JPH03209793A - Solder connecting structure for glass board - Google Patents

Abstract

PURPOSE:To effectively prevent a crack due to concentration of a thermal stress at a part of a glass board by disposing a bonding surface edge of a solder layer to a thin film electrode inward at a predetermined distance from the bonding surface edge of the electrode to the board. CONSTITUTION:A thin film electrode 2 is formed on a glass board 1, and a flexible printed circuit board 4 is disposed at the upper position from its left side. The electrode 2 is formed by plating an Ni film on an Al film formed directly on the board 1, and the board 1 is formed with a thin film electrode 42 of a copper foil on the lower surface of a flexible resin film 41. A solder layer 3 is formed between the ends of the electrodes 2 and 42 and connected therebetween. The layer 3 has a width smaller than that of the electrode 2, and the bonding surface edge 3a of the film 2 is disposed inward by a predetermined distance l from the bonding surface edge 2a of the board 1 to the electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solder connection structure for glass substrates, and more particularly to a solder connection structure that effectively prevents thermal stress cracking of a glass substrate at a connection portion.

[Prior Art] Conventionally, in a display device, it is generally known that a metal thin film electrode for conducting electricity is formed on a glass substrate, and a flexible printed wiring board connected to a display control device is connected to the thin film electrode by soldering. . To explain this with reference to FIGS. 8 and 9, a plurality of thin film electrodes 2 are formed in parallel strips on the end plate surface of the glass substrate 1, while a lower surface of a resin film 41 constituting the flexible printed wiring board 4 is formed. Thin film electrodes 42 are formed with the same width and pitch as the thin film electrodes 2, and a solder layer 3 of the same width is interposed between the ends of these thin film electrodes 2 and 42 to join them together.

[Problems to be Solved by the Invention] In the above connection structure, the glass substrate 1 has an extremely small coefficient of thermal expansion and is made of aluminum (A), which constitutes the thin film electrode 2.
9) Since the film 21 and the nickel (Ni) film 22 have different coefficients of thermal expansion and also have different coefficients of thermal expansion from the solder layer 3, sudden changes in ambient temperature can cause thermal stress at the edges of each joint surface. All of these thermal stresses are concentrated on the edge 2a of the bonding surface between the glass substrate 1 and the thin film electrode 2, often causing cracks in the glass substrate 1.

The present invention solves this problem, and aims to provide a solder connection structure that effectively prevents the occurrence of cracks due to concentration of thermal stress on a portion of a glass substrate.

[Means for Solving the Problems] The present invention will be described in detail in a connection structure in which a component 4 is connected by a solder layer 3 to a thin film electrode 2 formed on a glass substrate 1 (FIGS. 1 and 2). , the edge 3a of the bonding surface of the solder layer 3 with the thin film electrode 2 is located a certain distance g or more inward from the edge 2a of the bonding surface between the thin film electrode 2 and the glass substrate 1.

In the above structure, when the ambient temperature suddenly changes, thermal stress is generated at the edge 2a of the bonding surface between the glass substrate 1 and the thin film electrode 2, and at the edge 3a of the bonding surface between the solder layer 3 and the thin film electrode 2, respectively. Here, by positioning and separating the edge 3a further inward than the edge 2a by a certain distance ρ or more, the thermal stress exerted on the glass substrate is dispersed and is not concentrated in one part.

Thereby, generation of cracks in the glass substrate 1 is effectively prevented.

[First Example] FIG. 1 is a cross section of a connection structure, and FIG. 2 is a longitudinal section. In the fluorescent display device, a thin film electrode 2 is formed on a glass substrate 1 from the left side in FIG. 2, and a flexible printed wiring board 4 is formed above it from the right side. The thin film electrode 2 is formed by plating N1Jli on an Ag film that is directly formed on the glass substrate 1, and the printed wiring board 4 is made of a thin film of copper (Cu) foil on the lower surface of a flexible resin film 41. An electrode 42 is formed thereon.

A solder layer 3 is formed between the opposing ends of these thin film electrodes 2.42 to connect them.

This solder layer 3 is formed by applying a paste solder to a predetermined position of the thin film electrode 2, and then overlapping the ends of the printed wiring board 4 and irradiating laser light from above to melt it.

The width of the solder layer 3 formed in this way is the same as that of the thin film electrode 2.
(Fig. 1), and the edge 3a of the bonding surface with the thin film electrode 2 is located a certain distance 1 inward from the edge 2a of the bonding surface between the thin film electrode 2 and the glass substrate 1. ing. Note that the width of the printed wiring board 4 is the same as that of the solder layer 3.

Also, at the end position of the thin film electrode 2 (Fig. 2)
, Handa F! The edge 3a of the bonding surface between the thin film electrode 2 and the glass substrate 1 is a certain distance 1 from the edge 2a of the bonding surface between the thin film electrode 2 and the glass substrate 1.
only located inward.

