JPH08236921A - Method for soldering electronic parts - Google Patents

Abstract

PURPOSE: To surely solder electronic parts having warps or carrying bumps of different sizes to a printed board together with ordinary electronic parts carrying no bump. CONSTITUTION: On a printed board 1, small electrodes 5 to which the bumps 12 of electronic parts 10 carrying the bumps 12 are soldered and large electrodes 6 to which ordinary electronic parts 13 carrying no bump are soldered are provided. Cream solder is applied to the electrodes 5 and 6 by means of a screen printing device. The cream solder is applied to the small electrodes 5 by small amounts. Then the bumps 12 are put on the cream solder 4 applied to the small electrodes 5 and electrodes 14 are put on the cream solder 4 applied to the large electrodes 6. When the printed board 1 is heated in a heating furnace for reflowing the cream solder 4, the solder 4 and bumps 12 melt and the electronic parts 10 carrying the bumps 12 and electronic parts 13 carrying no bump are surely soldered to the small electrodes 5 and large electrodes 6, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for soldering electronic components having bumps and electronic components having no bumps, which are mixed and soldered on a printed board.

[0002]

2. Description of the Related Art Electronic components with bumps (protruding electrodes) are advantageous in increasing the density and integration of printed circuit boards, and have been increasingly used in many electronic devices in recent years. Hereinafter, a conventional soldering method in which an electronic component with bumps and an ordinary electronic component without bumps are mixedly mounted on a printed board and soldered will be described.

6 (a), (b), (c) and (d) are explanatory views showing a conventional method of soldering an electronic component in the order of steps.
In FIG. 6A, 1 is a printed circuit board, which is in contact with the lower surface of the screen 2 of the screen printing apparatus.
By sliding the squeegee 3 on the screen 2,
The cream solder 4 is applied onto the electrodes provided on the upper surface of the printed board 1 through the pattern holes formed in the screen 2.

As shown in FIG. 6B, the printed circuit board 1
A small electrode 5 for soldering an electronic component with bumps and a large electrode 6 for soldering a normal electronic component without bumps are provided on the upper surface of the above. However, in the process of FIG.
The cream solder 4 is applied only on the large electrode 6, and the cream solder 4 is not applied on the small electrode 5. Then, the flux 8 is applied onto the small electrode 5 by the dispenser 7.

Next, as shown in FIG. 6C, the bumped electronic component 10 is mounted on the small electrode 5. This mounting is performed by the mounting machine. The bumped electronic component 10 includes a large number of bumps 1 on the lower surface of the substrate on which the molded body 11 is formed.
2 are formed by projecting, and the bumps 12 are landed and mounted on the small electrodes 5. The bump 12 is made of solder. Further, a normal electronic component 13 is mounted on the large electrode 6. The electronic component 13 is, for example, a resistor chip or a chip capacitor, and has electrodes 14 on both sides thereof, and the electrodes 14 are mounted on the cream solder 4 applied to the large electrode 6 by landing.

As described above, the electronic component 10 with bumps is provided.
After the normal electronic component 13 is mixedly mounted on the printed circuit board 1, the printed circuit board 1 is then sent to a reflow heating furnace (not shown) to heat the printed circuit board 1 to a temperature above the melting temperature of the cream solder 4 and the bumps 12. . Then, the cream solder 4 and the bumps 12 are melted, and when the printed board 1 is subsequently cooled, the melted cream solder 4 and the bumps 12 are solidified, and the electronic component 10 with bumps and the electronic component 13 are solidified as shown in FIG. 6D. Are soldered to the printed circuit board 1.

[0007]

As shown in FIG. 6C, the bumped electronic component 10 often has a warp. Further, the bumps 12 have variations in size. Therefore, especially when the size of the bumps 12 on both sides is small, the bumps 12 on both sides float up from the small electrode 5 and are difficult to be soldered to the small electrode 5, as shown in FIG. 6D. Was.

Therefore, an object of the present invention is to provide a soldering method of an electronic component which can surely solder a bumped electronic component together with an ordinary electronic component having no bump to a printed circuit board.

