TWI477217B - Method for manufacturing printed circuit board having copper wrap layer - Google Patents

Description

Method for manufacturing printed circuit board with coated copper layer

The present invention relates to a method of fabricating a printed circuit board having a clad copper layer.

In general, conventional printed circuit boards include a substrate and multiple layers of metal. Then, the metal layers can be electrically connected to each other through a process such as drilling, copper plating, or the like. However, during the drilling process, cracks may occur near the wall of the hole, and the reliability of the printed circuit board is lowered.

In some designs that require high reliability, the material is filled into the holes and a copper capping layer covering material is formed. Fig. 1A is a schematic cross-sectional view showing a conventional printed circuit board. The printed circuit board includes a substrate 10, a metal layer 12, a copper layer 14, a material 16 and a copper cap layer 18. However, such printed circuit boards still have other problems. For example, when the printed circuit board is subjected to heat treatment, the interface between the copper layer 14 and the metal layer 12 may be separated from the substrate 10 (see the dotted line in FIG. 1A), or a crack may be formed in the copper layer 14.

In order to solve the above problems, please refer to IPC6012 C-2010 Class 2. Forming a copper wrap layer covering the pore walls and the metal layer. Figure 1B shows a schematic cross-sectional view of a printed circuit board having a layer of coated copper. The printed circuit board includes a substrate 10, a metal layer 12, a clad copper layer 14', a material 16 and a copper cap layer 18. As a result, the continuous structure of the clad copper layer 14' at the turn increases the strength of the coated layer, and the continuous contact area with the coated layer increases, thereby reducing stress or heat treatment. Separation occurs. The total thickness T of Fig. 1B includes the thickness of the metal layer 12, the clad copper layer 14' and the copper cap layer 18. If the number of coating processes is increased, the total thickness will be thicker, which is not conducive to the manufacture of high-density fine lines.

In view of the above, there is a need in the related art to develop a novel printed circuit board manufacturing method to solve the problem of cracks occurring near the hole wall during drilling, and to meet reliability and manufacture of high-density fine lines.

The present invention provides a method of manufacturing a printed circuit board. Since the printed circuit board has an alkali corrosion resistant layer, cracks in the substrate can be avoided during drilling. In addition, the printed circuit board has sufficient cladding layer thickness and a low total thickness for good reliability and can be used to manufacture high density fine lines.

One aspect of the present invention provides a method of fabricating a printed circuit board having a clad copper layer comprising the following steps. A substrate is provided, the substrate having a first surface and a second surface. The alkali-resistant layer and the metal layer are pressed onto the substrate, wherein the metal layer is opposite to the first surface of the substrate by an alkali-resistant layer. Removing a portion of the metal layer with an alkali solution to form a first opening to expose an alkali-resistant layer portion. Forming a first opening in the first opening through the first portion of the alkali-resistant layer and the substrate below the substrate, wherein the width of the first opening is smaller than the width of the first opening. Forming a first cladding copper layer to continuously coat the first portion of the alkali-resistant layer and the sidewall of the first opening. The first material is filled in the first opening, and the first material covers the first cladding copper layer. A first planarization process is performed to flatten the outer surface of the first material.

According to an embodiment of the invention, the step of pressing the alkali-resistant layer and the metal layer on the substrate comprises the following steps. An alkali-resistant layer is formed on the metal layer to form a composite layer. The composite layer is laminated on the substrate, wherein the alkali resistant layer contacts the first surface of the substrate.

According to an embodiment of the invention, the alkali-resistant layer has a material selected from the group consisting of tin, lead, chromium, nickel, indium, zinc, tungsten, molybdenum, and combinations thereof.

In accordance with an embodiment of the present invention, the step of forming an alkali-resistant layer is performed using a sputtering process, an electron beam deposition process, a chemical vapor deposition process, or a combination thereof to form an alkali-resistant layer.

According to an embodiment of the invention, the power of the sputtering process is 2-13 kW.

According to an embodiment of the invention, the method further comprises treating the metal layer with a plasma prior to the step of forming the alkali-resistant layer on the metal layer.

According to an embodiment of the invention, the power of the plasma is 600-1000 W.

According to an embodiment of the invention, the lye comprises ammonium chloride.

According to an embodiment of the invention, the step of forming the first cladding copper layer is The first cladding copper layer is formed using a plated through hole (PTH) or a direct plating (Direct Plating).

