JP2010283215A - Electronic device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic device with high connection reliability, and a method of manufacturing the electronic device. <P>SOLUTION: The electronic device 10 includes an electronic component 11, a substrate 12, solder 13, a first polymer layer 14, and a second polymer layer 15, wherein the electronic component 11 and substrate 12 are electrically connected to each other with the solder 13, the first polymer layer 14 is formed between the electronic component 11 and substrate 12 where the solder 13 is not present, and the second polymer layer 15 is formed in contact with a circumference of the electronic component 11 and the substrate 12 to surround at least part of a side face of the first polymer layer 14, the first polymer layer 14 having a lower elastic modulus than the second polymer layer 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  In recent years, electronic devices have been rapidly reduced in size and thickness, and it is also necessary to reduce the size and thickness of electronic components mounted on the substrate of the electronic device. For mounting electronic components on a board in an electronic device, for example, “Quad Flat Package (QFP)” in which lead wires are arranged around the electronic components is generally used. However, in this QFP, it is necessary to increase the external dimensions of the electronic component in order to increase the number of input / output terminals. Therefore, in order to realize further high density and downsizing, for example, it has a “Ball Grid Array (BGA)” structure in which ball-shaped protruding terminals (for example, terminals including solder balls) are arranged on the bottom surface of the electronic component. Electronic parts etc. are used.

  In mounting an electronic component on a substrate of an electronic device, the electronic component and the substrate are generally electrically connected by solder. Examples of the aforementioned solder include lead-free solder such as Sn—Ag—Cu alloy solder (melting point: 200 ° C. or higher). For this mounting, for example, a mounting process called reflow is used. In this mounting process, the interior of the reflow furnace is heated to a temperature higher than the melting point of the solder to melt the solder and connect the electronic component and the substrate. After reflow, the temperature in the reflow furnace is lowered to solidify the solder.

  In an electronic device in which an electronic component having the above-described BGA structure is mounted, for example, heat, impact, vibration, etc. in the usage environment are directly applied to the solder ball. In order to prevent adverse effects due to this (for example, cracking of solder balls, etc.), a gap called a gap between the electronic component and the substrate is filled with a resin called an underfill such as an epoxy resin, Heat cure to reinforce the solder balls. Thus, it is essential to prevent the solder ball from cracking and to ensure the reliability of the electrical connection between the electronic component and the substrate. In addition, as described above, since the electronic components are becoming smaller and thinner, the rigidity of the connection portion with the substrate tends to be lowered. For this reason, it is necessary to cover and reinforce between the electronic component and the substrate, for example, with a resin or the like in order to ensure the reliability of the electrical connection between the electronic component and the substrate, as described above. ing.

In such a background, in order to improve the reliability of the electrical connection between the electronic component and the substrate, for example, an electronic device described in Patent Document 1 has been proposed.
In the electronic device described in Patent Document 1, an underfill resin is formed immediately below the semiconductor chip for the purpose of preventing the breakdown of the low dielectric constant layer in the semiconductor chip on which the low dielectric constant layer is formed. An underfill resin having an elastic modulus lower than that of the underfill resin is formed on the outer periphery (see claim 1 of FIG. 1 and FIG. 1).

JP 2008-276731 A

  In recent years, an electronic device in which a plurality of electronic components are modularized and mounted on a mother board is increasing. In addition, electronic devices in which electronic components are three-dimensionally mounted have been used. When manufacturing such an electronic device, for example, a mounting process by reflow or the like is performed a plurality of times. In this case, the solder used for connection in the previous mounting process will be melted again when heated to a temperature equal to or higher than the melting point in the next mounting process. The molten solder expands in volume compared to the solidified state. For example, in the case of the above-mentioned Sn—Ag—Cu alloy solder, it expands by about 4%. When the underfill resin is formed around the solder, a high pressure is applied to the underfill resin due to the expansion of the solder, and the underfill resin may crack. When the crack occurs, the molten solder flows out through the crack. If the solder is solidified again in this state, the amount of solder may be insufficient, and the electrical connection between the electronic component and the board may be broken. As described above, the possibility of cracking in the underfill resin may significantly reduce the connection reliability of the electronic device.

