² )/(0.5 ² ×π)=89.2%.
The maximum void area ratio in this example was 3.9%.

(Example 8)
The solder paste application area in Example 8 will be explained with reference to FIG. 12. In the eighth embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The central area A2 has a square shape with a side length of 0.5 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 12.
The area of the central region A2 is 278% (=0.5 ² /0.3 ² ) of the area of each peripheral region A1.

The gap ratio GR in this example is 29.7%, the same as in Example 6.
The coating area ratio AR of this example is (0.3 ² ×6+0.5 ² )/(0.5 ² ×π)=100.6%.
The maximum void area ratio in this example was 13.9%.

(Example 9)
The solder paste application area in Example 9 will be explained with reference to FIG. 13. In the ninth embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The central area A2 has a square shape with a side length of 0.2 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 13.
The area of the central region A2 is 44.4% (=0.2 ² /0.3 ² ) of the area of each peripheral region A1.

The gap ratio GR in this example is 29.7%, the same as in Example 6.
The coating area ratio AR of this example is (0.3 ² ×6+0.2 ² )/(0.5 ² ×π)=73.9%.
The maximum void area ratio in this example was 12.3%.

(Example 10)
The solder paste application area in Example 10 will be explained with reference to FIG. 14. In the tenth embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (two) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located radially inside of the plurality of peripheral areas A1. and has. Each of the peripheral areas A1 and the central area A2 has a square shape with each side having a length of 0.3 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 14.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
Opposing sides a and b of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.

If the application area T of this embodiment is divided into four by two straight lines passing through the center O and extending in the vertical and horizontal directions, for example, a straight line L1 extending from the center O to the right side of the paper and a straight line L1 extending from the center O to the upper side of the paper. Since the section between the straight line L2 and the other three sections is the same or a mirror image, the ratio of the angle θ _G to 90° between the straight lines L1 and L2 was defined as the gap ratio GR in this example. The angle θ _G is an angle between the straight line L1 and a straight line L3 extending radially outward from the center O and touching the lower right vertex of the peripheral area A1 on the upper side of the paper. The peripheral area A1 is not arranged between the straight lines L1 and L3. Therefore, the gap ratio GR in this example is (arctan (0.35/0.15)/90°)=74.2%.
The coating area ratio AR of this example is (0.3 ² ×3)/(0.5 ² ×π)=34.4%.
The maximum void area ratio in this example was 3.1%.

(Example 11)
The solder paste application area in Example 11 will be described with reference to FIG. 15. In the eleventh embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (three) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 15.
The plurality of peripheral areas A1 are arranged at approximately equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
Opposing sides a and b of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.

If the coating area T of this embodiment is divided into two by a straight line passing through the center O and extending vertically, the right side of the straight line is a mirror image of the left side, so the straight line L1 extending upward from the center O The ratio of the sum of the angles θ _G1 , θ _G2 and θ _G3 to 180° between the straight line L2 extending downward from the center O was defined as the gap ratio GR in this embodiment. Angle θ _G1 is an angle between a straight line L3 extending from the center O to the right side of the paper and a straight line L4 extending radially outward from the center O and touching the lower right vertex of the peripheral area A1 on the upper side of the paper. , arctan (0.35/0.15). The angle θ _G2 is the angle between the straight line L2 and the straight line L5 extending radially outward from the center O and touching the lower left vertex of the peripheral area A1 at the lower right of the page, and is (90°−arctan(0 .45/0.35)). The angle θ _G3 is the angle between the straight line L3 and the straight line L6 that extends radially outward from the center O and touches the top right vertex of the peripheral area A1 at the bottom right of the page, and is equal to arctan(0.15/0 It is expressed as .65)). Therefore, the gap ratio GR in this example is (θ _G1 +θ _G2 +θ _G3 )/90°=65.4%.
The coating area ratio AR of this example is (0.3 ² ×4)/(0.5 ² ×π)=45.9%.
The maximum void area ratio in this example was 4.0%.

