Electronic device with a standoff member and method of manufacturing such an electronic device

BACKGROUND OF THE INVENTION

1. Field of The Invention

0001The present invention generally relates to an electronic device, a standoff member, and an electronic-device manufacturing method. More particularly, the present invention relates to an electronic device having the structure in which a semiconductor device and a mounting substrate are bonded together by flip-chip bonding with a predetermined standoff therebetween, and a method of manufacturing the electronic device.

2. Description of The Related Art

0002<figref idref="f0001">FIG. 1</figref> shows the outline composition of a conventional electronic device 1. The conventional electronic device 1 of <figref idref="f0001">FIG. 1</figref> generally contains the semiconductor device 2, the system board 3, and the heat sink 4.

0003The semiconductor device 2 has a BGA (ball grid array) type package structure and comprises the semiconductor chip 5, the package substrate 6, the lid 7, and the bumps 8. The flip-chip bonding of the semiconductor chip 5 is performed on the top surface of the package substrate 6.

0004Moreover, the plurality of bumps 8 are arranged on the bottom surface of the package substrate 6. The package substrate 6 is the multi-layer substrate and functions as an interposer which electrically connects the bumps 8 on the bottom surface of the package substrate 6 to the semiconductor chip 5 on the top surface of the package substrate 6.

0005Moreover, the lid 7 is arranged on the top surface of the package substrate 6 on which the semiconductor chip 5 is carried in order to protect the semiconductor chip 5 from dusts or damage.

0006Furthermore, the bumps 8 (solder balls) are arranged on the bottom surface of the package substrate 6, and the package substrate 6 is soldered to the system board 3 via the bumps 8. Thereby, the flip-chip bonding of the semiconductor device 2 to the system board 3 is formed.

0007On the other hand, the heat sink 4 is formed in order to dissipate the heat generated by the semiconductor chip 5 into the atmosphere. The semiconductor device 2 mentioned above is arranged on the top of the base 13, and the heat sink 4 is arranged on the top of the lid 7 through the heat transfer material 9.

0008The heat sink 4 is pressed onto the base 13 by the springs 10, so that the heat sink 4 contacts the lid 7 firmly under pressure. Therefore, thermal conduction of the heat generated by the semiconductor chip 5 to the heat sink 4 readily occurs through the lid 7 and the heat transfer material 9, and the heat sink 4 dissipates the heat into the atmosphere effectively.

0009In recent years, the quantity of the heat generated by the semiconductor chip 5 is increasing on a yearly basis with the improvement in the performance of the electronic system on which the electronic device 1 is carried. In order to improve the cooling performance, the size expansion of the heat sink 4, the material change of the heat sink 4 (for example, aluminum is changed to copper), etc. have been achieved. In connection with this, the weight of the heat sink 4 is increasing and the loading force of the springs 10 to press the heat sink 4 onto the semiconductor device 2 firmly is also increasing.

0010Thus, the difficulty arises in that the bumps 8 (solder balls) receive the increased weight of the heat sink 4, and the increased loading force of the springs 10, and fracture of the bumps 8 may occur if all the weight and the loads are impressed on the bumps 8.

0011Even though the fracture does not occur, deformation of the bumps 8 may occur, and the clearance between the system board 3 and the package substrate 6 becomes too narrow and uneven. In such circumstances, the deformation of the bumps 8 will cause a short circuit between the adjoining bumps 8.

0012Hereinafter, the clearance between the system board (mounting substrate) and the package substrate will be referred to as the standoff.

0013To obviate the above problem, arranging a standoff member (spacer) between the system board 3 and the package substrate 6 is known.

0014<figref idref="f0001">FIG. 2</figref> shows the bonded portion between the system board 3 and the package substrate 6 in the conventional electronic device 1 of <figref idref="f0001">FIG. 1</figref> in the vicinity of the standoff member.

0015In the conventional example of <figref idref="f0001">FIG. 2</figref>, the standoff member 11 is soldered to the package substrate 6 through the solder 12. The predetermined standoff is formed between the system board 3 and the package substrate 6 by this standoff member 11.

