JP4718031B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printed wiring board and a manufacturing method thereof.
[0002]
[Prior art]
The printed wiring board manufacturing method is roughly classified into a subtractive process and an additive process. The subtractive method is also called an etching method and is characterized by chemically corroding the surface copper foil of the copper clad laminate. Here, an example of a method for manufacturing the multilayer printed wiring board 41 using the subtractive method will be briefly described with reference to FIGS.
[0003]
First, while preparing the copper clad laminated board 44, it etches and forms the inner-layer conductor pattern 53 on both surfaces of the insulating base material 42. FIG. Then, a copper foil 55 having a thickness of about 12 μm is laminated and pasted on both surfaces of the insulating base material 42 via a prepreg 54 (see FIG. 10). A through-hole forming hole 45 is formed by drilling or the like at a predetermined location of the insulating base material 42 to which the copper foil 55 is adhered. A thin copper plating layer 47 is formed on the entire copper base layer 46 derived from the copper foil 55 and the inner wall surface of the through hole forming hole 45 by electroless copper plating (see FIG. 11). After such a panel plating process, a mask 48 is formed on the thin copper plating layer 47. Then, a thick copper plating layer 50 is formed by electrolytic copper plating at a portion exposed from the opening 49 of the mask 48 (see FIG. 12). After such a pattern plating step, an etching resist 56 is formed on the thick copper plating layer 50 by solder plating or the like, and the mask 48 is peeled off (see FIG. 13). Then, etching is performed in this state. By this etching, the thin copper plating layer 47 and the copper base layer 46 are removed, and the outer conductor patterns 52 are separated from each other. Finally, if the etching resist 56 is peeled off, a desired multilayer printed wiring board 41 is completed (see FIG. 14).
[0004]
[Problems to be solved by the invention]
However, in the above conventional manufacturing method, a fine pattern having a good shape cannot be accurately formed, and the bottom layer is considerably longer than the top due to etching characteristics. Prone. Therefore, it is difficult to form a pattern of a portion (for example, a bonding pad portion) that requires finer and higher precision.
[0005]
Therefore, a countermeasure for forming the copper base layer 46 using an extremely thin copper foil having a thickness of 10 μm or less instead of the copper foil 55 can be considered. This is because the thickness to be removed by etching in the conductor pattern cutting step can be reduced. Therefore, the outer layer conductor pattern 52 that has been divided is less likely to have a flared shape.
[0006]
However, since the copper foil is extremely thin, deformation and scratches are likely to occur. Therefore, when pattern formation is performed using a deformed copper foil, high yield and high reliability may not be realized. Therefore, in order to avoid such a deformation | transformation etc., it is necessary to handle a copper foil carefully at the time of handling, and productivity will fall naturally.
[0007]
The present invention has been made in view of the above problems, and its purpose is to provide a method for producing a printed wiring board and the like capable of forming a fine conductor pattern having a good shape without lowering productivity. It is to provide.
[0008]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, in the invention according to claim 1,Inner layer and outer layerIn a method for producing a printed wiring board provided with a conductor pattern,A step of forming an inner layer conductor pattern on an insulating substrate, and a thickness of 1 μm to 5 μmTransfer copper foil10 μm to 50 μm thickUsing a conductor layer transfer sheet held in a peelable state on a carrier copper foil, the transfer copper foil is passed through a prepreg.AboveA step of forming a copper underlayer by transferring and sticking to at least one surface of an insulating base material, and forming a mask on the copper underlayer, and copper plating on a portion exposed from the opening of the mask Forming the layer and removing the mask and then etching to remove the copper underlayerOuter layerThe gist of the method for manufacturing a printed wiring board is that a conductor pattern cutting step for cutting the conductor patterns is performed.