(Example 12)
The solder paste application area in Example 12 will be explained with reference to FIG. 16. In the twelfth embodiment, only the configurations that are different from the sixth embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (four) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Each of the peripheral areas A1 and the central area A2 has a square shape with each side having a length of 0.3 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 16.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
Opposing sides a and b of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.

If the application area T of this embodiment is divided into four by two straight lines passing through the center O and extending in the vertical and horizontal directions, for example, a straight line L1 extending from the center O to the right side of the paper and a straight line L1 extending from the center O to the upper side of the paper. Since the section between the straight line L2 and the other three sections is the same or a mirror image, the ratio of the angle θ _G to 90° between the straight lines L1 and L2 was defined as the gap ratio GR in this example. The angle θ _G is between a straight line L3 that extends radially outward from the center O and touches the upper left vertex of the peripheral area A1 on the right side of the paper, and a straight line L3 that extends radially outward from the center O and touches the lower right vertex of the peripheral area A1 on the upper side of the paper. This is the angle between the straight line L4 that is in contact with . The peripheral area A1 is not arranged between the straight lines L3 and L4. Therefore, the gap ratio GR in this example is (arctan(0.35/0.15)-arctan(0.15/0.35))=48.4%.
The coating area ratio AR of this example is (0.3 ² ×5)/(0.5 ² ×π)=57.1%.
The maximum void area ratio in this example was 2.6%.

(Example 13)
The solder paste application area in Example 13 will be described with reference to FIG. 17. In the thirteenth embodiment, only the configurations that are different from the sixth embodiment will be described below, and the description of the other configurations will be omitted.
The application area T includes a plurality of (four) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Further, the plurality of peripheral regions A1 have first regions A11 and second regions A12 having different circumferential lengths, and the first regions A11 and second regions A12 are arranged alternately in the circumferential direction. Two first areas A11 and two second areas A12 are provided. The first region A11 has a rectangular shape extending in one direction, and has a length in the longitudinal direction of 0.6 mm and a width in the transverse direction orthogonal to the longitudinal direction of 0.3 mm. The second area A12 and the central area A2 both have a square shape with a side length of 0.3 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of first regions A11, the plurality of second regions A12, and the central region A2 is shown in FIG. 17.
Opposing sides a and b of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.

The gap ratio GR in this example is calculated in the same manner as in Example 12, and is (arctan (0.35/0.15) - arctan (0.3/0.35)) = 29.1%.
The coating area ratio AR of this example is (0.6×0.3×2+0.3 ² ×3)/(0.5 ² ×π)=34.6%.
The maximum void area ratio in this example was 1.8%.

(Example 14)
The solder paste application area in Example 14 will be described with reference to FIG. 18. In the 14th embodiment, only the configurations that are different from the above-mentioned 6th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (six) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Each of the peripheral areas A1 and the central area A2 has a square shape with each side having a length of 0.3 mm. However, a portion of the peripheral region A1 that is radially outer than the outer edge of the pad P is excluded. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 18.
Opposing sides a and b of the plurality of circumferential regions A1 adjacent to each other in the circumferential direction are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.
Opposing sides c and d of the central region A2 and each peripheral region A1 are parallel to each other. Note that the opposing sides c and d may be non-parallel to each other.

The gap ratio GR in this example was calculated using the same method as in Example 6, but since the angle θ _G1 is expressed as arcsin (0.05/0.5), the gap ratio GR was calculated as (θ _G1 + θ _G2 )/90°=11.5%.
The coating area ratio AR of this example is approximately 60.1 %.
The maximum void area ratio in this example was 13.8%.

