JP2006156473A - External connection terminal and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To absorb stress due to thermal expansion between a substrate and a solder. <P>SOLUTION: External connection terminals 10 are formed in a shape curved in the shape of C character, and are formed on C4 pads 15 so that the lower ends thereof may be connected to a wiring pattern 14 on the substrate 12. The external connection terminals 10 have a multilayer structure wherein a plurality of conductive metals having a resiliency and a different coefficient of thermal expansion are stacked, and have an elastically deformable structure. The external connection terminals 10 are curved in the shape of C character and are elastically deformable, and so even if a relative position between bumps 20 of a flip chip and the external connection terminals 10 of the substrate 12 shifts due to a difference in coefficient of thermal expansion between the flip chip and the substrate 12, no stress acts on bump joints 22 for connecting the bumps 20 and the external connection terminals 10 and hence the occurrence of cracks in the bump joints 22 can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an external connection terminal and a manufacturing method thereof, and more particularly to an external connection terminal configured to relieve stress acting on solder when a terminal of a substrate is soldered and a manufacturing method thereof.

  For example, when an electronic component such as a flip chip is electrically connected to a terminal on a substrate made of epoxy resin or the like, a plurality of bumps formed on the lower surface of the flip chip and a plurality of part connection terminals formed on the substrate Are connected by solder.

  In such a solder connection structure, the thermal expansion coefficient of the flip chip and the thermal expansion coefficient of the substrate are different. Therefore, in an environment where temperature changes occur, the flip chip bumps and the external connection terminals of the substrate are positioned relative to each other. Deviation occurs. As the relative positions of the bumps and the external connection terminals are shifted, stress acts on the solder connecting the bumps and the external connection terminals, which may cause cracks in the solder.

As a method for solving such a problem, for example, there is a configuration in which an elastic deformation member for absorbing stress accompanying a temperature change is interposed between a substrate and a flip chip (for example, see Patent Document 1). . Further, the elastic deformable member is provided with a metal plate having a spring property on a resin plate, and a cut and raised portion of the metal plate is bent into an arc shape by press working, and the arc-shaped portion changes the radius of curvature. The relative displacement between the bump and the external connection terminal is absorbed by elastic deformation.
JP 2004-101224 A

  However, since the thing of the said patent document 1 is a structure which absorbs the relative displacement between a bump and an external connection terminal by the elastic deformation of the cut-and-raised part of a metal plate, a metal plate is interposed between a board | substrate and a flip chip. There is a problem that a space (gap) for interposing is required, and the height dimension is correspondingly increased, which hinders thinning.

  Furthermore, the thing of the said patent document 1 has the process for cutting and raising a fine elastic deformation part, and the press work process for curving an elastic deformation part, and also provided the elastic deformation part with the terminal of the board | substrate. A process of soldering to the resin plate is also necessary, and it was difficult to increase production efficiency.

  Then, an object of this invention is to provide the external connection terminal which solved the said subject, and its manufacturing method.

  In order to solve the above problems, the present invention has the following means.

  The invention according to claim 1 is a method of manufacturing an external connection terminal formed on a surface of a substrate, wherein a plurality of conductive metals having different thermal expansion coefficients are laminated on the substrate, and then the metal laminated portion is heat treated. It is characterized in that it is formed in a predetermined curved shape.

  The invention according to claim 2 is a method of manufacturing an external connection terminal formed on the surface of a substrate, wherein a first conductive metal layer having a relatively large thermal expansion coefficient is formed on the surface of the substrate, and the first A second conductive metal layer having a smaller coefficient of thermal expansion than the first conductive metal layer is formed on the surface of the conductive metal layer, and the first conductive metal layer and the second conductive metal layer are stacked. The metal laminate portion is heat-treated to form the metal laminate portion in a predetermined curved shape.

  According to a third aspect of the present invention, there is provided a method for manufacturing an external connection terminal, wherein the conductive metal is formed of an elastically deformable conductive material having a spring property.

  The invention according to claim 4 is characterized in that the metal laminated portion is subjected to Au plating.

  According to a fifth aspect of the present invention, the first conductive metal layer is made of Cu having a large thermal expansion coefficient, the second conductive metal layer is made of Ni-Co having a small thermal expansion coefficient, and the metal laminated portion Is characterized in that a Cu layer is formed on the outside of the curved portion curved by the heat treatment.

  The invention according to claim 6 is characterized in that the Cu layer has one end with a curved shape electrically connected to a wiring pattern formed on the substrate, and the other end with the curved shape is connected to the outside. .

  The invention according to claim 7 is an external connection terminal formed on the surface of the substrate, wherein a plurality of conductive metals having different thermal expansion coefficients are stacked on the substrate, and then the plurality of conductive metals are stacked. The metal laminated portion is formed into a predetermined curved shape by heat treatment.

