JPH10242149A - Method of connecting solder bumps - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of connecting solder bumps which aligns them at a high accuracy in the transverse and height directions. SOLUTION: The method comprises steps a) of forming a first solder layer 22 on a transferring carrier substrate 21, b) of aligning with electrodes 23 of LD5, c) soldering to form solder bumps 24 on electrodes 23, d) of aligning and melting a second solder layer formed on a second transferring substrate 26 with the bumps 24 and e) of obtaining second solder bumps 27 of desired size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a component to be soldered (such as a semiconductor element or
More particularly, the present invention relates to a solder bump connection method capable of performing high-precision lateral and height alignment using the surface tension of molten solder.

[0002]

2. Description of the Related Art An example of a conventional highly accurate alignment method using the surface tension and standoff of a solder bump is shown in FIG. 5 (KP Jackson et al., “A Compact Multicha”).
nnel Tranceiver Module Using Planar-Processed Opti
cal Waveguides and Flip-ChipOptoelectronic Compone
nts ", 42nd ECTC, 1992). A standoff 2 for positioning in the horizontal direction and a standoff 3 for positioning in the height direction are formed on the substrate 1, and the surface tension of the solder bump 4 is used. , A notch 6 of an LD (laser diode) 5 with two standoffs 2,
3 to perform high-accuracy positioning in the horizontal direction and the height direction. That is, in FIG. 5, the right bump (obliquely deformed) exerts a diagonally right pulling force due to surface tension. Therefore, since the standoff 2 is fitted into the cutout 6 on the right side of the LD 5, the position in the horizontal direction can be determined in accordance with the height direction. The standoff 3 can be positioned only in the height direction by the surface tension of the solder.

FIG. 6 shows a schematic process of a transfer type solder bump connection method which has been developed so far (see Japanese Patent Application Laid-Open No. Hei 5-166880). After patterning the dot-shaped solder layer 8 on the transfer carrier substrate 7 having poor solder wettability (a), the transfer carrier substrate 7 is positioned on the electrode 10 of the semiconductor element 9 (b). By melting the solder, the solder layer 8 on the transfer carrier substrate 7 is transferred onto the electrode 10 of the semiconductor element 9 to form a solder bump 11 (c). Furthermore, the method is such that the semiconductor element 9 is aligned with the electrode 13 on the wiring board 12 (d), and the solder bump 11 is reflowed to perform flip-chip connection (e).

[0004]

However, in the method of FIG. 5 using the surface tension and the standoff, the positioning accuracy greatly depends on the processing accuracy of the two standoffs 2 and 3 and the notch 6 of the LD 5. I do. This processing accuracy is mainly performed by a reactive ion etching method using a mask, and is 1 μm in consideration of the pattern forming accuracy using the mask and the processing accuracy by the reactive ion etching method.
There is a limit in obtaining the following processing accuracy.

[0005] Further, by using the solder bump 11 formed by the method of FIG.
FIGS. 7 and 8 show a method of aligning the light emitting portion of D5 with the optical fiber on the substrate 1. FIG. FIG. 7 shows the effect of variation in solder film thickness, and FIG. 8 shows the effect of variation in chip shape.
Respectively.

FIG. 7A shows an example in which the solder volume is optimized, and FIG. 7B shows a case in which the position displacement 16 in the height direction is smaller than the desired height due to a small solder volume. , (C) shows the case where the displacement of the solder in the height direction is larger than the desired height due to the large volume of the solder.

FIG. 8A shows an example in which the solder volume is optimized with respect to the weight of the chip, and FIG. 8B shows a case in which the shape of the chip (LD5) is large and heavy, so that the desired height is obtained. When the position shift 16 in the height direction smaller than
(C) shows the case where the position shift 16 in the height direction larger than the desired height occurs due to the small weight of the chip. As described above, regarding the alignment in the height direction, the thickness of the solder (solder volume) varies,
It is difficult to control the bump height with high accuracy due to variations in the shape (chip weight) of the chip to be bump-connected.

