JP3237909B2 - Terminal structure of flexible substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal structure of a flexible substrate made of a flexible printed wiring board, a film carrier or the like.

[0002]

2. Description of the Related Art As means for electrically connecting terminal leads 12 protruding from a base film 11 on a flexible substrate 1 and electrodes 22 on a substrate 21 on a printed circuit board 2,
The method shown in FIGS. 7 and 8 is employed. That is,
The flexible printed circuit board, pin portion of the flexible substrate 1 made of a film carrier or the like, as shown in FIG. 7, which is projected a terminal lead 12 from the base film 11, the leading end of the terminal lead 12 It is connected to a narrow base film 11a. Then, on the substrate 21 on the side of the printed circuit board 2 to be connected, the opposing electrode 2
2 is formed, and the electrode 3 is coated with the solder 3.

When connecting the flexible substrate 1 having such a configuration to the printed circuit board 2, as shown in FIG. 8, the terminal lead 12 of the projecting portion and the electrode 22 on the substrate 21 are overlapped (see FIG. 8). 8 (a)), the terminal lead 1 is
2 and the electrodes 22 of the printed circuit board 2 are thermocompression-bonded and soldered (FIG. 8B). An ideal state of soldering when soldering is performed by such means is expected to have a configuration as shown in FIG. That is, due to the heat and pressure of the pressurizing and heating tool 4, the solder 3 located at this portion is melted and pushed out to both sides of the pressurizing and heating tool 4, and this portion becomes the thermocompression bonding portion 31. Then, the solder 3 extruded from the thermocompression bonding portion 31 is wrapped around the upper surface of the terminal lead 12 to form a solder fillet 32.

If the connecting portion between the flexible substrate 1 and the printed circuit board 2 can be formed in the above-described configuration, a direct stress is applied to the layer of the solder 3 between the terminal lead 12 and the electrode 22 in the thermocompression bonding portion 31. Without this, the reliability of soldering can be ensured.

However, in reality, since the terminal lead 12 has flexibility, as shown in FIG.
Since the terminal leads 12 located on both sides of the terminal 3 jump up and the solder 3 enters under the terminal leads 12, the solder fillet 32 is not formed. In the case where the solder fillet 32 is not formed, as shown in FIG. 11, destruction occurs near the interface between the terminal lead 12 and the solder 3 from the destruction starting point 33,
As a result, the strength of that portion also decreases.

In order to prevent the terminal leads 12 from jumping up, pressing both sides of the pressing and heating tool 4 with the holding tool 5 or the like as shown in FIG.
As shown in FIG. 13, the solder 3 protrudes from the electrode 22, and the protruding solder 34 may short-circuit the adjacent electrode 22.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for connecting a terminal lead having flexibility and an electrode formed on a substrate by soldering with a pressurizing and heating tool between the electrode and the terminal lead. It is an object of the present invention to provide a terminal connection structure capable of forming a solder fillet by ensuring that the located solder flows around the upper surface of the terminal lead and performing a reliable connection.

[0008]

According to the present invention, in order to achieve the above object, a terminal formed on a base film of a flexible substrate and an electrode of a printed circuit board are connected via solder. In the terminal structure of the flexible substrate, a terminal lead protruding from the base film is formed, and the terminal lead is partially or entirely bent in the length direction .
It has a zigzag shape with irregularities .

Further, the present invention is characterized in that the zigzag-shaped terminal lead has a shape in which a curve is continuous or a shape in which a corner is made obtuse.

[0010]

According to the structure of the present invention, solder is arranged between the protruding terminal lead and the electrode of the printed circuit board, and when the center of the lead is thermocompression-bonded, the solder is formed in a concave portion of the terminal lead having a zigzag shape. Then, the wire goes around the upper surface of both ends of the lead from between the two, and a solder fillet can be formed on both ends of the lead.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a first embodiment relating to a terminal structure of a flexible substrate according to the present invention. About the same composition as a prior art, the same numerals are used. The terminal portion of the flexible substrate 1 has a terminal lead 12 protruding from the base film 11, as described in the related art.
The ends of the terminal leads 12 are connected by a base film 11a.

In this embodiment, the shape of the protruding terminal lead 12 is different from the conventional one in which the portion connected to the electrode 22 is straight, but the continuous shape is formed by bending the straight shape and forming concavities and convexities. The terminal lead 12 on the base film 11 is formed in a linear shape as a zigzag portion 12a, but the shape of this portion may be arbitrary. Zigzag part 12a
Consists recess 12a ₁ and the projections 12a ₂ Prefecture, the bent portion forms a corner portion 12a _3.

The board 2 on the side of the printed circuit board 2 to be connected
1, an opposing electrode 22 is formed, and the electrode 22
The solder 3 is coated thereon. The zigzag portion 12 a of the terminal lead 12 can be placed on the electrode 22.