[0009]
  In the invention according to claim 2, the plated through holeAnd inner and outer layersIn a method for producing a printed wiring board provided with a conductor pattern,A step of forming an inner layer conductor pattern on an insulating substrate, and a thickness of 1 μm to 5 μmTransfer copper foil10 μm to 50 μm thickUsing a conductor layer transfer sheet held in a peelable state on a carrier copper foil, the transfer copper foil is passed through a prepreg.AboveA step of forming a copper base layer by transferring and sticking to both surfaces of the insulating base, a hole forming step of forming a hole for forming a through hole at a predetermined location of the insulating base, the copper base layer and the through On the inner wall of the hole forming holeBy electroless copper platingForming a thin copper plating layer1And a mask is formed on the thin copper plating layer, and the portion exposed from the opening of the maskBy electrolytic copper platingA second plating step for forming a thick copper plating layer and etching after peeling the mask to remove the thin copper plating layer and the copper underlayer that were under the maskOuter layerThe gist of the method for manufacturing a printed wiring board is that a conductor pattern cutting step for cutting the conductor patterns is performed.
[0010]
According to a third aspect of the present invention, in the first or second aspect, the conductor pattern dividing step by the etching is performed in a state where no etching resist is provided on the copper plating layer located in the outermost layer.
[0011]
  A fourth aspect of the present invention provides the transfer copper foil according to any one of the first to third aspects.as well asThe carrier copper foilAre made of the same material and have the same thermal expansion coefficientIt was.
[0012]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the annealing step is performed between the time when the mask is removed and the etching is performed in the conductor pattern dividing step.
[0013]
  In invention of Claim 6,It is obtained by the method for manufacturing a printed wiring board according to any one of claims 2 to 5.In the printed wiring board, the aboveOuter layerConductor pattern is the thickness provided on the insulating substrate1 μm to 5 μmA copper underlayer, a first copper plating layer having a thickness of 3 μm or less formed on the copper underlayer, and a second copper plating layer having a thickness of 5 μm to 50 μm formed on the first copper plating layer, Consisting of the aboveOuter layerIn the cross section of the conductor pattern, the length of the side far from the insulating base is 0.9 to 1.2 of the length of the side close to the insulating base. The gist.
[0014]
  The “action” of the present invention will be described below.
  According to the first aspect of the invention, the transfer copper foil is peeled off from the carrier copper foil and transferred and pasted, whereby a thin copper underlayer derived from the transfer copper foil of the conductor layer transfer sheet on the insulating substrate. Is formed. And by forming the copper plating layer with the mask formed,Outer layerOnly the portion to be the conductor pattern is selectively thickened. After this, etching is performed to remove the copper underlayer that was under the mask,Outer layerConductor patterns are separated from each other. Since the copper underlayer of the present invention is relatively thin, the thickness to be removed by etching in the conductor pattern cutting step is considerably small. Therefore, it was divided and completed.Outer layerThe conductor pattern is less likely to have a flared shape, and a fine pattern with a good shape can be accurately formed.
[0015]
  Further, the transfer copper foil is held by a thicker carrier copper foil. Therefore, even if the transfer copper foil itself is extremely thin, it becomes a certain thickness when viewed as the entire conductor layer transfer sheet, and suitable rigidity is imparted to the entire conductor layer transfer sheet. For this reason, deformation | transformation and damage with a transfer copper foil are avoided, and handling property improves.In addition, by setting the thicknesses of the transfer copper foil and the carrier copper foil within the above preferred range, it is possible to reliably avoid the deformation and scratches of the transfer copper foil, and to reduce the productivity and cost. Can be reliably prevented.
[0016]
  According to the second aspect of the present invention, the transfer copper foil is peeled off from the carrier copper foil and transferred and pasted, whereby a thin copper underlayer derived from the transfer copper foil of the conductor layer transfer sheet on the insulating substrate. Is formed. And by forming a thick copper plating layer with the mask formed,Outer layerOnly the portion to be the conductor pattern is selectively thickened. After this, etching is performed to remove the thin copper plating layer and the copper underlayer that were under the mask,Outer layerConductor patterns are separated from each other. Since the copper underlayer of the present invention is relatively thin, the thickness to be removed by etching in the conductor pattern cutting step is considerably small. Therefore, it was divided and completed.Outer layerThe conductor pattern is less likely to have a flared shape, and a fine pattern with a good shape can be accurately formed.