According to an embodiment of the invention, direct electroplating is performed by directly plating a carbon ink (Graphite) to form a first cladding copper layer.

According to an embodiment of the invention, the step of performing the first planarization process comprises reducing the thickness of the first cladding copper layer.

According to an embodiment of the invention, the method further comprises pressing another metal layer on the second surface of the substrate.

According to an embodiment of the invention, the method further includes patterning the another metal layer to form a circuit layer after performing the first planarization processing step.

According to an embodiment of the invention, the method further comprises: after performing the first planarization processing step, pressing the substrate, the subsequent layer and the other substrate, wherein the layer is between the substrate and the other substrate, and the second surface of the substrate faces Floor. The other substrate is a substrate having one or more layers, one or more substrates containing a metal layer or a substrate having one or more circuit layers.

According to an embodiment of the invention, the method further comprises the following steps. Another portion of the metal layer is removed using an alkali solution to form a second opening to expose the second portion of the alkali resistant layer. Forming a second opening in the second opening through the second portion of the alkali-resistant layer and the substrate, the subsequent layer and the other substrate, wherein the width of the second opening is smaller than the width of the second opening. Forming a second cladding copper layer to continuously coat the second portion of the alkali resistant layer and the sidewall of the second opening. The second material is filled in the second opening, and the second material covers the second cladding copper layer. A second planarization process is performed to flatten the outer surface of the second material.

According to an embodiment of the invention, the method further comprises forming a copper cap layer covering the first cladding copper layer and the second cladding copper layer after performing the second planarization treatment.

According to an embodiment of the invention, the method further comprises: after the step of forming a copper cap layer, patterning the copper cap layer and the second cladding copper layer and the anti-alkaline layer underneath to form another circuit layer.

According to an embodiment of the invention, the step of forming the second cladding copper layer is performed by using a plated through hole or direct plating to form a second cladding copper layer.

According to an embodiment of the invention, the direct plating is performed by directly plating the carbon ink to form a second cladding copper layer.

According to an embodiment of the invention, the performing the second planarization processing step comprises reducing the thickness of the second cladding copper layer.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 ‧ ‧ steps

10, 110‧‧‧ substrate

110a‧‧‧ first surface

110b‧‧‧ second surface

120‧‧‧Anti-alkaline layer

120c‧‧‧ Exterior surface of alkali resistant layer

1201‧‧‧The first part of the anti-alkaline layer

1202‧‧‧The second part of the anti-alkaline layer

12, 130‧‧‧ metal layer

130’‧‧‧ another metal layer

130a‧‧‧first opening

130b‧‧‧second opening

130c‧‧‧ outside the metal layer

14‧‧‧ copper layer

14'‧‧‧ coated copper layer

1401‧‧‧First cladding copper layer

1401a‧‧‧The outer surface of the first cladding copper layer

1402‧‧‧Second cladding copper layer

1402a‧‧‧The outer surface of the second cladding copper layer

1501‧‧‧First material

1501a‧‧‧ Exterior surface of the first material

1502‧‧‧Second material

1502a‧‧‧ Surface of the second material

18, 160‧‧‧copper cover

200‧‧‧Next layer

310‧‧‧Other substrate

C1‧‧‧ circuit layer

C21, C22‧‧‧ another circuit layer

H1‧‧‧ first opening

H2‧‧‧second opening

L‧‧‧ composite layer

T, T ₁ , T ₂ ‧ ‧ total thickness

T _a ‧ ‧ anti-alkaline layer thickness

T _w1 ‧‧‧first cladding copper layer thickness

T _w2 ‧‧‧second cladding copper layer thickness

W _h1 ‧‧‧first opening width

W _h2 ‧‧‧second opening width

W _o1 ‧‧‧first opening width

W _o2 ‧‧‧second opening width

Fig. 1A is a schematic cross-sectional view showing a conventional printed circuit board.

Figure 1B is a schematic cross-sectional view showing a conventional printed circuit board having a clad copper layer.

2 is a flow chart showing the manufacture of a printed circuit board in accordance with an embodiment of the present invention.

3-10 are schematic cross-sectional views showing respective process stages of manufacturing a printed circuit board in accordance with an embodiment of the present invention.

Figure 11 is a partial flow chart showing the manufacture of a printed circuit board in accordance with another embodiment of the present invention.

12-19 are cross-sectional views showing respective process stages of manufacturing a printed circuit board in accordance with another embodiment of the present invention.