(Study of Examples 6 to 14)
The maximum void area ratio VR of Examples 6 to 14 was all lower than that of the comparative example. Therefore, it can be seen that in all of Examples 6 to 14, the size of the generated voids could be suppressed.
The reason why the void size was suppressed will be discussed below. First, since the peripheral area A1 and the central area A2 are smaller than the application area of the comparative example, it is thought that the resin components of the flux are easily discharged from the molten solder at an early stage, which is the same as in Examples 1 to 5. .
Furthermore, although all of Examples 6 to 14 have a central region A2, the solder powder in the solder paste applied to the central region A2 flows radially outward after melting. Note that the ratio of the gaps between the plurality of peripheral areas A1, which open radially outward from the center O of the pad P, to the entire circumference of the pad P is calculated as the gap ratio GR, and any of Examples 6 to 14 is calculated. It has been found that the opening is also opened from the center O toward the outside in the radial direction via the interval G. Therefore, it is thought that the molten solder from the central region A2 can appropriately flow radially outward through the gap G, and thereby the resin components of the flux and the like can be discharged radially outwardly.
In Examples 6 to 14, the area of the central region A2 was 44.4% or more and 278% or less of the area of each peripheral region A1.

(Example 15)
The solder paste application area in Example 15 will be described with reference to FIG. 19. In the 15th embodiment, only the configuration that is different from the 12th embodiment will be explained below, and the explanation of the other configurations will be omitted.
Embodiment 15 has a configuration in which central region A2 is excluded from Embodiment 12.
The gap ratio GR in this example is the same as in Example 12, and is 48.4%.
The coating area ratio AR of this example is (0.3 ² ×4)/(0.5 ² ×π)=45.7%.
The maximum void area ratio in this example was 13.4%.

(Example 16)
The solder paste application area in Example 16 will be described with reference to FIG. 20. In the 16th embodiment, only the configuration that is different from the 13th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The sixteenth embodiment has a configuration in which the central region A2 is excluded from the thirteenth embodiment.
The gap ratio GR in this example is the same as in Example 13, and is 29.1%.
The coating area ratio AR of this example is (0.6×0.3×2+0.3 ² ×2)/(0.5 ² ×π)=23.2%.
The maximum void area ratio in this example was 13.8%.

(Study of Examples 15 and 16)
The maximum void area ratios VR of Examples 15 and 16 were all lower than those of the comparative example. Therefore, it can be seen that in both Examples 15 and 16, the size of the generated voids could be suppressed.
Examining the reasons why the size of the voids could be suppressed as follows, it is possible that because the peripheral area A1 and the central area A2 are smaller than the application area of the comparative example, the resin components of the flux are easily discharged from the molten solder at an early stage. , is considered to be similar to Examples 1 to 5.

(Example 17)
The solder paste application area in Example 17 will be described with reference to FIG. 21. In the 17th embodiment, only the configurations that are different from the 6th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (six) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Each of the peripheral areas A1 and the central area A2 has a circular shape with a diameter of 0.3 mm. The center of each peripheral area A1 is located on the outer peripheral edge of the pad P. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 21.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
The area of the central region A2 is the same (100%) as the area of each peripheral region A1.
The plurality of peripheral regions A1 are arranged to overlap the outer edge of the pad P. That is, a portion of each peripheral region A1 is located on the outside of the pad P in the radial direction. Note that the plurality of peripheral regions A1 may all be arranged within the pad P.

The gap ratio GR in this embodiment is calculated. The angle θ _C is defined by the straight line L1 extending radially outward from the center O and passing through the center of the peripheral area A1 at the top right of the paper, and the straight line L2 extending radially outward from the center O and touching the peripheral area A1 at the top right of the paper. is the angle between arcsin (0.15/0.5). A peripheral area A1 is located between the straight lines L1 and L2. Therefore, the gap ratio GR in this example is (180°-6×θ _C )/180°=41.8%.
The coating area ratio AR of this example is (0.15 ² ×π × 7)/(0.5 ² ×π) = 63%.
The maximum void area ratio in this example was 10.9%.