When the terminal leads 12 of the zigzag portion 12a of the flexible substrate 1 having such a configuration are connected to the electrodes 22 of the printed circuit board 2 by soldering, as shown in FIG. Terminal lead 12 and substrate 21
When the upper electrode 22 is overlapped and the terminal lead 12 of the zigzag-shaped portion 12a and the electrode 22 are thermocompressed with a pressure heating tool (not shown), they are melted by the pressure heating tool,
The solder portions 31 are thermocompression bonding extruded, toward the recess 12a ₁ of the zigzag portion 12a to the protrusion 12a _2, flows toward the direction 3a of the solder flow indicated by the arrow in FIG. 2, the terminal lead 12 2, a solder fillet 32 as shown in FIG. 9 can be formed in FIG.

Further, even if an external force is applied to the connection portion after the soldering, the zigzag portion 12a is easily expanded and contracted, and the stress is relieved, so that the risk of disconnection of the terminal lead 12 is reduced. However, the recess 12a _1, the zigzag-shaped portion 12a consisting of the convex portion 12a _2, the recess 1
2a _1, when the angle portion 12a ₃ of the convex portion 12a ₂ is right angle or an acute angle, when a large external force was applied, tends to concentrate stress in the corners 12a _3. In this case, as shown in FIG.
The shape of the zigzag portion 12b, the concave portion 12a _1, the entire corner 12a ₃ of the convex portion 12a _2, by a zigzag portion 12b which forms a curved shape, it is possible to disperse the stress, the terminal lead 12 Disconnection can be prevented.

Further, if the processing the corner portion 12a ₃ in a curved shape difficult, as shown in FIG. 4, the corner portion 12a
_The terminal lead 12 is formed by forming a zigzag portion 12c having a shape from which the edge of FIG. ₃ is removed. As shown in FIG. 5, the terminal lead 12 is formed by connecting the zigzag portions 12d at a gentle angle, that is, at an obtuse angle. It may be composed of 12.

As another shape of the terminal lead 12 of the present invention, instead of forming the entire terminal lead in a zigzag shape as described above, as shown in FIG. 12e ₂ , the zigzag-shaped portions 12 e ₁ , 12 e
forming a e _1, it is possible to obtain the same advantageous effects as described above.

[0018]

According to the structure of the present invention, the solder melted and extruded by thermocompression has an effect that it can wrap around the upper surface of both ends of the lead to form a solder fillet accurately, and the solder layer without being directly stressed between the terminal lead and the electrode has the effect of improving the reliability of the soldered portion, and no irregularities were bent thereon di
Because of the zigzag shape, external force is applied after soldering
Also reduces the stress on the terminal leads,
This has the effect of improving the reliability against disconnection, and furthermore, if the zigzag terminal leads are curved, even if an external force is applied after soldering, the stress applied to the terminal leads will be divided .
And the reliability against disconnection of the terminal lead is further improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part showing a first embodiment relating to a terminal structure of a flexible substrate in the present invention.

FIG. 2 is a perspective view of a main part showing a connection state of a terminal structure of the flexible substrate of FIG. 1;

FIG. 3 is a plan view of a main part showing a second embodiment relating to a terminal structure of a flexible substrate in the present invention.

FIG. 4 is a plan view of a main part showing a third embodiment relating to a terminal structure of a flexible substrate according to the present invention.

FIG. 5 is a plan view of a main part showing a fourth embodiment relating to a terminal structure of a flexible substrate in the present invention.

FIG. 6 is a plan view of a main part showing a fifth embodiment relating to a terminal structure of a flexible substrate according to the present invention.

FIG. 7 is a perspective view showing a main part of a configuration for electrically connecting a conventional flexible substrate to another printed circuit board.

FIGS. 8A and 8B are cross-sectional views showing the relationship between a terminal lead, an electrode, and a pressing and heating tool, wherein FIG. 8A shows a state immediately before the pressing and heating tool is crimped, and FIG. Shown respectively.

FIG. 9 is a perspective view showing a main part in an ideal soldering state after performing thermocompression bonding.

FIG. 10 is a perspective view showing a state of a terminal lead when thermocompression bonding is performed by a conventional configuration.

FIG. 11 is a cross-sectional view of a main part in which a break has occurred near an interface between a terminal lead and solder when thermocompression bonding is performed by a conventional configuration.

FIG. 12 is a schematic cross-sectional view showing a state in which both sides of a pressurizing and heating tool are pressed by a pressing tool in order to prevent terminal leads from jumping up.

13 is a schematic sectional view showing a state where adjacent electrodes are short-circuited by solder in the configuration of FIG. 12;

[Explanation of symbols]

1 the flexible substrate 11 base film 12 terminal lead 12a to 12e ₁ zigzag portion 12a ₁ recess 12a ₂ projecting portion 12a ₃ corners 12e ₂ straight portion 2 printed circuit board 21 substrate 22 electrode 3 solder 3a solder flow 31 thermally Crimping part 32 Solder fillet 4 Pressure heating tool

Claims (2)

(57) [Claims] In a terminal structure of a flexible substrate, wherein terminals formed on a base film of the flexible substrate and electrodes of a printed circuit board are connected via solder, a terminal lead protruding from the base film. Is formed, and the terminal lead is partially or entirely bent in the length direction .
A flexible substrate terminal structure having a zigzag shape with irregularities . 2. The terminal structure of a flexible substrate according to claim 1, wherein the zigzag terminal lead has a shape with a continuous curve or a shape with an obtuse corner.