JP6615583B2 - Processing method of package substrate - Google Patents

Description

  The present invention relates to a method for processing a package substrate in which a resin layer is laminated on a metal substrate.

  Conventionally, in manufacturing a package substrate, a device chip is arranged on a wiring pattern on the substrate and then packaged by a resin mold or the like. The wiring pattern on the substrate is formed by thermocompression bonding with the wiring pattern sandwiched between resin green sheets (see, for example, Patent Document 1). As the base substrate, a ceramic substrate, a plastic substrate, a stainless steel substrate, or the like is used as a countermeasure against heat or corrosion. In particular, as a heat countermeasure, a stainless steel substrate that can be formed thin and has the advantage of transferring heat is used.

  When a resin layer is formed by heating a resin on a stainless steel substrate, convex warpage (curvature) occurs in the stainless steel substrate after cooling of the resin layer due to the difference in thermal expansion coefficient between the stainless steel and the resin. As a method of dividing the package substrate based on the stainless steel substrate, a method of preparing a dedicated processing table and correcting the warpage of the package substrate is conceivable. In addition, a method of holding and dividing a package substrate on a processing table in a warped state (see, for example, Patent Document 2), measuring a warpage amount of a package substrate, and selecting and processing only a package substrate having a small warpage amount. A method (for example, see Patent Document 3) has been proposed.

Japanese Patent Laid-Open No. 07-142628 JP 2011-0405542 A JP 2014-0753563 A

  However, according to the method described in Patent Document 2, the package substrate can be held and processed on the processing table while being warped, but it is difficult to obtain sufficient processing accuracy. Further, the method described in Patent Document 3 requires a measuring instrument for measuring the amount of warpage, and a package substrate having a large warpage cannot be processed because it is returned to the cassette. Furthermore, if the warp stress is left on the package substrate, that is, the stress balance between the upper and lower sides of the package substrate is broken, the warp is corrected and divided into individual packages. There was a problem to do.

  The present invention has been made in view of this point, and an object of the present invention is to provide a method for processing a package substrate that can be easily divided while suppressing warpage of the package substrate.

The processing method of a package substrate according to the present invention is a processing method of a package substrate in which a resin layer including a wiring pattern is formed on an upper surface of a metal substrate, and a laser having a wavelength that absorbs the metal substrate on the upper surface of the metal substrate. A warp forming step of irradiating the metal substrate by irradiating light, a resin layer forming step of forming a resin layer on the upper surface or the lower surface of the metal substrate after the warp forming step, and after the resin layer forming step, the metal substrate Forming a dividing groove along a planned dividing line, and dividing the resin layer on the upper surface of the metal substrate not irradiated with the laser beam before the warp forming step. after, a step of measuring the warpage of the metal substrate, with the reflected Ri forming step, the processing conditions of the laser beam is Ru is adjusted relative to the metal substrate based on the reflected Ri amount.

  According to this configuration, the warp of the metal substrate due to the irradiation of the laser beam is offset by the warp of the metal substrate due to the formation of the resin layer. That is, assuming that the metal substrate is warped when the resin layer is formed, the warp of the metal substrate is reduced after the resin layer is formed by warping the metal substrate in a reverse direction with a laser beam before the resin layer is formed. be able to. Therefore, a member such as a dedicated processing table or a measuring instrument for measuring the amount of warpage is not required, and the package substrate can be divided into individual packages with high accuracy by suppressing warpage. Moreover, since the stress balance between the upper surface side and the lower surface side of the package substrate is adjusted, the package after the division is not greatly warped.

  According to the present invention, assuming that the metal substrate is warped when the resin layer is formed, the metal substrate is warped in the reverse direction before the resin layer is formed, thereby reducing the warp of the metal substrate after the resin layer is formed. Thus, the package substrate can be accurately divided into individual packages.

It is sectional drawing of the package substrate of this Embodiment. It is a figure which shows an example of the curvature formation process of this Embodiment. It is a figure which shows an example of the resin layer formation process of this Embodiment. It is a figure which shows an example of the division | segmentation process of this Embodiment.

  Hereinafter, the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of the package substrate of the present embodiment. Note that the package substrate in FIG. 1 is an example, and may be configured in any manner as long as it is formed by laminating a resin layer on a metal substrate.

  As shown in FIG. 1, the package substrate W has a wiring layer 20 laminated on the upper surface of a substantially rectangular metal substrate 10, and the device chip C on the wiring layer 20 is sealed with a mold resin layer 30 so as to be integrally packaged. Have been The upper surface of the package substrate W is partitioned by grid-like division planned lines (not shown), and each device chip C is included in each region partitioned by the planned division lines. The package substrate W is divided into individual packages (for example, CSP: Chip Size Package) including the device chip C by being cut along a planned division line while being sucked and held on the chuck table 61.

