JP6127403B2 - Electronic component mounting method and intermediate sheet - Google Patents

Description

  The present invention relates to an electronic component mounting method and an intermediate sheet.

  In recent years, downsizing and high functionality of portable electronic devices have been promoted, and accordingly, further downsizing and thinning of semiconductor devices (LSI: Large Scale Integration) and other electronic components are demanded. .

  One of surface mount semiconductor devices suitable for miniaturization and higher functionality of electronic devices is a BGA (Ball Grid Array) semiconductor device. The BGA type semiconductor device has a support substrate, a semiconductor element (chip) mounted on the support substrate, and solder bumps arranged in a grid at a predetermined pitch under the support substrate.

  The solder bump is formed in a spherical shape by a solder alloy. When a semiconductor device is mounted on a circuit board (mother board), the solder bumps are heated and melted in a reflow furnace, and the semiconductor device and the circuit board are joined electrically and mechanically via the solder bumps.

JP-A-10-125726 JP 2000-340607 A JP 2011-71436 A

  It is an object of the present invention to provide a mounting method of an electronic component that can easily form a solder bump having high fatigue resistance, and an intermediate sheet used in the mounting method.

According to one aspect of the disclosed technology, an insulating sheet formed of polyphenylsulfide, a liquid crystal polymer, or polyimide as a resin , and a plurality of through holes penetrating from one surface of the insulating sheet to the other surface And a resin different from the resin forming the insulating sheet, formed of room temperature curable silicone resin or room temperature curable epoxy resin , containing thermally expandable microcapsules and attached to the wall surface of the through hole There is provided an intermediate sheet having an inflatable member and disposed between the circuit board and the electronic component.

According to another aspect of the disclosed technology, an electronic component is disposed on a circuit board with an intermediate sheet having a plurality of through holes and a thermally expandable member attached to a wall surface of the through holes interposed therebetween. Heating the solder bump above the melting temperature of the solder bump of the electronic component, melting the solder bump, and contacting the melted solder and the terminal of the circuit board through the through hole of the intermediate sheet; The intermediate sheet is heated to a temperature higher than the expansion start temperature of the thermally expandable member to expand the thermally expandable member, and the intermediate sheet is made of polyphenylsulfide, liquid crystal polymer, or polyimide as a resin. is formed, the heat expandable member is formed by room temperature curing silicone resin or room temperature curing epoxy resin as the resin a different type of resin for forming the intermediate sheet , Mounting method of the electronic component containing a thermal expandable microcapsule is provided.

  According to the mounting method of the intermediate sheet and the electronic component according to the above aspect, the shape of the solder bump can be a columnar shape or a shape in which the central portion is constricted. This improves the fatigue resistance of the solder bumps.

1A and 1B are diagrams showing a method of mounting a BGA type semiconductor device on a circuit board. FIG. 2 is a diagram for explaining the problem of the method shown in FIGS. FIG. 3 is a schematic diagram showing the shape of a solder bump having high fatigue resistance. FIG. 4 is a schematic diagram showing an example of a method for forming the solder bump shown in FIG. FIG. 5A is a plan view showing the intermediate sheet according to the first embodiment, and FIG. 5B is a cross-sectional view taken along the line II in FIG. 5A. 6A to 6C are perspective views illustrating a method for producing the intermediate sheet. FIG. 7 is a cross-sectional view (No. 1) illustrating the mounting method of the electronic component using the intermediate sheet according to the first embodiment. FIG. 8 is a cross-sectional view (No. 2) illustrating the electronic component mounting method using the intermediate sheet according to the first embodiment. FIGS. 9A and 9B are views showing an intermediate sheet according to the second embodiment. FIGS. 10A to 10D are perspective views illustrating a method for producing an intermediate sheet according to the second embodiment.

  Hereinafter, before describing the embodiment, a preliminary matter for facilitating understanding of the embodiment will be described.

  1A and 1B are diagrams showing a method of mounting a BGA type semiconductor device on a circuit board.

  As shown in FIG. 1A, the BGA type semiconductor device 10 includes a semiconductor element (chip) 11, a support substrate 12, and solder bumps 13.