[0017]
  Further, the transfer copper foil is held by a thicker carrier copper foil. Therefore, even if the transfer copper foil itself is extremely thin, it becomes a certain thickness when viewed as the entire conductor layer transfer sheet, and suitable rigidity is imparted to the entire conductor layer transfer sheet. For this reason, deformation | transformation and damage with a transfer copper foil are avoided, and handling property improves.In addition, by setting the thicknesses of the transfer copper foil and the carrier copper foil within the above preferred range, it is possible to reliably avoid the deformation and scratches of the transfer copper foil, and to reduce the productivity and cost. Can be reliably prevented.
[0018]
According to the third aspect of the present invention, in the conductor pattern dividing step, the step of forming and peeling the etching resist is not required, and as a result, man-hours are reduced and productivity is improved. In addition, the thickness of the copper plating layer that is removed with the etching at this time is extremely small, and the pattern formation accuracy and the like are not particularly adversely affected.
[0019]
  According to the invention of claim 4,Even if it passes through a heat press, it does not warp to transfer copper foil, and wrinkles, peeling, etc. do not occur, and it is convenient for achieving high accuracy and high reliability of the outer layer conductor pattern.
[0021]
According to the fifth aspect of the present invention, the stress inherent in the copper plating layer is released by heating by performing the annealing process after the mask is peeled off until etching is performed. As a result, pinholes are less likely to occur in the copper plating layer, and a highly reliable conductor pattern can be obtained.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a printed wiring board 1 according to an embodiment of the present invention and a manufacturing method thereof will be described in detail with reference to FIGS.
[0023]
As shown in FIG. 9, the printed wiring board 1 of the present embodiment includes conductor patterns 2 a and 2 b and plated through holes 3 formed by a subtractive method on the front and back sides of the insulating base 4. The multilayer printed wiring board 1 is a so-called four-layer board having four conductor layers. As the insulating base material 4, for example, a glass cloth base material impregnated with an epoxy resin, a polyimide resin, a BT (bismaleimide triazine) resin or the like is used. In this embodiment, a base material (so-called glass epoxy base material) impregnated with a relatively inexpensive epoxy resin is selected.
[0024]
Inner layer conductor patterns 2 a are formed on both front and back surfaces of the insulating base 4. The inner layer conductor pattern 2a is obtained, for example, by etching a copper foil provided on the insulating base material 4. Outer layer conductor patterns 2b are formed on the inner layer conductor patterns 2a on both the front and back surfaces via prepregs 34, respectively.
[0025]
As shown in FIG. 1, the outer conductor pattern 2 b includes a copper base layer 6, a thin copper plating layer 7 as a first copper plating layer, and a thick copper plating layer 8 as a second copper plating layer. Become. That is, the outer layer conductor pattern 2b has a three-layer structure. The thin copper plating layer 7 is formed on the copper underlayer 6, and the thick copper plating layer 8 is formed on the thin copper plating layer 7.
[0026]
The range in which the thickness of the copper underlayer 6 can be taken is less than 10 μm, and particularly preferably 1 μm to 5 μm. The range in which the thickness of the thin copper plating layer 7 can be taken is 3 μm or less, and particularly preferably 0.5 μm to 2 μm. The possible range of the thickness of the thick copper plating layer 8 is 5 μm to 50 μm, particularly 10 μm to 25 μm. Specifically, in the present embodiment, the thickness of the copper underlayer 6 is set to 3 μm, the thickness of the thin copper plating layer 7 is set to 1.5 μm, and the thickness of the thick copper plating layer 8 is set to 20 μm.
[0027]
Here, in the cross section of the outer layer conductor pattern 2b, the length of the side far from the insulating base material 4 (that is, the length of the top portion) is defined as L1, and the length of the side near the insulating base material 4 (ie, the length of the side near the insulating base material 4) The length of the bottom part) is defined as L2. In this case, the value of L1 / L2 is 0.9 to 1.2, which is a shape that is difficult to say so-called hem spreading. In the present embodiment, the space between the adjacent outer layer conductor patterns 2b is set to about 35 μm, and the line width (that is, L1 value) of the outer layer conductor pattern 2b is set to about 70 μm.
