JP2007165580A - Electronic component mounting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component mounting method for preventing poor bonding when a stacked mounting component with a plurality of electronic components stacked therein is mounted by solder bonding. <P>SOLUTION: The electronic component mounting method is used for mounting to a substrate 3 the stacked mounting component 11 where the plurality of electronic components 12, 13 are stacked with solder bumps 16 formed on the lower face of the lowest-layer electronic component 12. Solder paste 18 is printed on electrodes 3a of the substrate 3. The solder paste 18 is supplied to the solder bumps 16 by transfer. Then, the solder bumps 16 are respectively landed on the electrodes 3a via the solder paste 18. By this, it is possible to prevent the poor bonding when the stacked mounting component is mounted by solder bonding while increasing an amount of molten solder, and securing wetting spread of the molten solder by a solder component in the solder paste 18 even when there is a gap between the solder bump 16 and the electrode 3a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic component mounting method for mounting a stack mounting component in which a plurality of electronic components are stacked on a substrate by solder bonding.

In recent years, with the progress of miniaturization and high functionality of electronic devices, electronic components such as semiconductor packages incorporated in the electronic devices are required to be miniaturized and thinned and the mounting density to be further increased. As a mounting form to cope with such high-density mounting, a stack mounting structure in which a substrate module in which electronic components are mounted on a substrate is stacked (see, for example, Patent Document 1). In this patent document example, by mounting a plurality of semiconductor packages on which solder bumps are formed and mounting them on a substrate, it is possible to manufacture a mounting substrate having a high mounting density without increasing the substrate size.
JP 2005-26648 A

  By the way, since the semiconductor package used for the stack mounting structure is thin, it has a characteristic that it has low rigidity and is likely to be warped and deformed by heating during reflow for solder bonding. For this reason, the solder bumps are lifted due to warpage deformation during reflow, and the solder bumps are not normally soldered to the connection electrodes of the substrate, which tends to cause poor bonding such as poor conduction and insufficient bonding strength.

  Therefore, an object of the present invention is to provide an electronic component mounting method capable of preventing a bonding failure when a stack mounting component in which a plurality of electronic components are stacked is mounted by solder bonding.

  The electronic component mounting method of the present invention is an electronic component mounting method in which a stack mounted component in which a plurality of electronic components are stacked and a solder bump for external connection is formed on the lower surface of the lowermost electronic component is mounted on a substrate. A solder transfer step of supplying a solder paste to the solder bump by transfer, and mounting the stack mounting component on the substrate and landing the solder bump on the connection electrode of the substrate via the solder paste And a reflow step of soldering the stack mounting component to the substrate by heating the substrate together with the stack mounting component to melt solder components in the solder bumps and solder paste.

  According to the present invention, the electronic component is mounted on the substrate in a state where the solder paste is supplied to the solder bump by transfer, and the solder bump is landed on the connection electrode of the substrate via the solder paste, thereby connecting the solder bump to the solder bump. Even when there is a gap between the electrodes, the amount of molten solder is increased by the solder component in the solder paste, and wetting and spreading of the molten solder is ensured, so that the stack mounting parts are mounted by solder bonding. Defects can be prevented.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 is a configuration diagram of a mounting board manufacturing line according to an embodiment of the present invention, FIG. 2 is a plan view of an electronic component mounting apparatus according to an embodiment of the present invention, and FIG. 3 is a mounting according to the embodiment of the present invention. FIG. 4 is a process explanatory diagram of an electronic component mounting method according to an embodiment of the present invention, and FIG. 5 is a solder joint in the electronic component mounting method according to an embodiment of the present invention. It is explanatory drawing of a process.

  First, a mounting board manufacturing line will be described with reference to FIG. In FIG. 1, the mounting board manufacturing line is configured by connecting a screen printing machine M1, an electronic component mounting machine M2, and a reflow device M3 in series. The screen printing machine M1 prints a solder paste for joining electronic components on the substrate. The electronic component mounting machine M2 mounts the electronic component on the board on which the solder paste is printed. The reflow device M3 heats the substrate on which the electronic component is mounted, thereby melting the solder component in the solder paste and soldering the electronic component to the substrate.

  Next, the structure of the electronic component mounting machine M2 will be described with reference to FIG. In FIG. 2, a transport path 2 is arranged in the X direction at the center of the base 1. The conveyance path 2 conveys the substrate 3 on which electronic components are mounted, and positions the substrate 3 at the electronic component mounting position. A first component supply unit 4A is disposed on the front side of the transport path 2, and a stack mounting component formed by stacking a plurality of electronic components on a component tray provided in the first component supply unit 4A. 11 is held. A second component supply unit 4B is disposed on the rear side of the transport path 2, and the tape feeder 5 arranged in the second component supply unit 4B includes a lead-type electronic component 19 (see FIG. 4). The held tape is pitch-fed and supplied to the pickup position of the mounting head described below.