  The semiconductor element 11 is mounted on one surface side of the support substrate 12, and a large number of electrodes 12a are arranged in a grid at a predetermined pitch on the other surface side. The electrode 12a is electrically connected to the semiconductor element 11 through a conductive layer and a via (both not shown) formed in the support substrate 12. Also, solder bumps 13 formed in a spherical shape with a solder alloy are joined to the electrodes 12a.

  On the circuit board 15, electrodes 15 a are provided at positions corresponding to the respective electrodes 12 a of the support substrate 12. When mounting the semiconductor device 10 on the circuit board 15, the semiconductor device 10 is placed on the circuit board 15, and the solder bumps 13 are heated in a reflow furnace to be in a molten state. Thereby, the molten solder spreads on the electrode 15a. Thereafter, when the solder is cooled and solidified, the semiconductor device 10 and the circuit board 15 are electrically and mechanically connected via the solder bumps 13 as shown in FIG.

  By the way, since the semiconductor device 10 generates heat with the operation, the support substrate 12 thermally expands with the operation of the semiconductor device 10. In general, the solder bump 13 between the support substrate 12 and the circuit substrate 15 has a barrel shape in which the central portion is expanded as shown in FIG. For this reason, when the support substrate 12 is thermally expanded, stress concentrates on the connection portion between the solder bump 13 and the electrodes 12a and 15a.

  Then, when the support substrate 12 is repeatedly thermally expanded, as shown in FIG. 2, a crack is generated in the vicinity of the connection portion between the solder bump 13 and the electrode 12a and the electrode 15a, thereby causing a defect such as disconnection or an increase in the resistance value of the connection portion. May occur.

  In order to avoid such a problem, it has been proposed that the shape of the solder bump 13 is a columnar shape or a shape in which the central portion is constricted as shown in FIG. When the solder bumps 13 are formed in a columnar shape or a shape as shown in FIG. 3, stress concentration on the connection portion between the solder bumps 13 and the electrodes 12 a and 15 a is avoided, and the fatigue resistance of the solder bumps 13 is improved.

  In order to form the solder bumps in a columnar shape or the shape shown in FIG. 3, for example, as schematically shown in FIG. 4, the molten solder 13 a (the solder bump 13 is melted) contacts the circuit board 15. In this state, the support substrate 12 may be slightly raised by the jig 19 or the like.

  However, this method requires a mechanism for raising the support substrate 12 while the solder 13a is melted, which increases the equipment cost. In addition, since the number of manufacturing steps increases, there is a disadvantage that the time required for manufacturing becomes long.

  On the other hand, after joining the semiconductor device and the circuit board via the solder bumps, the semiconductor device and the circuit board are filled with a thermally expandable underfill and heated again at a temperature higher than the melting temperature of the solder bumps. A method has been proposed. In this method, the space between the semiconductor device and the circuit board is widened due to the thermal expansion of the underfill, and the solder bumps are cylindrical.

  However, this method requires a step of taking out the circuit board on which the semiconductor device is mounted from the reflow furnace and uniformly filling the narrow gap between the semiconductor device and the circuit board with the underfill. In addition, after filling the underfill, a process of heating again in the reflow furnace to melt the solder bumps and expanding the underfill is also necessary. Accordingly, the process becomes complicated and the manufacturing cost of the electronic device increases.

  In the following embodiments, an electronic component mounting method capable of easily forming solder bumps having high fatigue resistance, and an intermediate sheet used in the mounting method will be described.

(First embodiment)
FIG. 5A is a plan view showing the intermediate sheet according to the first embodiment, and FIG. 5B is a cross-sectional view taken along the line II in FIG. 5A.

  The intermediate sheet 21 includes an insulating sheet 21 a provided with through holes 22 arranged in a grid at a predetermined pitch, and a thermally expandable member 23 attached to the wall surface of the through holes 22. The thermally expandable member 23 is formed of a resin to which thermally expandable microcapsules are added.

  6A to 6C are perspective views illustrating a method for producing the intermediate sheet 21 in the order of steps.

  First, an insulating resin sheet 21a as shown in FIG. The resin sheet 21a is preferably formed of a resin having good heat resistance. For example, a resin sheet formed of polyphenylsulfide (PPS), liquid crystal polymer (LCP), or polyimide (PI) may be used. .

