JP2006120729A - Method of manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing wiring board by which sagging down etc., of paste can be corrected easily through a simple process, even if sagging down occurs, after the paste has been charged in a through hole due to the low viscosity of the paste. <P>SOLUTION: After a plate-like core 2 is arranged with its first main surface side on the upside, an uncured packing composition 130 is packed into through holes 12S and 12L from the first main surface-side openings of the holes 12S and 12L, in a state where the second main surface-side openings are not closed in the holes 12S and 12L covered with through hole conductors 12. Then the excessive packing composition 11 swollen from the second main surface-side openings of the through holes 12S and 12L in a sagging-down state is tore, in a state where the contained resin is uncured. In addition, after the tearing process of the excessive packing composition is completed, the uncured packing composition 130 is cured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a wiring board.

JP 2002-64263 A JP 2004-158441 A

  Resin dielectric layers on both sides of a plate-like core made of glass-reinforced resin as a wiring board on which semiconductor parts such as LSI and IC are mounted or various thick-film printing elements are built inside the board A multilayer wiring board in which wiring layers (metal conductor layers) are alternately stacked is used. The wiring layers distributed on both surfaces are electrically connected by a through-hole conductor that covers the inner surface of the through-hole formed in the plate-like core. The inner diameter of the through-hole is adjusted in a wide range, but the inner space cannot be filled only with the plated through-hole conductor, so the inside is filled with a resin-curing filling composition (paste), and the filling composition After curing, the resin dielectric layer and the wiring layer are built up to ensure the flatness of the multilayer wiring laminated portion.

  As for the filling of the paste into the through hole as described above, for example, a method using a printing mask and a squeegee, a method using a roll coater, and a method using a dedicated injector have been put into practical use. When filling the paste, it is necessary to adjust the viscosity of the paste appropriately so that voids and the like do not remain in the through-holes. Tend to be used. As described in Patent Document 1 and Patent Document 2, as the size of the substrate and the density of the wiring increase, the inner diameter of the through hole becomes smaller and the aspect ratio between the inner diameter and the hole depth tends to increase. Therefore, it is necessary to use a paste having a lower viscosity.

However, when filling the inside of the through hole using a low-viscosity paste, the following problem occurs.
(1) Filling the through hole with the paste is generally performed from the upper opening with the lower opening being opened to prevent voids remaining. However, if the viscosity of the paste to be filled is low, there is a problem that the paste leaks out from the lower opening. In this case, if the leaked paste is hardened in a swelled state, it takes a very long time to correct by polishing.
(2) Many of the thermosetting resins contained in the paste are transferred to a curing reaction after the viscosity is once further lowered during the curing heat treatment. Due to the decrease in the viscosity during the curing heat treatment, it may be lifted by the surface tension at the periphery of the filled through-hole opening and leak around the opening (so-called bleed out). A paste with a low viscosity from the beginning is very likely to bleed out, and a dent is formed on the upper surface of the cured paste filled in the through hole, which tends to deteriorate the flatness of the build-up layer.
(3) The through-hole pad integral with the through-hole conductor covering the inner surface is often plated on the periphery of the opening of the through-hole, but in order to suppress paste drooping due to gravity in (1), chemical treatment is used. When the surface roughening process is performed on the inner surface of the through-hole conductor, the surface roughening process is also performed on the surface of the through-hole pad. When the through-hole pad subjected to surface roughening exists at the periphery of the opening of the through-hole, the bleedout in (2) tends to be more likely to occur.

  The above problem is particularly likely to occur when through-holes of different sizes are mixedly formed on one wiring board as in Patent Document 1 and Patent Document 2. In other words, the viscosity of the paste needs to be adjusted according to the small-diameter through hole that is more difficult to fill, but if the viscosity of the paste that fits into the small-diameter through-hole becomes too small for the large-diameter through-hole, its viscosity increases. It is clear that the above-described paste sag and bleed-out are more likely to occur in the diameter through hole.

  Patent Document 2 discloses a method in which a paste with increased viscosity is used, and paste is filled and filled into a small-diameter through hole using a mask, and the raised portion is polished and removed after semi-curing. However, this method has a problem that it is necessary to perform the second stage paste printing for enlarging using a mask after filling the paste into large and small through holes, which increases the number of processes and costs for preparing the mask. . On the other hand, Patent Document 1 proposes a method in which the particle size standard deviation of the filler contained in the paste is made smaller in the large diameter through hole than in the small diameter through hole. However, in this method, pastes having different viscosities depending on the dimensions of the through holes need to be used properly in the same wiring board, and it goes without saying that the paste adjustment and printing application processes become complicated.