  In order to prevent the occurrence of cracks in the above-described underfill resin, for example, an underfill resin having a low elastic modulus may be used. However, when an underfill resin having a low elastic modulus is used, the reinforcement of solder such as solder balls is not sufficient. That is, the prevention of cracking of the underfill resin due to the volume expansion of the solder and the reinforcement of the solder are in a trade-off relationship. When the solder is not sufficiently reinforced, the impact resistance of the solder portion is lowered, and for example, cracks may occur in the solder due to stress such as impact. As described above, the possibility of cracks in the solder may significantly reduce the connection reliability of the electronic device.

  An object of the present invention is to provide an electronic device with high connection reliability.

In order to achieve the above object, an electronic device of the present invention includes:
An electronic component, a substrate, solder, a first polymer layer, and a second polymer layer;
The electronic component and the substrate are electrically connected by the solder,
The first polymer layer is formed in a portion where the solder does not exist between the electronic component and the substrate,
The second polymer layer is formed so as to be in contact with the periphery of the electronic component and the substrate and surround at least a part of a side surface of the first polymer layer;
The elastic modulus of the first polymer layer is lower than the elastic modulus of the second polymer layer.

  According to the present invention, an electronic device with high connection reliability can be provided.

(A) is a top view which shows the structure of an example in Embodiment 1 of the electronic device of this invention, (b) is sectional drawing seen in the II direction of the electronic device shown to (a). It is a top view which shows the other example in Embodiment 1 of the electronic device of this invention. (A) is a top view which shows the structure of the other example in Embodiment 1 of the electronic device of this invention, (b) is sectional drawing seen in the II-II direction of the electronic device shown to (a). It is. (A) is a top view which shows the structure of the other example in Embodiment 1 of the electronic device of this invention, (b) is sectional drawing seen in the III-III direction of the electronic device shown to (a). It is.

  Hereinafter, the electronic device and the method of manufacturing the electronic device of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

(Embodiment 1)
FIG. 1 shows a configuration of an example of an electronic apparatus according to this embodiment. FIG. 1A is a plan view of the electronic device according to the present embodiment, and FIG. 1B is a cross-sectional view taken along the line II in FIG. 1A. In both the drawings, the same parts are denoted by the same reference numerals. As shown in FIGS. 1A and 1B, the electronic device 10 includes an electronic component 11 having a BGA structure on which solder balls 13 are formed, a substrate 12, a first thermosetting resin layer 14, and the like. And a second thermosetting resin layer 15. The electronic component 11 and the substrate 12 are electrically connected by the solder ball 13. The first thermosetting resin layer 14 is formed over almost the entire area where the solder balls 13 do not exist between the electronic component 11 and the substrate 12. The second thermosetting resin layer is in contact with the entire periphery of the side surface on the lower end side of the electronic component 11 and the entire periphery of the side surface of the first thermosetting resin layer 14. 15 is formed. In the electronic device 10 of this embodiment, the elastic modulus of the first thermosetting resin layer 14 is lower than the elastic modulus of the second thermosetting resin layer 15.

  As described above, for example, when the mounting process such as reflow is performed a plurality of times, or when the electronic device of the present embodiment is used, when the temperature environment is higher than the melting point of the solder ball, the solder is It is melted again. In the electronic device of this embodiment, as described above, the elastic modulus of the first thermosetting resin layer is lower than the elastic modulus of the second thermosetting resin layer. For this reason, it is possible to prevent the first thermosetting resin layer from being cracked due to the volume expansion of the solder due to the melting. As a result, the electrical connection between the electronic component having the BGA structure and the substrate does not break. Further, when a stress such as a drop impact is applied to the electronic device, the bending rigidity of the electronic component changes. Due to this change in bending rigidity, the substrate is locally bent in the vicinity of the outer periphery of the electronic component, whereby a strong tensile force is generated in the first thermosetting resin layer. In such a case, cracks may occur in the first thermosetting resin layer. However, in the electronic device of this embodiment, the occurrence of the crack can be prevented.

  In the electronic device of the present embodiment, as described above, the elastic modulus of the second thermosetting resin layer is higher than that of the first thermosetting resin layer, and is formed as described above. Yes. For this reason, it is possible to sufficiently reinforce the solder balls, and as a result, it is possible to prevent cracks from occurring in the solder balls. Due to these effects, the electronic device of this embodiment has high connection reliability. In the electronic device of the present embodiment, the second thermosetting resin layer is formed so as to be in contact with the entire side surface of the first thermosetting resin layer. It is not limited to. If it is possible to prevent local deformation of the substrate that occurs on the outer periphery of the electronic component due to dropping or the like, the second thermosetting resin layer is not in contact with the first thermosetting resin layer, for example. It may be formed. In order to do this, the second thermosetting resin layer may be formed so as to firmly connect the electronic component having the BGA structure and the substrate, for example.