The embodiments of the present invention are disclosed in the following drawings, and the details of However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not necessary. In addition, some of the conventional structures and elements are shown in the drawings in a simplified schematic manner in order to simplify the drawings.

One aspect of the present invention provides a method of fabricating a printed circuit board having a clad copper layer. 2 is a flow chart showing the manufacture of a printed circuit board in accordance with an embodiment of the present invention. Figures 3-9 show schematic cross-sectional views of each process stage.

In step 1, a substrate 110 is provided as shown in FIG. The substrate 110 has a first surface 110a and a second surface 110b. The substrate 110 may be made of an insulating material. The insulating material is, for example, a prepreg containing an epoxy resin and a multilayer fiberglass cloth.

In step 2, the anti-alkaline layer 120 and the metal layer 130 are pressed onto the substrate 110 as shown in FIG. The alkali resistant layer 120 is located between the metal layer 130 and the substrate 110. In detail, the metal layer 130 is opposed to the first surface 110a of the substrate 110 via the alkali-resistant layer 120. Metal layer 130 can be, for example, a copper foil, an aluminum foil, or other metal foil. The metal layer 130 has a thickness of, for example, 9 to 50 μm. The alkali-resistant layer 120 has alkali resistance and is not easily lyophilized Corroded. In one embodiment, the alkali resistant layer 120 has a material selected from the group consisting of tin, lead, chromium, nickel, indium, zinc, tungsten, molybdenum, and combinations thereof. The thickness of the alkali-resistant layer 120 is, for example, 0.02 μm to 0.40 μm.

In an embodiment, pressing the anti-alkaline layer 120 and the metal layer 130 on the substrate 110 may include the following steps. First, an alkali-resistant layer 120 is formed on the metal layer 130 to form a composite layer L. Then, the composite layer L is thermocompression bonded onto the substrate 110, wherein the alkali resistant layer 120 contacts the first surface 110a of the substrate 110.

In one embodiment, the step of forming the anti-alkaline layer 120 is performed using a sputtering process. For example, the material of the alkali-resistant layer 120 may be a metal or an alloy such as tin, lead, chromium, nickel, indium, zinc, tungsten, molybdenum or a combination thereof. The metal or alloy species are loosened by an electron beam and deposited on the metal layer 130. The power of the sputtering process is, for example, 2-13 kW. The line speed is, for example, 1.8 to 5.2 m/min. The time is, for example, 40 to 120 seconds. The thickness of the alkali-resistant layer 120 formed is, for example, 0.02 μm to 0.40 μm. Of course, the alkali-resistant layer 120 can also be formed by other means, such as electron beam deposition, chemical vapor deposition, and the like.

In one embodiment, the surface of the metal layer 130 may be treated with a plasma prior to the step of forming the alkali resistant layer 120. The plasma treatment is used to clean the surface of the metal layer 130 while increasing the roughness of the surface. The power of the plasma process is, for example, 600 to 1000 W, and the time is, for example, 20 to 120 seconds.

In one embodiment, when the anti-alkaline layer 120 and the metal layer 130 are pressed onto the substrate 110, the other metal layer 130' can be simultaneously pressed onto the second surface 110b of the substrate 110, as shown in FIG. .

In step 3, a portion of the metal layer 130 is removed using an alkali solution to form a first opening 130a, and the first portion 1201 of the alkali-resistant layer 120 is exposed, as shown in FIG. In detail, a photoresist layer (not shown) may be formed to cover the metal layer 130, and then the portion of the metal layer 130 is removed through a lithography and etching process. In the etching process, the metal layer 130 is etched using a special alkali solution, but the alkali-resistant layer 120 is not corroded by the alkali solution, so the alkali-resistant layer 120 is not removed. It should be noted that the alkali-resistant layer 120 covers the substrate 110, and the substrate 110 can be protected from cracking during the drilling process (ie, step 4 below). The reason will be detailed in the description of step 4 below. In one embodiment, the lye used comprises ammonium chloride.