[0028]
The conductor patterns 2a and 2b of each layer are electrically connected through a plated through hole 3 formed so as to penetrate the insulating base material 4. The conductor layer in the plated through hole 3 is composed of a thin copper plating layer 7 formed on the inner wall surface of the through hole forming hole 10 and a thick copper plating layer 8 formed on the thin copper plating layer 7. Become. That is, the conductor layer in the plated through hole 3 has a two-layer structure. The land 3a of the plated through hole 3 has the same structure as that of the outer layer conductor pattern 2b, that is, a three-layer structure.
[0029]
Next, a procedure for manufacturing the multilayer printed wiring board 1 of the present embodiment will be described.
First, prior to this, the conductor layer transfer sheet 31 used in the present embodiment will be described. As shown in FIG. 2, the conductor layer transfer sheet 31 is roughly composed of a transfer copper foil 32 and a carrier copper foil 33.
[0030]
The transfer copper foil 32 is held on one side of the carrier copper foil 33 in a peelable state. Specifically, for example, the transfer copper foil 32 is attached to one side of the carrier copper foil 33 using an adhesive or pressure sensitive adhesive that does not have a large bonding force. The reason is that if the bonding force is too large, it is difficult to peel off the transfer copper foil 32, which leads to deformation and the like. Of course, the transfer copper foil 32 may be attached to and held on the carrier copper foil 33 without using an adhesive or the like.
[0031]
The carrier copper foil 33 is thicker than the transfer copper foil 32. Specifically, the thickness of the transfer copper foil 32 is preferably less than 10 μm, and more preferably 1 μm to 5 μm. The thickness of the carrier copper foil 33 is preferably 10 μm to 50 μm, and more preferably 30 μm to 40 μm.
[0032]
If the thickness of the transfer copper foil 32 is 10 μm or more, a sufficiently thin copper underlayer 6 cannot be formed, and the thickness to be removed by etching in the conductor pattern cutting step cannot be sufficiently reduced. Moreover, when the thickness of the carrier copper foil 33 is less than 10 μm, it is not possible to impart suitable rigidity to the entire conductor layer transfer sheet 31, and it is possible to reliably avoid deformation and scratches of the transfer copper foil 32. It becomes difficult. Further, the carrier copper foil 33 itself is likely to be deformed, and thus may not be reusable. When the thickness of the carrier copper foil 33 exceeds 50 μm, the rigidity becomes excessively strong, and on the contrary, the peeling operation becomes difficult, which may lead to a decrease in productivity. In addition, the cost increases due to the increased amount of copper used. In the present embodiment, in view of the above circumstances, the transfer copper foil 32 is set to a thickness of 3 μm, and the carrier copper foil 33 is set to a thickness of 35 μm, which is a common thickness. The reason for selecting the copper foil as the carrier foil is that copper is inexpensive and excellent in economic efficiency. The reason why the copper foil was selected as the transfer foil is that copper is inexpensive and excellent in economic efficiency, and also excellent in etching property.
[0033]
Then, using the copper-clad laminate 5 as a starting material, the inner layer conductor pattern 2a is formed on both the front and back surfaces of the insulating base material 4 constituting the copper clad laminate 5. And the said conductor layer transfer sheet 31 is laminated | stacked through the prepreg 34 on the front and back both surfaces of this insulating base material 4. FIG. At this time, the transfer copper foil 32 is directed to the inner layer side. And it heat-presses with a laminating apparatus, transfers and sticks the transfer copper foil 32 to the insulating base material 4 via the prepreg 34, and a copper base layer is applied to the entire front and back surfaces of the insulating base material 4 as shown in FIG. 6 is formed.