In consideration of the necessity of high-precision alignment of 1 μm or less in an optical coupling system between an LD or an optical waveguide type light receiving element and an optical fiber or an optical waveguide, the above two conventional methods require: There is a limit in performing high-precision alignment simultaneously in two directions, the horizontal direction and the height direction.

The present invention solves the above-mentioned conventional problems, and in addition to being capable of performing high-precision lateral alignment with the self-alignment force due to the surface tension of the original molten solder, the present invention is also applicable to a plurality of times. It is an object of the present invention to provide a transfer type solder bump connection method in which positioning in the height direction can be performed with high precision by transfer.

[0010]

According to the method for connecting solder bumps of the present invention, a plurality of dot-shaped solder layers having a predetermined shape and a predetermined pitch are formed on a transfer carrier substrate having poor solder wettability. The solder bump is formed by aligning the electrode portion of the component to be soldered at a position facing the solder layer, heating and melting the solder layer and transferring the solder layer to the electrode portion of the component to be soldered. Further, after the soldered component on which the solder bump is formed is aligned with an electrode portion of another soldered component, the solder bump is connected again by heating and melting the solder bump again. In the connection method, a solder bump having a desired size is formed by repeating the process of transferring using the transfer carrier substrate on which the solder layer is formed a plurality of times. It is intended to formed

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, FIG. 1 shows a schematic process for performing optical coupling between an LD and an optical fiber using solder bumps. After patterning the first solder layer 22 on the first transfer carrier substrate 21 having poor wettability with solder (a), the transfer carrier substrate 21 is positioned on the electrode 23 of the LD 5. (B) By melting the solder, the solder layer 22 on the transfer carrier substrate 21 is transferred onto the electrode 23 of the LD 5 to form the solder bump 24 in the first stage (c).
Further, the second transfer carrier substrate 26 on which the second solder layer 25 is formed and the LD5 on which the solder bumps 24 are formed
(D), and by melting the solder, the solder layer 25 on the transfer carrier substrate 26 is
Is transferred onto the electrode 23, and the solder bump 27 in the second stage is
(E). In this manner, after the light emitting portion 15 and the center of the optical fiber 14 are adjusted to have a desired bump height, the LD 5 is bumped onto the wiring board 12 by melting the solder bump 27 in the second stage. Connect and mount the optical fiber 14 (f).

According to the present invention, in the step of transferring the solder layer by the method as described above, the step of transferring using a transfer carrier substrate is repeated a plurality of times until a desired solder film thickness is obtained, thereby obtaining a desired shape. LD bumps with high precision alignment
And an optical waveguide type light receiving element and an optical coupling system between an optical fiber and an optical waveguide.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.
(N).

As a substrate material having poor wettability with solder, for example, a film-shaped film thickness resist (for example, a product name of DuPont) is formed on a first transfer carrier substrate 21 made of silicon, titanium, molybdenum or the like. A pattern is formed by using "liston" or a liquid resist (for example, AZ-based resist of Shipley), a solder is formed by a vacuum deposition method or the like, and then the resist is removed by a lift-off technique, and the first solder layer is formed. 22 is formed (a). The first solder layer 22 formed on the transfer carrier substrate 21 and the electrode 23 on the LD 5 are aligned,
The two are temporarily fixed by a slight pressure, placed on a carrier jig 28, and a flux 29 is applied so as to penetrate the first solder layer 22 (b). Next, a heating process is performed at a desired time and temperature using the hot plate 30 (c), and the transfer of the solder layer 22 as the solder bump 24 is completed (d). Next, using an organic solvent, flux 2
9 is removed by washing to complete the solder bump 24 in the first stage (e).

Further, the second transfer carrier substrate 26 on which the second solder layer 25 has been formed and the LD 5 on which the solder bumps 24 have been formed in the first stage are aligned again, and both are temporarily provisionally pressed by a slight pressure. Stop this and fix it to carrier jig 2
8 and a flux 29 is applied so as to penetrate the second solder layer 25 (f). Next, hot plate 3
Heating is performed at a desired temperature for a desired time using 0 (g),
The transfer of the solder layer 25 as the solder bump 27 is completed (h). Next, the flux 29 is washed away using an organic solvent to complete the solder bump 27 in the second stage (i).