(Example 18)
The solder paste application area in Example 18 will be explained with reference to FIG. 22. In the 18th embodiment, only the configurations that are different from the 17th embodiment will be described below, and the description of other configurations will be omitted.
The central region A2 has a circular shape with a diameter of 0.4 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 22.
The area of the central region A2 is 178% of the area of each peripheral region A1.
The gap ratio GR in this example is 41.8%, the same as in Example 17.
The coating area ratio AR of this example is (0.15 ² ×π×6+0.2 ² ×π)/(0.5 ² ×π)=43.1%.
The maximum void area ratio in this example was 4.6%.

(Example 19)
The solder paste application area in Example 19 will be explained with reference to FIG. 23. In the 19th embodiment, only the configurations that are different from the 17th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The central region A2 has a circular shape with a diameter of 0.5 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 23.
The area of the central region A2 is 278% of the area of each peripheral region A1.
The gap ratio GR in this example is 41.8%, the same as in Example 17.
The coating area ratio AR of this example is (0.15 ² ×π×6+0.25 ² ×π)/(0.5 ² ×π)=48.7%.
The maximum void area ratio in this example was 12.4%.

(Example 20)
The solder paste application area in Example 20 will be described with reference to FIG. 24. In the 20th embodiment, only the configuration that is different from the 17th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The central region A2 has a circular shape with a diameter of 0.2 mm. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 24.
The area of the central region A2 is 44.4% of the area of each peripheral region A1.
The gap ratio GR in this example is 41.8%, the same as in Example 17.
The coating area ratio AR of this example is (0.15 ² ×π×6+0.1 ² ×π)/(0.5 ² ×π)=35.7%.
The maximum void area ratio in this example was 17.8%.

(Example 21)
The solder paste application area in Example 21 will be explained with reference to FIG. 25. In the 21st embodiment, only the configurations that are different from the above-mentioned 6th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (two) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located radially inside of the plurality of peripheral areas A1. and has. Each of the peripheral areas A1 and the central area A2 has a circular shape with a diameter of 0.3 mm. The center of each peripheral area A1 is located on the outer peripheral edge of the pad P. The center region A2 is arranged so that its center coincides with the center O of the pad P in plan view. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 25.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
The gap ratio GR in this embodiment is (180°-2×θ _C )/180°=80.6%, referring to the 17th embodiment.
The coating area ratio AR of this example is (0.15 ² ×π×3)/(0.5 ² ×π)=27%.
The maximum void area ratio in this example was 3.8%.

(Example 22)
The solder paste application area in Example 22 will be explained with reference to FIG. 26. In the 22nd embodiment, only the configurations that are different from the above-mentioned 6th embodiment will be explained below, and the explanation of the other configurations will be omitted.
The application area T includes a plurality of (four) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P, and a central area A2 located inside the plurality of peripheral areas A1 in the radial direction. and has. Each of the peripheral areas A1 and the central area A2 has a circular shape with a diameter of 0.3 mm. The mutual positional relationship of the plurality of peripheral areas A1 and central area A2 is shown in FIG. 26.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
The gap ratio GR in this embodiment is (180°-4×θ _C )/180°=61.2%, referring to the 17th embodiment.
The coating area ratio AR of this example is (0.15 ² ×π × 5)/(0.5 ² ×π) = 45%.
The maximum void area ratio in this example was 4.9%.

(Study of Examples 17 to 22)
The maximum void area ratios VR of Examples 17 to 22 were all lower than those of the comparative example. Therefore, it can be seen that in all of Examples 17 to 22, the size of the generated voids could be suppressed.
The reason why the void size was suppressed will be discussed below. First, since the peripheral area A1 and the central area A2 are smaller than the application area of the comparative example, it is thought that the resin components of the flux are easily discharged from the molten solder at an early stage, which is the same as in Examples 1 to 5. .
Furthermore, although all of Examples 17 to 22 have a central region A2, the solder powder in the solder paste applied to the central region A2 flows radially outward after melting. Note that the ratio of the gaps between the plurality of peripheral areas A1 that open radially outward from the center O of the pad P to the entire circumference of the pad P is calculated as the gap ratio GR, It has been found that the opening is also opened from the center O toward the outside in the radial direction via the interval G. Therefore, it is thought that the molten solder from the central region A2 can appropriately flow radially outward through the gap G, and thereby the resin components of the flux and the like can be discharged radially outwardly.
In Examples 17 to 22, the area of the central region A2 was 44.4% or more and 278% or less of the area of each peripheral region A1.