  By the way, since the wiring layer 20 (resin layer) is formed on the metal substrate 10 by the heated resin, the metal substrate 10 is warped due to the difference in thermal expansion coefficient between the metal and the resin. In this case, since the metal substrate 10 is formed in a rectangular shape, it is curved in a dome shape in either the long side direction or the short side direction. Since the package substrate W based on the metal substrate 10 remains warped, it is difficult to suck and hold the package substrate W on the chuck table 61. Even if the package substrate W can be held on the chuck table 61, the package substrate W cannot be accurately divided into individual packages.

  For example, the package substrate W for small chips needs to have a narrow dividing line, and a small warp of the package substrate W greatly affects the dividing accuracy. It is also conceivable to divide the package substrate W by correcting it with a dedicated jig so as to be flat on the chuck table 61. However, even if the package substrate W is flattened and divided while the stress balance between the upper surface side and the lower surface side of the package substrate W is broken, the individual packages after the division remain warped. Thus, it is difficult to appropriately divide the package substrate W into individual packages due to the influence of the warp when the wiring layer 20 is formed on the metal substrate 10.

  Therefore, in the present embodiment, laser forming is performed on the metal substrate 10 before the formation of the wiring layer 20 (resin layer) on the metal substrate 10, thereby reversing the warp when the wiring layer 20 is formed. Causing warping. Thereby, the warp during the formation of the wiring layer 20 is offset by the warp of the metal substrate 10 due to laser forming, and the stress balance of the metal substrate 10 after the formation of the wiring layer 20 is adjusted. By adjusting the stress balance between the upper surface side and the lower surface side of the metal substrate 10, warpage of the package substrate W based on the metal substrate 10 can be suppressed, and the package substrate W can be accurately divided into individual packages.

  Laser forming is a bending technique in which the surface of the metal substrate 10 is irradiated with a laser beam to cause local thermoplastic deformation of the metal substrate 10. In the laser forming, the surface of the metal substrate 10 is intermittently irradiated with a laser beam, and the metal substrate 10 is warped by locally contracting when each irradiated portion is cooled. Further, since the metal substrate 10 is warped by thermoplastic deformation, the metal substrate 10 does not spring back after laser forming, and the desired warpage of the metal substrate 10 can be maintained.

  Hereinafter, a method for processing a package substrate according to the present embodiment will be described with reference to the accompanying drawings. 2 shows an example of a warp forming process, FIG. 3 shows an example of a resin layer forming process, and FIG. 4 shows an example of a dividing process. Note that the following processing method of the package substrate shows an example and can be changed as appropriate.

  As shown in FIG. 2A, a warp forming step is first performed. In the warp forming step, the metal substrate 10 is warped by irradiating the upper surface of the metal substrate 10 such as a stainless steel substrate with a laser beam having a wavelength that absorbs the metal substrate 10. In this case, the metal substrate 10 is carried into the laser forming apparatus, and the metal substrate 10 is placed on the processing table 41 of the laser forming apparatus. The metal substrate 10 is held with the upper surface exposed to the processing table 41 by a holder 42. Further, the processing head 43 is positioned above the metal substrate 10 and the processing table 41 is processed and fed in the X-axis direction, and the upper surface of the metal substrate 10 is intermittently irradiated with a laser beam. Thereby, the stress balance between the upper surface side and the lower surface side of the metal substrate 10 is broken at each irradiation position of the laser beam.

  Subsequently, the processing head 43 is indexed by one pitch in the Y direction in the Y axis direction, and further, the processing table 41 is processed and fed in the X axis direction, and the upper surface of the metal substrate 10 is intermittently irradiated with a laser beam. The By repeating this operation, the entire surface of the metal substrate 10 is irradiated with a laser beam at a predetermined pitch. By removing the metal substrate 10 from the processing table 41, the metal substrate 10 is released from the holder 42 and a warp is formed in the metal substrate 10. Since laser forming is performed before the device chip C (see FIG. 3) is disposed on the wiring layer 20 (see FIG. 3), the heat of the laser forming does not adversely affect the device chip C.

  As shown in FIG. 2B, the warping direction and the warping amount of the metal substrate 10 due to laser forming are adjusted assuming the warping direction and the warping amount of the metal substrate 10 in the subsequent resin layer forming step. In this case, the amount of warpage when the wiring layer 20 is formed on the metal substrate 10 is measured by forming the wiring layer 20 on the upper surface of the metal substrate 10 that has not been previously laser-formed by pressure heating of the resin sheet. The By actually forming the wiring layer 20 on the metal substrate 10 that has not been laser-formed, the warping direction and the warping amount of the metal substrate 10 according to the difference in thermal expansion coefficient between the resin and stainless steel, the wiring pattern, and the like are assumed. It is possible.