  In the electronic device of this embodiment, as described above, an electronic component having a BGA structure is used as the electronic component, but the present invention is not limited to this. Examples of the electronic component include an electronic component having a BFP structure and an electronic component having a QFP structure, for example. The electronic component may not be packaged.

  As the substrate, for example, a conventionally known substrate can be used. Examples of the substrate include an organic substrate and an inorganic substrate. Examples of the organic substrate include a glass epoxy substrate in which an epoxy resin is impregnated into a glass fiber, a liquid crystal polymer substrate, a Teflon (registered trademark) substrate, and the like. Examples of the inorganic substrate include a glass ceramic substrate. These substrates may be used alone or, for example, as a metal base substrate integrated with a metal plate such as Al or Cu.

  In the electronic device according to the present embodiment, as described above, the solder balls formed on the electronic component having the BGA structure are used as the solder, but the present invention is not limited to this. Conventionally known solder can be used as the solder. In the present invention, “solder” means a low melting point brazing alloy. The melting point is not particularly limited, but is, for example, 450 ° C. or lower. Examples of the solder include lead-free solder. Examples of the lead-free solder include high melting point solder such as Sn—Ag—Cu alloy solder (melting point: 200 ° C. or higher); low melting point such as Sn-52In (melting point: 117 ° C.), In-3Ag (melting point: 141 ° C.) For example, solder. For example, when the low-melting-point solder is used as the solder, the electronic device of the present embodiment is used at a temperature equal to or higher than the melting point of the low-melting-point solder (for example, in the vicinity of an engine room of an automobile or the like (about 120 ° C. ), The low-melting-point solder is in a molten state at the time of use. Even in such a case, the electronic device of this embodiment has high connection reliability due to the above-described effects. Can be secured. In such a case, since the solder is in a liquid phase at the time of use, an effect that the crack does not occur in the solder is also obtained.

  In the electronic device of this embodiment, as described above, the first thermosetting resin layer is used as the first polymer layer, but the present invention is not limited to this. The first polymer layer only needs to have a lower elastic modulus than the second polymer layer. In addition, when the mounting process such as reflow is performed a plurality of times, or when the electronic device of the present embodiment is used, the first polymer layer becomes a temperature environment equal to or higher than the melting point of the solder ball. However, it is preferable that the solder can be prevented from flowing out. Examples of the material for forming the first polymer layer include a thermosetting resin, a photocurable resin, a thermoplastic resin, and rubber. Examples of the thermosetting resin include an epoxy resin and a polyimide resin. As the material for forming the first polymer layer, one kind may be used alone, or two or more kinds may be used in combination.

  The elastic modulus of the first thermosetting resin layer is, for example, in the range of 0.001 to 10 GPa. The elastic modulus of the first thermosetting resin layer can be determined according to JIS K 6911, for example.

  In the electronic device of this embodiment, as described above, the second thermosetting resin layer is used as the second polymer layer, but the present invention is not limited to this. The second polymer layer only needs to have a higher elastic modulus than that of the first polymer layer. Except for this point, the material for forming the second polymer layer may be the same as the material for forming the first polymer layer.

  The elastic modulus of the second thermosetting resin layer is, for example, in the range of more than 10 GPa and 40 GPa or less. The elastic modulus of the second thermosetting resin layer can be determined according to JIS K 6911, for example. As a combination of the first thermosetting resin layer and the second thermosetting resin layer, for example, a material for forming the first thermosetting resin layer is a low-elasticity polyimide resin, and the second thermosetting resin layer is used. A combination of the material for forming the thermosetting resin layer is a highly elastic epoxy resin.

  Next, a method for manufacturing the electronic device of this embodiment will be described. The method for manufacturing the electronic device of the present embodiment includes a solder connection step, a first thermosetting resin layer forming step, and a second thermosetting resin layer forming step. In the method for manufacturing the electronic device of the present embodiment, the first polymer layer forming step and the second polymer layer forming step are respectively performed as the first thermosetting resin layer forming step and the second polymer layer forming step. The thermosetting resin layer forming step is used.

[Solder connection process]
First, an electronic component having a BGA structure on which solder balls are formed is mounted on a predetermined position of a substrate coated with cream solder. In this state, the solder ball is melted by setting the temperature condition to be equal to or higher than the melting temperature of the solder ball. Thereafter, the solder is solidified by lowering the temperature. In this way, the electronic component and the substrate are electrically connected using solder. This step can be performed by a conventionally known mounting step such as reflow, for example.

