JPH07302972A - Solder feed method - Google Patents

Abstract

PURPOSE:To provide a solder feed method in which solder is printed on a board by using a mask and in which the solder can be transferred stably and to provide a solder printing method which prevents a dislocation and a void from being generated and which forms a ball bump whose shape irregularity is small. CONSTITUTION:A mask 7 is placed on a board 4 in such a way that a pad 5 formed on the board 4 is aligned with an opening part 10 in the mask 7 (b). Then, a solder paste 9 is filled into the opening part 10 by using a squeegee 8 (c). While the mask 7 is being brought into contact with the board as it is, the board is heated by a hot plate 16 at a temperature which is lower than the melting point of solder (d). The mask is taken off from the board, and the solder paste is transferred to the pad 5 (e). In addition, the solder paste is melted, and a ball bump 6 is formed (f).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder supply method for soldering an electronic component to a printed circuit board, and particularly to B
The present invention relates to a solder supply method for forming a ball bump included in an electronic component such as a GA (Ball Grid Array).

[0002]

2. Description of the Related Art In the case of mounting electronic parts at a high density, electronic parts having ball bumps formed on a substrate plane have been used as electrodes. For example, FIG. 13 shows a perspective view of a BGA package component. Reference numeral 4 is a BGA substrate, 4a is a sealing resin in which electronic components such as LSI are sealed, 5 is a pad of the BGA substrate, and 6 is a ball bump which becomes an electrode of the BGA. The ball bumps 6 are arranged on a two-dimensional plane on the substrate 4, and the side on which the ball bumps 6 are arranged is mounted on, for example, another substrate.

As a method of forming a ball bump on the pad as described above, a ball setting method and a solder printing method are known. FIG. 14 shows a process diagram of forming a ball bump by the ball setting method. Reference numeral 1 is solder particles, 2 is a vacuum chuck for carrying the solder particles 1 by vacuum adsorption, and 3 is a flux, for example, that of Tamura Kaken RM-26 (RM type), and other reference numerals are the same as those in FIG. FIG. 14 (a)
As shown in, the solder particles 1 are vacuum chucked one by one.
Vacuum-adsorbs using flux 3 as shown in (b).
Is mounted on the pads on the BGA substrate 4 coated with.
After that, the solder bumps are heated and melted to form the ball bumps 6 (c).

Further, FIG. 15 shows a process diagram of forming a ball bump by a solder printing method. Reference numeral 7 is a printing mask, 8 is a squeegee, 9 is a solder paste containing solder, and 10 is an opening of the printing mask, which is opened at a position corresponding to a pad on which a ball bump is formed. The other symbols are the same as above. In FIG. 15A, the pad 5 and the opening 10
The print mask 7 is placed on the BGA substrate 4 so as to match with (b). As in (c), the opening is filled with the solder paste 9 using the squeegee 8. Thereafter, as shown in (d), the print mask 7 is removed from the BGA substrate 4, and the solder in the solder paste is heated and melted to form the ball bumps 6 (e).

Further, FIG. 16 shows a solder supply method disclosed in Japanese Patent Application Laid-Open No. 2-201996. 15A to 15C are similar to those in FIG. After filling the opening of the mask (metal screen in the publication) with solder paste,
Reflow the solder paste as it is (d). For example, when eutectic solder is used, it is heated at 150 ° C. for 3 minutes and 210 ° C. for 1 minute. Then, as shown in (e), the ball bump 6 is formed by removing the mask after cooling.

The solder paste is a mixture of solder particles and a resin (such as rosin) in a solvent (such as isopropyl alcohol). The solder paste shrinks by heating the solder paste. Then, the solder paste filled in the opening of the mask is separated from the wall surface of the opening due to this contraction, and the transfer amount of the solder is not shown in FIG.
It increases compared to the method.

[0007]

As described above, in the solder supply method based on the ball setting method (the method shown in FIG. 14), when the number of ball bumps increases, the time spent for ball setting increases in proportion to the number of ball bumps. . Therefore, in the case of BGA having a large number of I / O such as ASIC, the productivity is remarkably reduced. Further, since solder particles are mounted on the vacuum chuck, a certain amount of space is required between the ball bumps, making it difficult to form high-density ball bumps.

