JP5034885B2 - Electronic device and method of manufacturing the same - Google Patents

Description

  The present invention relates to an electronic device and a method for manufacturing the electronic device.

  In recent years, with the demand for miniaturization of devices in the mobile device market such as mobile phones, there is an increasing demand for mounting semiconductor elements at high density. In order to meet this demand, flip-chip bonding is often used in which a semiconductor element is connected face-down to a circuit board via a connection electrode, and a narrow pitch and a large number of pins can be realized.

  While this flip chip bonding progresses, cracks are generated in the connection electrode or the semiconductor element due to the stress caused by the difference in thermal expansion coefficient between the circuit board mainly composed of organic resin and the semiconductor element mainly composed of silicon. There is a problem that connection reliability is lowered.

  In order to relieve the difference in thermal expansion coefficient between the circuit board and the semiconductor element, various stress relaxation structures have been proposed.

  For example, in Patent Document 1, a resist pattern is formed on a processed substrate having a concavo-convex surface, and a minute portion having a bent portion reflecting the concavo-convex shape is formed on the processed substrate exposed from the resist pattern window. There has been proposed a stress relaxation structure in which a conductive connection portion is formed and a semiconductor element and a circuit board are connected by the conductive connection portion. According to this structure, the stress caused by the difference in thermal expansion coefficient is relieved by the bent portion of the conductive connection portion.

  However, the processed substrate necessary for forming the conductive connection portion has a high manufacturing cost, and therefore needs to be repeatedly used in order to reduce the manufacturing cost of the conductive connection portion. Therefore, there exists a problem that the cost which manages and maintains the process etc. of the mold release material for making it easy to peel an electroconductive connection part from a process board | substrate increases.

  In addition, since unevenness is formed on the surface of the processed substrate, sufficient flatness cannot be obtained in the photoresist applied on the processed substrate, and it becomes easy for focus shift to occur in the exposure process, and a fine resist pattern is formed. It becomes difficult to form.

  On the other hand, Patent Document 2 proposes a stress relaxation structure in which a circuit board and a semiconductor element are connected by an S-shaped lead and stress is relaxed by the lead.

  However, this method has a problem that the number of steps is large because two exposure steps are required to form the S-shaped lead and the spot at the tip thereof. Further, since under-etching is used to form terminals at both ends of the lead, there is a disadvantage that a terminal having an arbitrary shape cannot be formed as well as the need to strictly control the etching time and the like.

  In addition, there is a structure in which the circuit board and the semiconductor element are connected by wire bumps with spring properties. In this structure, it is necessary to form the wire bumps one by one. There is a problem that it is technically difficult to arrange them at a narrow pitch.

In addition to this, techniques related to the present invention are also disclosed in the following Patent Documents 3 to 4.
JP 2003-188209 A JP-A-10-256314 Japanese Patent No. 2986095 JP-A-6-268017 Japanese Patent Laid-Open No. 2005-166739

  An object of the present invention is to provide an electronic device that can easily relieve a stress difference between an electronic component and a substrate, and a manufacturing method thereof.

According to one aspect of the present invention, a circuit board having a first electrode formed on a first surface, an electronic component having a second electrode formed on a first surface, a first conductive film and a second stress having different stresses from each other. A conductive film is laminated, and has a laminated body that electrically connects the first electrode and the second electrode, and both the first conductive film and the second conductive film are made of the same material. In addition, the first conductive film and the second conductive film are formed under different plating conditions, the stress of the first conductive film is tensile stress, and the stress of the second conductive film is compressive stress. The circuit board and the electronic component are arranged so that the first surface of the circuit board and the first surface of the electronic component face each other, and the stacked body is formed in an arc shape with the second conductive film outside. And bending one end of the second conductive film to the first electrode, and the other of the second conductive film Electronic device the end joined to the second electrode is provided.

  According to another aspect of the present invention, a step of forming a laminated body formed by laminating a first conductive film and a second conductive film having different stresses in this order on a base substrate, and a first substrate Bonding one end of the second conductive film to the electrode, peeling the laminated body from the base substrate after the bonding, bending the laminated body due to the difference in stress, and electrons There is provided a method of manufacturing an electronic device including a step of bonding the other end of the second conductive film to a second electrode of a component.

  According to the present invention, the stress caused by the difference in thermal expansion coefficient between the electronic component and the circuit board is relieved by the laminate that is naturally curved due to the difference in internal stress between the first and second conductive films, and the electronic component or the like The risk of cracking can be reduced, and the connection reliability between the electronic component and the circuit board is improved.