[First thermosetting resin layer forming step]
Next, a material for forming the first thermosetting resin layer is filled in almost the entire region where the solder does not exist between the electronic component and the substrate. The material for forming the first thermosetting resin layer is as described above. In this state, the first thermosetting resin layer is formed by raising the temperature of the material to a temperature for thermosetting. As a material for forming the first thermosetting resin layer, a material whose curing temperature is, for example, equal to or lower than the melting temperature of the solder is selected. The elastic modulus of the first thermosetting resin layer is as described above. After the first thermosetting resin layer is formed, the molten solder can be held even if the solder is melted again as described above.

[Second thermosetting resin layer forming step]
Next, a material for forming the second thermosetting resin layer is formed such that the second thermosetting resin layer is formed in a state where the second thermosetting resin layer is in contact with the electronic component and the substrate. Apply over the entire circumference. In this state, the second thermosetting resin layer is formed by raising the temperature of the material to a temperature at which it is thermoset. As the material for forming the second thermosetting resin layer, one having an arbitrary curing temperature can be used. The elastic modulus of the second thermosetting resin layer is as described above. In this way, the electronic device of this embodiment can be manufactured. However, the method for manufacturing the electronic device of the present embodiment is not limited to this example. In the case of implementing the three-dimensional mounting, for example, the method for manufacturing the electronic device of the present embodiment may be repeated. By doing in this way, it can prevent that a crack generate | occur | produces in the 1st thermosetting resin layer with the volume expansion of the solder fuse | melted again.

  In the electronic device of this embodiment, for example, the second thermosetting resin layer may be formed in contact with a part of the electronic component. FIG. 2 shows a configuration of an example of this electronic device. In this figure, the same parts as those in FIG. As shown in FIG. 2, in the electronic device 20, the second thermosetting resin layer 25 is formed in the vicinity of the four corners of the electronic component 11. Other configurations are the same as those of the electronic device 10 described above. Even in such a form, it is possible to prevent local deformation of the substrate that occurs on the outer periphery of the electronic component due to dropping or the like. For this reason, the electronic device 20 can achieve the same effects as the electronic device 10 described above.

  In the electronic device of this embodiment, for example, the second thermosetting resin layer may be formed so as to cover the entire electronic component. FIG. 3 shows an example of the configuration of this electronic device. FIG. 3A is a plan view of the electronic device, and FIG. 3B is a cross-sectional view as viewed in the II-II direction of FIG. In both the drawings, the same parts as those in FIG. As shown in FIGS. 3A and 3B, in the electronic device 30, the second thermosetting resin layer 35 is formed so as to cover the entire electronic component 11. Other configurations are the same as those of the electronic device 10 described above. With such a configuration, the impact resistance can be further improved. For this reason, the electronic device 30 can achieve the same effect as the electronic device 10 described above.

  In the electronic device of the present embodiment, for example, the second thermosetting resin layer may be a laminated body including a plurality of layers. FIG. 4 shows an example of the configuration of this electronic device. FIG. 4A is a plan view of the electronic device, and FIG. 4B is a cross-sectional view as viewed in the III-III direction of FIG. In both the drawings, the same parts as those in FIG. As shown in FIGS. 4A and 4B, in the electronic device 40, the second thermosetting resin layer 45 includes a 2-1 thermosetting resin layer 45a and a 2-2 thermosetting. The laminated resin layer 45b and the second and third thermosetting resin layers 45c are laminated in this order from the side in contact with the electronic component 11 toward the outside of the substrate 12. The elastic modulus of the 2-1 thermosetting resin layer 45a is lower than the elastic modulus of the 2-2 thermosetting resin layer 45b. The elastic modulus of the 2-2 thermosetting resin layer 45b is lower than the elastic modulus of the 2-3 thermosetting resin layer 45c. Other configurations are the same as those of the electronic device 10 described above. In such a form, in addition to the same effect as the electronic device 10 described above, a layer having a higher elastic modulus can be formed as the second thermosetting resin layer, and It is possible to reduce the difference in elastic modulus at the portion in contact with the first thermosetting resin layer.

  As described above, the electronic device of the present invention has high connection reliability. Therefore, as an application of the electronic device of the present invention, for example, an application in which the use of an electronic component having a BGA structure as an engine control unit is being considered can be cited. However, its use is not limited and can be applied to a wide range of fields.