  An object of the present invention is to provide a method of manufacturing a wiring board that can be easily corrected by a simple process even if the paste has a low viscosity and sags after filling into a through hole.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, a method for manufacturing a wiring board according to the present invention includes:
A through-hole in which a conductor layer is formed on the first main surface and the second main surface of a plate-shaped core made of an insulator and covers the inner surface of the through-hole formed in the plate thickness direction of the plate-shaped core In the method for manufacturing a wiring board that is conductively connected by a conductor and further filled with a resin-curing filling composition inside the through-hole conductor,
The plate-like core is arranged so that the first main surface side is on top, and the opening on the second main surface side of the through hole covered with the through hole conductor is not blocked, and the first core surface side is placed inside the through hole. A composition filling step of filling an uncured filling composition from an opening on one main surface side;
After completion of the filling process, surplus filling composition scouring process in which the surplus filling composition swelled in a form depending on the second main surface side of the through hole is scraped off in a state where the resin contained is uncured. ,
And a curing step of curing the uncured filling composition after the surplus filling composition scraping step is completed.

  According to the present invention, when filling a through hole with a filling composition having a low viscosity, the surplus filling composition swells in a form that hangs down from the opening on the second main surface (back surface) side of the through hole. Since the resin contained is scraped off in an uncured state and then the filled uncured filling composition is cured, the bulging portion can be easily removed, and the flatness A good through hole filling state can be reliably achieved by a simple process.

  The above-described method of the present invention exhibits a particularly remarkable effect when the core substrate is formed with a mixture of through holes having different inner diameters. In other words, when the viscosity of the paste is adjusted to match the smaller diameter through hole that is more difficult to fill, the viscosity of the paste that fits into the smaller diameter through hole is too small for the large diameter through hole. Even if paste dripping occurs, it can be removed easily and without problems by the scraping process. As a result, it is possible to collectively fill the same kind of filling composition into through holes having different inner diameters, and the process can be greatly simplified as compared with the methods disclosed in Patent Document 1 and Patent Document 2. It becomes.

  It is easy to carry out the surplus filling composition scraping step by inverting the top and bottom of the plate-like core after the composition filling step. In this case, in the surplus filling composition scraping step, it is desirable to scrape off the surplus filling composition so that a filling composition layer having a constant thickness remains around the opening of the through hole. When the surplus filling composition is scraped off, the filling composition layer having a certain thickness remains around the opening of the through hole, so that even if the viscosity of the filling composition further decreases during the curing process, the filling composition layer is already present around the opening. By being present, the outflow of the filling composition from the through hole to the periphery of the opening is suppressed, and bleed out can be extremely effectively suppressed.

  In particular, when a through-hole pad integrated with a through-hole conductor is formed on the first main surface of the plate-shaped core in the peripheral region of the through-hole opening, in order to prevent the bleed-out, the filling composition layer is at least It is desirable to carry out a surplus filling composition scraping process so as to remain on the through-hole pad. In particular, when the surface of the through-hole pad is roughened together with the inner surface of the through-hole conductor, the surface of the through-hole pad is roughened, so that the wetting with the filling composition layer having reduced viscosity is achieved. As a result, the spillage and the bleed-out are more likely to occur during the curing process. Therefore, in this case, it is more effective to leave the filling composition layer on the through-hole pad in the surplus filling composition scraping process as described above.

  In addition, if a polishing step for removing the remaining filling composition layer by polishing is provided, it is possible to prevent the filling composition layer from remaining on the surface of the through-hole pad. It can suppress effectively. When the filling composition contains a thermosetting resin, the curing step includes a semi-curing step for semi-curing the uncured filling composition filled in the through holes, and a thermosetting resin after the semi-curing step is completed. It is desirable to carry out the above-described polishing step between the temporary drying step and the thermosetting treatment step, including a main curing step for main curing. If the remaining filling composition layer is in a semi-cured state, removal by polishing can be performed very simply. In addition, it is good to perform a semi-hardening process so that at least any one of low temperature or short time conditions may be satisfied rather than a main hardening process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a first embodiment of a wiring board of the present invention. In the wiring board 1, the conductor layers 3 and 23 are formed on the first main surface and the second main surface of the plate-shaped core 2 made of an insulator, and the conductor layers are formed in the plate thickness direction of the plate-shaped core 2. The through-hole conductors 12 that cover the inner surfaces of the through-holes 12S and 12L are electrically connected and the inner side of the through-hole conductor 12 is filled with a resin-curing filling composition 30. The plate-like core 2 is composed of a heat-resistant resin plate (for example, bismaleimide-triazine resin plate) or a fiber-reinforced resin plate (for example, glass fiber-reinforced epoxy resin), and a conductor layer is formed on both surfaces of the plate-like core 2. Core wiring pattern layers 3 and 23 are formed as 3 and 23, respectively. These core wiring pattern layers 3 and 13 include a power supply layer or a ground layer. On the other hand, the plate-like core 2 is formed with through-holes 12S and 12L drilled by a drill or the like, and through-hole conductors 120 for connecting the core wiring pattern layers 3 and 13 to each other are formed on the inner wall surfaces thereof. The through hole 12 is filled with the filling composition 30.