Further, the solder supply method by the solder printing method (method of FIG. 15) is superior in productivity as compared with the ball setting method, but the amount of transferred solder varies as shown in (d), and as a result, As shown in (e), the height of the ball bump 6 is insufficient and the variation becomes large. Therefore, when the amount of solder required for ball bump formation is transferred, the thickness of the opening is increased as much as possible so that more solder can be filled in the opening. However, the length of the opening of the opening (for example, if the opening is rectangular, the shortest side length,
If the thickness is circular, the solder transfer rate becomes worse as the thickness of the opening increases. On the contrary, if the opening area is increased in order to increase the transfer amount of solder, bumps on adjacent pads may be connected to each other when the solder is melted.

FIG. 15 (f) is a diagram showing the distribution of bump heights when ball bumps are formed by this solder printing method.
For BGA with 1mm pitch between pads, JEDEC
According to the standard, a bump with a height of 0.5 mm and a diameter of 0.6 mm (both with an allowable error range of ± 0.1 mm) is required, and it is extremely difficult to form a ball bump that meets this JEDEC standard. I understand.

FIG. 17 shows an LSI component such as QFP.
FIG. 16 is a process diagram of connecting (Quad-Flat-Package) to pads supplied with solder, but as shown in (a), solder is supplied in the same manner as in FIG. If there is a variation in the thickness, as shown in (b), after mounting the QFP 12 on the pad 5, the QFP 12 is connected by heating (c). Due to this variation in bump height, unsoldered defects 20 may occur in the connection portion, or even if they are connected, the joint strength may be insufficient. If the opening is made too large in order to compensate for the insufficient transfer amount of solder, adjacent solder will be connected during heating and a bridge defect will occur.

Further, with the method of FIG. 16, the transfer rate of solder can be increased, but the following problems occur. (1) When the positional displacement of the print mask with respect to the pad occurs, the positional displacement of the supplied solder occurs as it is. For example, FIG. 18 is a cross-sectional view showing how the bumps are displaced, and the bumps 6 are also displaced due to the displacement of the print mask. (2) Since the solder is influenced by the inner surface shape of the opening of the print mask, the shape and height of the ball bump formed after cooling are unstable. (3) Voids (voids) were generated in the solder by melting and cooling the solder paste with the mask attached. (4) By reflowing the solder paste with the print mask attached, the solvent in the solder paste evaporates,
The vaporized solvent is also generated between the solder and the pad, and there is a possibility that the solder is not joined to the pad as shown in FIG. (5) The print mask needs to be kept in close contact with the substrate until the solder reflows, the time required for the process is long, the productivity is poor, and automation is difficult.

The present invention has been made to solve the above problems, and provides a solder supply method capable of performing stable solder transfer onto a pad when supplying solder using a printing mask. It is intended for. It is another object of the present invention to provide a highly productive solder supply method capable of forming ball bumps having no variation in size and shape.

[0013]

According to the solder supply method of the present invention, the step of arranging the mask on the substrate and the step of arranging the mask on the substrate so that the openings of the mask and the pads formed on the substrate are substantially aligned. The method includes a step of filling the solder paste and a step of heating the solder paste at a temperature lower than the melting point of the solder in the paste while keeping the mask in close contact with the substrate to attach the solder paste to the pads.

Further, the step of placing the mask on the substrate, the step of filling the opening with solder paste, and the step of bringing the mask into close contact with the substrate so that the openings of the mask and the pads formed on the substrate are substantially aligned with each other. As it is, the steps include heating the solder paste to attach the solder paste to the pad, and removing the mask from the substrate with the solder fixed and then melting the solder.

Further, the step of placing the mask on the substrate, the step of filling the opening with solder paste, and the step of bringing the mask into close contact with the substrate so that the openings of the mask and the pads formed on the substrate are substantially aligned with each other. As it is, the solder paste filled in the opening with an aspect ratio (ratio of the depth of the opening to the shortest length of the opening of the mask) of 0.3 or more is heated to form a pad. It includes a step of attaching a solder paste.

Further, the step of placing the mask on the substrate, the step of filling the opening with solder paste, and the step of bringing the mask into close contact with the substrate so that the openings of the mask and the pads formed on the substrate are substantially aligned with each other. As it is, it includes a step of heating the solder paste to attach the solder paste to the pad, and a step of removing the mask from the substrate in a state where the solder is melted.