Further, the solder bump 27 in the second stage is used.
V for fixing the optical fiber 14 to the LD 5 formed with
The electrodes 13 on the wiring board 12 in which the grooves 31 are formed are aligned, temporarily fixed by a slight pressure, and placed on a carrier jig 28 so as to penetrate the solder bumps 27 in the second stage. The flux 29 is applied (j). next,
Heat treatment is performed at a desired temperature for a desired time using the hot plate 30 (k), and the bump connection is completed (l). next,
The flux 29 is washed and removed using an organic solvent, and LD5 is removed.
The bump connection to the wiring substrate 12 is completed (m). Finally, the optical fiber 14 is connected using the UV adhesive 32 (n). Thus, the light emitting section 15 of the LD 5 can be aligned with the center of the optical fiber 14.

In the above embodiment, an example of two transfer steps has been described. However, in order to obtain a desired bump shape, a transfer carrier substrate on which a solder layer having a predetermined thickness is formed is transferred twice or more. Obviously, it can be formed.

In the above embodiment, the example of the LD 5 has been described. However, the parts to be soldered are not limited to this, and it is obvious that the present invention can be applied to semiconductor elements and electronic parts.

In the above embodiment, the transfer solder bump 27 is formed on the LD 5 side. However, the transfer solder bump 2 having a desired shape is formed on the opposing wiring board 12 side.
7 can also be formed.

[0020]

As described above, according to the present invention, in the step of transferring the solder layer, the transfer step is repeated a plurality of times using a transfer carrier substrate having a solder layer of a predetermined thickness. Since the size of the solder bump is formed, the component to be soldered, such as an LD or an optical waveguide type light receiving element, and the optical connection between another component to be soldered, such as a fiber or an optical waveguide, with high precision alignment. A system can be realized.

[Brief description of the drawings]

FIG. 1 is a process chart showing one embodiment of the present invention.

FIG. 2 is a process chart showing one embodiment of the present invention.

FIG. 3 is a process drawing following FIG. 2 showing one embodiment of the present invention.

FIG. 4 is a process drawing following FIG. 3 showing one embodiment of the present invention.

FIG. 5 is a diagram illustrating a conventional highly accurate alignment method using solder bumps.

FIG. 6 is a diagram illustrating a conventional transfer type solder bump connection method.

FIG. 7 is a diagram illustrating an example of alignment using the connection method of FIG. 6;

FIG. 8 is a diagram illustrating an example of alignment using the connection method of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Horizontal positioning standoff 3 Height positioning standoff 4 Solder bump 5 LD 6 Notch 7 Transfer carrier substrate 8 Solder layer 9 Semiconductor element 10 Electrode of semiconductor element 11 Solder bump 12 Wiring board 13 Wiring Electrode on substrate 14 Optical fiber 15 Light emitting part 16 Position shift in height direction 21 First transfer carrier substrate 22 First solder layer 23 LD electrode 24 Solder bump in first stage 25 Second solder layer 26 Second transfer carrier substrate 27 Solder bump in second stage 28 Carrier jig 29 Flux 30 Hot plate 31 V groove 32 UV adhesive

Claims (1)

[Claims] 1. A plurality of dot-shaped solder layers having a predetermined shape and a predetermined pitch are formed on a transfer carrier substrate having poor solder wettability, and an electrode portion of a component to be soldered is provided at a position facing the solder layer. To form a solder bump by heating and melting the solder layer and transferring the solder layer to the electrode portion of the component to be soldered, and further, the component to be soldered having the solder bump formed thereon. In the transfer type solder bump connection method in which the solder bumps are connected again by heating and melting the solder bumps again after the positioning with the electrode portions of the other parts to be soldered, the method uses a transfer carrier substrate on which a solder layer is formed. A solder bump of a desired size is formed by repeating the above-mentioned step of transferring a plurality of times by soldering.