0016The weight of the heat sink 4 and the loading force of the springs 10 can be received by the standoff member 11 mainly, and the use of the standoff member 11 enables the force impressed to the bumps 8 to be reduced. For this reason, it is possible to prevent the deformation or fracture of the bumps 8, and, therefore, the package substrate 6 and the system board 3 can be electrically connected safely.

0017Moreover, the standoff member is not restricted to the composition shown in <figref idref="f0001">FIG. 1 and FIG. 2</figref>, and standoff members in various kinds of composition have been proposed.

0018Specifically, <patcit id="pcit0001" dnum="JP10013012A"><text>Japanese Laid-Open Patent Application No. 10-013012</text></patcit> discloses an example of the standoff member which employs a resin spacer provided between a semiconductor device and a system board (mounting substrate). Moreover, <patcit id="pcit0002" dnum="JP9213743A"><text>Japanese Laid-Open Patent Application No. 09-213743</text></patcit> discloses a spacer portion (standoff member) which defines a predetermined standoff between a semiconductor device and a wiring substrate, and this spacer portion is inserted in the positioning hole of the semiconductor device and the positioning hole of the wiring substrate in common. The spacer portion is arranged approximately in the center of the positioning pins which are provided for positioning of the semiconductor device and the wiring substrate.

0019In the conventional technology of <figref idref="f0001">FIG. 1 and FIG. 2</figref>, the standoff member 11 is fixedly soldered to the package substrate 6 by the solder 12. For this reason, it is necessary to improve the soldering wettability of the soldering surface of the standoff member 11. The surface treatment, such as Au plating, is required for the surface of the standoff member 11 confronting the solder 12 for this purpose, which causes the manufacturing cost to increase.

0020Moreover, the material and configuration of the standoff member 11 are different from those of the bumps 8, and there is the problem in that special consideration must be taken to the positioning and handling of the standoff member 11 and the bumps 8, which causes the efficiency of manufacture of the electronic device 1 to fall.

0021On the other hand, in the method of <patcit id="pcit0003" dnum="JP10013012A"><text>Japanese Laid-Open Patent Application No. 10-013012</text></patcit>, the resin spacer is used as the standoff member. For this reason, additional equipment for filling the resin in the space between the semiconductor device and the mounting board is required, which causes the equipment and facility cost to increase.

0022Moreover, in order to cure the resin, additional heat-treatment is required. Since the height of the resin spacer on the mounting board just after the filling of the resin is completed is still uneven, the leveling procedure is also needed. Therefore, the use of the resin spacer will make the manufacturing processes complicated.

0023Furthermore, in the method of <patcit id="pcit0004" dnum="JP9213743A"><text>Japanese Laid-Open Patent Application No. 09-213743</text></patcit>, the positioning of the semiconductor device and the wiring substrate is performed with the positioning pins in which the spacer portion (standoff member) is provided. For this reason, it is necessary to carry out the machining of the positioning pins and the positioning holes with high precision. The preparation of such positioning pins and holes is difficult and troublesome, and the manufacturing cost will be raised.

0024The prior art also comprises the documents <patcit id="pcit0005" dnum="US5136366A"><text>US-A-5 136 366</text></patcit>, <patcit id="pcit0006" dnum="EP0248566A"><text>EP-A-0 248 566</text></patcit><patcit id="pcit0007" dnum="US2004134680A1"><text>US 2004/134680 A1</text></patcit> and <patcit id="pcit0008" dnum="US2003145460A1"><text>US 2003/145460 A1</text></patcit>.

SUMMARY OF THE INVENTION

0025An object of the present invention is to provide an improved standoff member used in an electronic device in which the above-mentioned problems are eliminated.

0026Another object of the present invention is to provide an electronic device and an electronic-device manufacturing method in which the package substrate and the mounting substrate can be supported with the predetermined standoff using a simple and inexpensive composition.

0027In order to achieve the above-mentioned objects, the present invention provides an electronic device as defined in claim 1.

0028According to the present invention, the standoff between the package substrate and the mounting substrate can be maintained at the predetermined clearance. What is needed is just to insert the insertion portion of the standoff member into the hole of the mounting substrate and dispose the package substrate so as to contact the standoff portion.

0029For this reason, the fixing member for fixing the standoff member and the package substrate as required in the conventional method is no longer necessary, and reduction of the number of the required parts is possible.