The step of disposing the first mask on the substrate so that the opening of the first mask substantially matches the pad formed on the substrate, and the opening of the second mask The step of disposing the second mask on the first mask so that the openings of the first mask substantially match, the step of filling the solder paste in the openings of the first and second masks, the second The method includes a step of removing the mask from the first mask, heating the solder paste while keeping the first mask in close contact with the substrate, and attaching the solder paste to the pad.

Further, at least the surface of the opening of the mask is covered with a fluororesin.

Further, the solder paste filled in the opening is irradiated with a heating beam to heat the solder paste.

[0020]

[Operation] According to the solder supply method configured as described above,
Since the solder paste filled in the opening of the mask is heated below the melting point of the solder in the solder paste, the solder does not melt, the resin in the solder paste melts and agglomerates, and the pad and solder are brought into close contact with each other. In addition, the solder paste filled in the opening is transferred onto the pad while suppressing the amount of solvent vaporized.

Further, the solder paste filled in the opening of the mask is heated to adhere the solder paste to the pad, the mask is removed from the substrate in a state where the solder is fixed, and then the solder is melted. The misalignment of the attached solder paste is corrected, and the void in the solder is eliminated.

Further, since the solder paste filled in the opening having an aspect ratio of 0.3 or more is heated, the solder paste which is difficult to be transferred from the opening can be heated and attached to the pad.

Further, since the mask is removed from the substrate while the solder is melted, the positional deviation of the solder paste attached to the pad is corrected and the void in the solder is eliminated.

Further, the second mask is arranged on the first mask so that the openings are substantially aligned with each other, the openings are filled with the solder paste, and the second mask is removed from the first mask to remove the first mask. Since the solder paste is heated while keeping the mask in close contact with the substrate, the mask for printing the solder paste and the mask for heating in close contact with the substrate are separate bodies, and the solder is filled in the openings to print. The step of heating and the step of heating while keeping the mask in close contact with the substrate are performed simultaneously.

Further, since at least the surface of the opening of the mask is covered with the fluororesin, the repelling between the surface of the opening and the solder becomes good.

Further, since the solder paste filled in the openings is heated by irradiating the heating beam, the mask portion is not heated and the temperature rise of the mask can be suppressed.

[0027]

【Example】

Example 1. An example of the present invention will be described below. FIG. 1 is a process diagram of a solder supply method and a ball bump forming method according to this embodiment. In the figure, 4 is a BGA substrate, 5 is B
Cu pad on GA substrate, 6 is a ball bump, 7 is a print mask, 8 is a squeegee, and 9 is a solder paste. Usually, solder and resin (for example, rosin) are mixed in a solvent (organic alcohol such as isopropyl alcohol). It is a thing. Reference numeral 10 denotes an opening that opens at a position corresponding to the position of the pad 5 on the print mask 7, and is opened at least larger than the area of the pad 5. 16 is a hot plate.

Next, a solder supplying method and a ball bump forming method will be described. As shown in FIG.
The print mask 7 is the Cu pad 5 formed on the BGA substrate 4.
Positioning is performed so that the opening 10 substantially coincides with (diameter 0.5 mm), and the print mask 7 and the substrate 4 are brought into close contact with each other as shown in (b). As shown in (c), the opening 10 is filled with the solder paste 9 using the squeegee 8. The print mask 7 is made of SUS having a thickness of 0.6 mm and has a diameter of 0.65 m.
A circular opening 10 of m is formed. Then
In (d), the print mask 7 is placed on the hot plate 16 while being in close contact with the BGA substrate 4 and heated. The heating is performed at a temperature lower than the melting point of the solder in the solder paste 9. For example, when eutectic solder (melting point 183 ° C.) is used, it is heated at 170 ° C. for 3 minutes. After cooling, as shown in (e), by removing the print mask 7, the solder paste 9 is transferred to and adheres to the pad 5. Further, the transferred solder paste 9 is melted (heated at 210 ° C. for 1 minute) to form the ball bump 6 (f).