(Example 23)
The solder paste application area in Example 23 will be explained with reference to FIG. 27.
In Example 23, solder paste is applied to an application area T that is at least partially located within the pad P on the substrate B so as to form a non-application area N within the pad P. The application area T has a plurality of (two) peripheral areas A1 arranged at intervals G in the circumferential direction around the center O of the pad P. The two peripheral regions A1 are arranged in contact with each other at a portion of the radially inner side. In this embodiment, the contact point between the two peripheral areas A1 is arranged at the same position as the center O in plan view. The shape of each peripheral area A1 is a right-angled isosceles triangle whose apex is located at the center O and whose apex angle is 90°. The length of the base (the side facing the apex) of each peripheral area A1 is 1.0 mm. Further, the distance between the bases of the two peripheral areas A1 is also 1.0 mm. The circumferential width of each peripheral region A1 gradually increases from the center O of the pad P toward the outside in the radial direction.
The plurality of peripheral areas A1 are arranged at equal intervals in the circumferential direction. Note that the plurality of peripheral areas A1 may not be arranged at equal intervals in the circumferential direction.
The plurality of peripheral regions A1 are arranged to overlap the outer edge of the pad P. That is, a portion of each peripheral region A1 is located on the outside of the pad P in the radial direction. Note that the plurality of peripheral regions A1 may all be arranged within the pad P.
The gap ratio GR in this example is 50%.
The coating area ratio AR of this example is (1.0 ² /2)/(0.5 ² ×π)=63.7%.
The maximum void area ratio in this example was 12.5%.

(Example 24)
The solder paste application area in Example 24 will be described with reference to FIG. 28. In the 24th embodiment, only the configuration that is different from the 23rd embodiment will be explained below, and the explanation of the other configurations will be omitted.
The length of the base of each peripheral area A1 is 1.3 mm. Further, the distance between the bases of the two peripheral areas A1 is also 1.3 mm.
The coating area ratio AR of this example is (1.3 ² /2)/(0.5 ² ×π)=107.6%.
The maximum void area ratio in this example was 14.6%.

(Study of Examples 23 and 24)
The maximum void area ratios VR of Examples 23 and 24 were all lower than those of the comparative example. Therefore, it can be seen that in both Examples 23 and 24, the size of the generated voids could be suppressed.
The reason why the void size was suppressed will be discussed below. First, since the peripheral area A1 is smaller than the application area of the comparative example, it is considered that the resin components of the flux are easily discharged from the molten solder at an early stage, similar to Examples 1 to 5.
Furthermore, although Examples 23 and 24 do not have a central region, the radially inner portion of the peripheral region A1 reaches the central portion of the pad P. For this reason, the solder powder in the solder paste applied to the radially inner portion of the peripheral region A1 may flow radially outward in the horizontal direction in the drawing after melting. In addition, by calculating the gap ratio GR, it was found that in both Examples 23 and 24, the openings were opened from the center O toward the outside in the radial direction via the gap G. Therefore, the molten solder from the radially inner portion of the peripheral area A1 can appropriately flow radially outward through the gap G, and thereby the resin components of the flux, etc. can be discharged radially outwardly. it is conceivable that.