  Moreover, since the laminate naturally curves due to the difference in internal stress between the first and second conductive films, a special device for curving the laminate is unnecessary, and a connection structure can be easily obtained at low cost. Can do.

  Furthermore, when the first and second conductive films are formed in a resist pattern window that can be finely processed in a manufacturing process of a semiconductor device or the like, a laminate composed of these conductive films can be formed finely. In addition, the laminates can be arranged at a narrow pitch.

  Hereinafter, an electronic device according to an embodiment of the present invention will be described following the manufacturing process.

  1 to 5 are cross-sectional views of the electronic device according to the present embodiment during manufacture.

  First, steps required until a sectional structure shown in FIG.

  First, on the base substrate 10 made of metal or the like, a film made of a material whose adhesiveness is lower than that at room temperature (20 ° C.) due to heating, for example, a heat-foamed tape is attached as the release layer 11. In this embodiment, Riba Alpha manufactured by Nitto Denko is used as the thermal foam tape. In addition, you may comprise the release layer 11 with the material from which adhesiveness falls by UV hardening.

  In addition to the metal such as copper, copper alloy, or stainless steel, the base substrate 10 includes silicon and organic materials such as PET (Polyethylene terephthalate).

  Next, a titanium layer having a thickness of about 0.1 μm is formed on the release layer 11 as a seed layer 12 by sputtering. Note that a copper layer may be formed as the seed layer 12 instead of the titanium layer. In addition, the method for forming the seed layer 12 is not limited to the sputtering method, and the seed layer 12 may be formed by vapor deposition or electroless plating, or a rolled foil may be attached as the seed layer 12.

  Next, as shown in FIG. 1B, a photoresist is coated on the seed layer 12, and is exposed and developed to form a resist pattern 14 having a window 14a having a rectangular planar shape.

  Subsequently, as shown in FIG. 1C, if power is supplied to the seed layer 12, a nickel film is formed as a first metal film (first conductive film) 16a on the seed layer 12 exposed from the window 14a by electrolytic plating. Is formed to a thickness of 10 to 15 μm.

  The plating conditions are not particularly limited. In the present embodiment, the first metal film 16a is formed with the following plating solution composition and plating conditions.

(Plating solution composition)
Nickel sulfate: 240-300 g / liter Nickel chloride: 45-50 g / liter Boric acid: 30-40 g / liter (plating conditions)
Liquid temperature: 45-60 ° C
・ Current density: 2-8A / dm ²
The constituent material of the first metal film 16a is preferably a material that easily undergoes tensile stress, but such materials include Fe, Pd, Cu, Cr, and alloys thereof in addition to Ni.

  The stress value of the first metal film 16a can be adjusted by changing the film thickness, the plating solution composition, and the plating conditions.

  Next, as shown in FIG. 2A, a gold film is formed as a second metal film (second conductive film) 16b on the first metal film 16a by electrolytic plating while supplying power from the seed layer 12 to a thickness of 0. .01 to 2 μm.

  Although the plating conditions are not particularly limited, the following conditions are adopted in this embodiment.

(Plating solution composition)
・ Gold sodium sulfite: 10 g / liter ・ Sodium sulfite: 20 g / liter ・ Sodium hydrogen phosphate: 20 g / liter ・ Thallium: 0.01 g / liter (plating conditions)
Liquid temperature: 40-70 ° C
・ Current density: 0.1-3A / dm ²
It is preferable that the constituent material of the second metal film 16b is a material that easily becomes a compressive stress. As such a material, there are Zn, Sn, Bi, Co, Ag, and Ti in addition to Au, and the second metal film 16b may be formed of these materials.

  Further, similarly to the first metal film 16a, the stress value of the second metal film 16b may be adjusted by changing the film thickness, the plating solution composition, and the plating conditions.

  Thereafter, as shown in FIG. 2B, the resist pattern 14 is removed, and the first metal film 16 a and the second metal film 16 b are left as the stacked body 16 on the base substrate 10.

  Next, as shown in FIG. 2C, the portion of the seed layer 12 where the stacked body 16 is not formed is removed by wet etching. When a titanium layer is formed as the seed layer 12, for example, a mixed solution of hydrogen fluoride and nitric acid is used as the etching solution.

  Subsequently, as illustrated in FIG. 3A, a circuit board 50 mainly composed of an organic resin is prepared, and the circuit board is opposed to the stacked body 16.

  A solder resist 53 is formed on the main surface of the circuit board 50, and a first electrode 51 is formed inside the opening of the solder resist 53. Further, a conductive layer 52 made of an Sn-57Bi alloy having a melting point of 139 ° C. is formed on the surface of the first electrode 51. The conductive layer 52 is not limited to the Sn-57Bi alloy layer, and may be a plated layer made of any of Au, Cu, Sn, and Sn-based alloy, or a conductive paste.