FIG. 2 is an external view of the solder paste transferred to the pad in FIG. 1 (e). Figure 1 (d)
Then, by heating below the melting point of the solder containing the solder paste filled in the opening, the resin (rosin) in the solder paste melts without melting the solder and the solder paste filled in the opening Shrink and
The molten resin bonds the pad and the solder paste. Therefore, the shape of the opening is transferred as it is, leaving the solder paste inside the opening of the mask. In the figure, the cylindrical solder paste is transferred to the cylindrical opening. In addition, since the residual heat of the solder or less is heated, the amount of vaporized solvent in the solder paste is considerably reduced, so that bubbles of the solvent do not occur between the pad and the solder paste, and the bonding failure between the pad and the solder paste does not occur. As described above, the solder paste and the pad are bonded even if the solder is not reflowed and the solder melting point is lower than the melting point. Therefore, the heating time can be shortened and the productivity is improved.

Further, by designing the printing mask so that the opening area of the opening facing the pad is larger than the opening area of the opposite side (a cross-sectional view of the mask is shown in FIG. 3A). It is possible to easily bond the pad and the solder paste. Further, a cut (groove) smaller than the solder particles in the solder paste is formed on the side of the print mask that is in close contact with the substrate. A scribe 13 is formed on the mask surface as shown in FIG. The solvent in the solder paste can be released to this cut, and the vaporized solvent can be prevented from accumulating between the pad and the solder paste, thus facilitating the bonding between the pad and the solder paste.

FIG. 4 is a diagram showing the distribution of the heights of the ball bumps formed by reheating in FIG. 1 (f) (this figure shows the case where the pad pitch is 1 mm pitch).
Also, the height distribution of the ball bumps by the conventional ball bump forming method in which the solder paste is filled in the openings and then reflowed using the same printing mask is also shown. It is possible to form a ball bump that is higher than the conventional mask contact reflow method and has less variation in height. JEDEC standard (when the pad spacing is 1mm pitch, height 0.5mm, diameter 0.6mm, error ± 0.1m
m) is also sufficiently satisfied.

Further, FIG. 5A is a sectional view of the ball bump formed by the conventional method of FIG. 15, and FIG. 5B is a sectional view of the ball bump formed by this embodiment. When the positions of the openings of the mask and the pads are deviated, the solder paste is also deviated from the pads and transferred. In such a case, according to the conventional method, the ball bumps are formed by being misaligned as shown in (a). However, as in the present embodiment, even if the mask opening and the pad are misaligned by heating the mask at a temperature not higher than the melting point of the solder while closely adhering to the substrate, then removing the mask and melting the solder, The heating corrects the misalignment and successfully forms a ball bump on the pad (b). The void 6a in the ball bump is also eliminated by the method of this embodiment.

In this embodiment, the SUS printing mask is used, but it is also effective to use a material which does not easily get wet with solder, such as aluminum, nickel, ceramics, or fluororesin, as the mask material. Further, by using a material having a small coefficient of thermal expansion such as Invar for the mask, the thermal expansion of the mask is suppressed by heating and the positional deviation is prevented.

Although the hot plate is used as the heating method, if a halogen lamp, a xenon lamp, a carbon dioxide gas laser or the like is used, the time required for heating can be shortened and the warp of the mask can be suppressed. Further, when heating is performed by irradiating a beam with a laser, by squeezing the laser to irradiate a portion smaller than the opening, heating of the mask is suppressed as much as possible, and thermal displacement of the mask and displacement due to warpage are prevented. .

Although the solder paste was used for supplying the solder, it is also possible to use a material such as a Cu paste or an Ag paste, which has conductivity and can be printed by heating after filling the opening of the mask. .

Example 2. FIG. 6 is a process diagram of the solder supply method and the ball bump forming method in this embodiment. In the figure, the reference numerals are the same as in Example 1, the mask 7 has, for example, a thickness of 0.6 mm, and its opening 10 has a diameter of 0.65 mm with respect to the corresponding pad (circle having a diameter of 0.5 mm).
It has a circular shape. The ball bump forming method will be described. 6A to 6C show the same steps as in the first embodiment. Then, as shown in (d), the print mask 7 is applied to the BGA.
It is placed on the hot plate 16 while being in close contact with the substrate 4 and heated at a temperature equal to or higher than the melting point of the solder in the solder paste for reflow. When eutectic solder (melting point 183 ° C.) is used, it is heated at 150 ° C. for 3 minutes and 210 ° C. for 1 minute. After cooling, the print mask 7 is removed to form the ball bumps 6 as shown in (e).

