JPH02228613A - Optical waveguide fixing structure - Google Patents

Abstract

PURPOSE:To fix an optical waveguide with a desired positional precision and to avoid chip cracks due to thermal expansion by providing a first solder area forming an immobile fixing part against the external force in the intra-face direction and a second solder area which forms a thermal stress absorbing part to enable a chip to relatively move at the time of thermal expansion and is made of a solder softer than that of the first solder area. CONSTITUTION:A first solder area A which mainly forms the immobile fixing part against the external force in an about intra-face direction and a second solder area C which forms the thermal stress absorbing part to enable chip 5 to relatively move at the time of thermal expansion and is made of a solder softer than that of the first solder area A are provided on a solder junction surface. A desired chip positional precision is obtained because the first solder area A functions as the immobile fixing part against the external force in an about intra-face direction, and the chip can be relatively moved because the second solder area C functions as the thermal stress absorbing part for thermal expansion. Thus, the optical waveguide is fixed to a substrate 6 while keeping the desired positional precision, and trouble like cracks due to thermal expansion is effectively avoided.

Description

[Detailed Description of the Invention] [Summary] Regarding an optical waveguide fixing structure, a chip on which an optical waveguide is formed can be securely fixed to a substrate while maintaining desired positional accuracy, and the chip can be prevented from cracking due to thermal expansion. In a structure in which a chip on which an optical waveguide is formed is soldered to a substrate with the aim of providing an optical waveguide fixing structure that can avoid such problems, the first solder region forms an immovable fixing part mainly against external force in the direction inward of the road surface. and a second solder region made of softer solder than the first solder region, which forms a thermal stress absorbing portion that enables relative movement of the chip during thermal expansion, on the solder joint surface. do.

[Industrial application field]

The present invention relates to a structure for mounting and fixing a chip on which an optical waveguide is formed to a substrate.

[Conventional technology]

L+NbO, with an optical waveguide formed on its top surface (hereinafter referred to as
When fixing the LN chip 51 by soldering to the board, the surface of the LN chip 51 should be soldered with Au (gold) as shown in Figure 3.
After plating 52, a single piece of solder 54 is used to fix the substrate 53°. Such a substrate 53 is an LN chip 51
The solder 54 is made of a material such as stainless steel (SUS material) that has a linear expansion coefficient similar to that of the solder 54.
3 etc. is generally used.

[Issues that Hathu tries to solve]

However, when actually mounting the LN chip 51 together with the board 53 in the LN module and using it, the LN chip 51 is connected to a PC connector (8 in FIG. 1) as shown in FIG. An external force P such as an axial force (shown by ) may be applied. This force P causes the solder (SN
63) The creep of 54 occurs and the LN chip 51 is attached to the substrate 53.
It tends to shift overall (toward the left in the figure). Therefore, the performance as a leading wave tube may be significantly impaired. On the other hand, if a harder solder such as AuC (AuC)-3N (tin) is used instead of 5N63 solder to prevent creep from occurring, the LN chip 53 will suffer thermal stress due to the difference in thermal expansion coefficient with the substrate 53. may break.

In view of the above points, the present invention makes it possible to fix the LN chip while maintaining desired positional accuracy with respect to the substrate,
It is an object of the present invention to provide an optical waveguide fixing structure that can absorb thermal stress and effectively avoid problems such as cracking of the LN chip.

[Means to solve the problem]

In order to solve the above-mentioned problems, an optical waveguide fixing structure according to the present invention has a structure in which a chip on which an optical waveguide is formed is soldered to a substrate. and a second solder region made of softer solder than the first solder region, which forms a thermal stress absorbing portion that enables relative movement of the chip during thermal expansion, on the solder joint surface. is a structural feature.

[For production]

The first solder area functions as an immovable fixing part against external force in the direction inward of the road surface, so the desired chip positioning accuracy can be obtained, and the second solder area functions as a thermal stress absorbing part during thermal expansion, so it It becomes movable and chip cracking is less likely to occur.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a longitudinal sectional view of a so-called LD-LN module to which an optical waveguide fixing structure according to the present invention is applied. This L
The D-LN module has a laser section (LD module) and L
It has an integrated structure with N module, 1 is a photo diode (PD), 2 is a laser diode (LD)
, 3 and 4 are lenses for condensing light.

The LN chip 5, on which an optical waveguide (not shown) is formed, is fixed to a stainless steel substrate 6 whose cross section is shown in FIG. 2 by soldering, which will be described later. It is fixed to the base 7 through both ends.The left end of the LN chip 5 (optical waveguide) has a slight gap with the lens 4 to allow for axial fluctuation (expansion and contraction). On the other hand, the right end of (the optical waveguide of) the LN chip 5 is brought into contact with the end of the PC connector ferrule 8 fixed to the base 7 with the optical axis aligned.

To fix the LN chip 5 to the board 6, as seen from the PC connector ferrule side, part A uses hard Au'-3n solder (first solder area), part B does not use solder, and uses relatively soft 5N63 solder. Two types of solder having different properties are used for the C part (second solder area). As a result, the Au-
The part A soldered with 3n is firmly attached to the board 6 (
Since the PC connector ferrule 8 and the right end of the optical waveguide are fixed (immovable), it can withstand even if an external force from the PC connector ferrule 8 acts on the LN chip 5 in the in-plane direction, and creep is less likely to occur. The mutual positional relationship (accuracy) between them can be effectively maintained stably. Also, B
and relatively soft low melting point 5N63 in the C part.
Even if the LN chip 5 thermally expands due to the solder, it can follow this to some extent (absorbs stress), so the LN chip 5 will not crack.

The LN chip 5 has a height of about 0.5 to 1 mm and a width of 1 m.
It is about 60mm in length and Au-3n
The length of the part A to be soldered is set to such a length that the LN chip 5 will not break at this part even due to thermal expansion during actual use, for example, about 10 strokes. Further, the portion B to which soldering is not performed may be masked to prevent Au plating (vapor deposition). However, the idea of the present invention itself does not require the provision of this blank portion (portion B), that is, portions A and C do not necessarily need to be separated via the blank portion.

〔Effect of the invention〕

As described above, according to the present invention, the optical waveguide can be fixed to the substrate while maintaining desired positional accuracy, and problems such as cracking due to thermal expansion can be effectively avoided.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the LD-LN module according to the present invention, Fig. 2 is a cross-sectional view of the LD-LN module of Fig. 1 taken along line n-■, and viewed from the direction of the arrow. FIG. 3 is a diagram for explaining an optical waveguide fixing structure. 5... LN chip, 6... Substrate, 7.
...Base, 8...PC connector ferrule.

Claims (1)

[Claims] 1. In a structure in which a chip (5) on which an optical waveguide is formed is soldered to a substrate (6), the first solder region (A) forms an immovable fixing part mainly against external force in the direction inward of the road surface, and the first solder region (A) The first solder region (A
) A second solder region (C) made of softer solder is defined on the solder joint surface.