  The invention according to claim 8 is characterized in that the metal laminated portion is formed of an elastically deformable conductive material having a spring property.

  The invention according to claim 9 is characterized in that the metal laminated portion is formed by laminating a Ni—Co layer having a small thermal expansion coefficient on the surface of a Cu layer having a large thermal expansion coefficient, and the Cu layer is disposed outside the curved portion curved by heat treatment. It is characterized by being formed.

  According to the present invention, a plurality of conductive metals having different thermal expansion coefficients are laminated on a substrate, and then the metal laminated portion is formed into a predetermined curved shape by heat treatment, so that the curved shape portion is elastically deformed and becomes an external connection terminal. Since the acting stress can be absorbed and the external connection terminal can be formed efficiently, the production efficiency can be improved and the external connection terminal can be formed on the substrate, which is advantageous for thinning.

  In addition, according to the present invention, the first conductive metal layer having a relatively large thermal expansion coefficient is formed on the surface of the substrate, and the thermal expansion coefficient of the first conductive metal layer is higher than that of the first conductive metal layer. A small second conductive metal layer is formed, and the metal laminated portion obtained by laminating the first conductive metal layer and the second conductive metal layer is heat-treated to form the metal laminated portion in a predetermined curved shape. The external connection terminal can be processed into a shape that can be elastically deformed, and can be reduced in thickness.

  Further, according to the present invention, by subjecting the metal laminated portion to Au plating treatment, the electrical resistance of the external connection terminal can be reduced and the corrosion resistance can be improved.

  According to the present invention, the first conductive metal layer is made of Cu having a large thermal expansion coefficient, the second conductive metal layer is made of Ni—Co having a small thermal expansion coefficient, and the metal laminated portion is curved by heat treatment. Since the Cu layer is formed outside the bent portion, the conductivity of the external connection terminal can be ensured and the strength can be reinforced, and the durability can be enhanced.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing an embodiment of an external connection terminal according to the present invention. As shown in FIG. 1, the external connection terminal 10 is formed in a C-shaped curve, and the C4 pad 15 is connected so that the lower end is connected to the wiring pattern 14 on the substrate 12. Is formed. Further, the surface of the substrate 12 is covered with a solder resist layer 16, and the external connection terminals 10 protrude above the solder resist layer 16.

  The external connection terminal 10 has a laminated structure in which a plurality of conductive metals having different thermal expansion coefficients having spring properties are laminated, and is configured to be elastically deformable.

  The external connection terminal 10 is formed by laminating a first conductive metal layer made of Cu having a large thermal expansion coefficient and a second conductive metal layer made of Ni—Co having a small thermal expansion coefficient. The portion is curved by heat treatment, and a Cu layer is formed outside the curved portion. Furthermore, the external connection terminal 10 is subjected to Au plating treatment on the surface of the metal laminated portion, thereby reducing the electrical resistance and enhancing the corrosion resistance.

  In the external connection terminal 10, the Cu layer of the metal laminated portion is electrically connected to the wiring pattern 14 having one end of the curved shape formed on the substrate, and the other end of the curved shape is connected to the bump 20 of the flip chip. Is done. Since the external connection terminal 10 is curved in a C shape and can be elastically deformed, a difference between the thermal expansion coefficient of the flip chip and the thermal expansion coefficient of the substrate 12 causes a difference between the flip chip bumps 20 and the outside of the substrate 12. Even if the position is shifted relative to the connection terminal 10, no stress acts on the bump coupling portion 22 that connects the bump 20 and the external connection terminal 10, and it is possible to prevent the bump coupling portion 22 from cracking.

  Here, a method of manufacturing the external connection terminal 10 will be described with reference to FIGS. In the substrate processing step shown in FIG. 2, the wiring pattern 14 is formed on the substrate 12, and then the solder resist layer 16 is formed on the surface of the substrate 12 and the wiring pattern 14. Thereafter, an opening is formed by patterning at a position communicating with the solder resist layer 16 on the wiring pattern 14, and electrolytic copper plating is applied to the opening to form a C4 pad 15 for mounting a flip chip.

  Next, after the dry film resist 30 is attached to the surface of the solder resist layer 16, an opening 30a is formed at a position facing the C4 pad 15 by a patterning process, and the upper end of the C4 pad 15 is exposed. The dry film resist 30 has a two-layer structure in which a protective film (PET: polyethylene terephthalate) is laminated on the upper surface of the photoresist layer, and is stuck in a state where the photoresist layer is in close contact with the surface of the solder resist layer 16. Worn. The photoresist layer is a negative resist layer made of a photosensitive organic material that has adhesiveness until it is exposed, and a portion that is not exposed can be dissolved and removed by a developer.