FIG. 7 shows various aspect ratios (with respect to the minimum length of the opening) when solder is printed on a printing mask, the printing mask is removed from the substrate as it is without heating, and the solder is transferred to the pad. FIG. 8 is a data diagram showing a transfer rate of (a thickness of an opening) to the opening. Here, the transfer rate represents the volume of the transferred solder with respect to the volume of the opening. A SUS mask was used as the print mask. As shown in the figure, when the aspect ratio is 0.3 or more, the transfer rate remarkably decreases. However, by heating the solder paste filled in the openings having an aspect ratio of 0.3 or more as in step (d) of FIG.
Solder was transferred to the pads at a transfer rate of 0% (not shown in Figure 7). In FIG. 6, the aspect ratio is 0.92 (= 0.6
mm / 0.65 mm) opening is used, and the solder paste is successfully transferred by heating. On the other hand, when the aspect ratio is less than 0.3, transfer is performed without heating.

FIG. 8 shows that when the solder bump filled in the openings as shown in FIG. 6 is heated, and the ball bumps are formed by removing the printing mask after cooling, the ball bumps for the openings having various aspect ratios are formed. It is the data figure which showed the ratio of formation. Here, the rate of ball bump formation represents the ratio of the number of ball bumps satisfying the JEDEC standard to the number of ball bumps formed by openings having a certain aspect ratio. A SUS mask was used as the print mask. According to the conventional method in which the printing mask is removed after the openings are filled with solder and then the ball bumps are formed by heating, the ratio is almost zero when the openings having the aspect ratio of 0.3 or more are used. (Not shown in FIG. 8). However, according to the method of this embodiment (the method of FIG. 6), the rate of ball bump formation was considerably improved. However, the aspect ratio is 1.0
If it becomes above, the ratio of the formed bump will become remarkably small. This can be improved by using a fluororesin as the mask material, but when the aspect ratio becomes 2.0 or more, the rate of ball bump formation becomes small again. As described above, the maximum aspect ratio of the opening of the print mask for forming the ball bump is preferably 2.0. Particularly, according to the method of this embodiment, the aspect ratio of 0.3 or more and 2.0 or less is obtained. Masks with specific openings are preferred.

FIG. 9 shows a process diagram of forming ball bumps and mounting an LSI component on the substrate on which the ball bumps are formed. 7 is a 0.15 mm thick SUS printing mask, 12
a and 12b are LSI parts and are QFPs. QFP12
a and 12b are 0.3 mm pitch and 0.65 mm, respectively
It has pitched electrodes. Reference numeral 15 is a halogen light beam for heating the solder plague. 10c is QFP
In the opening formed in the print mask 7 corresponding to 12a,
The opening has a rectangular shape of 0.15 mm × 1.2 mm. On the other hand, 10d is an opening formed in the print mask 7 corresponding to the QFP 12b, and the opening is 0.55 mm × 1.5 m.
Make a rectangle of m. In FIG. 9A, the pad 5 and the opening 10
The print mask 7 is placed on the substrate 4 while aligning c and 10d.
In close contact with. The opening 10 is formed by using the squeegee 8 in (b).
The solder paste 9 is filled in a and 10b. (C)
As described above, the opening 10c is irradiated with the halogen light beam 15 to heat the solder paste (200 ° C. for 1 minute). Alternatively, a laser is used to irradiate the beam only to the solder paste filled in the openings. The print mask 7 is removed in (d). Further, as in (e), the QFP 12a,
12b is mounted on a predetermined pad and soldered as it is in a reflow furnace.

The aspect ratio of the opening 10c is 1.0,
On the other hand, the aspect ratio of the opening 10d is 0.27. The solder paste filled in the opening 10d is directly transferred onto the pad without heating, but when the solder paste in the opening 10c is not heated, a part of the solder paste remains in the opening 10c. However, by heating the opening 10c in this manner, all the solder paste is transferred. By selectively heating the solder paste in the openings that are difficult to be transferred in this way, reliable and efficient transfer of solder becomes possible. Further, the heating amount can be reduced and the heating time can be shortened by selectively heating rather than by heating the entire opening, thus improving the productivity. As shown in FIG. 7, it is preferable to heat the solder paste of the opening having an aspect ratio of 0.3 or more. Further, when a predetermined amount of solder is not printed on the pad, when mounting an electronic component such as an LSI component, the height of the formed bump may vary, which may lead to a joint failure. Since uniform solder transfer is possible, defective joints can be prevented.