  The filling composition 30 is based on a thermosetting resin such as an epoxy resin, in which a filler made of dielectric particles such as silica is dispersed. In addition, when it is desired to provide conductivity to the filling composition 30 itself, such as when both ends of the through-hole conductor 12 are to be plugged with an electrolytic plating layer, a conductive filler such as metal powder or carbon black can be blended. is there. As shown in FIG. 5, the filling composition 30 is filled into the through holes 12S and 12L by mixing uncured thermosetting resin particles 90 and filler particles 80 and adjusting the viscosity with a solvent (uncured paste 130). It can be carried out using a known printing apparatus, roll coater or injector.

  Returning to FIG. 1, first resin build-up layers 4 and 14 are formed on the core wiring pattern layers 3 and 13, respectively. Further, first wiring pattern layers 5 and 15 are formed on the surfaces by Cu plating, respectively. The core wiring pattern layers 3 and 13 and the first wiring pattern layers 5 and 15 are connected to each other by via conductors 32 and 33, respectively. Similarly, second resin build-up layers 6 and 16 using the photosensitive filling composition of the present invention are formed on the first wiring pattern layers 5 and 15, respectively. Second wiring pattern layers 7 and 17 are formed on the surfaces by Cu plating, respectively. The first wiring pattern layers 5 and 15 and the second wiring pattern layers 7 and 17 are interconnected by via conductors 34 and 35, respectively.

  As shown in FIG. 1, the core substrate 2 is formed with through holes 12S and 12L having different inner diameters. The through holes 12S and 12L having different inner diameters are filled with the same type of filling composition 30. Yes. Specifically, as the through holes 12S and 12L, a large diameter through hole 12L having a filling inner diameter of the filling composition 30 of 200 μm or more and 350 mm or less, and a small diameter through hole 12S having a filling inner diameter of the filling composition 30 of 75 μm or more and less than 200 μm, Is formed. As shown in FIG. 2, a plurality of small-diameter through holes 12S are densely arranged in a grid (or zigzag) in the dedicated region 3, and the large-diameter through holes 12L are arranged so as to surround the periphery thereof.

  On the first main surface and the second main surface of the plate-like core 2, a through-hole pad 13 integrated with the through-hole conductor 12 is formed in the opening peripheral region of the through-holes 12 </ b> S and 12 </ b> L. As shown in FIG. 5, the inner surface of the through-hole conductor 12 and the surface of the through-hole pad 13 are subjected to surface roughening treatment in order to increase the adhesion strength between the filling composition in the through-hole and the upper resin buildup layer. (Roughening treatment: based on chemical treatment such as blackening treatment or chelate etching treatment). In FIG. 1, the same surface roughening treatment is also applied to the surfaces of the core wiring patterns 3 and 13, the first wiring pattern layers 5 and 15, and the second wiring pattern layers 7 and 17.

  As shown in FIG. 1, on the second resin buildup layer 6, a large number of base conductive pads 10 that are electrically connected to the second wiring pattern layer 7 are provided. These base conductive pads 10 are arranged in a square shape at the substantially central portion of the substrate by electroless Ni-P plating and Au plating, and form chip mounting portions 40 together with the solder bumps 11 formed thereon, respectively. . On the other hand, on the side where the second wiring pattern layer 7 is formed and the side where the second wiring pattern layer 17 is formed, solder resist layers 8 and 18 are formed so as to cover the wiring pattern layers 7 and 17. Each is formed.

Hereinafter, a method for manufacturing the wiring board of FIG. 1 according to the present invention will be described.
First, as shown in Step 1 of FIG. 3, a small-diameter through hole 12S and a large-diameter through hole 12L are formed in the plate-like core 2 by drilling or the like, and further, through-hole conductors 12 and through-holes are formed in the respective through holes 12S and 12L. The hole pad 13 is formed by plating. Next, as shown in Step 2 and Step 3, a mask 109 is disposed on the first main surface of the plate-like core 2, and the uncured filling composition is placed in each of the through holes 12S and 12L through the opening of the mask 109. The paste 130 is printed and filled. Filling the through holes 12S and 12L with the paste 130 is performed by opening the lower side (second main surface side) of the hole and preventing the voids from remaining in the through holes. From the opening. As a matter of course, the two types of through holes 12S and 12L are collectively filled with the paste 130 having the same composition.