[0009]

To this end, the present invention provides a step of applying a cream solder by screen printing on an electrode provided on the upper surface of a printed circuit board, and bumps on the cream solder applied on the electrode. The steps of landing and mounting the bumps of the electronic component and the electrodes of the electronic component, and the step of heating the printed circuit board to melt and solidify the cream solder and the bumps for soldering were configured.

In applying the cream solder to the electrodes on which the bumps are mounted, the application area of the cream solder is made smaller than the area of the electrodes, and a small amount of the cream solder is applied.

[0011]

According to the above structure, since the cream solder is applied to the electrodes to which the bumps of the electronic component with bumps are soldered, the electronic component with bumps is warped, or the size of the bumps on both sides is increased. Even when the size is small, the bump can land on the cream solder on the electrode and be reliably soldered. Also, by applying a small amount of cream solder,
It is possible to prevent the occurrence of bridges due to excess solder.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. 1 (a), (b), (c), and (d) are explanatory views showing a method of soldering an electronic component according to an embodiment of the present invention in the order of steps. The same elements as those in the conventional example shown in FIG. 6 are designated by the same reference numerals.

First, as shown in FIG. 1A, the printed circuit board 1 is brought into contact with the lower surface of the screen 2 of the screen printing apparatus, and a squeegee 3 is slid on the screen 2 to reduce the size of the upper surface of the printed circuit board 1. The cream solder 4 is applied on the electrode 5 and the large electrode 6 through pattern holes. FIG.
(B) is a printed circuit board 1 coated with cream solder 4
Is shown.

Next, as shown in FIG. 1C, a mounting machine mounts the electronic component 10 with bumps and the normal electronic component 13 having no bumps on the printed board 1. As shown in the figure, the bumped electronic component 10 is mounted with the bump 12 landing on the cream solder 4 on the small electrode 5, and the normal electronic component 13 has the electrode 14 on the cream solder 4 on the large electrode 6. It will be mounted on the ground.

As described above, the electronic component 10 with bumps is provided.
After the normal electronic component 13 is mixedly mounted on the printed circuit board 1, the printed circuit board 1 is then sent to a reflow heating furnace (not shown) to heat the printed circuit board 1 to a temperature above the melting temperature of the cream solder 4 and the bumps 12. . Then, the cream solder 4 and the bumps 12 are melted, and then when the printed circuit board 1 is cooled, the melted cream solder 4 and the bumps 12 are solidified, and the electronic component 10 with bumps and the electronic component 13 are solidified as shown in FIG. 6D. Are soldered to the printed circuit board 1.

As described above, the electronic component 10 with bumps is provided.
Has a warp, and the size of the bump 12 varies. However, in this method, the cream solder 4 is applied also on the small electrodes 5, and the bumps 12 are landed on the cream solder 4.
By this, it is surely soldered to the small electrode 5 of the printed circuit board 1, and as a result, as shown in FIG.
A warp of 0 is corrected.

FIG. 5 is an explanatory view of a method of soldering an electronic component according to an embodiment of the present invention. As shown in FIG. 5, a printed circuit board 1 on which an electronic component 10 with bumps and an electronic component 13 are soldered. The probe 20 is brought into contact with the pad 21 to make it conductive, and the inspection device 22 inspects the electrical performance of the printed circuit board 1. If the printed circuit board 1 is normal, it is sent to the next step, and if it is defective, it is collected. By performing an electrical performance inspection of the printed circuit board 1 thus soldered, only good products can be selected and a high quality printed circuit board 1 can be provided.

By the way, when the amount of cream solder 4 applied on the small electrode 5 is large, the amount of solder (the sum of the amount of solder by the bump 12 and the amount of solder by cream solder) becomes excessive and the amount of cream solder 4 and the bump 12 becomes large. When melted, bridging is likely to occur. Therefore, next, a method of eliminating the occurrence of the bridge will be described.

FIG. 2 is a partially enlarged sectional view of a screen and a printed circuit board according to an embodiment of the present invention, FIGS. 3 (a) and 3 (b) are plan views of a small electrode and a large electrode of the printed circuit board, and FIG. 4 (a).
(B) is a side view of the small electrode and the large electrode. As shown in FIG. 2, the size of the pattern hole 2b of the screen 2 corresponding to the large electrode 6 is completely or almost equal to the size of the large electrode 6, but the size of the pattern hole 2a corresponding to the small electrode 5 is small. Smaller than size 5.

