JPH118468A - Mounting method of electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the mounting method of an electronic component by which precoat solder layers having proper thicknesses corresponding to a mounted electronic component can be formed stably on the electrodes of a board. SOLUTION: Solder balls 7 and 8, which have different diameters corresponding to electrodes 2 and 3 formed on a board 1 and having different sizes corresponding to the type and size of a mounted electronic component, are transferred onto the respective electrodes 2 and 3 by suction tools 11 and 12. After that, the solder balls 7 and 8 are melted by heating the board 1 to form precoat solder layers 7' and 8' on the electrodes 2 and 3. The electronic component is mounted by soldering with the precoat solder layers 7' and 8'. By selecting the sizes of the solder balls, the precoat solder layers 7' and 8' with proper thicknesses corresponding to the electronic component can be formed stably with high efficiency and moreover without variations in the film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting an electronic component on a substrate.

[0002]

2. Description of the Related Art As a method for mounting an electronic component on a substrate,
2. Description of the Related Art There is known a method of soldering an electronic component using a solder layer formed in advance on an electrode of a substrate, so-called precoat solder. As a method for forming pre-coated solder, a method using solder plating has been widely practiced.

[0003]

There are cases where a plurality of electronic components of different sizes and types are soldered to the same substrate. In such a case, it is desirable that the precoat solder formed on the electrode to which the electronic component is soldered has an appropriate solder film thickness according to the type and size of each electronic component.

However, in the method using solder plating, since the thickness of the solder plating formed on the surface of the electrode is almost the same for the same substrate, a pre-coated solder having a solder film having a different thickness depending on the electrode is formed. Can not do it. Also, solder plating has many problems when applying pre-coated solder by solder plating to the mounting of electronic components, such as the absolute value of the thickness of the solder film that can be formed at one time is small, and the thickness varies widely depending on the plating conditions. There was a point.

Accordingly, the present invention provides a method of mounting an electronic component capable of stably forming a pre-coated solder having an appropriate solder film thickness according to the type and size of the electronic component mounted on an electrode of a substrate. The purpose is to provide.

[0006]

According to the present invention, there is provided a method for mounting an electronic component, comprising the steps of: transferring solder balls of different sizes to the electrodes of a substrate in accordance with the size of the electrodes; Forming pre-coated solder on the electrodes, transferring a plurality of electronic components of different types and sizes on the pre-coated solder, and heating the substrate on which the electronic components have been transferred to form the pre-coated solder. Melting and soldering the electronic component to an electrode of the substrate.

[0007]

According to the present invention having the above structure, solder balls of different sizes are transferred onto the electrodes of a substrate, and the solder balls are melted and solidified by heating to form the solder balls on the electrodes. By forming the pre-coated solder, it is possible to stably form a pre-coated solder having an appropriate solder film thickness according to the type and size of the electronic component.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a solder ball transfer device according to an embodiment of the present invention, and FIGS. 2 (a), (b), (c), 3 (a), (b), (c) FIG. 3 is an explanatory view of a process of the electronic component mounting method.

First, the structure of a solder ball transfer device will be described with reference to FIG. In FIG. 1, a plurality of electrodes 2 and 3 having different sizes are formed on a substrate 1. One electrode 2 is larger than the other electrode 3. The substrate 1 is held by two parallel rails 4. On the front side of the rail 4, supply units 5 and 6 for two solder balls are provided. Solder balls 7 and 8 of different sizes are stored inside the supply units 5 and 6. Behind the rail 4, a flux application section 9 is provided. Coating section 9
Is composed of a thin box, in which a flux 10 is stored.

A transfer head 13 is provided above the substrate 1. A plurality of suction tools 11 and 12 corresponding to different types of solder balls are mounted on the transfer head 13. The suction tools 11 and 12 are moved up and down by vertical moving means built in the transfer head 13, and vacuum pick-up the solder balls 7 and 8 by suction holes provided on the lower surface thereof to pick up. The transfer head 13 is mounted on an X table 17 via a bracket 14, and the X table 17 is mounted on a pair of left and right Y tables 16.
X table 17 and Y table 1 which are movable tables
6, the transfer head 13 moves in the horizontal direction.

This solder ball transfer device has the above-described configuration. Next, the operation will be described with reference to FIG. First, the X table 17 and the Y table 16 are driven to move the transfer head 13 above the supply units 5 and 6. Next, the vertically moving means of the transfer head 13 is driven to drive the suction tool 11,
12 is lowered into the supply units 5 and 6, respectively. When the suction tools 11 and 12 suction the solder balls 7 and 8 by vacuum, the transfer head 13 is raised, and the X table 17 and the Y table 16 are driven again to move the transfer head 13 above the flux applying section 9. . Next, the suction tools 11 and 12 are lowered, and the solder balls 7 and 8 vacuum-adsorbed to the lower ends of the suction tools 11 and 12 are brought into contact with the surface of the flux 10 stored in the solder application section 9. As a result, the flux 10 is applied to the tips of the solder balls 7 and 8. Thereafter, the transfer head 13 rises again, moves above the rail 4, and waits.