[0034]
Thereafter, the carrier copper foil 33 is peeled and peeled from the transfer copper foil 32 to remove the carrier copper foil 33 and expose the transfer copper foil 32. The carrier copper foil 33 scraped off may be used again as the conductor layer transfer sheet 31 by collecting and attaching a new transfer copper foil 32.
[0035]
In the subsequent drilling step, through-hole forming holes 10 having a diameter of 0.1 mm to 0.2 mm are formed by drilling at predetermined locations of the insulating base material 4 that has undergone the copper underlayer forming step (see FIG. 4). When it is desired to form the through-hole forming hole 10 having a smaller diameter, laser processing may be performed instead of drilling.
[0036]
When such a drilling process is performed, smear may occur in the through-hole forming hole 10 due to heat generation. In such a case, the copper clad laminate 5 may be treated with a desmear solution in order to dissolve and remove the generated smear. Note that desmear treatment can also be performed by a plasma method. In the desmear process, desmear is performed under conditions such that the ultrathin transfer copper foil 32 does not disappear, specifically, under conditions such that the thickness of the transfer copper foil 32 is reduced to 1/10 to 1/2 of the initial thickness. It is better to treat the liquid. In this case, a solution of sulfuric acid, chromic acid, alkaline permanganate or the like is used as the desmear liquid.
[0037]
After the desmear process is performed as necessary, a catalyst nucleus for depositing plating on the inner wall surface of the through-hole forming hole 10 is then applied, and the catalyst nucleus is activated. For imparting the catalyst nucleus, noble metal ions, noble metal colloids and the like are used, and generally palladium chloride, palladium colloids and the like are used.
[0038]
After applying the catalyst nucleus and its activation treatment, the thin copper plating layer 7 is then formed by electroless copper plating on the entire surface of the copper underlayer 6 and the inner wall surface of the through hole forming hole 10 (FIG. 5). reference).
[0039]
In the first plating step, an electroless copper plating bath, which is a kind of electroless plating bath, is used, and a thin copper plating layer 7 having a thickness of 3 μm or less, preferably 0.5 μm to 2 μm is formed using the same. Is done. If the thin copper plating layer 7 is too thin, there is a possibility that the electrolytic copper plating cannot be reliably deposited on the entire inner wall surface of the through hole forming hole 10 in the subsequent plating step. Therefore, the conduction failure of the plated through hole 3 may be caused, and the reliability may not be sufficiently improved. On the contrary, if the thin copper plating layer 7 is formed too thick, the productivity is reduced and the cost is increased, and the thickness to be removed by etching in the conductor pattern cutting process cannot be sufficiently reduced. There is a fear.
[0040]
After the first plating step, a predetermined mask 11 serving as a plating resist is then formed on the thin copper plating layer 7. In this case, the mask 11 is preferably formed using a commercially available dry film photoresist. This is because the use of a photosensitive material contributes to the improvement of pattern formation accuracy. Then, after laminating such a dry film photoresist, exposure and development are performed according to a conventional method. As a result, as shown in FIG. 6, a mask 11 having a thickness of 35 μm and having an opening 12 at a predetermined location is formed.
[0041]
After the mask formation step, a thick copper plating layer 8 is formed in a portion exposed from the opening 12 using an electrolytic copper plating bath which is a kind of electrolytic plating (see FIG. 7). When such a thick copper plating layer 8 is formed, only the portion that will later become the outer layer conductor pattern 2b is selectively thickened. In this embodiment, a copper sulfate plating bath is used as the electrolytic copper plating bath. As a result of the second plating, a thick copper plating layer 8 having a thickness of about 5 μm to 50 μm is formed on the thin copper plating layer 7 located at the exposed portion. If the thick copper plating layer 8 is made too thin, the thickness of the finally obtained outer conductor pattern 2b cannot be secured sufficiently. On the other hand, if the thick copper plating layer 8 is too thick, there is a risk that productivity will be reduced and costs will be increased.
[0042]
After the second plating step, the mask 11 that is no longer needed is peeled off, and the thin copper plating layer 7 located thereunder is exposed (see FIG. 8).