  In the next electroless plating step shown in FIG. 3, a Cu layer (first conductive metal layer) 32 is formed on the surface of the dry film resist 30 and the opening 30a by electroless copper plating. The Cu layer 32 is formed to a thickness of 1.5 μm and is laminated on the C4 pad 15, so that it is electrically connected to the wiring pattern 14.

  In the patterning process shown in FIG. 4, a negative solder resist layer 34 is formed on the surface of the Cu layer 32. Then, an opening 34a is formed in the negative solder resist layer 34 by a patterning process. That is, the negative solder resist layer 34 is exposed and cured, and the unexposed portion is removed with a developer. By such a patterning process, the opening 34a for forming the external connection terminal 10 is dissolved.

  In the next bimetal plating step shown in FIG. 5, a Cu layer (first conductive metal layer) 36 is formed in the opening 34a of the negative solder resist layer 34 by electrolytic copper plating. Therefore, a 15 μm thick Cu layer 36 is deposited on the Cu layer 32 formed in the opening 34 a in the electroless plating step. Thereby, Cu layer 32 and Cu layer 36 are united together, and Cu layers 32 and 36 having a thickness of 16.5 μm thicker than a normal plating layer are formed. The Cu layers 32 and 36 are conductive, are relatively soft metal materials, and have a spring property that can be elastically deformed.

  Furthermore, a Ni—Co layer (second conductive metal layer) 38 is deposited on the surface of the Cu layer 36 by electrolytic plating. The Ni—Co layer 38 has a smaller thermal expansion coefficient than the Cu layers 32 and 36, and is formed to have a film thickness of about 5 μm. The Ni—Co layer 38 is formed thinner than the Cu layer, but has a high rigidity, and therefore functions as a reinforcing material that reinforces the Cu layers 32 and 36. The Ni—Co layer 38 has a thermal expansion coefficient of 12 to 13, whereas the Cu layers 32 and 36 have a thermal expansion coefficient of 16.8.

  In the first resist stripping step shown in FIG. 6, the negative solder resist layer 34 is stripped and removed. That is, the negative resist layer 34 is removed by swelling and peeling using a stripping solution (for example, an alkaline aqueous solution, caustic soda, etc.).

  In the etching process shown in FIG. 7, the region excluding the external terminal region where the Cu layer 36 and the Ni—Co layer 38 are not stacked (the portion serving as the external connection terminal 10) is removed by etching. To do.

  In the second resist stripping step shown in FIG. 8, the dry film resist 30 is stripped from the solder resist layer 16 and removed. Accordingly, the base ends of the Cu layers 32 and 36 and the Ni—Co layer 38 constituting the external connection terminal 10 are supported with the C4 pad 15 as a support, the other end is floated from the solder resist layer 16 and is horizontal. Supported in a state extending in the direction.

  In the heat treatment step shown in FIG. 9, for example, an annealing process is performed in which the surface of the substrate 12 is irradiated with a laser beam by a laser processing machine and heated. In the double structure in which two kinds of metals having different thermal expansion coefficients are laminated as described above, for example, when heated to a high temperature of 250 ° C., as shown in FIG. 10, Cu layers 32 and 36 having a large thermal expansion coefficient. Will expand more, and the Ni—Co layer 38 having a small thermal expansion coefficient will expand smaller.

  Furthermore, in this embodiment, the thickness of the Cu layers 32 and 36 is 16.5 μm, whereas the thickness of the Ni—Co layer 38 is 5 μm. The layers 32 and 36 are configured to act so that the thermal expansion of the layers 32 and 36 is three times or more that of the Ni—Co layer 38.

  As a result, the Ni—Co layer 38 is bent on the inner peripheral side, and the whole is deformed in an arc shape so that the Cu layers 32 and 36 are bent on the outer peripheral side. Thereby, in the lamination | stacking part used as the external connection terminal 10, it deform | transforms into the state curved in the C shape by the thermal expansion difference of said 2 types of metals.

  In the Au plating step shown in FIG. 11, Au plating is performed so that soldering can be easily performed on the surface of the external connection terminal 10 curved in a C shape as described above. Thereby, the Au plating layer 40 is formed to have a film thickness of approximately 0.07 μm by electroless plating, and Au is deposited on the exposed portion of the Ni—Co layer 38, and the curved Cu layers 32 and 36 and the Ni— The entire surface of the Co layer 38 is coated. Thereby, while reducing the electrical resistance of the external connection terminal 10, corrosion resistance can be improved.

  In this way, a plurality of conductive metals having different thermal expansion coefficients are laminated on the substrate 12, and then the metal laminated portion is formed into a predetermined curved shape by heat treatment, so that the curved shape portion is elastically deformed to form the external connection terminal 10. Since the acting stress can be absorbed and the external connection terminal 10 can be formed efficiently, the production efficiency can be increased, and the external connection terminal 10 can be formed on the substrate 12, which is advantageous for thinning.