0030Moreover, since it is unnecessary to prepare the standoff member with a selected material which is suitable for the soldering, the flexibility at the time of choosing the material of the standoff member can be increased.

0031The above-mentioned electronic device is configured so that the standoff portion has a flat, smooth contact surface which contacts the package substrate. According to the present invention, the package substrate is in the state where the package substrate can be displaced to the standoff member, so that relative displacement of the semiconductor device to the mounting substrate is possible. For this reason, it is expected that the self-alignment of the semiconductor device occurs by the surface tension generated when the bumps are fused at the time of flip-chip bonding of the semiconductor device to the mounting substrate. Therefore, positioning of the semiconductor device and the mounting substrate can be performed easily and with high precision, without providing the additional positioning mechanism etc. at the time of flip-chip bonding.

0032Moreover, the above-mentioned electronic device may be configured so that the insertion portion has a tapered portion at a leading edge of the insertion portion. According to the present invention, the standoff member having the tapered portion at the leading edge of the insertion portion can be easily inserted in the hole of the mounting substrate.

0033Moreover, the above-mentioned electronic device may be configured so that the semiconductor device has a BGA type structure. The above-mentioned electronic device may be configured so that a pressing member is disposed at an upper part of the semiconductor device to press the semiconductor device onto the mounting substrate.

0034According to the present invention, the standoff member has a simple composition which includes the insertion portion and the standoff portion, and the productivity is good and reduction of the manufacturing cost is possible.

0035In order to achieve the above-mentioned objects, the present invention provides a method as defined in claim 5.

0036According to the present invention, the processing which carries out flip-chip bonding of the semiconductor device and the mounting substrate can be performed easily, and the standoff between the package substrate and the mounting substrate can be maintained at the predetermined level stably.

BRIEF DESCRIPTION OF THE DRAWINGS

0037Other objects, features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a diagram showing the composition of the conventional electronic device.</li><li><figref idref="f0001">FIG. 2</figref> is a diagram showing a portion of the conventional electronic device in the vicinity of the standoff member.</li><li><figref idref="f0002">FIG. 3</figref> is a diagram showing the composition of the electronic device in one preferred embodiment of the invention.</li><li><figref idref="f0003">FIG. 4</figref> is a diagram showing a portion of the electronic device of the present embodiment in the vicinity of the standoff mechanism.</li><li><figref idref="f0003">FIG. 5A and FIG. 5B</figref> are diagrams showing the standoff member in the electronic device of the present embodiment.</li><li><figref idref="f0004">FIG. 6A and FIG. 6B</figref> are diagrams for explaining the state in which the standoff member is contained in the embossed tape.</li><li><figref idref="f0004">FIG. 7</figref> is a diagram for explaining the procedure to attach the standoff member to the system board in the electronic-device manufacturing method in one preferred embodiment of the invention.</li><li><figref idref="f0005">FIG. 8</figref> is a diagram for explaining the procedure to dispose the package substrate on the standoff member attached to the system board in the electronic-device manufacturing method of the present embodiment.</li><li><figref idref="f0005">FIG. 9</figref> is a diagram for explaining the procedure to perform the reflow processing in the electronic-device manufacturing method of the present embodiment.</li></ul>

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0038A description will now be given of the preferred embodiments of the present invention with reference to the accompanying drawings.

0039<figref idref="f0002">FIG. 3</figref> shows the composition of the electronic device 20 in the preferred embodiment of the invention.

0040The electronic device 20 of <figref idref="f0002">FIG.3</figref> comprises the semiconductor device 22, the system board 23 (the mounting substrate), the heat sink 24, and the standoff mechanism 40.

0041The semiconductor device 22 is has a BGA (ball grid array) type package structure and comprises the semiconductor chip 25, the package substrate 26, the lid 27, and the bumps 28.

0042The semiconductor chip 25 operates at the accelerated rate and a large mount of heat is generated during operation. The flip-chip bonding of the semiconductor chip 25 is formed on the top surface of the package substrate 26. Furthermore, the under-fill resin 34 is disposed between the semiconductor chip 25 and the package substrate 26 where the flip-chip bonding is formed, in order to raise the bonding reliability.