According to experiments conducted by the inventors, it is necessary to ensure that the above-mentioned constant distance g is at least 0.05 rm. When the distance ρ is 0.05 nwn, the maximum thermal stress generated in the glass substrate 1 is reduced by about 40% compared to the conventional case. Further, in a thermal shock test, cracks occurred in the glass substrate 1 after 500 cycles in the conventional structure, but no cracks were observed in the structure of the example even after 1000 cycles. The thin film electrodes used in the experiment were composed of an AI film and a Ni film each having a thickness of 1 μm.

[Second Example] As shown in FIG. 3, A and Q films 21 constituting the thin film electrode 2
The ends of the Ni film 22 are formed in a step-like manner so that each 121
．． By shifting the edge position of 22, thermal stress can be distributed even better. In addition, if the thin film electrode 2 is made up of three or more layers, such as by further forming a gold (Au> film) on the Ni film 21, and the edges of these films are formed in a stepped shape, thermal stress can be further dispersed. be able to.

[Third Embodiment] The thin film electrode 2 shown in FIG.
g) It is constructed by forming a film 23, and this Ag film 23 is made by applying a paste and firing it, and its edges are sloped gently from the stepped positions. Such a structure also allows for further dispersion of thermal stress.

[Fourth Example] The thin film electrode 2 shown in FIG.
It is composed of a single film, and its edges are sloped to disperse thermal stress during paste molding.

[Fifth Embodiment] In FIG. 6, the lower half of the solder layer 3 is connected to the joint surface edge 3a.
It is a sloped surface facing towards the direction. Such a structure also provides the same effects as those of the above embodiments.

Note that the connection structures shown in the first to fifth embodiments are suitable for connection with the lead electrode 51 extending from the IC package 5 and connection with various other parts, for example, as shown in FIG. Can be applied.

[Sixth Embodiment] By the way, in applying the present invention, as described above, the edge 3a of the joint surface between the thin film electrode 2 and the solder layer 3 is set 0°05 mm away from the edge 2a of the thin film electrode 2 and the glass substrate 1. Distance greater than 1
However, if the width of the thin film electrode becomes small, it is difficult to perform soldering while ensuring the above distance 1.

Structures that prevent such difficulties are shown in FIGS. 8 and 9. In the figure, a solder mask layer 6 made of epoxy resin or the like is formed on a glass substrate 1 to cover a thin film electrode 2 and to be in contact with the lower end of a solder layer 3. That is, the solder mask layer 6 is formed between the glass substrate 1 and the thin film electrode 2, as shown in FIG.
At the end of the thin film electrode 2, a rectangular region 24 which is smaller than the edge by the distance p is excluded, and the thin film electrode 2 is exposed only in this region 24.

When the solder paste is applied, the solder comes into contact with the thin film electrode 2 only in the rectangular area 24, and is welded to the thin film electrode 2 only in this area. In this way, soldering can be easily performed.

Note that if the solder mask layer 6 is formed sufficiently thick or made of a material with greater rigidity such as S i 02 or glass, stress concentration at the edge of the bonding surface between the thin film electrode 2 and the glass substrate 1 can be reduced. The dispersion can be further relaxed.

The connection structure of this embodiment is, for example, as shown in FIG.
It can be applied not only to the connection between the lead electrode 51 extending from the C package 5 and the thin film electrode 2, but also to the connection with various parts.

[Effects of the Invention] As described above, the connection structure of the present invention effectively disperses thermal stress concentration on the glass substrate due to changes in ambient temperature in a structure in which various components are soldered onto a glass substrate. This makes it possible to avoid cracks in the glass substrate.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention;
2 is a longitudinal sectional view of the connection structure, FIGS. 3 to 6 are cross sectional views of the connection structure showing second to fifth embodiments of the present invention, respectively. 8 to 11 show a sixth embodiment of the present invention, and FIG. 8 is a cross-sectional view of the connection structure, and the cross-sectional part is the 10th embodiment. Items along the ■-■ line in the diagram, No. 9
10 is a perspective view of the end of a substrate on which a solder mask layer is formed, FIG. 11 is a partially sectional side view showing still another application example of the present invention, FIG. 12 and FIG.
Figure 3 shows a conventional example, Figure 12 is a perspective view of the connection structure, Figure 13 is a cross-sectional view of the connection structure, and xm-xm in Figure 12.
FIG. 1... Glass substrate 2... Thin film electrode 2a... Bonding surface edge 3... Solder layer 3a... Bonding surface edge 4... Flexible printed circuit board 5... IC package (component) 6...Solder mask (parts) 3a 2a Fig. 10

Claims (1)

[Claims] In a connection structure in which components are connected by a solder layer on a thin film electrode formed on a glass substrate, the edge of the bonding surface of the solder layer with the thin film electrode is set to be lower than the edge of the bonding surface between the thin film electrode and the glass substrate. A solder connection structure for glass substrates characterized by being positioned inward by a certain distance or more.