JPH0982759A - Method of connecting substrates having protruding electrodes - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to prevent a short circuit from occurring between adjacent protruding electrodes, and to prevent a connection failure even if the connection terminal portion of the circuit board is uneven. . [Structure] Film substrate 2 of flexible wiring substrate 21
A protruding electrode 27 made of nickel plating is formed on the connection pad 24 formed on the second electrode 2, and a solder layer 28 made of solder plating is formed thicker than the protruding electrode 27 on the surface of the protruding electrode 27. Next, when heat treatment is performed, the solder layer 28 is once melted, and then the solder layer 28 is rounded by the surface tension and the protruding electrode 27 is formed.
And the solder balls 29 are formed on the surface. Then, the protruding electrodes 27 of the flexible wiring board 21 and the connection terminals 33 of the circuit board 31 are connected via the solder balls 29. In this case, even if the solder ball 29 melts, it does not flow in the lateral direction, and since the amount of solder is large, it is possible to prevent a connection failure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting substrates having protruding electrodes.

[0002]

2. Description of the Related Art FIG. 3 shows an example in which a flexible wiring board 1 and a hard circuit board 11 are connected. In the flexible wiring board 1, the wiring 3 made of copper or the like is formed on the film substrate 2, and the insulating film 5 made of a solder resist is formed on the entire upper surface of the wiring 3 except the portion to be the connection pad 4, and the insulating film 5 is formed. In this structure, a protruding electrode 7 made of nickel plating is formed on the connection pad 4 exposed through the opening 6 formed in the above, and a solder layer 8 made of solder plating is formed on the surface of the protruding electrode 7. There is. On the other hand, the circuit board 11 has a structure in which the wiring 14 including the connection terminal 13 made of copper or the like is formed on the lower surface of the hard board 12. The protruding electrodes 7 of the flexible wiring board 1 and the connection terminals 13 of the circuit board 11 are connected via the solder layer 8.

[0003]

By the way, since the plating grows isotropically, the solder layer 8 is formed not only on the bump electrodes 7 but also on the insulating film 5 around the bump electrodes 7. It will be. For this reason, if the thickness of the solder layer 8 is increased, the space between the solder layer 8 formed on the insulating film 5 around the protruding electrode 7 in the lateral direction also increases, and as a result, the protruding electrode 7 and the connection terminal 13 are separated from each other. When connecting via the solder layer 8, the molten solder on the insulating film 5 around the protruding electrodes 7 flows in the lateral direction and spreads widely, and when a fine pitch is achieved, short-circuiting occurs between the adjacent protruding electrodes 7. May occur. Therefore, the thickness of the solder layer 8 is reduced to, for example, about 0.03 mm, but when the connection terminals 13 of the circuit board 11 are uneven,
Since the amount of solder is small, there is a problem that it is not possible to deal with unevenness of the circuit board 11 and connection failure may occur. An object of the present invention is to prevent a short circuit from occurring between adjacent protruding electrodes, and to prevent a defective connection even when the connection terminal portion of the circuit board is uneven. .

[0004]

According to the first aspect of the present invention,
A protrusion electrode made of metal plating is formed on the connection pad formed on the substrate and exposed through the opening formed in the insulating film formed on the substrate, and a solder plating is formed on the surface of the protrusion electrode. Forming a solder layer thicker than the bump electrode, heat-treating the solder layer to once melt and then solidify it to form a solder ball on the surface of the bump electrode, The protruding electrode is connected to the connection terminal of another substrate. According to a third aspect of the present invention, a protruding electrode made of metal plating is formed on a connection pad formed on a substrate and exposed through an opening formed in an insulating film formed on the substrate. A solder layer made of solder plating is formed on the surface of the bump electrode to be thicker than the bump electrode, and a spacer having a thickness smaller than the total height of the bump electrode and the solder layer is formed on the insulating film around the solder layer. In this state, the protruding electrode is connected to the connection terminal of another substrate through the solder layer.