  In the warp forming step, the laser beam irradiation surface and the processing conditions for the metal substrate 10 are changed based on the warp direction and the warp amount of the metal substrate 10. When the metal substrate 10 is warped upward, the upper surface of the metal substrate 10 is irradiated with a laser beam. When the metal substrate 10 is warped downwardly concave, the lower surface of the metal substrate 10 is irradiated with a laser beam. The Further, the laser beam irradiation interval (pitch) is narrowed when the metal substrate 10 is warped, and the laser beam irradiation interval is widened when the metal substrate 10 is warped. In this way, the warping direction is adjusted by changing the surface on which the laser beam strikes the metal substrate 10, and the warping amount of the metal substrate 10 is adjusted by adjusting the irradiation interval of the laser beam on the metal substrate 10.

  For example, in the example shown in FIG. 2B, when the wiring layer 20 is formed on the metal substrate 10 that is not laser-formed, the wiring layer 20 expands and the metal substrate 10 is warped in an upward convex shape. For this reason, as shown in FIG. 2A, in the warp forming step, the laser beam is applied to the upper surface of the metal substrate 10 so that the metal substrate 10 warps in a downward concave shape by laser forming. The laser beam irradiation interval is adjusted by changing processing conditions such as the feed rate of the processing table 41 and the index interval of the processing head 43. The warpage amount of the metal substrate 10 may be measured by an optical height sensor or the like, or may be measured by a scale by an operator. If the warping direction and the warping amount of the metal substrate 10 at the time of forming the wiring layer 20 are known, it is not necessary to form the wiring layer 20 on the metal substrate 10 in advance and check the warping direction and the warping amount.

  As shown in FIG. 3A, a resin layer forming step is performed after the warp forming step. In the resin layer forming step, a wiring layer forming step is first performed. In the wiring layer forming step, the wiring layer 20 is formed on the upper surface of the metal substrate 10. In this case, the metal substrate 10 is carried into the resin layer forming apparatus, and the metal substrate 10 is placed on the processing table 51 in the resin layer forming apparatus. The metal substrate 10 is held with the upper surface exposed to the processing table 51 by a holder 52, and the warp of the metal substrate 10 is suppressed by the holder 52. On the upper surface of the metal substrate 10, a resin sheet 22 sandwiching the wiring pattern 21 is placed.

  In addition, a heater 53 is positioned above the resin sheet 22, and the wiring layer 20 is formed on the upper surface of the metal substrate 10 when the resin sheet 22 is heated and pressurized by the heater 53. When the resin layer heated by the heater 53 expands, a warp in a direction opposite to the warp due to laser forming occurs on the metal substrate 10. The warp of the metal substrate 10 due to laser forming is offset by the warp of the metal substrate 10 due to the formation of the wiring layer 20, and the stress balance between the upper surface side and the lower surface side of the metal substrate 10 is adjusted. Thus, by warping the metal substrate 10 in the opposite direction before the formation of the wiring layer 20, the warpage of the metal substrate 10 is reduced after the formation of the wiring layer 20.

  As shown in FIG. 3B, in the resin layer forming step, a device chip carrying step is performed after the wiring layer forming step. In the device chip transfer process, the device chip C is transferred onto the wiring layer 20. In this case, the transfer means 55 is moved above the metal substrate 10 held on the processing table 51, and the device chip C held on the transfer means 55 is disposed on the wiring layer 20 of the metal substrate 10. The device chip C on the wiring layer 20 is electrically connected to the wiring pattern 21 via the bumps of the device chip C. Thus, the device chip C is transported by the transport means 55 toward the chip mounting position on the wiring layer 20.

  As shown in FIG. 3C, in the resin layer forming step, the mold resin layer forming step is performed after the device chip carrying step. In the mold resin layer forming step, the device chip C on the wiring layer 20 is sealed with the mold resin, and the mold resin layer 30 is formed. In this case, the dispenser 56 is moved above the metal substrate 10 held on the processing table 51, and the device chip C is packaged by the mold resin supplied from the dispenser 56. In this way, the package substrate W in which the resin layer including the wiring pattern 21 is laminated on the upper surface of the metal substrate 10 is formed.

  In the present embodiment, it is assumed that the metal substrate 10 is warped in advance by laser forming, assuming warpage when the wiring layer 20 is formed on the metal substrate 10. It is not limited. Assuming warpage when the mold resin layer 30 is formed together with the wiring layer 20 on the metal substrate 10, the warpage may be formed on the metal substrate 10 by laser forming in advance. That is, the wiring layer 20 may be the resin layer that causes the metal substrate 10 to warp, and the wiring layer 20 and the mold resin layer 30 may be the resin layer that causes the metal substrate 10 to warp.