As already described, the large-diameter through hole 12L has a filling inner diameter (the inner diameter after the through-hole conductor 12) of the filling composition 30 is set to 200 μm or more and 350 mm or less. The filling inner diameter of the composition 30 is as small as 75 μm or more and less than 200 μm (particularly 150 μm or less, or 100 μm or less). The aspect ratio expressed by the hole depth / inner diameter is 23 to 40 for the large diameter through hole 12L, whereas the aspect ratio of the small diameter through hole 12S is 4.0 to 10.7 (particularly 5. 3 or more, or 8.0 or more), and the filling condition of the paste 130 is considerably stricter than that of the large-diameter through hole 12L. Therefore, the paste 130 has a low viscosity, for example, 22 ± 3 ° C. (that is, normal temperature) and the shear rate is set to 21 s ⁻¹ for the purpose of relaxing the filling conditions for the small diameter through-hole 12S. A viscosity of 300 Pa · s or less (further 200 Pa · s or less: the lower limit is, for example, 10 Pa · s) is employed.

  As described above, when the viscosity of the paste 130 is adjusted in accordance with the small-diameter through hole 12S that is more difficult to fill, the viscosity of the paste 130 that fits the small-diameter through-hole 12S is too small in the large-diameter through-hole 12L. As shown in FIG. 4, in the large-diameter through-hole 12L, the excess paste (filling composition) 11 swells in a form that hangs down from the opening on the second main surface side increases. When the leaked paste 130 is hardened in a swelled state, it takes a very long time for correction by polishing (that is, removal of the hardened material of the swelled excess paste).

  Therefore, the present invention employs a process as shown in FIG. After filling the through hole 12 with the filling composition as in step 3 above, the plate core 2 is turned upside down as in step 4. Then, as shown in step 5, the surplus filling composition 11 that swells in a form that hangs down from the opening on the second main surface side of the through holes 12S and 12L is scraped off in a state where the resin contained is uncured. In this embodiment, the scraping process is performed by moving the edge of a squeegee 110 (for example, made of plastic) on the plate surface while pressing and urging the edge of the squeegee 110 with a certain pressure.

  In addition, by sufficiently increasing the pressing force of the squeegee 110 against the plate-like core 2, it is possible to make the residue of the composition on the plate surface extremely small except inside the through hole 12. However, in the present embodiment, the surplus filling composition 11 is scraped off so that the filling composition layer 31f having a certain thickness remains around the openings of the through holes 12S and 12L. This residual thickness can be adjusted by adjusting the pressing force of the squeegee 110 against the plate-like core 2.

  In this state, as shown in step 6, the filled paste 130 is semi-cured. This semi-curing treatment is performed so as to satisfy at least one of the conditions of a lower temperature or a shorter time than the final curing treatment, ie, the main curing treatment (for example, the half-curing in the case of using an epoxy resin as a thermosetting resin). Examples of the curing treatment conditions include the conditions of heating at 120 ° C. for 20 minutes and then heating at 140 ° C. for 70 minutes). The thermosetting resin such as the epoxy resin contained in the paste 130 is once melted to lower the viscosity during the curing process, and then the curing reaction proceeds. Due to the decrease in the viscosity during the curing heat treatment, the filled through holes 12S and 12L are likely to bleed out due to surface tension that is lifted by the surface tension and leaks around the openings. Since the paste 130 employed in the present embodiment is inherently kept low in viscosity, it can be said that this bleedout is more likely to occur. When the bleed-out occurs, as shown in FIG. 6, a dent 12c is formed on the upper surface of the cured paste filled in the through holes 12S and 12L.

  However, as shown in Step 5 of FIG. 4, when the surplus filling composition 30 is scraped off, the filling composition layer 31 f having a certain thickness remains around the opening of the through holes 12 </ b> S and 12 </ b> L, so that the filling composition 30 is cured during the curing process. Even if the viscosity of the liquid is further reduced, the filling composition layer 31f is already present in the periphery, so that the outflow of the filling composition 30 from the through holes 12S and 12L to the periphery of the opening is suppressed. As described above, dents due to bleed-out are less likely to occur. In the present embodiment, a through-hole pad 13 that is integral with the through-hole conductor 12 is formed in a region around the opening of the through-holes 12S and 12L, and the main surface of the plate core 2 including the surface of the through-hole pad 13 is The filling composition layer 31f is left so as to be covered. Since the surface of the through-hole pad 13 as well as the inner surface of the through-hole conductor 12 has been subjected to surface roughening as described above and has high wettability, the filling composition layer 31f with reduced viscosity is more easily spread, leading to lead-out. Is more likely to occur. However, the bleed-out prevention effect is more remarkably exhibited by covering the through-hole pad 13 whose surface is roughened by the filling composition layer 31f.