0043Moreover, the lid 27 is disposed on the surface on which the semiconductor chip 25 of the package substrate 26 is carried, in order to protect the semiconductor chip 25 from dusts or damage. The lid 27 is formed from the metal with a high thermal conductivity, and this lid 27 is soldered to the package substrate 26. The heat transfer material 35 is disposed between the top surface of the lid 27 and the top surface of the semiconductor chip 25, and, therefore, the thermal conduction between the semiconductor chip 25 and the lid 27 is possible.

0044The bumps 28 (formed of solder balls) are arranged on the bottom surface of the package substrate 26. This bottom surface of the package substrate 26 confronts the system board 23. The package substrate 26 is the multi-layer substrate and functions as an interposer which electrically connects the bumps 28 on the bottom of the package substrate 26 to the semiconductor chip 25 on the top of the package substrate 26.

0045The bumps 28 are arranged on the bottom surface of the package substrate 26 in a matrix formation except for the position where the standoff mechanism 40 (which will be mentioned later) is disposed. That is, the bottom surface of the package substrate 26 at the position corresponding to the arrangement position of the standoff mechanism 40 is made into a flat and smooth surface.

0046On the other hand, the heat sink 24 is provided in order to dissipate the heat generated by the semiconductor chip 25. This heat sink 24 is attached to the semiconductor device 22 by the attachment mechanism. The attachment mechanism comprises the springs 30, the base 31, the shafts 32, and the fastening nuts 33.

0047The shafts 32 are formed on the base 31 in the upright condition, and these shafts 32 are inserted in the through holes which are formed in the heat sink 24 at the corresponding positions.

0048In order to attach the heat sink 24 to the semiconductor device 22, the semiconductor device 22 is disposed on the base 31, and thereafter, the heat sink 24 is fitted to the shafts 32. At this time, the heat transfer material 29 is disposed beforehand on the top surface of the lid 27 which constitutes part of the semiconductor device 22.

0049And when the heat sink 24 contacts the semiconductor device 22 through the lid 27 and the heat transfer material 29, the springs 30 are attached to the shafts 32 which extending upward from the heat sink 24, and the fastening nuts 33 are secured to the upper ends of the shafts 32 which are threaded beforehand.

0050Accordingly, the heat sink 24 is pressed onto the base 31 by the springs 30 so that the heat sink 24 contacts the semiconductor device 22 firmly through the lid 27 and the heat transfer material 29. Thus, thermal conduction of the heat generated in the semiconductor chip 25 to the heat sink 24 readily occurs through the lid 27 and the heat transfer material 29, and the heat sink 24 dissipates the heat of the semiconductor chip 25 effectively.

0051In recent years, the quantity of the heat generated by the semiconductor chip 25 is increasing. In order to improve the cooling performance, the size expansion of the heat sink 24, the material change of the heat sink 24 (for example, aluminum is changed to copper), etc. have been achieved. In connection with this, the weight of the heat sink 24 is increasing and the loading force of the springs 30 to press the heat sink 24 onto the semiconductor device 20 is also increasing.

0052To avoid the problem that all the weight of the heat sink 24 and the loads of the springs 30 are impressed on the bumps 28 (solder balls), the standoff mechanism 40 is used in this embodiment in order to support the package substrate 26 on the system board 23.

0053Next, the composition of the standoff mechanism 40 will be explained.

0054<figref idref="f0003">FIG. 4</figref> shows the bonded portion between the system board 23 and the package substrate 26 in the electronic device 20 of <figref idref="f0002">FIG. 3</figref> in the vicinity of the standoff mechanism 40.

0055As shown in <figref idref="f0003">FIG. 4</figref>, the package substrate 26 (the semiconductor device 22) is supported by the standoff mechanism 40 on the system board 23. And this standoff mechanism 40 forms a predetermined standoff between the system board 23 and the package' substrate 26. The predetermined standoff means the clearance indicated by the arrow H in <figref idref="f0003">FIG. 4</figref>.

0056Accordingly, the weight of the heat sink 24 and the loading force of the springs 30 are mainly received by the standoff mechanism 40, and the force impressed to the bumps 28 can be reduced by the standoff mechanism 40. This makes it possible to prevent the deformation or fracture of the bumps 28, and, therefore, the electrical connection of the system board 23 and the package substrate 26 can be made stable.