In step 4, as shown in FIG. 6, a first opening h1 is formed in the first opening 130a through the first portion 1201 of the etch-resistant layer 120 and the substrate 110 below it. The width W _{h1 of the} first opening _{h1 is} smaller than the width W _{o1 of the} first opening 130a. As a result, only the alkali-resistant layer 120 is formed at the corner of the first opening h1, and the metal layer 130 is absent, which is advantageous for reducing the total thickness at the corner. Since the anti-alkaline layer 120 covers the substrate 110, the first portion 1201 of the anti-alkaline layer 120 is penetrated through the substrate 110 instead of directly penetrating the substrate 110 during drilling. Thereby, the substrate 110 can be prevented from being cracked in the drilling process. The first opening h1 may be formed by mechanical drilling or laser drilling, but is not limited thereto.

In step 5, the first cladding copper layer 1401 is formed to continuously coat the first portion 1201 of the alkali-resistant layer 120 and the sidewall of the first opening h1, as shown in FIG. For example, a first cladding copper layer 1401 of a sufficient thickness can be formed using a plated through hole (PTH) method. Of course, the first cladding copper layer 1401 can also be formed by direct plating such as carbon ink. The thickness T _{w1 is,} for example, 500 to 800 μm. Since only the alkali-resistant layer 120 and the first cladding copper layer 1401 are located at the corner of the first opening h1 without the metal layer 130, the total thickness T ₁ includes only the thickness T _{a of the} alkali-resistant layer 120 and the first package. The thickness T _{w1 of the} copper clad layer 1401. The akali thickness T _a thin layer 120 (e.g., 0.02 microns to 0.40 microns), it will not cause too much of _an impact on the overall thickness T.

In step 6, the first material 1501 is filled in the first opening h1 as shown in FIG. The first material 1501 is located on the first cladding copper layer 1401. The first material 1501 is, for example, a conductive ink or a non-conductive ink.

In step 7, a first planarization process is performed to flatten the outer surface 1501a of the first material 1501 as shown in FIG. For example, the outer surface 1501a can be aligned with the outer surface 1401a of the first cladding copper layer 1401.

In an embodiment, when step 7 is performed, the first cladding copper layer 1401 of a certain thickness may be removed. That is, the thickness T _{w1 of} the first cladding copper layer 1401 is made small. For example, the outer surface 1401a of the first cladding copper layer 1401 may be aligned with the outer surface 130c of the metal layer 130 or between the outer surface 130c of the metal layer 130 and the outer surface 120c of the alkali resistant layer 120. T _w1 only needs to be greater than or equal to the thickness required by the IPC or custom requirements, and may not include the full thickness of the metal layer 130 or the first cladding copper layer 1401.

In one embodiment, after performing step 7, the metal layer 130' on the second surface 110b and the first cladding copper layer 1401 are patterned to form a circuit layer C1, as shown in FIG.

In order to form a printed circuit board having a plurality of circuit layers, in another embodiment, after performing step 7, the substrate 110 and the other substrate may be A step of pressing a substrate. Figure 11 is a subsequent flow chart showing the manufacture of a printed circuit board having a multilayer circuit layer. Step 8 shown in Fig. 11 is followed by step 7 shown in Fig. 1. Figures 12-17 show cross-sectional views corresponding to steps 8-13 of Figure 11, respectively.

In step 8, the substrate 110, the subsequent layer 200 and the other substrate 310 are laminated, as shown in FIG. Layer 200 is then positioned between substrate 110 and substrate 310. The first surface 110a of the substrate 110 faces outward, and the second surface 110b faces the adhesive layer 200. The substrate 310 may be a substrate having one or more layers, one or more substrates containing a metal layer, or a substrate having one or more circuit layers, but is not limited thereto. As shown in Fig. 12, in the present embodiment, the substrate 110 is pressed against the printed circuit board produced in accordance with the above steps 1 to 7.

In step 9, another portion of the metal layer 130 is removed using an alkali solution to form a second opening 130b, and the second portion 1202 of the alkali-resistant layer 120 is exposed, as shown in FIG. In detail, a photoresist layer (not shown) may be formed to cover the first cladding copper layer 1401, and then pass through a lithography and etching process to remove a portion of the first cladding copper layer 1401 and a metal layer therebelow. 130. The oxide on the surface of the first cladding copper layer 1401 may be removed prior to forming the photoresist layer.

In step 10, as shown in FIG. 14, a second opening h2 is formed in the second opening 130b through the second portion 1202 of the etch-resistant layer 120 and the substrate 110, the subsequent layer 200, and the substrate 310 below. The width W _{h2 of the} second opening _{h2 is} smaller than the width W _{o2 of the} second opening 130b. As a result, only the alkali-resistant layer 120 is located at the corner of the second opening h2, and the metal layer 130 is absent, which is advantageous for reducing the total thickness at the corner. Similar to step 4, since the alkali-resistant layer 120 is coated on the substrate 110, the substrate 110 can be prevented from being cracked in the step 10.