According to the first aspect of the present invention, even if the thickness of the solder layer is increased, the solder layer is formed into a solder ball by heat treatment. Therefore, even if the solder ball is melted, it does not flow laterally. Therefore, it is possible to prevent a short circuit from occurring between adjacent protruding electrodes, and even if the connection terminal portion of the circuit board is uneven, the amount of solder is large, so that a connection failure will not occur. be able to. According to the third aspect of the present invention, even if the thickness of the solder layer is increased, the flow of the solder can be blocked by the spacer, so that a short circuit can be prevented from occurring between the adjacent protruding electrodes. Even if the connection terminal portion of the circuit board is uneven, the amount of solder is large, so that connection failure can be prevented.

[0006]

1 (A) to 1 (C) show respective steps of a method of connecting substrates having protruding electrodes according to an embodiment of the present invention. Therefore, the connection method of this embodiment will be described with reference to these drawings in order.

First, a flexible wiring board 21 as shown in FIG. 1 (A) is prepared. In this flexible wiring board 21, a wiring 23 made of copper or the like is formed on a film substrate 22, and an insulating film 25 made of a solder resist is formed on the entire upper surface of the wiring 23 except a portion to be a connection pad 24. In this structure, the protruding electrode 27 made of nickel plating is formed on the connection pad 24 exposed through the opening 26 formed in 25, and the solder layer 28 made of solder plating is formed on the surface of the protruding electrode 27. ing. In this case, the size of each part is, as an example, the thickness of the film substrate 22 is 25 μm, and the wiring 2 including the connection pad 24 is included.
3 has a thickness of 35 μm, the insulating film 25 has a thickness of 10 μm, the opening 26 has a size of 0.2 mm, the protruding electrode 27 has a height of 0.1 mm, and the solder layer 28 has a thickness of 0.15 mm. ing. Therefore, the total height of the bump electrode 27 and the solder layer 28 is 0.25 mm.

Next, as shown in FIG. 1B, heat treatment is performed to melt the solder layer 28 once, and then the solder layer 28 is rounded by the surface tension and gathered on the surface of the bump electrode 27.
By solidifying in this state, solder balls 29 are formed on the surfaces of the protruding electrodes 27. In this case, the solder ball 29
The height on the insulating film 25 is about 0.3 mm.
In addition, as a method of heat treatment, the opening 26 of the insulating film 25 is used.
It may be performed by irradiating with a laser using a photomask used when the above is formed by photolithography. Next, a circuit board 31 as shown in FIG. 1C is prepared. The circuit board 31 has a structure in which a wiring 34 including a connection terminal 33 made of copper or the like is formed on a lower surface of a hard board 32. And the flexible wiring board 2
The one protruding electrode 27 and the connection terminal 33 of the circuit board 31 are connected via the solder ball 29.

By the way, the thickness of the solder layer 28 is set to 0.15 m.
Even if the thickness is increased to m, since the solder layer 28 is formed into the solder ball 29 by heat treatment, the protruding electrode 27 and the connection terminal 33 are formed.
The solder balls 2 when connecting the
Even if 9 is melted once, this melted solder is
Does not run away from the surface of the solder ball 29
Does not flow in the lateral direction even when melted, so that it is possible to prevent a short circuit from occurring between adjacent protruding electrodes. Further, even if the connection terminals 33 of the circuit board 31 are uneven, the amount of solder is large, so that connection failure can be prevented.

In the above embodiment, the solder layer 28 is heat treated to form the solder balls 29, and the projecting electrodes 27 and the connection terminals 33 are connected via the solder balls 29. However, the present invention is not limited to this. Not a thing. For example, the flexible wiring board 21 shown in FIG. 1A is prepared, and then, as shown in FIG. 2A, a spacer 41 made of a resin sheet such as polyimide having an opening 42 at a portion corresponding to the solder layer 28. Is pasted on the insulating film 25. In this case, the thickness of the spacer 41 is smaller than the total height of the protruding electrode 27 and the solder layer 28 of 0.25 mm, for example, 0.2 mm. Therefore, in the state shown in FIG. 2A, the solder layer 28 is projected to the front surface side of the spacer 41 by 0.05 mm. The spacer 4
1 is formed by applying a film made of polyimide or the like on the entire upper surface of the insulating film 25 including the solder layer 28, and then forming an opening by photolithography in a portion of the film corresponding to the solder layer 28. It may be formed.