  Subsequently, as shown in step 7 of FIG. 4, the semi-cured filling composition layer 31f is polished and removed by a polishing apparatus using a surface grinder or a lapping machine. This polishing is performed to such an extent that the metal surface of the through-hole pad 13 is exposed (as shown in an enlarged view in the drawing, the surface layer portion of the through-hole pad 13 may be partially polished). Further, around the through hole pad 13, a filling composition layer 31 f corresponding to the thickness of the through hole pad 13 remains. The semi-cured filling composition layer 31f is relatively soft, and the polishing time required for its removal can be shortened.

  Next, the paste (filling composition) in which the through-holes 12 are filled is fully cured (the condition for the main curing is, for example, about 150 hours at 150 ° C.). After this main curing, as shown in step 8, if necessary, both surfaces of the cured filling composition 30 can be covered with the cover plating layer 31C together with the through-hole pads 13 (however, this step may be omitted). . Thus, as shown in FIG. 7, the filling composition 30 can be filled with good flatness in all the through holes 12S and 12L. Thereafter, if a wiring layer and a resin buildup layer are further laminated on both surfaces of the plate-like core 2, the laminated structure of the wiring substrate 1 shown in FIG. 1 is completed.

Sectional drawing which shows typically one Embodiment of the wiring board used as the application object of this invention. The top view which shows the formation form of the through hole of the wiring board of FIG. 1 as an example. The 1st figure which shows the manufacturing process of the wiring board of FIG. 1 by this invention. The second figure. The conceptual diagram of the paste for forming a filling composition. The figure explaining the leak of paste and the indentation generation | occurrence | production by bleed-out. The 3rd figure which shows the manufacturing process of the wiring board of FIG. 1 by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring board 2 Plate core 5 1st surface conductor 7 Conductor line 9 2nd surface conductor 12S, 12L Through-hole 13 Through-hole pad 30 Filling composition 130 Uncured filling composition (paste)

Claims (8)

A conductor layer is formed on the first main surface and the second main surface of the plate-shaped core made of an insulator, and the conductor layer covers the inner surface of the through-hole formed in the plate thickness direction of the plate-shaped core. In the method of manufacturing a wiring board that is conductively connected by a hole conductor and is further filled with a resin-curing filling composition inside the through-hole conductor,
The plate-like core is disposed so that the first main surface side is on the top, and the opening on the second main surface side of the through hole covered with the through-hole conductor is not blocked, inside the through-hole. A composition filling step of filling the uncured filling composition from the opening on the first main surface side;
After the filling step, the surplus filling composition that swells in a form that hangs down from the opening on the second main surface side of the through-hole is scraped off in a state in which the contained resin is uncured. Process,
A curing step of curing the uncured filling composition after the surplus filling composition scraping step is completed;
A method of manufacturing a wiring board, comprising: 2. The method of manufacturing a wiring board according to claim 1, wherein the through-holes having different inner diameters are mixedly formed on the core substrate, and the same kind of filling composition is collectively filled into the through-holes having different inner diameters. 3. The method for manufacturing a wiring board according to claim 1, wherein after the completion of the composition filling step, the plate-like core is turned upside down to perform the surplus filling composition scraping step. 4. The surplus filling composition is scraped off so that a filling composition layer having a certain thickness remains around the opening of the through hole in the surplus filling composition scraping step. 5. The manufacturing method of the wiring board as described in 2 .. On the first main surface of the plate-shaped core, a through-hole pad integrated with the through-hole conductor is formed in a region around the opening of the through-hole, and the filling composition layer remains at least on the through-hole pad. The manufacturing method of the wiring board of Claim 4. 6. The method of manufacturing a wiring board according to claim 5, wherein the composition filling step is performed after the surface of the through-hole pad is roughened together with the inner surface of the through-hole conductor. The method for manufacturing a wiring substrate according to claim 4, further comprising a polishing step of removing the remaining filling composition layer by polishing. The filling composition contains a thermosetting resin, and the curing step includes a semi-curing step for semi-curing the uncured filling composition filled in the through holes, and a semi-curing step after the semi-curing step is completed. The method for manufacturing a wiring board according to claim 7, further comprising: a main curing step of main curing the thermosetting resin in a cured state, wherein the polishing step is performed between the semi-curing step and the main curing step.

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