In this embodiment, the heating is performed above the melting point of the solder, but the heating may be performed below the melting point as in the first embodiment.

Example 3. In FIG. 6 of the second embodiment, the solder paste 9 is heated, and after cooling, the print mask 7 is attached to the BGA substrate 4
Although it was removed from the print mask 7 in FIG.
The print mask 7 may be placed on the hot plate 16 while being in close contact with the substrate 4 and heated at 150 ° C. for 3 minutes and 210 ° C. for 1 minute, and the print mask 7 may be removed while the solder is melting in (e). Then, the ball bumps 6 can be formed by cooling as it is. In this case, since the printing mask 7 is removed during the melting of the solder, even if the solder is transferred onto the pad while being displaced, the molten solder becomes spherical while correcting the displacement due to its surface tension. , Ball bumps are formed. In addition, the generation of voids is prevented, and the mask is removed before the solder is solidified, so that the contact time of the mask can be reduced, so that the yield and the productivity can be prevented from lowering.

Example 4. FIG. 10 is a process drawing of the method for forming the ball bumps shown in this embodiment. FIG. 6 of Example 2
In (e), the BGA substrate 4 on which the ball bumps 6 are formed is reheated to melt the ball bumps 6. Figure 10 (a)
Then, the flux 3 (Tamura Kaken RM-26; RM type) is applied on the BGA substrate 4 (this is for facilitating melting of the oxide film formed on the surface of the ball bump), (b) 21 on the hot plate 16 like
Heat at 0 ° C. for 1 minute.

Even if the ball bump formed in FIG. 6 of the second embodiment is misaligned and formed on the pad, this misalignment is corrected by reheating as described above. In addition, as shown in FIG. 10A, the shape of the ball bump formed in FIG. 6E is not spherical but is similar to the shape of the opening of the print mask before reheating. (For example, if the opening is cylindrical, the formed bump is also cylindrical). By this reheating, the bump shape can be made closer to a true sphere. FIG. 11 is a data diagram showing the distribution of the heights of the ball bumps formed before and after the reheating when forming a plurality of ball bumps on a plurality of BGA substrates. It is represented by the number of individual ball bumps to be formed with respect to the height (μm) of the ball bumps. Before the reheating, the ball bump height varies, but the reheating reduces the variation in height (the bump height is formed in the vicinity of 490 to 499 μm). At the same time, voids 6a are formed in the solder bumps as shown in FIG.
Even if occurs, the mask is removed and reheating is performed, so the void escapes to the outside and is successfully resolved.

Example 5. FIG. 12 is a process drawing of the solder supply method and the ball bump forming method shown in this embodiment. In the figure, 7a is a template serving as a first mask, 7b
Is a print mask which serves as a second mask, 10a and 10b are a template 7a, an opening of the print mask 7b, and 1 respectively.
4 is a fixing member for fixing the template 7a to the substrate,
For example, wood screws are used. Other symbols are the same as those in the first embodiment.

Next, a solder supply method and a ball bump forming method will be described. As shown in FIG. 12A, the template 7a is previously fixed so as to be in close contact with the substrate 4 so that the pad 5 and the opening 10a are aligned with each other. In the figure, it is fixed using wood screws 14. As shown in (b), the opening 10
the template 7 so that a and the opening 10b match.
The print mask 7b is brought into close contact with a. Here, the template 7a is made of SUS having a thickness of 0.5 mm and has a diameter of 0.65 m.
m openings. On the other hand, the print mask 7b has a thickness of 0.1.
It is made of SUS of mm and has an opening with a diameter of 0.65.
Solder paste 9 using squeegee 8 as in (c)
Is filled in the openings 10a and 10b. Thereafter, as shown in (d), the print mask 7b is removed, and as shown in (e), it is placed on the hot plate 16 and heated. When eutectic solder having a melting point of 183 ° C. is used, it is heated at 150 ° C. for 3 minutes and 210 ° C. for 1 minute. After cooling, the template 7a is removed to form ball bumps.