  A Y-axis table 6A and a Y-axis guide 6B are disposed at both ends of the base 1 in the X direction, and an X-axis table 7 is installed on the Y-axis table 6A and the Y-axis guide 6B. A mounting head 8 is mounted on the X-axis table 7. The mounting head 8 is a multiple mounting head including a plurality of unit mounting heads 8 a and moves integrally with the substrate recognition camera 9. By driving the X-axis table 7 and the Y-axis table 6A, the mounting head 8 moves in the X and Y directions, the stack mounting component 11 from the first component supply unit 4A, and the electronic component 19 from the second component supply unit 4B. Is taken out by the suction nozzle 20 (see FIG. 4C) of the unit mounting head 8a and mounted on the substrate 3 positioned on the transport path 2.

  A line camera 10, a nozzle stocker 14, and a solder paste transfer table 15 are disposed between the transport path 2 and the first component supply unit 4A. While the mounting head 8 picking up the electronic component from each component supply unit moves to the substrate 3, the mounting head 8 passes above the line camera 10, so that the electronic component held by the mounting head 8 is removed. recognize.

  The nozzle stocker 14 stores a plurality of types of suction nozzles corresponding to the types of electronic components mounted on the substrate 3, and the mounting head 8 accesses the nozzle stocker 14, so that suction is performed according to the electronic components to be mounted. A nozzle can be selected and mounted. The paste transfer table 15 supplies solder paste in a thin film state on the table by mixing solder components into the flux and making it viscous. When the mounting head 8 holding the electronic component is moved up and down with respect to the paste transfer table 15, the solder paste is supplied to the solder bump formed on the lower surface of the electronic component by transfer.

  Next, the stack mounting component 11 will be described with reference to FIG. As shown in FIG. 3, the stack mounting component 11 includes the electronic component 12 and the electronic component 12 by bonding the bump 17 formed on the lower surface of the electronic component 13 to the upper surface of the electronic component 12 having the bump 16 formed on the lower surface. The components 13 are stacked. Both the electronic component 12 and the electronic component 13 are thin package components formed by resin-sealing semiconductor elements. When the stack mounting component 11 is mounted on the substrate, the solder bumps 16 for external connection formed on the lower surface of the lowermost electronic component 12 are soldered to the electrodes of the substrate.

Next, an electronic component mounting method for mounting the stack mounting component 11 on the substrate 3 will be described with reference to FIGS. In FIG. 4A, electrodes 3 a and 3 b (connection electrodes) are formed on the upper surface of the substrate 3. The electrodes 3a are arranged in the same arrangement as the bumps 16 of the stack mounting component 11, and the electrodes 3b are formed in the same arrangement as the leads 19a of the electronic component 19. The substrate 3 is first carried into the screen printing machine M1 shown in FIG. 1, and here, as shown in FIG. 4B, the solder paste 18 is supplied to the electrodes 3a and 3b of the substrate 3 by screen printing (solder printing process). ). Next, the board 3 after supplying the solder is carried into the electronic component mounting machine M2 and positioned at the mounting position on the transport path 2. Then, the mounting head 8 is moved onto the substrate 3 and the substrate 3 is imaged by the substrate recognition camera 9 to recognize the position of the substrate 3 (first recognition step).

  Thereafter, the solder paste is transferred to the stack mounting component 11. That is, the stack mounting component 11 taken out from the first component supply unit 4 </ b> A by the mounting head 8 moves to the paste transfer table 15 while being held by the suction nozzle 20. Then, as shown in FIG. 4C, the solder paste 18 is transferred to the lower surface side of the solder bump 16 by moving the stack mounting component 11 up and down with respect to the coating film of the solder paste 18 (solder transfer). Process).

  Next, as shown in FIG. 4D, the mounting head 8 mounts the electronic component after the solder paste transfer onto the substrate 3 after the solder printing. First, the stack mounting component 11 is aligned with the electrode 3a of the substrate 3 based on the recognition result of the first recognition process, and then the solder bump 16 is landed on the electrode 3a via the solder paste 18 and mounted. (Installation process). In this mounting process, the electronic component 19 is also mounted, and the lead 19a is positioned and mounted on the electrode 3b.