  Then, as shown in the figure, one end A of the second metal film 16b constituting the stacked body 16 and the first electrode 51 of the circuit board 50 are aligned.

  Next, as shown in FIG. 3B, while heating the conductive layer 52 to a temperature of 150 to 180 ° C. at which the conductive layer 52 melts, the base substrate 10 is pressed toward the circuit board 50, and the conductive layer 52 Thus, the stacked body 16 is joined to the first electrode 51. At this time, the pressure applied to the base substrate 10 is not particularly limited, but in the present embodiment, a pressure of 0.5 to 10 g is applied to each first electrode 51.

  Subsequently, as shown in FIG. 4A, the base substrate 10 is attached to the circuit board 50 while heating the release layer 11 to a temperature (about 200 ° C.) at which the release layer 11 made of the heat-foaming tape foams. Pulled upward, the laminate 16 is peeled off from the base substrate 10. When the release layer 11 is made of a material whose adhesiveness is reduced by UV curing, the laminate 16 may be peeled from the base substrate 10 by irradiating the release layer 11 with UV.

  When peeled in this way, due to the difference in stress between the metal films 16a and 16b, the stacked body 16 is curved in an arc shape with the second metal film 16b on the outside.

  When the adhesion between the first metal film 16a and the seed layer 12 is weak, the etching process of the seed layer 12 in FIG. 2C is omitted, and the stacked body 16 is peeled from the seed layer 12 in this process. It may be. Further, when the adhesion between the seed layer 12 and the base substrate 10 is weak and the laminate 16 can be peeled off in this process as well, the release layer 11 may be omitted.

  Next, as shown in FIG. 4B, a semiconductor element (electronic component) 60 mainly composed of silicon having the second electrode 61 formed on the circuit formation surface is prepared. On the second electrode 61, a connection terminal 62 made of Sn-3.5Ag alloy is bonded in advance. The material of the connection terminal 62 is not particularly limited, and the connection terminal 62 may be composed of a plating film made of any of Au, Cu, Sn, and Sn-based alloy, or a conductive paste.

  Next, the semiconductor element 60 is pressed toward the circuit board 50 in a face-down state while heating the connection terminal 62 to a temperature of 221 ° C. or higher, which is the melting point of the connection terminal 62. In the present embodiment, for example, the semiconductor element 60 is pressed so that a pressure of 0.5 to 5 g is applied to the second electrode 61 per one.

  As a result, the other end B of the second metal film 16b constituting the stacked body 16 is joined to the second electrode 61, and the first and second electrodes 51, 61 are electrically and mechanically connected to each other by the stacked body 16. It is connected.

  Instead of pressing the semiconductor element 60 as described above, the stacked body 16 may be bonded to the second electrode 61 by its own weight. In that case, the flux may be transferred to the connection terminal 62 in advance, the connection terminal 62 may be temporarily attached to the laminate 16 with the flux, and the connection terminal 62 may be reflowed in the reflow apparatus.

  Thereafter, in order to reinforce the connection strength of the laminate 16, a sealing resin 70 is poured between the circuit board 50 and the semiconductor element 60 as shown in FIG. As the sealing resin 70, for example, an epoxy resin or a cyanate ester resin can be used. Note that the sealing resin 70 may be supplied in advance to the substrate side or the chip side, and the connection of the connection terminals and the resin sealing may be performed simultaneously.

  Thus, the basic structure of the electronic device according to this embodiment is completed.

  According to the present embodiment described above, as shown in FIG. 5, the stress caused by the difference in thermal expansion coefficient between the semiconductor element 60 and the circuit board 50 is relieved by the curved laminate 16, so that the semiconductor element 60 Thus, the risk of cracks is reduced, and the connection reliability between the semiconductor element 60 and the circuit board 50 is improved.

  In addition, as shown in FIG. 4A, the laminate 16 naturally curves due to the difference in internal stress between the first and second metal films 16a and 16b. The connection structure can be easily obtained at low cost.

  Further, as shown in FIGS. 1B to 2B, the metal films 16a and 16b are formed in the windows 14a of the resist pattern 14 that can be finely processed in the manufacturing process of the semiconductor device. In addition to the fact that the laminate 16 composed of these metal films can be finely formed, the laminates 16 can be arranged at a narrow pitch.

  By the way, in the said embodiment, although the 1st metal film 16a was made into the tensile stress and the 2nd metal film 16b was made into the compressive stress, the combination of the stress of each film | membrane 16a, 16b is not limited to this.