0057The standoff mechanism 40 described above comprises the standoff member 41, and the hole 42 formed in the system board 23.

0058The material of the standoff member 41 may be the material which can receive the weight of the heat sink 24 and the loading force of the springs 30. It is not limited to a special material, and a metal (for example, aluminum or copper), a resin, ceramics, etc. can be used for the material of the standoff member 41.

0059The standoff member 41 in this embodiment comprises the standoff portion 43 and the insertion portion 44 which are formed integrally.

0060The standoff portion 43 is configured in the disc-like form, and the height of the standoff portion 43 on the system board 23 is set to be equal to the predetermined standoff H mentioned above.

0061The contact surface 50 formed on the top surface of the standoff portion 43 is the surface which comes in contact with the bottom surface of the package substrate 26, and this surface is made into a flat and smooth surface.

0062Moreover, the insertion portion 44 has the cylindrical configuration, and this insertion portion 44 is formed so that it extend in the lower part from the bottom surface of the standoff portion 43 in same axle with the standoff portion 43. The diameter D3 of this insertion portion 44 the diameter D1 of the standoff portion 43, and it is set as the size smaller than the diameter D2 of the hole 42.

0063Moreover, the diameter D1 of the standoff portion 43 is set up more greatly than the diameter D2 of the hole 42 (D1>D2>D3). The standoff portion 43 considered as the composition, the insertion portion 44 and the system board 23 is equipped by inserting in the hole 42.

0064Under the present circumstances, the standoff shown in <figref idref="f0003">FIG. 5A and FIG. 5B</figref> forming the tapered portion 45 at the leading edge (lower end) of the insertion portion 44 like the member 41 the standoff member 41 procedure inserted in the hole 42 can be performed easily.

0065Moreover, the standoff member 41 is the easy composition that the pillar-like insertion portion 44 extended on the bottom surface of the standoff portion 43 of disk form, and the standoff member 41 may be contained in and conveyed on the embossed tape 47 as shown in <figref idref="f0004">FIG. 6A and FIG. 6B</figref>.

0066<figref idref="f0004">FIG. 6A</figref> is a plan view of the embossed tape 47, and <figref idref="f0004">FIG. 6B</figref> is a cross-sectional view of the embossed tape 47 taken along the line A-A in <figref idref="f0004">FIG. 6A</figref>.

0067As shown in <figref idref="f0004">FIG. 6B</figref>, the recess 49 is formed in the embossed tape 47, and the standoff member 41 can be contained in the recess 49.

0068In addition, the portion on the left-hand side of <figref idref="f0004">FIG. 6B</figref> shows the state where the standoff member 41 is contained, and the right-hand side portion shows the state where the standoff member 41 is not contained.

0069Usually, the cover tape (not shown) is attached to the top surface of the embossed tape 47, and separation of the standoff member 41 is prevented.

0070The standoff member 41 concerning this embodiment is the easy composition that the pillar-like insertion portion 44 extended on the bottom surface of the standoff portion 43 of disk form as mentioned above.

0071For this reason, after containing the standoff member 41 on the embossed tape 47, it became possible to stick the cover tape, and it enabled this to use the embossed tape 47 for conveyance procedure of the standoff member 41.

0072The embossed tape is widely used for the automatic mounting process of carrying the electronic parts on the substrate automatically in the semiconductor manufacturing processes. Since the standoff member 41 is configured so that it can be contained in the embossed tape 47, the procedure to insert the standoff member 41 in the hole 42 of the system board 23 can be automated. Accordingly, the efficiency of manufacture of the electronic device 20 can be increased.

0073Next, with reference to <figref idref="f0004 f0005">FIG. 7 through FIG. 9</figref>, the manufacturing method of the electronic device 20 using the standoff mechanism 40 will be explained.

0074In the present embodiment, the manufacturing method of the electronic device 20 uses the standoff mechanism 40 on the system board 23, and the flip-chip bonding of the package substrate 26 is performed with the standoff mechanism 40 disposed, so that the predetermined standoff is formed. Other steps of the manufacture method in the present embodiment are essentially the same as those of the conventional manufacturing methods.