Therefore, when the squeegee 3 is slid on the screen 2 and the cream solder 4 is applied to the small electrode 5 and the large electrode 6 through the pattern holes 2a and 2b, as shown in FIGS. A large amount of the cream solder 4 is applied on the electrode 6 over its area, but a small amount of the cream solder 4 is applied on the small electrode 5 in an area smaller than the area of the small electrode 5. In this way, if the area of the cream solder 4 applied is smaller than the area of the small electrode 5 and a small amount of the cream solder 4 is applied, the amount of solder is reduced and the occurrence of bridges can be prevented.

[0021]

As described above, according to the present invention, even if the electronic component with bumps is warped or the dimensions of the bumps are uneven and the dimensions of the bumps on both sides are small, the bumps are provided. It can be securely soldered to the electrodes of the printed circuit board together with the electronic components. Further, by applying a small amount of cream solder, it is possible to prevent the occurrence of bridges due to excess solder.

[Brief description of drawings]

FIG. 1A is an explanatory view showing a method for soldering an electronic component according to an embodiment of the present invention in order of steps. FIG. 1B is an explanatory view showing a method for soldering an electronic component according to an embodiment of the present invention in order of a step. ) An explanatory view showing a method of soldering an electronic component according to one embodiment of the present invention in the order of steps (d) An explanatory view showing a method of soldering an electronic component according to one embodiment of the present invention in a order of the steps

FIG. 2 is a partially enlarged sectional view of a screen and a printed circuit board according to an embodiment of the present invention.

3A is a plan view of a small electrode and a large electrode of a printed circuit board according to an embodiment of the present invention. FIG. 3B is a plan view of a small electrode and a large electrode of a printed circuit board according to an embodiment of the present invention.

FIG. 4A is a side view of a small electrode and a large electrode of a printed circuit board according to an embodiment of the present invention. FIG. 4B is a side view of a small electrode and a large electrode of a printed circuit board according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a soldering method for electronic components according to an embodiment of the present invention.

6A is an explanatory view showing a conventional electronic component soldering method in order of steps. FIG. 6B is an explanatory view showing a conventional electronic component soldering method in order of steps. FIG. 6C is a conventional electronic component soldering method. Explanatory drawing which shows in order of process (d) Explanatory drawing which shows the soldering method of the conventional electronic component in order of process

[Explanation of symbols]

 1 Printed Circuit Board 2 Screen 3 Squeegee 4 Cream Solder 5 Small Electrode 6 Large Electrode 10 Electronic Component with Bump 12 Bump 13 Electronic Component

Claims (4)

[Claims] 1. A soldering method for an electronic component, wherein an electronic component with bumps having bumps and an electronic component having no bumps are mixedly mounted on a printed circuit board and soldered, and an electronic component is provided on an electrode provided on an upper surface of the printed circuit board. Applying cream solder by screen printing, landing and mounting the bumps of the electronic component with bumps and the electrodes of the electronic component on the cream solder applied on the electrodes, and heating the printed circuit board. And a step of soldering by melting and solidifying the cream solder and the bumps, and a soldering method for an electronic component. 2. When applying the cream solder to the electrodes on which the bumps are mounted, the application area of the cream solder is made smaller than the area of the electrodes and a small amount of the cream solder is applied. A method for soldering the described electronic component. 3. A soldering method for an electronic component, wherein an electronic component with bumps having bumps and an electronic component having no bumps are mixedly mounted on a printed circuit board and soldered, and the method is provided on an electrode provided on an upper surface of the printed circuit board. Applying cream solder by screen printing, landing and mounting the bumps of the electronic component with bumps and the electrodes of the electronic component on the cream solder applied on the electrodes, and heating the printed circuit board. And then soldering by melting and solidifying the cream solder and the bumps; and an electrical performance inspection of the printed circuit board to which the electronic component with bumps and the electronic component without bumps are soldered And a method of soldering an electronic component, comprising: 4. When applying cream solder to the electrodes on which the bumps are mounted, the application area of the cream solder is made smaller than the area of the electrodes and a small amount of the cream solder is applied. A method for soldering the described electronic component.