In step 11, the second cladding copper layer 1402 is formed to continuously coat the sidewalls of the second portion 1202 of the alkali-resistant layer 120 and the second opening h2, as shown in FIG. For example, a second cladding copper layer 1402 of sufficient thickness can be formed using a plated through hole. Of course, the second cladding copper layer 1402 can also be formed by directly plating a carbon ink. The thickness T _{w2 is,} for example, 500 to 800 μm. Since the corner of the second opening h2 has only the alkali-resistant layer 120 and the second cladding layer 1402, and no metal layer 130, the total thickness T ₂ includes only the thickness T _{a of the} alkali-resistant layer 120 and the second package. The thickness T _{w2 of the} copper clad layer 1402. The akali thickness T _a thin layer 120 (e.g., 0.02 microns to 0.40 microns), it will not cause too much impact on the ₂ overall thickness T.

In step 12, the second material 1502 is filled in the second opening h2 as shown in FIG. The second material 1502 is located on the second cladding copper layer 1402. The second material 1502 can be the same or different than the first material 1501.

In step 13, a second planarization process is performed to flatten the outer surface 1502a of the second material 1502, as shown in FIG. For example, the outer surface 1502a can be aligned with the outer surface 1402a of the second cladding copper layer 1402.

In an embodiment, when step 13 is performed, the second cladding copper layer 1402 of a certain thickness may be removed. That is, the thickness _{Tw2 of} the second cladding copper layer 1402 is made small. For example, the outer surface 1402a can be aligned with the outer surface 1401a of the first cladding copper layer 1401. It is even possible to align the outer surface 1402a with the outer surface 130c of the metal layer 130 or between the outer surface 130c of the metal layer 130 and the outer surface 120c of the etch resistant layer 120. T _w2 only needs to be greater than or equal to the thickness required by the IPC or custom requirements, and may not include the full thickness of the metal layer 130, the first cladding copper layer 1401 or the second cladding copper layer 1402.

In one embodiment, after performing step 13, a copper capping layer 160 is formed to cover the first cladding copper layer 1401 and the second cladding copper layer 1402, as shown in FIG.

In one embodiment, after the step of forming the copper cap layer 160, the copper cap layer 160 and the second cladding copper layer 1402, the first cladding copper layer 1401, the metal layer 130, and the anti-alkaline layer 120 are patterned. To form circuit layers C22, C21, as shown in Figures 18-19. For example, a photoresist layer (not shown) may be formed to cover the copper cap layer 160, and then subjected to a photolithography process to form circuit layers C21 and C22. In one embodiment, the copper cap layer 160, the second clad copper layer 1402, the first clad copper layer 1401, the metal layer 130, and the anti-alkaline layer 120 may be etched using an acid solution. In other words, the alkali-resistant layer 120 is not etched by the lye but is etched by the acid. In one embodiment, the acid used comprises ferric chloride.

As shown in FIG. 19, the circuit layer C21 comprises a total thickness T _1, a first copper clad layer 1401, the thickness of the copper cladding layer 1402 of the second cap layer 160 and copper layer 120 of the alkali etching. The total thickness T _{2 of the} circuit layer C22 includes the thickness of the alkali-resistant layer 120, the second cladding copper layer 1402, and the copper cap layer 160. The total thicknesses T ₁ , T ₂ at the corners may not include the thickness of the metal layer 130, so that the total thicknesses T1, T2 of one embodiment of the present invention are thinner, which is advantageous for manufacturing high-density fine lines. At the same time, the corner of the first opening h1 has a sufficient thickness T _w1 , and the corner of the second opening h2 has a sufficient thickness T _w2 . Therefore, when the printed circuit board is subjected to heat treatment, the continuous structure of the first cladding copper layer 1401 and the second cladding copper layer 1402 at the turn causes the bonding strength of the cladding layer to be increased, and continuous contact with the coated layer. The increased area reduces the occurrence of cracks due to stress cracking or heat treatment, and the printed circuit board has good reliability.