At this point, it is desirable to perform an annealing process at a predetermined temperature and a predetermined temperature. The reason is that the stress inherent in the thick copper plating layer 8 is released by heating during annealing, and the thick copper plating layer 8 is in a so-called baked state. As a result, pinholes are less likely to occur in the thick copper plating layer 8, and a highly reliable outer layer conductor pattern 2b can be obtained. The annealing temperature is preferably set to about 100 ° C. to 200 ° C., and is set to 150 ° C. in this embodiment. The annealing time is preferably set to about 0.1 to 3 hours, and in this embodiment is set to 1 hour.
[0043]
Next, an etching process is performed using a sulfuric acid / hydrogen peroxide etchant capable of dissolving copper, and the thin copper plating layer 7 and the copper underlayer 6 are completely removed. Here, since the process is carried out without particularly providing an etching resist on the thick copper plating layer 8 located at the outermost layer, the surface layer of the thick copper plating layer 8 is also etched by about 2 to 3 μm. And through the above process, outer layer conductor pattern 2b was parted, and the multilayer printed wiring board 1 of FIG. 9 was completed.
[0044]
Therefore, according to the present embodiment, the following effects can be obtained.
(1) In the manufacturing method of this embodiment, the conductor layer transfer sheet 31 having the above-described configuration is used. Accordingly, the transfer copper foil 32 is peeled off from the carrier copper foil 33 and transferred and pasted, whereby an extremely thin copper underlayer 6 derived from the transfer copper foil 32 can be formed on the insulating base 4. Then, by forming the thick copper plating layer 8 in a state where the mask 11 is formed, only the portion that will later become the outer conductor pattern 2b is selectively thickened. Thereafter, etching is performed to remove the thin copper plating layer 7 and the copper base layer 6 that are under the mask 11, thereby separating the outer layer conductor patterns 2b from each other.
[0045]
Since the copper underlayer 6 of this embodiment is extremely thin, the thickness to be removed by etching in the conductor pattern cutting step is considerably small, 2 μm to 3 μm. Therefore, the outer layer conductor pattern 2b that has been divided is less likely to have a flared shape, and a fine pattern having a good shape as shown in FIG. 1 can be accurately formed.
[0046]
(2) The transfer copper foil 32 is held by a carrier copper foil 33 that is thicker than that. Therefore, even if the transfer copper foil 32 itself is extremely thin, a thickness of 35 μm or more is secured when viewed as the entire conductor layer transfer sheet 31, and suitable rigidity is imparted. For this reason, deformation and scratching of the transfer copper foil 32 are avoided, and handling is improved. That is, it is not necessary to handle as carefully as when the transfer copper foil 32 is used alone. Therefore, the productivity is not lowered due to the difficulty in handling. In addition, as a result of avoiding the deformation | transformation and damage | wound of the transfer copper foil 32, the yield improvement and high reliability of the multilayer printed wiring board 1 are realizable.
[0047]
(3) The carrier copper foil 33 of the present embodiment can be recycled by collecting it after peeling and holding a new transfer copper foil 32. For this reason, it is very economical and contributes to the reduction of the manufacturing cost of the multilayer printed wiring board 1.
[0048]
(4) Since the carrier copper foil 33 and the transfer copper foil 32 are made of the same material, the thermal expansion coefficients are also equal. For this reason, even if it passes through heat press, it does not warp to transfer copper foil 32, but wrinkles, exfoliation, etc. occur, and it is convenient when achieving high accuracy and high reliability of outer layer conductor pattern 2b.
[0049]
(5) Since the carrier copper foil 33 is made of copper having excellent thermal conductivity, the carrier copper foil 33 does not become a thermal resistance at the time of hot pressing, and heat can be reliably transmitted to the transfer copper foil 32 side. Therefore, the transfer copper foil 32 can be securely attached to the prepreg 34. This also contributes to the improvement of reliability.