  For example, the stress of the first metal film 16a may be the same tensile stress as described above, and the stress of the second metal film 16b may be a tensile stress weaker than the tensile stress of the first metal film 16a.

  Alternatively, the stress of the first metal film 16a may be a compressive stress, and the stress of the second metal film 16b may be a compressive stress stronger than the compressive stress of the first metal film 16a.

  Also by these, as shown in FIG. 4A, the laminated body 16 curved in an arc shape with the second metal film 16b on the outside can be obtained.

  The direction of the stress of the film is substantially determined by the material. When forming a film having a tensile stress as the metal films 16a and 16b, the film may be formed of any one of Ni, Cr, Cu, Fe, and Pd, or an alloy thereof.

  On the other hand, when a compressive stress film is formed as the metal films 16a and 16b, the film may be formed of any one of Au, Zn, Sn, and Bi or an alloy thereof.

  Further, the stress value can be adjusted according to the composition of the plating solution, the plating conditions, and the film thickness as described above, whereby the laminate 16 curved with a desired curvature can be obtained.

  In the above description, the stacked body 16 is configured by two layers of the first and second metal films 16a and 16b. However, the number of stacked layers may be three or more.

  FIG. 6 is an enlarged cross-sectional view showing an example of a laminate 16 having a three-layer structure.

  In this example, a third metal film (third conductive film) 16c is further formed on the second metal film 16b. The third metal film 16c can be formed by plating on the second metal film 16b in the window 14a, for example, in the state of FIG.

  The direction and value of the stress of the third metal film 16c are not particularly limited.

  However, the material of the third metal film 16c is such that the stress values of the first to third metal films 16a to 16c monotonously decrease or increase from the first metal film 16a toward the third metal film 16c. It is preferable to set the plating conditions and the like. In this way, by changing the stress monotonously, compared to the case where the stacked body 16 is configured by only the first and second metal films 16a and 16b, the difference between the stresses of the films 16a to 16c causes the interface between them. The applied stress is relaxed, and the risk of cracks inside the laminate 16 can be reduced.

  Further, in the above description, the laminate 16 is configured by two layers of the first and second metal films 16a and 16b made of different materials. However, the first and second metal films 16a and 16b are the same. By forming them with materials and forming them under different plating conditions, the stresses of the metal films 16a and 16b may be made different, and the laminate 16 may be curved as shown in FIG.

  Further, instead of one of the first and second metal films 16a and 16b, a resin film made of polyimide or epoxy resin may be formed. As such a resin film, for example, a commercially available film such as a Kapton film manufactured by Toray DuPont Co., Ltd. can be used.

  In the case of using such a resin film, in the step of FIG. 1A, after forming the resin layer on the release layer 11, a resist pattern is formed on the resin film. Then, a metal film such as a copper film or a nickel film is formed on the resin film exposed from the resist pattern window by electroless plating. Thereafter, the resist pattern is removed together with the metal film formed thereon, so that a laminate composed of the resin film and the metal film is formed on the release layer 11. The laminate is curved as described with reference to FIG. 4A with the metal film facing outward due to the difference in stress between the metal film and the resin film.

  The features of the present invention are added below.

(Appendix 1) a circuit board on which a first electrode is formed;
An electronic component on which a second electrode is formed;
A laminated body that is formed by laminating a first conductive film and a second conductive film having different stresses, and electrically connects the first electrode and the second electrode;
The laminated body is curved, one end of the second conductive film is bonded to the first electrode, and the other end of the second conductive film is bonded to the second electrode. Electronic equipment.

  (Supplementary note 2) The electronic device according to supplementary note 1, wherein the first conductive film is a first metal film made of metal, and the second conductive film is a second metal film made of metal.

  (Supplementary Note 3) At least one of the first conductive film and the second conductive film is one of Ni, Fe, Pd, Cu, Cr, Au, Sn, Bi, Zn, Co, Ag, and Ti, or these The electronic device according to attachment 2, wherein the electronic device is made of an alloy of

  (Supplementary note 4) The electronic device according to supplementary note 1, wherein the stacked body is curved in an arc shape with the second conductive film facing outside.

  (Supplementary note 5) The electronic device according to supplementary note 1, wherein the stress of the first conductive film is a tensile stress, and the stress of the second conductive film is a compressive stress.

  (Additional remark 6) The stress of the said 1st electrically conductive film is a tensile stress, The stress of the said 2nd electrically conductive film is a tensile stress weaker than the said tensile stress of the said 1st electrically conductive film. The electronic device described.