When solder printing is automated, solder printing is performed using a printing machine in which a nozzle (not shown) for supplying solder paste and a printing mask 7b are integrated. When there is no template 7a, the printing mask 7b provided in the printing machine is brought into close contact with the substrate, solder is printed, and then heated. However, the print mask must remain in intimate contact with the substrate during heating and the printer cannot be used for solder printing on other substrates during heating. Therefore, productivity is not good. However, if the template 7a is brought into close contact with the substrate in advance as in the present embodiment and then the solder paste is printed by a printing machine having the printing mask 7b, the printing machine only needs to be brought into close contact with the substrate only when printing the solder paste. The inside is removed from the substrate, and the template 7a remains in close contact with the substrate. The printer can perform solder printing on other substrates one after another when heated. Therefore, a process for automation using a printing machine is prepared, and productivity can be dramatically improved.
In addition, no excess solder paste remains on the template 7a, and the excess solder paste is not supplied more than necessary to the pad of the substrate by heating.

In this embodiment, the wood screw is used to fix the template, but it is also possible to use a ratchet screw or a load for close contact. When heating, the solder paste may be heated at a temperature lower than the melting point of the solder and adhered to the pad as in the first embodiment.

Example 6. In addition, Embodiments 1 to 5
So, I used a SUS mask as a print mask.
A mask made of S may be covered with a fluororesin.
By coating with a fluororesin, the repelling of the solder is improved and transfer from the print mask onto the pad is facilitated. Further, as shown in FIG. 8, when the ball bumps are formed using the fluororesin-coated printing mask, the rate of ball bump formation is improved and the aspect ratio is 1. Even if 0 or more openings are used, the occurrence of defective bump formation can be suppressed.

[0050]

As described above, according to the solder supply method of the first aspect, the step of filling the opening portion of the mask with the solder paste, and the solder melting point in the solder paste while the mask is kept in close contact with the substrate. Since it includes the step of heating the solder paste at a lower temperature and attaching the solder paste to the pad, it is possible to suppress the evaporation amount of the solvent in the solder paste at the time of heating, and it is possible to suppress the evaporation between the pad and the solder paste on the board. There is an effect that stable solder transfer can be performed on the pad without the accumulation of the bubbles.

According to the solder supply method of the second aspect, the solder paste filled in the opening of the mask is heated to adhere the solder paste to the pad, and the mask is removed from the substrate with the solder fixed. Then, since the solder is melted after that, there is an effect that a solder bump having no displacement or void is formed, and the yield can be improved.

According to the solder supply method of the third aspect, the aspect ratio (ratio of the depth of the opening to the shortest length of the opening of the mask) of the opening is 0 while the mask is kept in close contact with the substrate. Since the solder paste filled in the openings formed in 3 or more is heated, the solder paste filled in the openings is hard to be transferred and the solder paste can be stably transferred onto the pad. Produce an effect.

According to the solder supply method of the fourth aspect, since the solder paste is heated while the mask is in close contact with the substrate and the mask is removed from the substrate in a state where the solder is melted, there is no displacement or void. Solder bumps are formed, and the yield can be improved.

According to the solder supply method of the fifth aspect, the first mask is arranged on the substrate, and the opening of the second mask and the opening of the first mask are substantially aligned with each other. A step of arranging the second mask on the first mask, a step of filling the solder paste in the first and second openings, a step of removing the second mask from the first mask, and a step of placing the first mask on the substrate. Since it includes the step of heating the solder paste while adhering to the substrate and adhering the solder paste to the pad, while the second mask is being adhered to the substrate and the substrate is heated while being adhered to the substrate, The solder paste can be transferred, productivity can be improved, process design can be performed for automation, and for example, a printing machine having the above-mentioned first mask can be used.

Further, according to claim 6, since at least the surface of the opening of the mask is covered with the fluororesin, the solder paste supplied from the surface of the opening to the opening can be repelled by the fluororesin, and the solder is opened. The effect is that it can be transferred to the substrate without being left inside.

According to the seventh aspect, the solder paste is heated by irradiating the solder paste filled in the opening with a heating beam, so that the mask does not increase in temperature and prevents thermal expansion. The effect of suppressing the positional deviation between the pad position of the substrate and the opening is obtained.