[0050]
(6) In this embodiment, the conductive layer in the multilayer printed wiring board 1 is formed by using an electroless copper plating bath in the first plating step and using an electrolytic copper plating bath in the second plating step. is doing. In other words, an electroless copper plating bath is used only when plating is deposited on the inner wall surface of the through-hole forming hole 10, and thereafter an electrolytic copper plating bath that is extremely inexpensive and has a high plating deposition rate is used. For this reason, cost efficiency and productivity can be improved further.
[0051]
(7) The multilayer printed wiring board 1 includes a copper base layer 6 having a thickness of less than 10 μm, a thin copper plating layer 7 having a thickness of 3 μm or less formed thereon, and a thickness of 5 μm formed thereon. A conductor pattern 2b having a three-layer structure including a thick copper plating layer 8 having a thickness of ˜50 μm is provided. Moreover, the metal which forms these three layers is the same kind (namely, copper). Further, the value of L1 / L2 in the conductor pattern 2b is 0.9 to 1.2. The conductor pattern 2b has a sufficient thickness and conductivity as a conductive portion, a suitable cross-sectional shape, and the like. Therefore, the multilayer printed wiring board 1 is excellent in reliability, cost, and pattern formation accuracy, and has high functionality and high density.
[0052]
In addition, you may change embodiment of this invention as follows.
The present invention is not limited to the four-layer board as in the embodiment, and may be further embodied in a multilayered printed wiring board. For example, the multilayer printed wiring board 1 of the embodiment may be a core substrate or a base substrate, and the outer layer conductor pattern 2b may be further formed on one side or both sides of the substrate using the conductor layer transfer sheet 31. In other words, a plurality of outer layer conductor patterns 2 b having the copper base layer 6 derived from the conductor layer transfer sheet 31 may be present on the same side surface of the insulating substrate 4. In addition, it can replace with formation of the outer layer conductor pattern 2b using the conductor layer transfer sheet 31, and can also form a buildup layer by a conventionally well-known method.
[0053]
-It may replace with the wet method as described in embodiment, and may perform the desmear process by the dry process represented by the plasma method etc., for example. Of course, the desmear process may be omitted unless particularly necessary.
[0054]
-The plated through hole 3 is not an essential component and may be omitted. Note that, when the plated through hole 3 is not formed, the first plating step for conducting in the plated through hole 3 is also omitted.
[0055]
The transfer copper foil 32 may be transferred and pasted on both sides of the insulating base material 4, or may be transferred and pasted only on one side. In other words, the copper base layer 6 may be formed on both surfaces of the insulating base material 4 or may be formed only on one surface.
[0056]
Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments are listed below together with their effects.
(1) Using a conductor layer transfer sheet in which the transfer copper foil is releasably held on a carrier copper foil that is thicker than the transfer copper foil, the transfer copper foil is placed on at least one surface of the insulating substrate via the prepreg. A method of reusing a carrier copper foil, wherein after the transfer / sticking, a new transfer copper foil is held again on the carrier copper foil to newly produce a conductor layer transfer sheet. Therefore, according to the invention described in this technical idea 1, it is economical because the carrier copper foil can be recycled.
[0057]
(2) In a method for producing a multilayer printed wiring board comprising a plurality of conductor patterns, a step of forming an inner layer conductor pattern on an insulating substrate, and a transfer copper foil is peeled off on a carrier copper foil thicker than the transfer copper foil A step of forming a copper underlayer by using a conductor layer transfer sheet held in a possible state and transferring and sticking the transfer copper foil to the inner layer conductor pattern forming surface of the insulating substrate via a prepreg; Forming a mask on the copper underlayer and forming a copper plating layer at a portion exposed from the opening of the mask; and removing the mask to perform etching, A method for producing a multilayer printed wiring board, comprising: conducting a conductor pattern dividing step of removing the ground layer and dividing the outer layer conductor patterns.
[0058]
【The invention's effect】
As described above in detail, according to the inventions described in claims 1 to 5, there is provided a printed wiring board manufacturing method capable of forming a fine conductor pattern having a good shape without being accompanied by a decrease in productivity. Can be provided.