  Next, examples of the present invention will be described. The present invention is not limited or restricted by the following examples.

[Example 1]
The electronic device 10 shown in FIG. 1 was produced. The configuration of the electronic device used in Example 1 will be described below.

[Production of electronic devices]
1. First, an electronic component having a BGA structure (manufactured by NEC Electronics Co., Ltd., fine pitch BGA) was used as the electronic component 11. In this electronic component 11, the solder balls 13 have a pitch size: 0.5 mm, a solder diameter: 0.3 mm, and a height: 0.25 mm. The material of the solder ball 13 is Sn-3.0Ag-0.5Cu lead-free solder (melting point: 220 ° C., volume expansion coefficient: about 4%). A substrate coated with cream solder (made by Toppan NEC Circuit Solutions, a build-up printed wiring board) was used as the substrate 12. The electronic component 11 was mounted on a predetermined position of the substrate 12 and introduced into a reflow furnace. In this state, the furnace was heated to a temperature higher than the solder melting temperature (220 ° C. or higher) to melt the solder ball 13 and then cooled to room temperature. In this way, the electronic component 11 and the substrate 12 were electrically connected using the solder balls 13.

2. First Thermosetting Resin Layer Formation Step Next, a first heat is applied to almost the entire area where the solder 13 does not exist between the electronic component 11 and the substrate 12 (height: about 0.25 mm). The material for forming the curable resin layer 14 was filled. In this state, the material was cured by heating to 85 ° C. Thus, the 1st thermosetting resin layer 14 was formed. As this material, an underfill material (product name “Underfill U8443” manufactured by NAMICS Co., Ltd.) was used. The elastic modulus of this underfill material is 6.5 GPa. Since this underfill material has a low viscosity, it can be filled even when the height between the electronic component 11 and the substrate 12 is as narrow as 0.25 mm.

3. Second Thermosetting Resin Layer Forming Step Next, a material for forming the second thermosetting resin layer 15 was applied over the entire outer surface of the electronic component 11. In this state, the material was cured by heating to 90 ° C. In this way, a second thermosetting resin layer 15 was formed. As this material, an underfill material (trade name “Underfill U8449” manufactured by Namics Co., Ltd.) was used. The elastic modulus of this underfill material is 14.0 GPa. Thus, the 2nd thermosetting resin layer 15 was formed and the electronic apparatus 10 of a present Example was produced.

[Example 2]
An electronic device 10 of this example was fabricated in the same manner as in Example 1 except that Sn—In lead-free solder (melting point: 117 ° C.) was used as the material of the solder ball 13.

10, 20, 30, 40 Electronic device 11 Electronic component having BGA structure (electronic component)
12 Substrate 13 Solder ball (solder)
14 1st thermosetting resin layer (1st polymer layer)
15, 25, 35, 45 Second thermosetting resin layer (second polymer layer)
45a 2-1 thermosetting resin layer 45b 2-2 thermosetting resin layer 45c 2-3 thermosetting resin layer

Claims (6)

An electronic component, a substrate, solder, a first polymer layer, and a second polymer layer;
The electronic component and the substrate are electrically connected by the solder,
The first polymer layer is formed in a portion where the solder does not exist between the electronic component and the substrate,
The second polymer layer is formed so as to be in contact with the periphery of the electronic component and the substrate and surround at least a part of a side surface of the first polymer layer;
An electronic device, wherein an elastic modulus of the first polymer layer is lower than an elastic modulus of the second polymer layer. The elastic modulus of the one polymer layer is in the range of 0.001 to 10 GPa,
The electronic device according to claim 1, wherein the elastic modulus of the second polymer layer is in a range of more than 10 GPa and not more than 40 GPa.   3. The electronic device according to claim 1, wherein the first polymer layer and the second polymer layer are thermosetting resin layers.   The electronic device according to claim 1, wherein the solder is lead-free solder. The solder includes solder balls;
5. The electronic device according to claim 1, wherein the electronic component is an electronic component having a BGA structure including the solder balls. 6. A solder connection step of electrically connecting the electronic component to the substrate using the solder;
A first polymer layer forming step of forming the first polymer layer in a portion where the solder is not present between the electronic component and the substrate;
A second polymer layer forming step of forming the second polymer layer so as to contact the periphery of the electronic component and the substrate and surround at least a part of the side surface of the first polymer layer; A method for manufacturing an electronic device according to any one of claims 1 to 5, further comprising:

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