Next, as shown in FIG. 2B, the protruding electrodes 27 of the flexible wiring board 21 and the connection terminals 33 of the circuit board 31 are connected via the solder layer 28. in this case,
Even if the thickness of the solder layer 28 is increased to 0.15 mm, the flow of solder can be blocked by the spacer 41, so that a short circuit can be prevented from occurring between the adjacent protruding electrodes 27. Further, even when the connection terminal 33 portion of the circuit board 31 is uneven, by increasing the amount of solder protruding to the surface side of the spacer 41 in the state shown in FIG. You can choose not to.

In the above embodiment, the case where the protruding electrode 27 of the flexible wiring board 21 and the connection terminal 33 of the hard circuit board 31 are connected has been described, but the present invention is not limited to this. For example, the present invention can also be applied to the case where a protruding electrode formed on a semiconductor substrate made of a silicon substrate or the like is connected to a connection terminal formed on a flexible wiring substrate or a hard circuit substrate.

[0013]

As described above, according to the first aspect of the invention, even if the thickness of the solder layer is increased, the solder layer is formed into the solder ball by the heat treatment. Also does not flow in the lateral direction, so that it is possible to prevent a short circuit from occurring between adjacent protruding electrodes, and even if the connection terminal portion of the circuit board is uneven, the amount of solder is large, It is possible to prevent connection failure. Further, according to the invention of claim 3, even if the thickness of the solder layer is increased, the spacer can block the flow of the solder, so that a short circuit does not occur between the adjacent protruding electrodes. In addition, even when the connection terminal portion of the circuit board is uneven, the amount of solder is large, so that a connection failure can be prevented.

[Brief description of drawings]

1A to 1C are cross-sectional views showing respective steps of a method of connecting substrates having protruding electrodes according to an embodiment of the present invention.

2A and 2B are cross-sectional views showing respective steps of a method of connecting substrates having protruding electrodes according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view shown for explaining a conventional method for connecting substrates having protruding electrodes.

[Explanation of symbols]

 21 flexible wiring board 24 connection pad 25 insulating film 26 opening 27 protruding electrode 28 solder layer 29 solder ball 31 circuit board 33 connection terminal 41 spacer

Claims (4)

[Claims] 1. A protrusion electrode made of metal plating is formed on a connection pad formed on a substrate and exposed through an opening formed in an insulating film formed on the substrate. A solder layer formed of solder plating on the surface is formed to be thicker than the protruding electrodes, and a heat treatment is performed to melt and then solidify the solder layers to form solder balls on the surfaces of the protruding electrodes. A method of connecting a substrate having a protruding electrode, comprising connecting the protruding electrode to a connection terminal of another substrate via a ball. 2. The bump electrode according to claim 1, wherein the heat treatment is performed by irradiating a laser with a photomask used when forming the opening of the insulating film by photolithography. A method of connecting substrates having a. 3. A protrusion electrode made of metal plating is formed on a connection pad formed on a substrate and exposed through an opening formed in an insulating film formed on the substrate, and the protrusion electrode of the protrusion electrode is formed. A solder layer made of solder plating is formed on the surface to be thicker than the protruding electrode, and a spacer having a thickness smaller than the total height of the protruding electrode and the solder layer is provided on the insulating film around the solder layer. A method of connecting a substrate having a protruding electrode, comprising connecting the protruding electrode to a connection terminal of another substrate via the solder layer in this state. 4. The method for connecting substrates according to claim 3, wherein the spacer is made of a resin sheet attached on the insulating film.