Next, the substrate 1 is transported and held between the rails 4. Electrodes 2 and 3 having different sizes are formed on the substrate 1 according to the type and size of the electronic component to be mounted. When the transfer head 13 is positioned with respect to the substrate 1 and the suction tools 11 and 12 move up and down, the solder balls 7 having different sizes according to the electrodes 2 and 3 are placed on the electrodes 2 and 3 of the substrate 1. 8 is transferred. FIG. 2A shows a state in which the suction head 13 sucks the solder balls 7 and 8 having different sizes on the suction tools 11 and 12 and descends onto the substrate 1, and FIG. Sano solder ball 7,
8 shows a state where the reference numeral 8 is transferred onto the corresponding electrodes 2 and 3, respectively.

Next, as shown in FIG. 2C, the substrate 1 is sent to a reflow furnace and heated. As a result, the solder balls 7 and 8 are melted and then solidified to form the electrodes 2 and 8.
3 are formed with pre-coated solders 7 'and 8'. The pre-coated solders 7 'and 8' formed in this manner have an appropriate solder film thickness according to the type and size of the electronic component to be mounted. Further, by selecting a solder ball having a necessary and sufficient amount of solder, the absolute value of the film thickness is larger than that of the conventional method by solder plating only by transferring and melting and solidifying the solder ball once. The precoat solders 7 ', 8' can be efficiently and stably formed on the electrodes 2, 3 of the substrate 1 with no variation in film thickness. Further, since it is not necessary to form a circuit pattern for supplying an electrolytic power to each electrode on the substrate 1 which is required by the method using electrolytic solder plating, the formation of pre-coated solder is smaller than the conventional method using electrolytic solder plating. Can be reduced.

Next, a plurality of electronic components 21 and 22 of different types and sizes are mounted on the electrodes 2 and 3 on which the pre-coated solders 7 'and 8' are formed. FIG.
(A) shows a state where the electronic component 21 is aligned on the electrode 2 and the electronic component 22 is aligned on the electrode 3. Next, the electronic components 21 and 22 land on the pre-coated solders 7 'and 8', and furthermore, the pre-coated solders 7 'and 8'
Pressed against 8 '.

FIG. 3B shows that, as a result of pressing the electronic components 21 and 22, the tip of the bump 21 a of the electronic component 21 is placed on the surface of the pre-coated solder 7 ′ and the bump 2
2a shows a state in which the surface of the precoat solder 8 'is stuck into the surface. Since the pre-coated solders 7 ', 8' formed by the above-described method have a sufficient solder film thickness, the bumps 21a, 22a are thus formed by the pre-coated solder 7 ',
8 ′ can be inserted into the electronic component 21, thereby preventing the electronic components 21 and 22 from being displaced in the horizontal direction when the substrate 1 is transported.

Thereafter, the substrate 1 is sent to a reflow furnace and heated. Thereby, the precoat solders 7 ', 8' are melted, and the bumps 21a, 22a of the electronic components 21, 22 are soldered to the electrodes 2, 3, respectively. Next, the electronic component 2
An underfill resin 2 is provided in the gap between the substrate 1 and 22 and the substrate 1.
3 is injected, and the mounting of the electronic components 21 and 22 on the substrate 1 is completed.

[0017]

According to the present invention, solder balls of different sizes are transferred onto the electrodes of the substrate according to the size of the electrodes, and the solder balls are heated and melted to form pre-coated solder on the electrodes. As a result, it is possible to form a pre-coated solder having an appropriate solder film thickness in accordance with the type and size of the electronic component mounted on the electrode. Precoat solder having a large absolute value of the thickness can be efficiently and stably formed. In addition, the circuit pattern for electrolytic power supply to each electrode on the substrate, which was required by the method using electrolytic solder plating, is not required, and the cost required for forming pre-coated solder is reduced compared to the conventional method using electrolytic solder plating. can do. Further, when mounting an electronic component having a metal bump on the pre-coated solder having a sufficient solder film thickness formed in this way, the metal bump can be inserted into the pre-coated solder. It is possible to prevent the displacement in the direction, and thus to reduce the mounting failure due to the displacement.

[Brief description of the drawings]

FIG. 1 is a perspective view of a solder ball transfer device according to an embodiment of the present invention.

FIGS. 2A and 2B are process explanatory views of an electronic component mounting method according to an embodiment of the present invention; FIG. 2B are process explanatory views of an electronic component mounting method according to an embodiment of the present invention; Process explanatory diagram of the electronic component mounting method of one embodiment

FIG. 3A is a process explanatory view of an electronic component mounting method according to an embodiment of the present invention. FIG. 3B is a process explanatory view of an electronic component mounting method according to an embodiment of the present invention. Process explanatory diagram of the electronic component mounting method of one embodiment

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 3 electrode 4 Rail 7, 8 Solder ball 7 ', 8' Precoat solder 10 Flux 11, 12 Suction tool 13 Transfer head 21, 22, Electronic component 21a, 22a Bump 23 Underfill resin

Claims (1)

[Claims] A step of transferring solder balls having different sizes on the electrodes of the substrate in accordance with the size of the electrodes; a step of heating and melting and solidifying the solder balls to form a pre-coated solder on the electrodes; Transferring a plurality of electronic components of different types and sizes onto the solder, heating the substrate on which the electronic components have been transferred, melting the pre-coated solder, and soldering the electronic components to the electrodes of the substrate; A method for mounting an electronic component, comprising: