JP2007110051A - Device for adjusting warpage amount of circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for adjusting a warpage amount of a circuit board capable of easily adjusting the warpage amount with high precision, even if the circuit board is formed of a material whose resilience return is large after removing charge. <P>SOLUTION: While a sealed pressure room 21 is formed at the back side of a flexible diaphragm 20, the plane periphery of a circuit board W is fixed on a substrate holding plate 38. Surface contact between the circuit board W and the diaphragm 20 is established in a state that the circuit board W is fixed on the substrate holding plate 38. Internal pressure in the pressure room 21 is controlled by controlling a pump 60 and an electropneumatic regulator 61 in accordance with deviation between a measured value and a desired value of a warpage amount of the circuit board W by a displacement sensor 40. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board warpage amount adjusting device for adjusting a circuit board warpage amount.

  FIG. 14 shows an exploded perspective view of an example of a semiconductor package mounted on a circuit board or the like of an electronic device. As shown in FIG. 14, a stiffener 103, which is a frame plate having a square opening at the center, is joined to the upper surface 102a of the circuit board 102 of the semiconductor package on which the semiconductor element 101 is mounted. A lid 104, which is a lid plate that closes the opening, is joined to the upper surface. Thus, the semiconductor element 101 is sealed in a closed space surrounded by the circuit board 102, the stiffener 103, and the lid 104.

  A conductive ball 105 such as solder is provided at a position corresponding to each external connection terminal of the semiconductor element 101 at the center of the upper surface 102a of the circuit board 102 on which the semiconductor element 101 is mounted. Further, as shown in FIG. 15A, the same number of lands 106 as the conductor balls 105 are formed on the back surface 102b of the circuit board 102 connected to the external board. It is electrically connected to the corresponding conductor ball 105 through a circuit formed therein.

Such a semiconductor package is manufactured through the following steps (1) to (3).
(1) The lower surface of the stiffener 103 is bonded to the upper surface 102a of the circuit board 102.
(2) The semiconductor element 101 is placed on the circuit board 102 so that the external connection terminal is aligned with the mounting position of the corresponding conductor ball 105, the conductor ball 105 is reflowed by heat treatment, and the semiconductor element 101 is placed on the circuit board 102. Are electrically and mechanically connected.
(3) The lid 104 is joined to the stiffener 103 so as to close the opening on the upper surface of the stiffener 103.

  The semiconductor package manufactured in this way is mounted on the external substrate so as to connect the land 106 and the land of the external substrate, whereby electrical connection between the semiconductor element 101 sealed in the semiconductor package and the external substrate is achieved. It has come to be illustrated.

Also, in recent years, multiple layers of via-holes filled with conductive paste formed on a thermoplastic resin film with a circuit pattern made of conductive foil are stacked and integrated by heating and pressing with a vacuum press. Techniques for forming circuit boards have also been put into practical use. Although such a multilayer circuit board is relatively inexpensive, the circuit can be easily miniaturized, and a large number of lands can be easily formed at a high density. Therefore, the use of such a multilayer circuit board is considered promising as the circuit board 102 of the semiconductor package as described above.
JP 2004-127970 A

  However, when a resin circuit board such as the multilayer circuit board is employed as the circuit board 102 of the semiconductor package, as shown in FIG. Thermal distortion may occur in 102 and it may be greatly warped and deformed. Incidentally, the amount of heat transfer to the circuit board 102 at the time of reflow increases as the number of conductor balls 105 mounted increases. Therefore, the amount of warp deformation at the time of reflow is larger in a circuit board on which a semiconductor element having a larger number of terminals is mounted. It tends to grow. For example, the warpage amount e is about 0.2 mm under the condition that the semiconductor package size is 38 × 38 mm, the semiconductor element size is 12 × 12 mm, and the number of external connection terminals of the semiconductor element is 2000. Cases have also been confirmed.

  However, since the semiconductor element 101 after sealing is pressed from above by the lid 104, the warp of the circuit board 102 as described above is corrected to some extent. However, even in this case, the circuit board 102 is curved in a W shape as shown in FIG. Particularly in recent years, the number of external connection terminals tends to increase in accordance with the higher functionality of the semiconductor element 101, and the size of the semiconductor package also tends to increase. Therefore, the circuit board 102 can be obtained only by pressing the lid 104. It is difficult to sufficiently correct the warpage. Further, when the size of the semiconductor package is increased, it is difficult to ensure sufficient rigidity of the lid 104. If the correction of the warp due to the pressing of the lid 104 is insufficient, the positions of the bottom surfaces of the lands 106 are not uniform, and there is a possibility that the contact failure of the lands 106 may occur when mounted on the external substrate. In such a case, it is difficult to cause thermal distortion as compared with the resin circuit board as described above, but an expensive ceramic circuit board must be employed.

  Conventionally, in Patent Document 1, in a metal circuit board on which electronic components are mounted by soldering, prior to mounting, the circuit board is pressed with a punch having a curved tip, A technique for flattening a circuit board after mounting by previously warping and deforming in a direction opposite to the warp due to thermal distortion of the device is disclosed. Similarly, if the circuit board 102 of the semiconductor package is warped and deformed in advance in a direction opposite to the warp generated during the mounting prior to the mounting of the semiconductor element 101, the occurrence of the above contact failure can be avoided. It is possible to do.

  However, in recent years, the size and pitch of the lands 106 have been miniaturized in accordance with the increase in the density of the semiconductor element 101 and the circuit board 102, and in order to avoid the above contact failure, it is on the order of several tens of μm. It is necessary to warp the circuit board 102 with high accuracy in advance, and such high-precision processing is difficult in press processing. In particular, in the resin circuit board as described above, the elastic return after unloading is large, and it is extremely difficult to ensure the accuracy of warp deformation by press working.

  Incidentally, for example, when the circuit board is flattened by correcting the warp, the same warp amount adjustment may be required. Further, it is sometimes necessary to adjust the amount of warpage of a circuit board formed of a material other than the resin as described above and a circuit board used for applications other than a semiconductor package. In any case, when adjusting the amount of warping of a circuit board made of a material having a large elastic return after unloading, or when adjusting the amount of warping with extremely high accuracy, there is a method for realizing it easily and appropriately. There is still no current situation, and there is a need to establish such a method.

  The present invention has been made in view of such circumstances, and the object thereof is to easily and accurately adjust the amount of warpage of a circuit board formed of a material having a large elastic return after unloading. An object of the present invention is to provide a circuit board warpage adjustment device.

  In order to achieve such an object, in the invention described in claim 1, as a circuit board warpage amount adjusting device for adjusting the warpage amount of the circuit board, a flexible diaphragm and a rear side of the diaphragm are formed and sealed. A pressurizing chamber, a pressurizing unit that pressurizes the pressurizing chamber, and a circuit board fixing unit that fixes the circuit board so as to be in surface contact with the diaphragm while holding a planar peripheral edge of the circuit board And a configuration comprising:

  In the above configuration, when the pressurizing means pressurizes the pressurizing chamber while the circuit board is fixed by the circuit board fixing means, the flexible diaphragm is deformed into a convex shape by the internal pressure, and the circuit board is fixed. The center of the plane of the circuit board that is not held by the means is pressed. Then, the pressing causes plastic deformation so that the circuit board is warped. The magnitude of the pressure applied to the circuit board at this time can be easily and accurately adjusted by controlling the internal pressure in the pressurizing chamber. Therefore, even if the substrate is formed of a material having a large elastic return after unloading, for example, a resin circuit substrate, the amount of warpage can be adjusted easily and with high accuracy.

  Further, in the apparatus for adjusting a warp amount of a circuit board according to claim 1, according to the invention according to claim 2, a measuring means for measuring the warp amount of the circuit board fixed by the circuit board fixing means, It is desirable to further comprise control means for controlling the internal pressure of the pressurizing chamber in accordance with the deviation between the measured value of the warpage amount by the measuring means and the target value. According to such a configuration, the internal pressure of the pressurizing chamber is feedback-controlled by the control means in accordance with the deviation between the measured value of the warpage amount of the circuit board by the measuring means and the target value. The amount of warpage of the circuit board can be adjusted with higher accuracy by controlling the applied pressure more accurately.

  Specifically, the control of the internal pressure of the pressurizing chamber is, for example, according to the invention described in claim 3, in which the control unit obtains a measurement value of the warpage amount by the measurement unit; Calculating a pressurization target value in the pressurization chamber based on the deviation between the acquired measurement value and the target value; and controlling the pressurization means based on the calculated pressurization target value to This is realized by controlling the internal pressure of the pressurizing chamber while repeatedly performing the step of pressurizing the pressurizing chamber sequentially. Through such control by the control means, while the amount of warping of the circuit board due to plastic deformation is confirmed, the application of pressure to the circuit board due to pressurization in the pressurizing chamber is repeatedly executed, so the warpage amount of the circuit board can be further increased with high accuracy. Will be able to adjust.

  Further, in the circuit board warpage amount adjusting device according to claim 2 or 3, as in the invention according to claim 4, the measuring means is provided at the center of the plane of the circuit board and the peripheral edge of the plane. If configured to include a plurality of displacement sensors that respectively measure the displacement amount of the circuit board in a direction perpendicular to the substrate surface, the warpage amount of the circuit board can be easily and accurately measured through the plurality of displacement sensors. Will be able to.

  Further, in the circuit board warpage amount adjusting device according to any one of claims 1 to 4, as in the invention according to claim 5, the portion of the diaphragm that is in surface contact with the mounting position of the semiconductor element on the circuit board. Furthermore, if the auxiliary block made of a rigid body is fixed, the mounting position of the semiconductor element on the circuit board is kept flat when adjusting the amount of warping of the circuit board. For this reason, it becomes possible to place the semiconductor element on the circuit board in a stable state, and as a result, the semiconductor element can be easily mounted on the circuit board.

  Moreover, in the curvature adjustment apparatus of the circuit board in any one of Claims 1-4, as the invention of Claim 6, on the back surface side of the circuit board fixed to the circuit board fixing means, It is also effective to further include a limiter block made of a rigid body that comes into contact with the back surface portion of the circuit board at the mounting position of the semiconductor element when the warping amount of the circuit board exceeds a certain amount. In this way, when adjusting the amount of warping of the circuit board, the back surface of the circuit board and the limiter block come into contact with each other, so that the mounting position of the semiconductor element on the circuit board can be kept flat. Therefore, as in the fifth aspect of the invention, the semiconductor element can be easily mounted on the circuit board.

  In this case, as in the seventh aspect of the present invention, if the limiter block is movably supported so as to be close to and away from the circuit board fixed to the circuit board fixing means, a circuit is provided. It is possible to adjust the amount of warping that the back surface of the substrate contacts the limiter block, and even if the target value of the amount of warping of the circuit board changes, the mounting position of the semiconductor element can be flattened in an optimum state. become.

  For example, according to the invention described in claim 8, the circuit board warpage amount adjusting device is configured such that, for a circuit board on which a semiconductor element is mounted through reflow of a conductor ball by heating, the circuit board by heating at the time of mounting. The amount of warpage is adjusted in order to give a warp in the opposite direction to the warp prior to the mounting.

(First embodiment)
A first embodiment in which the present invention is embodied as a warp amount adjusting device for adjusting the warp amount of a circuit board constituting the semiconductor package will be described below with reference to FIGS. In the present embodiment, a resin circuit board having a large elastic return after bending stress unloading is assumed as a circuit board for adjusting the warpage amount. Note that a conductor ball to be bonded to the external connection terminal of the semiconductor element is placed on the upper surface of the circuit board, that is, the mounting surface of the semiconductor element, prior to the adjustment of the warp amount by the warp amount adjusting device of the present embodiment. In addition, a frame-shaped stiffener is joined. Further, a land for electrical connection to an external board is also provided on the back surface of the circuit board in advance before adjusting the amount of warpage.

  As shown in FIG. 1, the warpage amount adjusting device of the present embodiment is configured to include a flat base 10 that is horizontally fixed at the center. Cylindrical guide posts 11 and 12 extending upward are erected on the upper surfaces on both sides of the base 10, and a flat plate 13 is fixed to the upper ends of the guide posts 11 and 12. ing.

  A rectangular frame 22 is fixed to the center of the lower surface of the top plate 13. The frame 22 is formed so that the cross-sectional area of the hollow portion is slightly larger than the surface area of the circuit board W, and a flexible diaphragm 20 is stretched. In the present embodiment, the diaphragm 20 is a laminate of a plurality of fluororesin sheets having low friction and excellent dust resistance and flexibility.

  A pressure chamber 21 sealed with the diaphragm 20, the inner periphery of the frame 22, and the lower surface of the top plate 13 is defined in the rear side of the diaphragm 20. The top plate 13 is provided with a pressure supply port 13 a communicating with the pressurizing chamber 21. The pressurizing chamber 21 is connected to an electropneumatic regulator 61 that adjusts the pressure in the pressurizing chamber 21 and a pressurized air source 60 that supplies pressurized air into the pressurizing chamber 21 through the pressure supply port 13a. It is connected.

  On the other hand, an opening 10 a penetrating in the vertical direction is formed at the center of the base 10. Cylindrical linear guides 30 and 31 whose axial direction is perpendicular to the upper surface of the base 10 are fixed to both sides of the opening 10a of the base 10 so as to penetrate the base 10 in the vertical direction. Further, cylindrical guide shafts 32 and 33 are inserted into the linear guides 30 and 31 so as to be linearly movable along the inner peripheral surfaces of the linear guides 30 and 31, respectively.

  A flat substrate holding plate 38 is horizontally fixed to the upper ends of the guide shafts 32 and 33. An opening 38 a is formed through the center of the substrate holding plate 38. A substrate fixing frame 38b is provided on the upper surface of the substrate holding plate 38 so as to surround the opening 38a. The outer shape of the substrate fixing frame 38 b is formed so as to fit into the opening of the frame 22 of the pressurizing chamber 21. Further, a notch 38c for holding the planar peripheral edge of the circuit board W is formed on the upper part of the board fixing frame 38b. Specifically, the notch 38 c is composed of a horizontal portion that comes into contact with the flat peripheral edge portion of the back surface of the circuit board W and a side wall portion that comes into contact with the outer peripheral edge of the circuit board W. The depth of the notch 38c is formed to be the same as or slightly shallower than the thickness of the circuit board W. In FIG. 1 and FIGS. 2 to 4 to be described later, the conductor balls, stiffeners, and lands provided on the upper and rear surfaces of the circuit board W are not shown.

  On the other hand, a flat sensor holding plate 36 is horizontally fixed to the lower ends of the guide shafts 32 and 33. Further, substrate clamp cylinders 34 and 35 that can be expanded and contracted in the vertical direction by air pressure or hydraulic pressure are fixed to the lower surface of the base 10 at the sides of the guide shafts 32 and 33, respectively. A plate 36 is suspended. By such expansion and contraction of the substrate clamp cylinders 34 and 35, the substrate holding plate 38 and the sensor holding plate 36 are moved up and down together while being held horizontally.

  A box-shaped sensor fixing base 37 is fixed at the center of the upper surface of the sensor holding plate 36. The upper surface of the sensor fixing base 37 can protrude above the upper surface of the base 10 through the opening 10a. A plurality of displacement sensors 40 having reciprocating contact needles 40a are fixed to the upper part of the sensor fixing base 37 so that the moving direction of the contact needles 40a is the vertical direction. These displacement sensors 40 are configured to detect the amount of displacement of the object in contact with the tip of the contact needle 40a based on the amount of displacement of the contact needle 40a reciprocating. Here, each displacement sensor 40 is configured such that when the circuit board W is placed on the notch 38c of the board fixing frame 38b, the tip of the contact needle 40a comes into contact with the back surface of the circuit board W, and the contact It arrange | positions so that the displacement amount of the thickness direction of the circuit board W in a contact part may each be detected.

  The detection signal of each displacement sensor 40 is input to the control unit 50. The controller 50 includes a microcomputer and a memory, and controls operations of the pressurized air source 60 and the electropneumatic regulator 61 based on the detection results of the displacement sensors 40.

  In the warp amount adjusting device of the present embodiment configured as described above, the circuit board is fixed to the notch 38c on the upper side of the board fixing frame 38b together with the board holding plate 38 by shortening the board clamp cylinders 34 and 35. When W is raised, the upper surface of the circuit board W comes into contact with the diaphragm 20 as shown in FIG.

  In this state, when a signal is sent to the electropneumatic regulator 61 to pressurize the inside of the pressurizing chamber 21, the diaphragm 20 bends downward and comes into close contact with the upper surface of the circuit board W to press the circuit board W. . At this time, the diaphragm 20 formed by laminating the flexible fluororesin sheets as described above is brought into close contact with the upper surface of the circuit board W following a step formed by a conductor ball, a stiffener, or the like. Therefore, a substantially uniform surface pressure can be applied to the entire upper surface of the circuit board W without damaging the board surface, conductor balls, and the like.

  The warpage amount e of the circuit board W whose surface has been deformed in this way is measured based on the detection results of the displacement sensors 40. The measurement of the warpage amount e is specifically performed in the following manner. That is, as shown in FIG. 3, the contact needle 40a of each displacement sensor 40 is disposed so as to abut on the planar central portion P0 of the circuit board W and the planar peripheral edge portions P1 to P4 at the four corners. Therefore, as shown in FIG. 4, the warpage amount e of the circuit board W whose surface is deformed by the pressure from the diaphragm 20 is the displacement amount in the thickness direction of the plane center portion P0 of the circuit board W and the plane peripheral portions P1 to P4. It can be measured as a deviation from the displacement amount in the thickness direction. More specifically, an average value of deviations in displacement in the thickness direction between the plane center portion P0 and each of the plane peripheral edge portions P1 to P4 or a maximum value thereof is obtained as the warp amount e of the circuit board W. ing.

  The control unit 50 controls the pressure in the pressurizing chamber 21 while referring to the measurement result of the warp amount e so as to adjust the pressure Pf applied to the circuit board W via the diaphragm 20. As a result, the circuit board W is warped and deformed in advance to the downward convex side only by offsetting the amount of warpage of the circuit board W toward the upward convex side due to thermal distortion during reflow of the conductor ball when mounting the semiconductor element. .

Hereinafter, the details of the warpage amount adjustment of the circuit board W in the warpage amount adjustment device of the present embodiment based on the control of the control unit 50 will be described with reference to FIGS.
A warpage correction target value E is registered in advance in the memory of the control unit 50. This warpage amount correction target value E is set to an estimated value of the warpage amount of the circuit board W toward the upward convex side generated when the semiconductor element is mounted, and the value is set for each combination of the semiconductor element and the circuit board W. It is obtained by conducting experiments and simulations in advance.

  In addition, the correspondence between the pressure applied to the pressurizing chamber 21 and the amount of warp applied to the circuit board W according to the application of the pressure is also obtained in advance by performing experiments and simulations. Based on the obtained correspondence, a pressure required to set the warpage amount e of the circuit board W to the warpage amount correction target value E is calculated, and the inside of the pressurizing chamber 21 is pressurized to that pressure. Above, it is possible to adjust the amount of warping of the circuit board W by only one pressurization. However, in actuality, there is a certain amount of variation in the warp amount e of the circuit board W due to pressurization. Therefore, if the circuit board W is warped to the warp amount correction target value E by only one pressurization, the circuit board There is a possibility that W exceeds the warp amount correction target value E and warps excessively. Once the circuit board W is warped excessively, the circuit board W must be fixed upside down on the board fixing frame 38b, and pressure must be applied in the opposite direction to return the excessive warpage.

  Therefore, in the present embodiment, the pressure application to the pressurizing chamber 21 is repeatedly performed while gradually increasing the pressure gradually from a pressure lower than the pressure necessary to warp the circuit board W to the warp amount correction target value E. This prevents the circuit board W from being excessively warped during the warpage adjustment. Specifically, the warp amount adjustment in the present embodiment is performed by the control unit 50 executing the warp amount adjustment control shown in FIG. This warpage adjustment control is started after the upper surface of the circuit board W fixed to the board fixing frame 38b is brought into contact with the diaphragm 20. Note that at the start time, the inside of the pressurizing chamber 21 is open to the atmospheric pressure.

  As shown in the figure, when the warp amount adjustment control is started, the control unit 50 first measures the warpage amount e of the circuit board W at the start of the warp adjustment through the displacement sensors 40 as a process of step S10. To get. And the control part 50 calculates the estimated pressurization target value Pt based on the measurement result as a process of step S11. This estimated pressurization target value Pt is obtained by setting the circuit board W to the warp amount correction target value E obtained from the correspondence between the pressure applied to the pressurizing chamber 21 and the warp amount of the circuit board W obtained in the above-described experiment or the like. The pressure in the pressurizing chamber 21 necessary for warping is shown. Such a correspondence relationship is stored in advance in a map format in the memory of the control unit 50, and the control unit 50 calculates the estimated pressurization target value Pt here using the map.

  Furthermore, the control part 50 sets the pressure lower than the said estimated pressurization target value Pt as actual pressurization target value Pa which is the pressure actually applied to the pressurization chamber 21 as a process of following step S12. Note that the actual pressurization target value Pa does not warp the circuit board W more reliably than the warp amount correction target value E in consideration of variations in the warp amount of the circuit board W after pressurization. The value is set to a pressure sufficiently smaller than the estimated pressurization target value Pt.

  And the control part 50 pressurizes the inside of the pressurization chamber 21 to the actual pressurization target value Pa by controlling the electropneumatic regulator 61 as a process of step S13. In step S14, the control unit 50 maintains the pressure in the pressurizing chamber 21 at the pressurization target value until the pressurizing time T elapses. In addition to releasing to atmospheric pressure, the current warpage amount e of the circuit board W measured through each of the displacement sensors 40 in that state is acquired as the processing of the subsequent step S16.

  Thereafter, the control unit 50 determines whether or not the acquired warpage amount e of the circuit board W is equal to the warpage amount correction target value E as the process of step S17. Actually, the warp amount correction target value E has a certain allowable range before and after it, and if the measured value of the warp amount e is within the allowable range, it is determined that they are equal. . If it is determined that the warpage amount e is equal to the warpage amount correction target value E, the control unit 50 completes the current warpage amount adjustment control.

  On the other hand, when it is determined in step S17 that the warpage amount e is not equal to the warpage amount correction target value E, the control unit 50 increases and corrects the actual pressurization target value Pa as a process in step S18. The increase correction amount at this time may be a fixed value or a variable value according to the deviation between the measured warpage amount e of the circuit board W at present and the warpage amount correction target value E. In any case, the increase correction amount needs to be set to a value that does not cause the circuit board W to be excessively warped by the pressurization by the actual pressurization target value Pa after the increase correction.

  After the actual pressurization target value Pa is corrected in this way, the control unit 50 returns the process to step S13. Thereafter, the control unit 50 repeatedly executes the processing from step S13 to step S17 until the warpage amount e of the circuit board W reaches the warp amount correction target value E. As described above, the control unit 50 gradually brings the warpage amount e of the circuit board W closer to the warpage amount correction target value E while repeating pressurization of the pressurizing chamber 21 and release of the atmospheric pressure.

  When the circuit board W is warped in a convex shape more than the warp amount correction target value E with respect to the mounting direction of the semiconductor element from the beginning, the back surface of the circuit board W (the surface opposite to the mounting surface of the semiconductor element). Is placed on the notch 38 c of the substrate holding plate 38 so as to face the diaphragm 20. In this state, the warp amount adjustment control is executed to reduce the warp amount e of the circuit board W to the warp amount correction target value E.

  An example of the transition mode of the pressure in the pressurizing chamber 21 and the warp amount e of the circuit board W during the warp amount adjustment control as described above is shown in FIG. In the example of the figure, the circuit board W before the warp amount adjustment has a warp amount e of “0”, that is, is flat.

  At the timing t1 in FIG. 6, that is, at the start of the warp amount adjustment control, the warp amount e of the circuit board W is “0” as described above. At this timing t1, the inside of the pressurizing chamber 21 is pressurized to a pressure P1 lower than the estimated pressurization target value Pt according to the deviation (= E) between the warp amount e and the warp amount correction target value E. ing. Due to the pressurization in the pressurizing chamber 21, the warpage amount e of the circuit board W increases with time, and eventually saturates.

  Thereafter, when the pressure chamber 21 is opened to atmospheric pressure at the timing t2 when the pressurization time T has elapsed, the pressure on the circuit board W by the diaphragm 20 is released. For this reason, after this timing t2, the warpage amount e of the circuit board W gradually decreases to the warpage amount e1 corresponding to the permanent strain due to plastic deformation due to elastic return.

  At the subsequent timing t3, the second pressurization is started. The inside of the pressurizing chamber 21 at this time is pressurized to a pressure P2 higher than the pressure P1 because the actual pressurization target value Pa is corrected to be increased. Therefore, during the pressurization at this time, the circuit board W is warped and deformed more than at the first pressurization. When the pressurization chamber 21 is opened to atmospheric pressure at the timing t4 when the pressurization time T has elapsed, the warpage amount e of the circuit board W decreases by the elastic return. However, the warpage amount e2 of the circuit board W at this time is larger than the warpage amount e1.

  Further, at the timing t5, the third pressurization is started. Since the actual pressurization target value Pa at this time is corrected to be further increased than in the second pressurization, the inside of the pressurization chamber 21 is applied to a pressure P3 higher than the pressure P2 during the second pressurization. Pressed. As a result, the circuit board W is further warped and deformed during this pressurization, and the warp amount e3 remaining on the circuit board W after elastic return after releasing the atmospheric pressure of the pressurization chamber 21 at timing t6 is It becomes larger than the warpage amount e2. Here, since the warpage amount e3 at this time coincides with the warpage amount correction target value E, the warpage amount adjustment of the circuit board W is completed here.

  As described above, in the present embodiment, the circuit board W is warped stepwise while measuring the warp amount e of the circuit board W only by plastic deformation excluding the elastic deformation by intermittently releasing the pressurization. Therefore, the warpage amount e can be adjusted with high accuracy. As a result, prior to the mounting of the semiconductor element, the warping in the opposite direction is applied to the circuit board W accurately in the same amount as the warping of the circuit board W due to the thermal stress at the time of mounting. By the way, warpage amount correction target value in a circuit board such as size: 45 × 45 mm, size of semiconductor element to be mounted: 20 × 20 mm, number of external connection terminals of semiconductor element (= number of conductor balls placed): 5000 pieces When the warp amount was adjusted with E being 0.25 mm, the warp amount could be adjusted within an error range of ± 0.02 mm.

  As shown in FIG. 7, the circuit board W after the warpage adjustment is mounted on the upper surface 72 a by mounting the semiconductor element 71 through the reflow of the conductor ball 75 provided at the center, and further on the stiffener 73. The lid 74 is joined to form a semiconductor package in which the mounted semiconductor element 71 is sealed. When the semiconductor element 71 is mounted here, as shown in FIG. 8A, the circuit board W has a back surface 72b provided with a land 76 for electrical connection to an external board so as to be convex. The amount of warpage is warped in advance, and the amount of warpage is accurately adjusted to be the warp amount correction target value E.

  When the semiconductor element 71 is mounted on such a circuit board W, the circuit board W is warped and deformed to the convex side toward the upper surface 72a due to thermal distortion caused by reflow of the conductor balls 75 due to heat treatment. However, since the circuit board W is warped in advance to the side convex to the back surface 72b side as described above, the back surface 72b side of the circuit board W is caused by warping deformation due to thermal strain at this time. The amount of warpage will decrease. And since the said curvature amount correction target value E is made into the estimated value of the curvature amount to the upper surface 72a side by the thermal strain at this time, finally, as shown in FIG.8 (b). The circuit board W is flat. By the way, in the circuit board with the above-mentioned size of 45 × 45 mm, the warpage amount of the circuit board after mounting the semiconductor element is 0.05 mm or less as a result of performing the warpage adjustment, although the circuit board is relatively large. The connection of the land to the board could be kept at a level with no problem.

  As shown in FIG. 8C, the lid 74 is bonded to the circuit board W on which the semiconductor element 71 is mounted. Since the circuit board W at this time has already been flattened, the lid 74 It is not necessary to correct the warping of the circuit board W by pressing from above, and it is not necessary to increase the rigidity of the lid 74 as much as necessary for such correction.

  Thus, according to the above-described warp amount adjustment, an increase in the warp amount of the circuit board W accompanying an increase in the size of the semiconductor package or an increase in the number of mounted conductive balls can be suppressed, and the semiconductor package and the external substrate can be controlled. Contact failure can be suitably suppressed.

  In this embodiment, the pressurized air source 60 and the electropneumatic regulator 61 are the pressurizing unit, the substrate holding plate 38, the substrate fixing frame 38b, and the notch 38c are the circuit board fixing unit, the displacement sensor 40 and The contact needle 40a corresponds to the measurement means, and the control unit 50 corresponds to the control means.

As described above, according to the warp amount adjusting apparatus according to the present embodiment, the following effects can be obtained.
(1) The flexible diaphragm 20 and the circuit board W fixed to the substrate holding plate 38 are brought into surface contact, and the inside of the pressurizing chamber 21 formed on the back side of the diaphragm 20 is pressurized. At this time, the control unit 50 controls the internal pressure of the pressurizing chamber 21 in accordance with the deviation between the warpage amount e measured by the displacement sensor 40 and the warpage amount correction target value E. As a result, the flexible diaphragm 20 is deformed in a convex shape toward the circuit board W by the internal pressure of the pressurizing chamber 21, so that the central portion of the plane of the circuit board W is pressed and plastic deformation is performed so that the circuit board W is warped. To do. Such pressing to the circuit board W is performed in several steps while measuring the warpage amount e of the circuit board W. For this reason, the warp amount of the circuit board W gradually approaches the warp amount correction target value E by the warp amount adjusting device, and the warp amount of the circuit board W can be adjusted with high accuracy.

  (2) The amount of warping of the circuit board W is measured in a state where a slight pressure is applied to the pressurizing chamber 21. As a result, the warpage amount e of the circuit board W in a state in which the circuit board W is in close contact with the diaphragm 20 without being deformed is measured. Therefore, the warpage amount e of the circuit board W due to plastic deformation excluding elastic return. Can be confirmed accurately. And since the application of the pressure with respect to the circuit board W by the pressurization in the pressurization chamber 21 is repeatedly performed, confirming the curvature amount e of the circuit board W by plastic deformation in this way, the warp amount e of the circuit board W Can be adjusted with higher accuracy.

(3) The warpage amount e of the circuit board W is measured by the five displacement sensors 40 brought into contact with the back surface of the circuit board W. Therefore, the warpage amount e of the circuit board W can be easily and accurately measured through the plurality of displacement sensors 40.
(Second Embodiment)
Next, a second embodiment in which the circuit board warpage adjustment device of the present invention is embodied will be described. In the present embodiment, members having structures and functions similar to or similar to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As described above, if the circuit board is warped in advance in the opposite direction to the warp caused by the thermal strain caused by the reflow of the conductor ball during mounting before mounting the semiconductor element, the warping of the circuit board after mounting is suppressed. be able to. However, if the circuit board is warped, it may be difficult to align the external connection terminal and the conductor ball of the circuit board when mounting the semiconductor element.

  Therefore, in the circuit board warp amount adjusting device of the present embodiment, in the diaphragm that presses the circuit board at the time of adjusting the warp amount, an auxiliary block made of a rigid body is provided at a portion in surface contact with the mounting position of the semiconductor element on the circuit board. By fixing, the mounting area of the semiconductor element is held on a flat surface while the circuit board is warped. As a result, the semiconductor element can be mounted more accurately.

  As shown in FIG. 9A, in the circuit board warpage amount adjusting device according to the present embodiment, a square columnar auxiliary block 80 made of a rigid body is fixed to the rear rear surface of the diaphragm 20. The auxiliary block 80 is formed of a material sufficiently rigid with respect to the diaphragm 20 such as metal or ceramics, so that the auxiliary block 80 is hardly deformed by the bending of the diaphragm 20 due to the pressurization of the pressurizing chamber 21. It has become.

  When the circuit board W is brought into surface contact with the diaphragm 20 to which the auxiliary block 80 is fixed and the inside of the pressurizing chamber 21 is pressurized, the diaphragm 20 has a convex shape toward the circuit board W as shown in FIG. Transforms into However, as described above, since the auxiliary block 80 is fixed to the rear rear surface of the diaphragm 20, the diaphragm 20 at this time is deformed in a state where the region where the auxiliary block 80 is fixed is held flat. To do. For this reason, the circuit board W is warped and deformed in a state where the center portion of the plane is kept flat.

  As shown in FIG. 10, the auxiliary block 80 in the diaphragm 20 is fixed at a position where the auxiliary block 80 contacts the mounting area S of the semiconductor element on the circuit board W. The area is the same as or slightly larger than the area of the semiconductor element mounting region S.

  Therefore, as shown in FIG. 11, the circuit board W as a whole is warped in the opposite direction to the warp due to thermal strain at the time of mounting the semiconductor element 71. Only about is a flat surface as shown by the two-dot chain line. For this reason, the semiconductor element 71 can be mounted more easily and reliably.

As described above, according to the warp amount adjusting apparatus according to the present embodiment, in addition to the effects (1) to (3), the following new effects can be obtained.
(4) The auxiliary block 80 is fixed to the rear back surface of the diaphragm 20 that is brought into surface contact with the mounting position of the semiconductor element mounting region S of the circuit board W. Thereby, when adjusting the amount of warping of the circuit board W, the mounting position of the semiconductor element 71 on the circuit board W is kept flat. For this reason, it becomes possible to more easily and reliably mount the semiconductor element 71 on the circuit board W.
(Third embodiment)
Next, a third embodiment in which the circuit board warpage adjustment device of the present invention is embodied will be described. Similarly to the circuit board warpage amount adjusting device in the second embodiment, the circuit board warpage amount adjusting device according to the present embodiment is flat in the mounting region of the semiconductor element while warping the circuit board. The semiconductor element can be mounted more accurately by holding it on the surface. Hereinafter, such a circuit board warpage adjustment apparatus will be described with reference to FIGS. In the present embodiment, members having structures and functions similar to or similar to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the circuit board warpage adjustment apparatus according to the present embodiment, a limiter block made of a rigid body is provided while maintaining a certain distance from a portion of the back surface of the circuit board corresponding to the mounting position of the semiconductor element on the circuit board. While mounting the circuit board, the mounting area of the semiconductor element is held on a flat surface.

  As shown in FIG. 12 (a), this circuit board warpage amount adjusting device replaces the substrate holding plate 38 in the first embodiment or the second embodiment with the contact of the displacement sensor 40. An opening 38d through which the needle 40a can be inserted and a substrate holding plate 38A through which an opening 38e is transparently provided. A substrate fixing frame 38b formed in a shape that fits into the opening of the frame 22 of the pressurizing chamber 21 is provided on the upper surface of the substrate holding plate 38A, and above the substrate fixing frame 38b. A notch 38c for holding the planar peripheral edge of the circuit board W is formed.

  In the board holding plate 38A, the opening 38d is provided at a position corresponding to the planar peripheral edge of the circuit board W when the circuit board W is fixed to the board fixing frame 38b. Further, in the substrate holding plate 38A, a limiter block 90 made of a rigid body such as metal is provided in the opening 38e so that the position thereof can be adjusted in the vertical direction. That is, the limiter block 90 is movably supported so as to be close to and away from the circuit board W. Specifically, the limiter block 90 has a substantially cylindrical shape extending in the vertical direction, and a screw portion 90b is provided on the lower end surface portion thereof. A screw thread is formed on the peripheral surface of the screw portion 90b. On the other hand, on the back surface of the substrate holding plate 38A, a ring 38f having a thread groove corresponding to the threaded portion 90b formed on the inner peripheral surface is fixed so as to surround the opening 38e. The position of the limiter block 90 can be adjusted in the vertical direction by fitting the thread of the threaded portion 90b with the thread groove of the ring 38f. Further, on the upper end surface of the limiter block 90, a quadrangular columnar contact portion 90a is provided horizontally. The limiter block 90 is positioned so that the upper surface of the contact portion 90a is located at a position separated from the back surface of the circuit board W by a distance g in a state where the circuit board W is placed on the board fixing frame 38b. It has been adjusted. The distance g is set to a distance shorter than the distance indicated by the warp amount correction target value E. In the present embodiment, when the circuit board W is warped by the warp amount correction target value E, the contact portion The size is set such that the entire upper surface of 90 a substantially contacts the back surface of the circuit board W.

  The circuit board warp amount adjusting device includes a sensor fixing base 37A in place of the sensor fixing base 37 in the first or second embodiment. The sensor fixing base 37A also has a box shape, and the upper surface thereof can protrude above the upper surface of the base 10 through the opening 10a. The displacement sensor 40 is fixed to the upper part of the sensor fixing base 37A so that the contact needle 40a passes through the opening 38d of the substrate holding plate 38A and comes into contact with the planar peripheral edge of the circuit board W. Yes. However, in the present embodiment, the number of displacement sensors 40 is one.

  Under such a configuration, when the circuit board W is brought into surface contact with the diaphragm 20 and the inside of the pressurizing chamber 21 is pressurized, the diaphragm 20 is deformed in a convex shape toward the circuit board W as shown in FIG. To do. As the diaphragm 20 is deformed, the circuit board W is deformed in a convex shape toward the limiter block 90, and when the amount of warpage of the circuit board W exceeds the distance g, the back surface portion of the circuit board W comes into contact with the limiter block 90. It becomes. For this reason, the circuit board W at this time undergoes surface deformation in a state where the region in contact with the contact portion 90a of the limiter block 90 is held flat. That is, the circuit board W is warped and deformed in a state in which the center portion of the plane is kept flat.

  As shown in FIG. 13, the limiter block 90 in the substrate holding plate 38 </ b> A has its contact portion 90 a facing the back surface of the circuit board W corresponding to the mounting area S of the semiconductor element on the circuit board W. Is provided. The area of the contact portion 90a is the same as or slightly larger than the area of the semiconductor element mounting region S.

  Therefore, also in the circuit board warpage adjustment apparatus according to the present embodiment, as shown in FIG. 11, the circuit board W as a whole is warped due to thermal distortion during the mounting of the semiconductor element 71. However, only the mounting region S of the semiconductor element 71 is a flat surface as indicated by a two-dot chain line.

As described above, according to the warp amount adjusting apparatus according to the present embodiment, in addition to the effects (1) to (3), the following new effects can be obtained.
(5) The limiter block 90 made of a rigid body is provided so as to face the back surface portion of the circuit board W corresponding to the mounting position of the mounting area S of the semiconductor element 71 on the circuit board W while maintaining a certain distance g. The distance g is set to a size such that the entire upper surface of the contact portion 90a is substantially in contact with the back surface of the circuit board W when the circuit board W is warped by the warp amount correction target value E. Thereby, when adjusting the amount of warping of the circuit board W, the mounting position of the semiconductor element 71 on the circuit board W is kept flat. For this reason, it becomes possible to more easily and reliably mount the semiconductor element 71 on the circuit board W.

  (6) The limiter block 90 is provided so that the position of the limiter block 90 can be adjusted in the vertical direction so that the limiter block 90 approaches and separates from the circuit board W. For this reason, it is possible to adjust the amount of warping that the back surface portion of the circuit board W contacts the limiter block 90, and even if the target value of the amount of warping of the circuit board W changes, the flattening of the mounting position of the semiconductor element 71 is optimal. It will be possible to do in the state.

The warpage amount adjusting device according to the present invention is not limited to the above-described embodiment, and may be implemented as, for example, the following form obtained by appropriately changing the embodiment.
In the third embodiment, when the position adjustment of the limiter block 90 is unnecessary, such as when the warp amount correction target value E is fixed, the limiter block 90 is fixed integrally to the substrate holding plate 38A. You may do it.

  The number of displacement sensors 40 for measuring the displacement amount of the circuit board W is arbitrary. For example, the number of displacement sensors 40 may be increased or decreased according to the warp deformation mode of the circuit board W.

  In place of the contact-type displacement sensor 40 employed in the warp amount adjusting device of the above-described embodiment, the amount of warp of the circuit board is measured using other detection means such as a non-contact type displacement sensor. You may do it.

  If the correspondence between the amount of warpage of the circuit board W and the pressure applied by the pressurizing chamber 21 is accurately determined, the amount of warpage may be adjusted by only one pressurization. Also in this case, if the circuit board W is pressed through the flexible diaphragm 20, the size of the pressing can be easily and accurately adjusted through the pressure control in the pressurizing chamber 21, The warpage amount e of the circuit board W can be adjusted easily and with high accuracy. Further, even with a circuit board having a step on the surface, if the diaphragm 20 having sufficient flexibility is used, the diaphragm 20 can be pressed in a state of being in close contact with the entire surface of the circuit board, and the surface is almost uniform. The circuit board can be appropriately warped by applying pressure.

  If the above correspondence is accurately obtained and the amount of warpage of the circuit board W can be adjusted appropriately without measuring the amount of warpage during the adjustment of the amount of warpage, the displacement sensor 40 may be omitted. Good. Further, when measuring the warpage amount during the warpage amount adjustment, if the circuit board W is removed from the warpage amount adjustment device each time and measured, the displacement sensor 40 is not provided in the warpage amount adjustment device. You can also.