[0059]
According to invention of Claim 6, the printed wiring board excellent in reliability, cost property, and pattern formation precision can be provided.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of an outer layer conductor pattern in a multilayer printed wiring board according to an embodiment embodying the present invention.
FIG. 2 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board according to the embodiment.
FIG. 3 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 4 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 5 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 6 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 7 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 8 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.
FIG. 9 is a partial schematic cross-sectional view of the multilayer printed wiring board.
FIG. 10 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.
FIG. 11 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.
FIG. 12 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.
FIG. 13 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.
FIG. 14 is a partial schematic cross-sectional view of a conventional multilayer printed wiring board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Multilayer printed wiring board as a printed wiring board, 2a ... (inner layer) conductor pattern, 2b ... (outer layer) conductor pattern, 3 ... Plating through hole, 4 ... Insulating base material, 6 ... Copper base layer, 7 ... 1st Thin copper plating layer as a copper plating layer, 8 ... Thick copper plating layer as a second copper plating layer, 10 ... Through hole forming hole, 11 ... Mask, 12 ... Mask opening, 31 ... Conductor layer transfer Sheet, 32 ... transfer copper foil, 33 ... carrier copper foil, 34 ... prepreg, L1 ... length of the side far from the insulating base, L2 ... length of the side near the insulating base.

Claims (6)

In a method for producing a printed wiring board comprising an inner layer and an outer layer conductor pattern,
Forming an inner layer conductor pattern on the insulating substrate;
Of the conductor layer transfer sheet is held at a thickness of peelable state transfer copper foil thickness 10μm~50μm the carrier copper foil of 1 m to 5 m, the insulating base material and the transfer copper foil via the prepreg A step of forming a copper base layer by transferring and sticking to at least one side;
Forming a mask on the copper underlayer, and forming a copper plating layer in a portion exposed from the opening of the mask;
A method of manufacturing a printed wiring board, comprising: performing a conductor pattern dividing step of removing the copper base layer and dividing the outer conductor patterns by performing etching after removing the mask. In the manufacturing method of a printed wiring board provided with a plated through hole and an inner layer and an outer layer conductor pattern,
Forming an inner layer conductor pattern on the insulating substrate;
Of the conductor layer transfer sheet is held at a thickness of peelable state transfer copper foil thickness 10μm~50μm the carrier copper foil of 1 m to 5 m, the insulating base material and the transfer copper foil via the prepreg A process of forming a copper underlayer by transferring and sticking to both sides;
Forming a hole for forming a through hole at a predetermined position of the insulating base;
A first plating step of forming a thin copper plating layer by electroless copper plating on an inner wall surface of the copper underlayer and the through-hole forming hole;
A second plating step of forming a mask on the thin copper plating layer and forming a thick copper plating layer by electrolytic copper plating on a portion exposed from the opening of the mask;
Conducting a conductor pattern cutting step of removing the thin copper plating layer and the copper base layer under the mask and separating the outer conductor patterns by performing etching after peeling the mask. A method for producing a printed wiring board. The method for producing a printed wiring board according to claim 1, wherein the conductor pattern dividing step by etching is performed in a state where an etching resist is not provided on the copper plating layer located in the outermost layer. The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the transfer copper foil and the carrier copper foil are made of the same material and have the same thermal expansion coefficient . 5. The method of manufacturing a printed wiring board according to claim 1, wherein an annealing process is performed between the time when the mask is peeled off and the etching is performed in the conductor pattern dividing process. 6. The printed wiring board obtained by the manufacturing method of the printed wiring board of any one of Claims 2 thru | or 5 WHEREIN : The said outer layer conductor pattern is a copper base layer with a thickness of 1 micrometer- 5 micrometers provided in the insulating base material. The outer layer comprises a first copper plating layer having a thickness of 3 μm or less formed on the copper underlayer and a second copper plating layer having a thickness of 5 μm to 50 μm formed on the first copper plating layer. In the cross section of the conductor pattern, the length of the side far from the insulating base is 0.9 to 1.2 of the length of the side close to the insulating base.

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