  The size of the resin sheet 21a may be set according to the size of the semiconductor device to be mounted. Here, it is assumed that the size of the resin sheet 21a is 50 mm (width) × 50 mm (length) × 0.5 mm (thickness).

  Next, as shown in FIG. 6B, through holes 22 are formed in the resin sheet 21a by a method such as drilling, punching, or laser processing. The diameter of the through hole 22 is set according to the diameter of the solder bump of the semiconductor device to be mounted. In the present embodiment, it is assumed that the diameter of the solder bump is 0.6 mm and the diameter of the through hole 22 is 0.85 mm.

  The through hole 22 is formed at a position corresponding to the solder bump of the semiconductor device. In the present embodiment, the through holes 22 are formed at a pitch of 1 mm along two directions (X direction and Y direction) orthogonal to each other.

  On the other hand, for example, a room temperature curable silicone resin or a room temperature curable epoxy resin is prepared as a material of the thermally expandable member 23. And the thermally expansible microcapsule is added to the resin material in the ratio of about 10 vol%-30 vol%, for example. As the thermally expandable microcapsule, for example, those commercially available from Kureha Co., Ltd. or Matsumoto Yushi Seiyaku Co., Ltd. can be used.

  There are many types of commercially available thermally expandable microcapsules. For example, the particle size (particle size before expansion) is 5 μm to 50 μm, the volume expansion coefficient is 50 times to 100 times, and the expansion start temperature is 180 ° C. to A 220 ° C. thermal expansion capsule is used.

  If the thermally expandable microcapsule expands before the solder bump melts, the solder bump may not be bonded to the circuit board electrode. For this reason, it is preferable that the expansion start temperature of the thermally expandable microcapsule is higher than the melting temperature of the solder bump.

  Next, as shown in FIG.6 (c), the resin 24 of the resin sheet 21a is filled with the resin 24 of the uncured state which added the thermally expansible microcapsule, and the resin 24 is hardened after that.

  Next, as shown in FIG. 6D, a through hole 24a is formed in the center of the resin 24 by a method such as drilling, punching, or laser processing. The diameter of the through hole 24a is slightly larger than the diameter of the solder bump of the semiconductor device to be mounted. In this embodiment, since the diameter of the solder bump is 0.6 mm as described above, the diameter of the through hole 24a is set to 0.7 mm. In this way, the intermediate sheet 21 shown in FIGS. 5A and 5B is completed.

  7-8 is sectional drawing which shows the mounting method of the electronic component using the above-mentioned intermediate sheet 21 in order of a process.

  First, as shown in FIG. 7A, the intermediate sheet 21 is disposed on the circuit board 15. At this time, alignment is performed so that the center of the electrode 15a of the circuit board 15 and the center of the through hole 22 of the intermediate sheet 21 coincide.

  Next, as illustrated in FIG. 7B, the semiconductor device 10 is disposed on the circuit board 15 with the intermediate sheet 21 interposed therebetween. At this time, alignment is performed so that the solder bumps 13 of the semiconductor device 10 and the electrodes 15a of the circuit board 15 are in contact with each other.

  Next, the solder bump 13 is heated to a temperature higher than its melting temperature in a reflow furnace. As a result, as shown in FIG. 7C, the solder bump 13 is melted to become a liquid solder 13a, and the liquid solder 13a spreads on the surface of the electrode 15a.

  Next, the intermediate sheet 21 is heated to a temperature higher than the expansion start temperature of the thermally expandable microcapsule. This heating may be performed in a reflow furnace or in a heating furnace different from the reflow furnace.

  By this heating, the microcapsules in the thermally expandable member 23 start to expand. Then, as shown in FIG. 7D, the thermally expandable member 23 pushes up the support substrate 12 and tightens the central portion of the molten solder 13a from the side. Thereby, the solder 13a becomes a columnar shape or a shape in which the central portion is constricted.

  Thereafter, when the solder 13a is cooled and solidified, the mounting of the semiconductor device 10 on the circuit board 15 is completed, and the solder bump 13 having a cylindrical shape or a constricted central portion as shown in FIG. 8 is obtained. The circuit board 15 on which the semiconductor device 10 is mounted is incorporated in a predetermined housing, and the electronic device is completed.