In summary, the embodiments of the present invention provide a method of manufacturing a printed circuit board having an alkali-resistant layer, which can avoid cracking of the substrate during drilling. In addition, the printed circuit board has sufficient cladding copper thickness and a low total thickness, and has good reliability and can be applied to manufacture high-density fine lines.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

110‧‧‧Substrate

120‧‧‧Anti-alkaline layer

1201‧‧‧The first part of the anti-alkaline layer

130‧‧‧metal layer

130’‧‧‧ another metal layer

1401‧‧‧First cladding copper layer

H1‧‧‧ first opening

T ₁ ‧‧‧ total thickness

T _a ‧ ‧ anti-alkaline layer thickness

T _w1 ‧‧‧first cladding copper layer thickness

Claims (20)

A method of manufacturing a printed circuit board having a copper-clad layer, comprising: providing a substrate having a first surface and a second surface; pressing an alkali-resistant layer and a metal layer on the substrate, wherein The metal layer is opposite to the first surface of the substrate via the alkali-resistant layer; a portion of the metal layer is removed using an alkali solution to form a first opening to expose a first portion of the alkali-resistant layer; Forming a first opening in the first opening through the first portion of the etch-resistant layer and the substrate below the substrate, wherein the first opening has a width smaller than a width of the first opening; forming a first cladding copper a layer continuously covering the first portion of the etch-resistant layer and a sidewall of the first opening; filling a first material in the first opening, the first material covering the first cladding copper layer; A first planarization process is performed to flatten the outer surface of one of the first materials. The method of claim 1, wherein the step of pressing the alkali-resistant layer and the metal layer on the substrate comprises: forming the alkali-resistant layer on the metal layer to form a composite layer; and pressing The composite layer is on the substrate, wherein the alkali resistant layer contacts the first surface of the substrate. The method of claim 1, wherein the etch-resistant layer has a material selected from the group consisting of tin, lead, chromium, nickel, indium, zinc, tungsten, molybdenum, and combinations thereof. The method of claim 2, wherein the step of forming the alkali-resistant layer is performed using a sputtering process, an electron beam deposition process, a chemical vapor deposition process, or a combination thereof to form the alkali-resistant layer. The method of claim 4, wherein the sputtering process has a power of 2-13 kW. The method of claim 2, further comprising treating the metal layer with a plasma before the step of forming the alkali-resistant layer on the metal layer. The method of claim 6, wherein the power of the plasma is 600-1000 W. The method of claim 1, wherein the lye comprises ammonium chloride. The method of claim 1, wherein the step of forming the first cladding copper layer forms the first cladding copper layer using a plated through hole (PTH) or direct plating (Direct Plating). The method of claim 9, wherein the direct electroplating is directly electroplating a carbon ink to form the first clad copper layer. The method of claim 1, wherein the performing the first planarization processing step comprises reducing a thickness of the first cladding copper layer. The method of claim 1, further comprising pressing another metal layer on the second surface of the substrate. The method of claim 12, further comprising, after performing the first planarization processing step, patterning the another metal layer to form a circuit layer. The method of claim 1, further comprising: after performing the first planarization processing step, pressing the substrate, an adhesive layer and another substrate, the adhesive layer being located between the substrate and the other substrate, The second surface of the substrate faces the bonding layer, wherein the other substrate is a substrate having one or more layers, one or more substrates comprising a metal layer or a substrate having one or more circuit layers. The method of claim 14, further comprising: removing another portion of the metal layer using the alkali solution to form a second opening to expose a second portion of the alkali-resistant layer; forming a second portion in the second opening a second opening penetrating the second portion of the etch-resistant layer and the substrate, the back layer and the other substrate, wherein the width of the second opening is smaller than the width of the second opening; a second cladding layer continuously coating the second portion of the alkali resistant layer and one sidewall of the second opening; Filling a second material in the second opening, the second material covers the second cladding copper layer; and performing a second planarization treatment to flatten an outer surface of the second material. The method of claim 15, further comprising forming a copper cap layer covering the first cladding copper layer and the second cladding copper layer after performing the second planarization process. The method of claim 16, further comprising: after the step of forming the copper cap layer, patterning the copper cap layer and the second clad copper layer and the anti-alkaline layer underneath to form another circuit layer . The method of claim 15, wherein the step of forming the second cladding layer is performed by using a plated via or direct plating to form the second cladding layer. The method of claim 15, wherein the performing the second planarization processing step comprises reducing a thickness of the second cladding copper layer. The method of claim 18, wherein the direct electroplating directly electroplating the carbon ink to form the second clad copper layer.