(Modification of Examples 23 and 24)
The following modifications can be considered for Examples 23 and 24.
Although two peripheral areas A1 are provided in these embodiments, the number of peripheral areas A1 may be three or more. In this case, the rate at which the width of each peripheral region A1 in the circumferential direction increases toward the outside in the radial direction may be reduced. Further, the contact point between the two peripheral regions A1 may be arranged at a position different from the center O of the pad P in plan view.

(Example 25)
The solder paste application area in Example 25 will be explained with reference to FIG. 29.
In Example 25, solder paste is applied to an application area T that is at least partially located within the pad P on the substrate B so as to form a non-application area N within the pad P. The application area T has an extension area A3 that includes the center O of the pad P and extends in one direction (in the left-right direction in the drawing in this embodiment). The extension area A3 has a rectangular shape in plan view, and has a length in the longitudinal direction of 1.3 mm and a width in the transverse direction of 0.3 mm.
The extension region A3 is arranged to overlap the outer edge of the pad P. That is, a portion of the extension region A3 is located on the radially outer side of the pad P. In this embodiment, both ends of the extension region A3 in the longitudinal direction are located on the outside of the pad P in the radial direction. Note that the entire extension region A3 may be arranged within the pad P, or only one end of the extension region A3 in the longitudinal direction may be located outside the pad P in the radial direction.
In this embodiment, since the extension region A3 reaches the radially outer side of the pad P, the gap ratio GR cannot be calculated.
The coating area ratio AR of this example is (1.3×0.3)/(0.5 ² ×π)=49.7%.
The maximum void area ratio in this example was 17.5%.

(Example 26)
The solder paste application area in Example 26 will be described with reference to FIG. 30. In the 26th embodiment, only the configurations that are different from the 25th embodiment will be described below, and the description of other configurations will be omitted.
The application region T further includes a plurality of (two) side regions A4 arranged across the extension region A3 in a direction intersecting the longitudinal direction of the extension region A3. The shape of each side region A4 in plan view is a square with a side length of 0.3 mm, and one side of the square extends in the vertical direction of the paper. The mutual positional relationship of the plurality of side regions A4 and extension region A3 is shown in FIG. 30.
Opposing sides a and b of the extension area A3 and each side area A4 are parallel to each other. Note that the opposing sides a and b may be non-parallel to each other.
The plurality of side regions A4 are arranged to overlap the outer edge of the pad P. That is, a portion of each side region A4 is located on the outside of the pad P in the radial direction. Note that the plurality of side regions A4 may all be arranged within the pad P.
The coating area ratio AR of this example is (1.3×0.3+0.3 ² ×2)/(0.5 ² ×π)=72.6%.
The maximum void area ratio in this example was 15.0%.

(Study of Examples 25 and 26)
The maximum void area ratios VR of Examples 25 and 26 were all lower than those of the comparative example. Therefore, it can be seen that in both Examples 25 and 26, the size of the generated voids could be suppressed.
Examining the reasons why the size of the voids could be suppressed as follows, it is found that since the extension area A3 and the side area A4 are smaller than the application area of the comparative example, the resin components of the flux are easily discharged from the molten solder at an early stage. This is considered to be the same as in Examples 1 to 5.

(Modification of Examples 25 and 26)
The following modifications can be considered for Examples 25 and 26.
For example, the number of the plurality of side regions A4 may be three or more.

Table 1 shows the gap ratio GR, coating area ratio AR, and maximum void area ratio VR of Examples 1 to 26 described above.

The maximum void area ratio VR of Examples 1 to 26 was all lower than that of the comparative example. Therefore, it can be seen that in all of the examples, the size of the generated voids could be suppressed. Therefore, it is possible to ensure proper electrical connection between the substrate or other coating object and both electrodes of the electronic component, and it is also possible to prevent a decrease in the strength of the solder that connects the two electrodes, resulting in a surface-mounted substrate that is resistant to impact. can be provided.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Additions, omissions, substitutions, and other changes to the configuration are possible without departing from the spirit of the invention.