  In the above embodiment, the circuit board W is brought into close contact with the cutout portion 38c by applying a slight pressure into the pressurization chamber 21, but a weight is provided in the pressurization chamber 21 so that the circuit board W is placed in the cutout portion 38c. You may make it closely_contact | adhere.

  In each of the above embodiments, the diaphragm 20 formed by laminating a plurality of fluororesin sheets is used, but a diaphragm made of other materials such as a rubber sheet may be used. In short, any material that does not allow air to pass therethrough and has sufficient flexibility can be employed as a diaphragm for the warpage adjustment device.

  The warpage amount adjusting device of the present invention can be similarly applied to a circuit board made of a material other than resin, and the circuit board is formed of a material having a large elastic return after unloading. This is particularly effective when adjusting the warping amount with extremely high accuracy.

Sectional drawing which shows the whole structure about 1st Embodiment of the curvature adjustment apparatus concerning this invention. Sectional drawing which shows the expanded cross-section structure of the pressurization chamber vicinity about the curvature adjustment apparatus of the embodiment. The A arrow directional view of FIG. Sectional drawing which shows the curvature amount measuring aspect of the circuit board in the curvature amount adjusting device of the embodiment. The flowchart which shows the process sequence of the curvature amount adjustment control which the control part performs about the curvature amount adjustment apparatus concerning 1st and 2nd embodiment. The time chart which shows transition of the curvature amount of the circuit board in execution of the curvature amount adjustment control, and the pressure in a pressurization chamber. The perspective view which shows the formation aspect about the semiconductor package using the circuit board by which the curvature amount was adjusted with the curvature amount adjustment apparatus of 1st Embodiment. (A)-(c) is sectional drawing which shows the formation procedure about the said semiconductor package. (A), (b) is sectional drawing which shows the cross-sectional structure of the diaphragm periphery of the curvature amount adjusting device concerning 2nd Embodiment. FIG. 9B is a view as viewed from arrow B in FIG. Sectional drawing which shows the decomposition | disassembly structure about the semiconductor package using the circuit board by which the curvature amount was adjusted with the curvature adjustment apparatus of 2nd Embodiment. (A), (b) is sectional drawing which shows the cross-sectional structure of the diaphragm periphery of the curvature amount adjusting device concerning 3rd Embodiment. C arrow line view of Fig.12 (a). The perspective view which shows the disassembled perspective structure about the conventional semiconductor package. (A)-(c) is sectional drawing which similarly shows the manufacture procedure about the conventional semiconductor package.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Base, 10a, 38a, 38d, 38e ... Opening, 38f ... Ring, 11, 12 ... Guide post, 13 ... Top plate, 13a ... Pressure supply port, 20 ... Diaphragm, 21 ... Pressurization chamber, 22 ... Frame , 30, 31 ... Linear guide, 32, 33 ... Guide shaft, 34, 35 ... Substrate clamp cylinder, 36 ... Sensor holding plate, 37, 37A ... Sensor fixing base, 38, 38A ... Substrate holding plate, 38b ... Substrate fixing frame 38c ... Notch part, 40 ... Displacement sensor, 40a ... Contact needle, 50 ... Control part, 60 ... Pressurized air source, 61 ... Electropneumatic regulator, 71, 101 ... Semiconductor element, W, 102 ... Circuit board, 72a, 102a ... Upper surface, 72b, 102b ... Back surface, 73, 103 ... Stiffener, 74, 104 ... Lid, 75, 105 ... Conductive ball, 76, 106 ... Command, 80 ... auxiliary block, 90 ... limiter unit, 90a ... contact portion, 90b ... thread portion.

Claims (8)

In the circuit board warpage amount adjusting device for adjusting the warpage amount of the circuit board,
A flexible diaphragm;
A pressurized chamber formed on the back side of the diaphragm and sealed;
A pressurizing means for pressurizing the pressurizing chamber;
Circuit board fixing means for fixing the circuit board so as to be in surface contact with the diaphragm while holding the planar peripheral edge of the circuit board;
An apparatus for adjusting a warp amount of a circuit board, comprising: In the circuit board curvature adjustment apparatus according to claim 1,
Measuring means for measuring the amount of warping of the circuit board fixed by the circuit board fixing means;
Control means for controlling the internal pressure of the pressurizing chamber according to the deviation between the measured value of the warpage amount by the measuring means and the target value;
An apparatus for adjusting a warp amount of a circuit board, further comprising: The control means obtains a measurement value of the amount of warp by the measurement means, and calculates a pressurization target value in the pressurization chamber based on a deviation between the obtained measurement value and the target value. 3. The internal pressure of the pressurizing chamber is controlled while sequentially repeating the step of controlling the pressurizing unit based on the calculated pressurization target value and pressurizing the pressurizing chamber. Device for adjusting the amount of warpage of a circuit board as described in 1. The measurement means is configured to include a plurality of displacement sensors that respectively measure displacement amounts of the circuit board in a direction perpendicular to the substrate surface at a planar central portion of the circuit board and a peripheral edge portion of the planar circuit board. 3. A circuit board warpage adjustment apparatus according to 3. The circuit board warpage amount adjusting device according to any one of claims 1 to 4, wherein an auxiliary block made of a rigid body is fixed to a portion of the diaphragm that is in surface contact with a mounting position of a semiconductor element on the circuit board. . A limiter made of a rigid body that is in contact with the back surface portion of the circuit board at the mounting position of the semiconductor element when the warping amount of the circuit board exceeds a certain amount on the back surface side of the circuit board fixed to the circuit board fixing means. The circuit board warpage adjustment apparatus according to claim 1, further comprising a block. The circuit board warpage amount adjusting device according to claim 6, wherein the limiter block is movably supported so as to approach and separate from the circuit board fixed to the circuit board fixing means. The circuit board warpage adjustment device is intended to give a warp in a direction opposite to the warpage of the circuit board due to heating at the time of mounting the circuit board on which the semiconductor element is mounted through reflow of the conductive ball by heating. The apparatus for adjusting a warp amount of a circuit board according to any one of claims 1 to 7, wherein the warp amount is adjusted.

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