  As shown in FIG. 4, a dividing step is performed after the resin layer forming step. In the dividing step, the metal substrate 10 is divided by forming the dividing grooves 35 along the planned dividing lines. In this case, the package substrate W is carried into the laser processing apparatus, and the package substrate W is placed on the chuck table 61 of the laser processing apparatus. Since the package substrate W is substantially flat with the warp removed, the package substrate W is sucked and held on the holding surface of the chuck table 61. A lattice-shaped escape groove 36 is formed on the holding surface of the chuck table 61, and a line to be divided of the package substrate W is aligned with the escape groove 36.

  In addition, the processing head 62 is aligned with the division line of the package substrate W, and the processing head 62 irradiates the package substrate W with a laser beam having an absorptive wavelength. Then, when the chuck table 61 is processed and fed in the X-axis direction, the package substrate W is fully cut along the scheduled division line. When the package substrate W is fully cut along one division planned line, the processing head 62 is aligned with the adjacent division line and the package substrate W is fully cut. By repeating this processing operation, the package substrate W is divided into individual packages P.

  As described above, since the warpage of the package substrate W is reduced, the package substrate W can be accurately divided into the individual packages P in a state where the package substrate W is sucked and held by the chuck table 61. Further, since the package substrate W is divided in a state in which the warpage is reduced from the package substrate W, a large warp does not remain in the individual package P after the division. Further, since the package substrate W is divided by laser processing, the dividing line can be narrowed, and in particular, the package substrate W for small chips can be divided with high accuracy.

  In the dividing step, the package substrate W is divided into individual packages P by ablation. However, the package substrate W can be divided by any method as long as the package substrate W can be divided into individual packages P. Also good. For example, the package substrate W may be divided by blade dicing using a cutting blade. Ablation means that when the irradiation intensity of a laser beam exceeds a predetermined processing threshold, it is converted into electronic, thermal, photochemical and mechanical energy on the solid surface, resulting in neutral atoms, molecules, positive and negative A phenomenon in which ions, radicals, clusters, electrons, and light are explosively emitted and the solid surface is etched.

  As described above, according to the processing method of the package substrate W of the present embodiment, the warp of the metal substrate 10 due to laser forming is offset by the warp of the metal substrate 10 due to the formation of the wiring layer 20. That is, assuming that the metal substrate 10 is warped when the wiring layer 20 is formed, the metal substrate 10 is warped in a reverse direction by laser forming before the wiring layer 20 is formed, so that the metal substrate 10 is formed after the wiring layer 20 is formed. Ten warpages can be reduced. Therefore, a member such as a dedicated processing table or a measuring instrument for measuring the amount of warpage is not required, and the package substrate W can be accurately divided into individual packages P with a simple apparatus configuration while suppressing warpage. In addition, since the stress balance between the upper surface side and the lower surface side of the package substrate W is adjusted, the package P after the division does not greatly warp.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the present embodiment described above, the laser beam is irradiated on the upper surface of the metal substrate 10, but the irradiation direction of the laser beam depends on the thermal expansion coefficient of the material of the metal substrate 10 and the material of the wiring layer 20. Are appropriately changed.

  In the above-described embodiment, the metal substrate 10 is warped in the warp forming process so as to cancel out the warp of the metal substrate 10 generated in the resin device forming process. Need not be completely offset. The metal substrate 10 may remain warped to the extent that the package substrate W can be sucked and held on the chuck table 61 in the dividing step.

  In the above-described embodiment, the resin layer forming step is configured to form the resin layer by sealing the device chip C with a mold after disposing the device chip C on the wiring layer 20. It is not limited to this configuration. The resin device forming step may be any configuration as long as the resin layer including the wiring pattern 21 is formed on the metal substrate 10. For example, the resin layer may be formed by forming the wiring layer 20 on the metal substrate 10. .

  As described above, the present invention has an effect that it can be easily divided while suppressing warpage of the package substrate, and is particularly useful for a processing method of a package substrate in which a resin layer is laminated on a metal substrate. .

10 Metal substrate 20 Wiring layer (resin layer)
21 wiring pattern 22 resin sheet 30 mold resin layer (resin layer)
35 Divided groove W Package substrate

Claims (1)

A processing method of a package substrate, wherein a resin layer including a wiring pattern is formed on an upper surface of a metal substrate,
A warp forming step of warping the metal substrate by irradiating the upper surface of the metal substrate with a laser beam having a wavelength that is absorptive with respect to the metal substrate;
A resin layer forming step of forming a resin layer on the upper surface of the metal substrate after the warp forming step;
After the resin layer forming step, a dividing step of dividing the metal substrate by forming a dividing groove along a planned dividing line ,
Before the warp forming step, after forming the resin layer on the upper surface of the metal substrate not irradiated with the laser beam, performing a step of measuring the warp amount of the metal substrate,
In the reflected Ri forming step, the processing method of a package substrate processing conditions of the laser beam relative to the metal substrate Ru is adjusted based on the reflected Ri amount.

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