For example, in the embodiment, the pad P on the substrate B, which is the object to be coated, has a circular shape in plan view, but is not limited to this, and may be rectangular or polygonal, for example.

In the embodiment described above, a printed circuit board made of a hard plate-like base material is used as the object to be coated, but a flexible board may also be used as the object to be coated with the solder paste. Furthermore, when directly connecting one electronic component to another electronic component, solder paste may be applied to the electrode surface of the first electronic component as an object to be applied. The object to be coated may be any member as long as it can be coated with solder paste.

In the embodiment described above, screen printing using a mask M is used when applying the solder paste to the object to be applied. A method of directly applying the solder paste to the application area as shown in 26 without using a mask or the like may be used.

Further, the present invention may include the following aspects.
A fourth aspect of the present invention is a mask for applying solder paste to an object to be applied, wherein at least a portion of the solder paste is formed in the bonding area of the object so as to form a non-applying area in the bonding area of the object. An opening is formed at a position corresponding to the application area, and the opening has a plurality of peripheral openings spaced apart in a circumferential direction around the center of the bonding area.
A fifth aspect of the present invention is a mask for applying solder paste to an object to be applied, wherein at least a portion of the solder paste is formed in the bonding area of the object so as to form a non-applying area in the bonding area of the object. An opening is formed at a position corresponding to the application area, and the opening has an extending opening that includes the center of the bonding area and extends in one direction.

The present invention is applicable to a method of applying solder paste to an object to be applied, such as a printed circuit board, and a mask used for the application, and even if voids are formed in the solder during surface mounting, the voids can be removed. The size of can be suppressed.

A1 Peripheral area A11 First area A12 Second area A2 Central area A3 Extended area A4 Side area B Substrate (object to be coated)
N Non-applying area O Center P Pad (bonding area)
S Solder paste T Application area

Claims (11)

A method of applying solder paste to an object to be applied, which is used in a method of joining the object to be applied and the electronic component by performing reflow with solder paste applied between the object to be applied and the electronic component, ,
a step of applying solder paste to a coating area at least partially located within the bonding area of the object to be coated so as to form a non-coating area within the bonding area including the electrode;
The application area has a plurality of peripheral areas arranged at intervals in a circumferential direction around the center of the joining area, and a central area located radially inside the plurality of peripheral areas,
The ratio of the gaps between the plurality of peripheral regions, which open radially outward from the center of the joint region, to the entire circumference of the joint region is 11.5% or more and 80.6% or less (provided that 11.5% or more and 80.6% or less .5% or more and 16.7% or less). The method of applying solder paste according to claim 1, wherein the number of the plurality of peripheral areas is 2 to 6. The solder paste application method according to claim 1 or 2, wherein the plurality of peripheral areas are arranged at equal intervals in the circumferential direction. The plurality of peripheral regions have a first region and a second region having different lengths in the circumferential direction,
The solder paste application method according to any one of claims 1 to 3, wherein the first region and the second region are alternately arranged in the circumferential direction. 5. The solder paste application method according to claim 1, wherein opposing sides of the plurality of circumferential regions adjacent to each other in the circumferential direction are parallel to each other. 6. The solder paste application method according to claim 1, wherein opposing sides of the central region and each peripheral region are parallel to each other. 7. The solder paste application method according to claim 1, wherein the area of the central region is 44.4% or more and 278% or less of the area of each peripheral region. Application of the solder paste according to any one of claims 1 to 7 , wherein the area to which the solder paste is applied within the bonding area is 17.5% or more and 60.1% or less of the area of the bonding area. Method. The solder paste application method according to any one of claims 1 to 8 , wherein the plurality of peripheral areas are arranged to overlap an outer edge of the bonding area. The solder paste application method according to any one of claims 1 to 8 , wherein the plurality of peripheral areas are arranged within the bonding area. A mask used in the solder paste application method according to any one of claims 1 to 10 ,
A mask having an opening formed at a position corresponding to the application area.

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