  In the above-described embodiments, the external connection terminals 10 to which the flip chip bumps 20 are soldered are described as an example. However, the present invention is not limited thereto, and for example, external connection terminals used for a probe of an inspection device for inspecting a semiconductor chip. It is also possible to form a curved shape by the above manufacturing method. In this case, the curved external connection terminal can elastically deform and absorb the impact generated when the external connection terminal as a probe is brought into contact in the semiconductor chip inspection process.

  In the above embodiment, the configuration in which the Ni—Co layer having a small thermal expansion coefficient is laminated on the surface of the Cu layer having a large thermal expansion coefficient is taken as an example, but other conductive metals having different thermal expansion coefficients may be combined. Is possible.

  In the above embodiment, the thickness of the Cu layer having a large thermal expansion coefficient is set to 16.5 μm, and the thickness of the Ni—Co layer having a small thermal expansion coefficient is set to 5 μm. Of course, each film thickness may be set so that the ratio between the film thickness of the Cu layer and the film thickness of the Ni—Co layer is different from the above.

It is a longitudinal cross-sectional view which shows one Example of the external connection terminal which becomes this invention. FIG. 5 is a process diagram illustrating a substrate processing process of the method for manufacturing the external connection terminal 10. FIG. 4 is a process diagram showing an electroless copper plating process of the method for manufacturing the external connection terminal 10. FIG. 6 is a process diagram illustrating a patterning process of the method for manufacturing the external connection terminal 10. 5 is a process diagram illustrating a bimetal plating process of the method for manufacturing the external connection terminal 10. FIG. 5 is a process diagram illustrating a first resist stripping process of the method for manufacturing the external connection terminal 10. FIG. FIG. 6 is a process diagram illustrating an etching process of the method for manufacturing the external connection terminal 10. FIG. 6 is a process diagram illustrating a second resist stripping process of the method for manufacturing the external connection terminal 10. FIG. 4 is a process diagram showing a heat treatment process of the method for manufacturing the external connection terminal 10. It is an enlarged view for demonstrating the bending effect | action by the difference in the thermal expansion coefficient of Cu layer and Ni-Co layer in the heat processing process. FIG. 5 is a process diagram showing an Au plating process of the method for manufacturing the external connection terminal 10.

Explanation of symbols

10 External connection terminal 12 Substrate 14 Wiring pattern 15 C4 pad 16 Solder resist layer 20 Bump 30 Dry film resist 32, 36 Cu layer 38 Ni-Co layer 34 Negative solder resist layer 40 Au plating layer

Claims (9)

A method of manufacturing an external connection terminal formed on the surface of a substrate,
Laminating a plurality of conductive metals having different thermal expansion coefficients on the substrate,
Next, the method of manufacturing an external connection terminal, wherein the metal laminated portion is formed into a predetermined curved shape by heat treatment. A method of manufacturing an external connection terminal formed on the surface of a substrate,
Forming a first conductive metal layer having a relatively large thermal expansion coefficient on the surface of the substrate;
Forming a second conductive metal layer having a smaller coefficient of thermal expansion than the first conductive metal layer on the surface of the first conductive metal layer;
A method of manufacturing an external connection terminal, comprising: heat-treating a metal laminated portion in which the first conductive metal layer and the second conductive metal layer are laminated to form the metal laminated portion in a predetermined curved shape. .   The method of manufacturing an external connection terminal according to claim 1, wherein the conductive metal is formed of an elastically deformable conductive material having a spring property.   The method for manufacturing an external connection terminal according to any one of claims 1 to 3, wherein the metal laminated portion is subjected to Au plating. The first conductive metal layer is made of Cu having a large thermal expansion coefficient,
The second conductive metal layer is made of Ni-Co having a small coefficient of thermal expansion,
5. The method for manufacturing an external connection terminal according to claim 2, wherein the metal layered portion is formed with a Cu layer on the outside of the curved portion curved by heat treatment.   6. The external connection according to claim 5, wherein one end of the Cu layer is electrically connected to a wiring pattern formed on the substrate, and the other end of the curve shape is connected to the outside. Terminal manufacturing method. An external connection terminal formed on the surface of the substrate,
Laminating a plurality of conductive metals having different thermal expansion coefficients on the substrate,
Next, the external connection terminal is characterized in that the metal laminated portion in which the plurality of conductive metals are laminated is formed in a predetermined curved shape by heat treatment.   The external connection terminal according to claim 7, wherein the metal laminated portion is formed of an elastically deformable conductive material having a spring property. The metal laminated portion is characterized in that a Ni-Co layer having a low thermal expansion coefficient is laminated on the surface of a Cu layer having a large thermal expansion coefficient, and a Cu layer is formed outside the curved portion bent by heat treatment. The external connection terminal according to claim 7 or 8.

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