  In the present embodiment, as described above, the intermediate sheet 21 having the through hole 22 and the thermally expandable member 23 attached to the wall surface of the through hole 22 is used, so that the solder having a cylindrical shape or a constricted central portion is used. The bump 13 can be easily obtained. Moreover, in this embodiment, since the shape of the solder bump 13 becomes a columnar shape or a shape in which the central portion is constricted, the fatigue resistance of the solder bump 13 is high, and the reliability of the electronic device is improved.

(Second Embodiment)
FIGS. 9A and 9B are views showing an intermediate sheet according to the second embodiment. FIG. 9A shows a state before expansion of the thermally expandable member attached to the wall surface of the through hole of the intermediate sheet, and FIG. 9B shows a state after expansion of the thermally expandable member.

  As in the first embodiment, the intermediate sheet 31 includes an insulating sheet 31a provided with through holes 32 arranged in a grid at a predetermined pitch, and a thermally expandable member 33 attached to the wall surface of the through holes 32. Have

  As shown in FIG. 9A, the thermally expandable member 33 includes three resin layers 33 a, 33 b, and 33 c that are stacked in the thickness direction of the intermediate sheet 31. These resin layers 33a, 33b, and 33c all include thermally expandable microcapsules 35.

  In the present embodiment, the contents of the thermally expandable microcapsules in the lower resin layer 33a and the upper resin layer 33c are both 10 vol%. Moreover, the content rate of the thermally expansible microcapsule of the resin layer 33b arrange | positioned between those resin layers 33a and 33c is 30 vol%. Further, the thickness of the resin layers 33a and 33c is 0.12 mm, and the thickness of the resin layer 33b is 0.26 mm.

  As described above, in the present embodiment, the heat-expandable member 33 has a three-layer structure, and the content of the heat-expandable microcapsules in the central resin layer 33b is set to the thermal expansion of the upper and lower resin layers 33a and 33c. Higher than the content of the functional microcapsules.

  Therefore, as shown in FIG. 9B, the resin layer 33b expands more than the resin layers 33a and 33c, and the central portion of the solder bump becomes thinner.

  In addition, the shape of the solder bump can be variously changed by variously changing the thickness of the resin layers 33a to 33c, the content of the thermally expandable microcapsule, the kind of the thermally expandable microcapsule to be added, and the like. Further, the number of layers of the thermally expandable member 33 is not limited to three, and may be two or four or more.

  FIGS. 10A to 10D are perspective views illustrating a method for manufacturing the intermediate sheet 31 according to the present embodiment in the order of steps.

  First, as shown to Fig.10 (a), the insulating resin sheet 31a is prepared and the through-hole 32 is formed in the resin sheet 31a.

  Next, as shown in FIG. 10 (b), after injecting a resin containing 10 vol% of thermally expandable microcapsules into the through hole 32, the resin is cured and a resin layer having a thickness of 0.12 mm. 33a is formed.

  Thereafter, a resin containing 30 vol% of thermally expandable microcapsules is injected into the through-hole 32, and then the resin is cured to form a resin layer 33b having a thickness of 0.26 mm. Further, after a resin containing 10 vol% of thermally expandable microcapsules is injected into the through hole 32, the resin is cured to form a resin layer 33c having a thickness of 0.12 mm.

  In this way, as shown in FIG. 10C, after forming the three-layered thermally expandable member 33 in the through hole 32, the through hole 34 a is formed at the center of the thermally expandable member 33. In this way, the intermediate sheet 31 according to this embodiment shown in FIG. 9A is completed.

  Since the electronic component mounting method using the intermediate sheet 31 is basically the same as in the first embodiment, the description thereof is omitted here.

  The following additional notes are disclosed with respect to the above embodiments.

(Appendix 1) an insulating sheet;
A plurality of through holes penetrating from one surface of the insulating sheet to the other surface;
A thermally expandable member attached to the wall surface of the through hole,
An intermediate sheet disposed between a circuit board and an electronic component.

  (Supplementary note 2) The intermediate sheet according to supplementary note 1, wherein the thermally expandable member is formed of a resin containing thermally expandable microcapsules.

  (Additional remark 3) The said thermally expansible member is laminated | stacked on the thickness direction of the said insulating sheet, and is formed of the several resin layer from which an expansion coefficient differs mutually, The additional remark 1 or 2 characterized by the above-mentioned. Intermediate sheet.