  Thereafter, the substrate 3 is carried into the reflow apparatus M3. Here, the substrate 3 on which the stack mounting component 11 and the electronic component 19 are mounted is heated to a reflow temperature higher than the solder melting temperature together with these electronic components, so that the solder bumps 16 of the stack mounting component 11 are electroded on the substrate 3. 3a and the lead 19a of the electronic component 19 are soldered to the electrode 3b (reflow process). This solder bonding is performed by melting the solder components in the solder bumps 16 and the solder paste 18. As a result, a high mounting density of a configuration in which the stack mounting component 11 formed by stacking a plurality of electronic components 12 and 13 and having solder bumps 16 for external connection formed on the lower surface of the lowermost electronic component 12 is mounted on the substrate 3. The mounting board is completed.

  The solder joining process in the above reflow process will be described with reference to FIG. Here, an example in which the solder bumps 16 of the stack mounting component 11 are soldered to the electrodes 3a of the substrate 3 is described. As described above, since the stack mounting component 11 is a thin semiconductor package, when the stack mounting component 11 is mounted on the substrate 3, the solder bumps 16 are lifted due to upward warping deformation of the package body at the time of reflow. As shown in FIG. 5A, a gap d is likely to occur between the solder bump 16 and the electrode 3a.

  Even when there is a gap between the solder bump 16 and the electrode 3a in this way, in the present embodiment, the solder paste 18 is further transferred to the solder bump 16 prior to component mounting. Furthermore, since the solder paste 18 is supplied also to the electrode 3a by printing, the upper surface of the electrode 3a to be joined and the lower surface of the solder bump 16 are covered with a sufficient amount of the solder paste 18. It is in the state.

And reflow is performed in such a state. That is, in the process where the solder is melted by heating, the molten solder 18a in which the solder component of the solder paste 18 is melted has a sufficient amount, and as shown in FIG. In a state where the surface of 3a is connected, it spreads in the viscous liquid resin component 18b. At this time, a force acts to pull the solder bump 16 toward the electrode 3a side by the surface tension of the molten solder 18a and to narrow the gap d that originally existed.

  Thereafter, by further heating, the solder bump 16 is melted and integrated with the molten solder 18a, and as shown in FIG. 5C, the solder joint 16a that connects the stack mounting component 11 and the electrode 3a. Is formed. Then, after cooling, the solder joint portion 16a is solidified, whereby the solder joint of the stack mounting component 11 to the substrate 3 is completed. Since this solder joint portion 16a is obtained by adding the solder amount in the solder paste 18 to the solder amount obtained by melting the solder bumps 16, the stack mounting component 11 and the board 3 have a sufficient solder amount. By soldering, sufficient bonding strength and electrical conductivity are ensured.

  In the above embodiment, the solder is supplied to the connection electrode 3a of the substrate 3 by printing in advance. However, the degree of warping deformation of the package is relatively small, and the solder to be additionally supplied to the solder bumps. When the amount is small, the supply of solder to the bonding electrode may be omitted.

  The electronic component mounting method of the present invention has an effect that it is possible to prevent poor bonding when a stack mounting component in which a plurality of electronic components are stacked is mounted by solder bonding, and is formed by sealing a semiconductor element with resin. This is useful in the field of mounting a thin packaged component to a substrate by solder bonding.

The block diagram of the mounting substrate manufacturing line of one embodiment of this invention The top view of the electronic component mounting apparatus of one embodiment of this invention Structure explanatory drawing of the stack mounting components mounted on the mounting board of one embodiment of the present invention Process explanatory drawing of the manufacturing method of the mounting substrate of one embodiment of the present invention Explanatory drawing of the soldering process in the electronic component mounting method of one embodiment of this invention

Explanation of symbols

3 Substrate 3a, 3b Electrode 11 Stack mounting component 12, 13, 19 Electronic component 16 Solder bump 18 Solder paste

Claims (2)

An electronic component mounting method for mounting a stack mounting component in which a solder bump for external connection is formed on the lower surface of the lowermost electronic component formed by stacking a plurality of electronic components on a substrate,
A solder transfer step of supplying a solder paste to the solder bump by transfer, a mounting step of mounting the stack mounting component on the substrate and landing the solder bump on the connection electrode of the substrate via the solder paste; An electronic component comprising: a reflow process for soldering the stack mounting component to the substrate by heating the substrate together with the stack mounting component to melt the solder component in the solder bump and the solder paste. Implementation method. 2. The electronic component mounting method according to claim 1, further comprising a solder printing step of printing a solder paste on the connection electrode in advance.

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