  (Supplementary note 7) The supplementary note 1 is characterized in that the stress of the first conductive film is a compressive stress, and the stress of the second conductive film is a compressive stress stronger than the compressive stress of the first conductive film. The electronic device described.

  (Supplementary Note 8) A third conductive film is further formed on the second conductive film, and each stress value in the first to third conductive films is directed from the first conductive film to the third conductive film. The electronic device according to appendix 1, wherein the electronic device monotonously decreases or increases.

(Additional remark 9) The process of forming on the base substrate the laminated body formed by laminating | stacking the 1st conductive film and the 2nd conductive film from which a stress mutually differs in this order,
Bonding one end of the second conductive film to the first electrode of the substrate;
After the bonding, peeling the laminate from the base substrate, bending the laminate due to the difference in stress,
Bonding the other end of the second conductive film to the second electrode of the electronic component;
A method for manufacturing an electronic device, comprising:

(Additional remark 10) It further has the process of forming a release layer on the said base substrate,
The method for manufacturing an electronic device according to appendix 9, wherein in the step of forming the laminate, the laminate is formed on the release layer.

(Supplementary Note 11) As a material for the release layer, a material whose adhesiveness is lower than that at room temperature by heating is used.
The method of manufacturing an electronic device according to appendix 10, wherein the release layer is heated in the step of peeling the laminate from the base substrate.

(Additional remark 12) The process of forming the said laminated body,
Forming a resist pattern with a window on the base substrate;
Forming the first conductive film and the second conductive film in this order on the base substrate in the window of the resist pattern;
The method of manufacturing an electronic device according to appendix 9, further comprising a step of removing the resist pattern and leaving the first conductive film and the second conductive film on the base substrate as the stacked body. Method.

  (Supplementary Note 13) In the step of forming the first conductive film and the second conductive film, the first conductive film and the second conductive film are formed by electrolytic plating, and the plating conditions, the plating solution composition, The method of manufacturing an electronic device according to appendix 12, wherein the stress of the first conductive film and the second conductive film is adjusted by a film thickness.

1A to 1C are cross-sectional views (part 1) in the course of manufacturing the electronic device according to the embodiment of the present invention. 2A to 2C are cross-sectional views (part 2) in the middle of manufacturing the electronic device according to the embodiment of the present invention. 3A and 3B are cross-sectional views (part 3) in the course of manufacturing the electronic device according to the embodiment of the present invention. 4A and 4B are cross-sectional views (part 4) in the middle of manufacturing the electronic device according to the embodiment of the present invention. FIG. 5 is a cross-sectional view (part 5) of the electronic device according to the embodiment of the present invention during manufacture. FIG. 6 is an enlarged cross-sectional view showing an example of a three-layer laminate in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Base substrate, 11 ... Release layer, 12 ... Seed layer, 14 ... Resist pattern, 14a ... Window, 16a-16c ... 1st-3rd metal film, 16 ... Laminated body, 50 ... Circuit board, 51 ... 1st DESCRIPTION OF SYMBOLS 1 electrode, 52 ... Conductive layer, 53 ... Solder resist, 60 ... Semiconductor element, 61 ... 2nd electrode, 62 ... Connection terminal, 70 ... Sealing resin.

Claims (3)

A circuit board having a first electrode formed on a first surface;
An electronic component having a second electrode formed on the first surface;
A laminated body that is formed by laminating a first conductive film and a second conductive film having different stresses, and electrically connects the first electrode and the second electrode;
The first conductive film and the second conductive film are both made of the same material, and the first conductive film and the second conductive film are formed under different plating conditions, and the stress of the first conductive film Is tensile stress, stress of the second conductive film is compressive stress,
Arranging the circuit board and the electronic component such that the first surface of the circuit board and the first surface of the electronic component face each other;
The laminate is curved in an arc shape with the second conductive film outside, the one end of the second conductive film is joined to the first electrode, and the other end of the second conductive film is connected to the first electrode. An electronic device characterized by being joined to a second electrode. Forming a laminated body formed by laminating a first conductive film and a second conductive film having different stresses in this order on a base substrate;
Bonding one end of the second conductive film to the first electrode of the substrate;
After the bonding, peeling the laminate from the base substrate, bending the laminate due to the difference in stress,
Bonding the other end of the second conductive film to the second electrode of the electronic component;
A method for manufacturing an electronic device, comprising: The step of forming the laminate includes
Forming a resist pattern with a window on the base substrate;
Forming the first conductive film and the second conductive film in this order on the base substrate in the window of the resist pattern;
3. The electronic device according to claim 2 , further comprising a step of removing the resist pattern and leaving the first conductive film and the second conductive film as the stacked body on the base substrate. Production method.

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