(Additional remark 4) The process of arrange | positioning an electronic component on the circuit board on both sides of the intermediate sheet which has several through-holes and the thermally expansible member adhering to the wall surface of this through-hole,
Heating the solder bump above the melting temperature of the solder bump of the electronic component to melt the solder bump, and contacting the melted solder and the terminal of the circuit board through the through hole of the intermediate sheet;
And a step of expanding the thermally expandable member by heating the intermediate sheet above the expansion start temperature of the thermally expandable member.

  (Supplementary note 5) The electronic component mounting method according to supplementary note 4, wherein the thermally expandable member of the intermediate sheet is formed of a resin containing thermally expandable microcapsules.

  (Supplementary note 6) The electron according to supplementary note 4 or 5, wherein the thermally expandable member is formed of a plurality of resin layers laminated in the thickness direction of the intermediate sheet and having different expansion coefficients. Component mounting method.

(Appendix 7) a circuit board;
Electronic components mounted on the circuit board via solder bumps;
An intermediate sheet that is disposed between the circuit board and the electronic component and includes a through hole provided at a position corresponding to the solder bump and a thermally expandable member attached to a wall surface of the through hole; ,
The electronic device according to claim 1, wherein the thermally expandable member is in contact with a side portion of the solder bump, and the solder bump has a cylindrical shape or a constricted central portion.

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor device, 11 ... Semiconductor element, 12 ... Support substrate, 12a ... Electrode, 13 ... Solder bump, 13a ... Solder (molten solder), 15 ... Circuit board, 15a ... Electrode, 21, 31 ... Intermediate sheet, 21a, 31a ... resin sheet, 22, 32 ... through hole, 23, 33 ... thermal expansion member, 24 ... resin, 33a, 33b, 33c ... resin layer, 35 ... thermal expansion microcapsule.

Claims (5)

An insulating sheet formed from polyphenylsulfide, a liquid crystal polymer, or polyimide as a resin;
A plurality of through holes penetrating from one surface of the insulating sheet to the other surface;
Thermally expandable that is formed of room temperature curable silicone resin or room temperature curable epoxy resin as a different type of resin from the resin that forms the insulating sheet, contains thermally expandable microcapsules, and adheres to the wall surface of the through hole And having a member
An intermediate sheet disposed between a circuit board and an electronic component.   The intermediate sheet according to claim 1, wherein the thermally expandable member is formed of a plurality of resin layers that are laminated in a thickness direction of the insulating sheet and have different expansion coefficients. Placing an electronic component on a circuit board with an intermediate sheet having a plurality of through holes and a thermally expandable member attached to the wall surface of the through holes;
Heating the solder bump above the melting temperature of the solder bump of the electronic component to melt the solder bump, and contacting the melted solder and the terminal of the circuit board through the through hole of the intermediate sheet;
Heating the temperature of the intermediate sheet above the expansion start temperature of the thermally expandable member to expand the thermally expandable member, and
The intermediate sheet is formed of polyphenylsulfide, liquid crystal polymer, or polyimide as a resin,
The heat-expandable member is formed of a room-temperature-curable silicone resin or a room-temperature-curable epoxy resin as a different type of resin from the resin forming the intermediate sheet, and contains a heat-expandable microcapsule. Component mounting method.   4. The electronic component mounting method according to claim 3, wherein an expansion start temperature of the thermally expandable microcapsule of the thermally expandable member is higher than a melting temperature of the solder bump. A circuit board;
Electronic components mounted on the circuit board via solder bumps;
An intermediate sheet that is disposed between the circuit board and the electronic component and includes a through hole provided at a position corresponding to the solder bump and a thermally expandable member attached to a wall surface of the through hole; ,
The intermediate sheet is formed of polyphenylsulfide, liquid crystal polymer, or polyimide as a resin,
The thermally expandable member is formed of a room temperature curable silicone resin or a room temperature curable epoxy resin as a different kind of resin from the resin forming the intermediate sheet, and contains a thermally expandable microcapsule,
The electronic device according to claim 1, wherein the thermally expandable member is in contact with a side portion of the solder bump, and the solder bump has a cylindrical shape or a constricted central portion.

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