[Brief description of drawings]

FIG. 1 is a process diagram of a solder supply method according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the solder paste transferred onto the pads of the substrate in the first embodiment.

3A and 3B are a cross-sectional view of an opening of a mask described in Example 1 and a perspective view of a cut formed on a mask surface.

FIG. 4 is a height distribution diagram of ball bumps formed by the solder supply method in Example 1.

5 is a sectional view of a ball bump formed by a solder supply method in Example 1. FIG.

FIG. 6 is a process diagram of a solder supply method shown in a second embodiment of the present invention.

FIG. 7 is a data diagram showing a paste transfer rate with respect to an aspect ratio of a mask opening in Example 2.

FIG. 8 is a data diagram showing a bump formation ratio with respect to an aspect ratio of a mask opening in Example 2.

FIG. 9 is a process diagram for forming a solder bump and mounting an electronic component according to the second embodiment.

FIG. 10 is a process drawing of the solder supply method according to the fourth embodiment of the present invention.

FIG. 11 is a height distribution diagram of ball bumps formed by the solder supply method in Example 4.

FIG. 12 is a process drawing of a solder supply method shown in a fourth embodiment of the present invention.

FIG. 13 is a perspective view of a BGA mounted component.

FIG. 14 is a process diagram of a method of forming a ball bump according to a conventional technique.

FIG. 15 is a process drawing of another ball bump forming method according to the related art.

FIG. 16 is a process drawing of another ball bump forming method according to the prior art.

FIG. 17 is a process diagram for forming a ball bump and mounting an electronic component according to a conventional technique.

FIG. 18 is a sectional view of a ball bump formed by a conventional technique.

[Explanation of symbols]

4 ... Substrate 5 ... Cu pad 6 ... Ball bump 6a ...
Void 7 ... Printing mask 7a ... Template 8 ... Squeegee 9 ... Solder paste 10 ... Mask opening
11 ... Printed circuit board 12 ... QTP 13 ... Cutting
14 ... Fixing member 15 ... Halogen light beam 16 ... Hot plate 17 ... Fluorine resin

Claims (7)

[Claims] 1. A step of arranging the mask on the substrate so that an opening of the mask and a pad formed on the substrate are substantially aligned, a step of filling the opening with a solder paste, and the mask While keeping it in close contact with the substrate,
A solder supply method comprising the step of heating the solder paste at a temperature lower than the melting point of the solder in the solder paste to attach the solder paste to the pads. 2. A step of arranging the mask on the substrate so that an opening portion of the mask and a pad formed on the substrate are substantially aligned, a step of filling the opening portion with a solder paste, and the mask While keeping it in close contact with the substrate,
Solder supply characterized by including a step of heating the solder paste to attach the solder paste to the pad, a step of removing the mask from the substrate in a state where the solder is fixed, and then melting the solder. Law. 3. A step of arranging the mask on the substrate such that an opening of the mask and a pad formed on the substrate are substantially aligned, a step of filling the opening with a solder paste, and the mask While keeping it in close contact with the substrate,
Of the openings, the solder paste filled in the openings having an aspect ratio (ratio of the depth of the openings to the shortest length of the openings of the mask) of 0.3 or more is heated and soldered to the pads. A solder supply method comprising a step of attaching a paste. 4. A step of arranging the mask on the substrate so that an opening portion of the mask and a pad formed on the substrate are substantially aligned, a step of filling the opening portion with a solder paste, and the mask While keeping it in close contact with the substrate,
A solder supplying method comprising: a step of heating the solder paste to attach the solder paste to the pad; and a step of removing the mask from the substrate in a state where the solder is melted. 5. The step of arranging the first mask on the substrate so that the opening of the first mask substantially coincides with the pad formed on the substrate, and the opening of the second mask. And placing the second mask on the first mask so that the openings of the first mask and the openings of the first mask substantially match, and filling the openings of the first and second masks with solder paste. Step, including removing the second mask from the first mask, and while keeping the first mask in close contact with the substrate, heating the solder paste, and attaching the solder paste to the pad A solder supply method characterized by the above. 6. The solder supply method according to claim 1, wherein at least the surface of the opening of the mask is covered with a fluororesin. 7. The solder paste filled in the opening is heated by irradiating the solder paste with a heating beam to heat the solder paste. Solder supply method.