0075For this reason, in the following explanation, only the steps of assembling the electronic device 20 with the standoff mechanism 40 will be described, and a description of the other steps of the manufacturing method will be omitted.

0076In order to arrange the package substrate 26 on the system board 23 using the standoff mechanism 40, the standoff member 41 which constitutes part of the standoff mechanism 40 is inserted in the hole 42 which is formed beforehand in the system board 23, as shown in <figref idref="f0004">FIG. 7</figref>.

0077Specifically, the system board 23 is equipped with the standoff member 41 by inserting the insertion portion 44 of the standoff member 41 in the hole 42.

0078Under the present circumstances, it is only inserting in the hole 42 and the insertion portion 44 does not perform adhesion etc.

0079For this reason, the number of the required parts does not increase and the insertion procedure is easy to be performed, and the manufacturing cost can be reduced.

0080Moreover, as described above, by using the embossed tape 47, the procedure to insert the standoff member 41 in the hole 42 can also be automated, and manufacture efficiency can be further raised in this case.

0081Furthermore, it is not necessary to position the standoff member 41 to the system board 23. For this reason, in the state which fitted in loosely to the hole 42 is sufficient as the insertion portion 44, and therefore, even if the size accuracy of the diameter D2 of the hole 42 and the diameter D3 of the insertion portion 44 is comparatively low, it can be managed by it.

0082Thus, the machining of the hole 42 and the insertion portion 44 can be performed easily, and improvement and cost reduction of manufacture efficiency can be aimed at.

0083If the system board 23 is equipped with the standoff member 41, the package substrate 26 (semiconductor device 22) will be continuously laid on the system board 23.

0084<figref idref="f0005">FIG. 8</figref> shows the state in which the package substrate 26 is disposed on the system board 23.

0085Next, after the standoff member 41 is interposed between the package substrate 26 and the system board 23, the reflow processing is performed, and flip-chip bonding of the package substrate 26 is carried out by fusing the bumps 28 at the system board 23.

0086In addition, the material which the standoff member 41 does not transform with the heat by the reflow processing is selected. If the bumps 28 are fused at the time of the reflow processing, the package substrate 26 will contact the contact surface 50 of the standoff member 41 by prudence of the semiconductor device 22.

0087Since this contact surface 50 is the flat and smooth surface as described above, in the state where the package substrate 26 contacted the contact surface 50, the package substrate 26 will be in the state where it can be displaced on the contact surface 50 (the standoff portion 43).

0088On the other hand, when the surface tension occurs by the fusing of the bumps 28, the package substrate 26 by itself acts to move to the center of the electrodes (not shown) formed on the system board 23 corresponding to the bumps 28. This action is called the self-alignment action.

0089Therefore, the package substrate 26 moves to the system board 23 by this self-alignment action, so that the system board 23 and the package substrate 26 can be positioned, without the need for providing additional positioning mechanism or the like. Thus, the positioning of the system board 23 and the package substrate 26 can be performed easily with high precision by using the manufacture method of the present embodiment.

0090In addition, <figref idref="f0005">FIG. 9</figref> shows the state in which the reflow processing is completed.

0091As described above, in the manufacture method of this embodiment, the standoff member 41 is inserted in the hole 42 of the system board 23 and the package substrate 26 is disposed on the upper part of the standoff member 41, and thereafter, the flip-chip bonding of the package substrate 26 is carried out to the system board 23 through the reflow processing.

0092For this reason, while the standoff H between the system board 23 and the package substrate 26 is maintained at the predetermined level, the flip-chip bonding of the package substrate 26 (the semiconductor device 22) can be carried out in the state in which the package substrate 26 is positioned with high precision on the system board 23.

0093Moreover, when bonding the package substrate 26 to the system board 23, the soldering processing as needed in the conventional method is no longer necessary, and simplification of the manufacturing procedure of the electronic device 20 is possible.

0094Moreover, since it is unnecessary to prepare the standoff member 41 with a selected material which is suitable for the soldering, the flexibility at the time of choosing the material of the standoff member 41 can be increased.

0095The present invention is not limited to the above-described embodiments, and variations and modifications may be made without departing from the scope of the present invention.