JP2003264360A - Method of manufacturing printed wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a printed wiring substrate having excellent circuit accuracy by controlling the side etching of a circuit forming area in a process to manufacture a printed wiring substrate by a subtract method. <P>SOLUTION: A circuit is formed on the surface of the substrate by a process that a copper foil layer composed of a thick portion as a circuit forming portion and a thin portion as a recess forming portion is obtained by forming a recess by etching, from both surfaces, a part not covered with an etching resist after both surfaces of the circuit forming portion of the copper foil layer of a uniform thickness are covered with the etching resist; a process that one etching resist among the etching resists covering both surfaces of the copper foil layer is peeled and the etching resist peeling surface is then adhered to the surface of the substrate; and a process that the copper foil layer adhered to the surface of the substrate covering the etching resist at the circuit forming portion is etched to dissolve and remove the thin portion and thereafter the etching resist is peeled. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a printed wiring board by a subtraction method. 2. Description of the Related Art A conventional method for forming a circuit on a printed wiring board will be described with reference to FIG. Note that FIG.
(A) to (e) show partial cross sections of a printed wiring board manufactured by a subtractive method. Copper foil layer 2
Is formed by dissolving and removing the other portions by etching while leaving only necessary portions selectively. That is, in the conventional method of manufacturing a printed wiring board using a subtraction method, the circuit shown in FIG. ), Polyimide or polyethylene terephthalate (PE
T), a copper foil layer 2 having a uniform layer thickness is attached to the surface of a substrate 1 made of an insulating resin such as epoxy, and an etching resist 3 is coated on a circuit forming portion on the surface of the copper foil layer 2 (FIG. 5 (b)), and then, as shown in FIG. 5 (c), the copper foil is dissolved and removed by eroding the etching solution from the portion not covered with the etching resist 3 (FIG. 5 (d)).
Then, after selectively etching only the circuit forming portion and other portions, the etching resist 3 was peeled off (see FIG. 5E) to form the circuit 20 on the substrate surface. That is, the range of dissolution and removal by the etchant is gradually widened from the surface of the copper foil layer that has been exposed to the etchant, and the copper foil layer is selectively left only in necessary portions to etch other portions to form a circuit. However, in the conventional etching, since the copper foil is gradually etched from one of the surfaces of the copper foil layer (circuit surface side), the copper foil not coated with the etching resist is etched. When the portions are completely dissolved and removed, and the copper foil between the circuit forming portions is completely etched (see FIGS. 5C and 5D), the copper foil portions coated with the etching resist, In other words, the circuit forming portion was also etched from the side (side etch), and the circuit surface side was largely shaved, forming a trapezoidal circuit (see FIG. 5E). In particular, when a fine circuit is formed, there has been a problem that the circuit surface is shaved by side etching of a circuit forming portion, and sufficient connection cannot be achieved at the time of semiconductor mounting. Therefore, in manufacturing a printed wiring board by a subtractive method, it has been desired to suppress side etching of a circuit forming portion and form a circuit with good circuit accuracy on the surface of the board. Therefore, a method of manufacturing a printed wiring board according to the present invention is to form a circuit on the surface of a substrate by selectively leaving only a necessary portion of a copper foil layer and etching other portions. In the manufacture of a printed wiring board, after etching resist is coated on both sides of a circuit forming portion of a copper foil layer having a uniform layer thickness, a portion where the etching resist is not coated is etched from both sides to form a concave portion, and a circuit is formed. A step of obtaining a copper foil layer composed of a thick part that is a forming part and a thin part that is a concave part forming part, and peeling off one of the etching resists of the etching resists coated on both surfaces of the copper foil layer After that, a step of bonding this etching resist peeling surface to the substrate surface and a step of bonding the substrate to the substrate surface to cover the circuit forming portion with the etching resist Removing the etching resist after dissolving and removing the thin-walled portion by etching the copper foil layer, and forming a circuit on the substrate surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS. In a preferred embodiment of the method of manufacturing a printed wiring board according to the present invention, a copper foil layer 2 having a uniform thickness is etched from both sides to form a copper foil layer 2 having a thick portion 2A and a thin portion 2B. (See FIG. 1) and the copper foil layer 2
(See FIG. 2) and etching the copper foil layer 2 attached to the surface of the substrate 1 to form a thin portion 2
B is etched to leave only the circuit forming portion and other portions (see FIG. 3).
The circuit 20 is formed on the surface of. In this embodiment, first, an etching resist 3 is coated on both surfaces of a circuit forming portion of the copper foil layer 2 having a uniform thickness (see FIG. 1A), and the etching resist 3 is not coated. An etching solution is poured from both surfaces of the portion (see FIG. 1B), and the copper foil is dissolved and removed by eroding the portion exposed to the etching solution (see FIG. 1B) to form the concave portion 4 (see FIG. 1B). FIG. 1 (c)). That is, the copper foil layer 2 in which both surfaces of the circuit forming portion are covered with the etching resist 3 is half-etched, and the non-circuit forming portion of the copper foil layer 2 is melted from both surfaces to form the concave portion 4, thereby forming the circuit forming portion. Thick portion 2A and thin portion 2B that is a recess forming portion
Is obtained. In this embodiment, a portion of the copper foil layer 2 which is not covered with the etching resist 3 is eroded by an etchant (wet etching), and the copper foil is dissolved and removed by the etchant to form a concave portion 4. However, the copper foil may be etched by dry etching or the like. [0010] In the production example according to the present invention, 2 to 18 µm
Both sides of the circuit forming portion of the thick copper foil layer 2 are coated with an etching resist 3 having a thickness of 2 to 50 μm, and the copper foil layer 2 is immersed in an etching solution from both sides to perform half-etching. A concave portion 4 is formed in a portion of the both surfaces of which is not covered with the etching resist, and a thick portion 2A and a thin portion 2 are formed.
A copper foil layer 2 consisting of B was obtained. The formation of the concave portion 4 by half-etching allows the portion of the copper foil layer 2 that is not covered with the etching resist 3 to have a thickness of 0.5 to 10 μm.
The etching was completed with the thin portion 2B having a thickness of m being left. Subsequently, one of the etching resists 3 covering both surfaces of the copper foil layer 2 is peeled off, and the etching resist peeling surface 21 is removed.
With polyimide or polyethylene terephthalate (PE
T), bonding to the surface of the film-shaped substrate 1 made of an insulating resin such as epoxy. In this embodiment, as shown in FIG. 2, after the peeling suppressing resist 5 is coated on the etching resist 3 coated on the side opposite to the etching resist 3 to be peeled (see FIG. 2A). ), By peeling off the etching resist 3 on the side not covered with the peeling-resisting resist 5, and then peeling off the peeling-resisting resist 5, only one etching resist 3 is peeled off and the other etching resist is removed. 3 obtained the copper foil layer 2 as it was coated. The stripping of the etching resist 3 on the side not covered with the stripping-preventing resist 5 can be stripped by a DF stripping line (alkali stripping line) used for stripping of the etching resist 3 in general. Then, an adhesive 6 is applied to the etching resist stripping surface 21 of the copper foil layer 2 (see FIG. 2C).
By attaching the etching resist stripping surface 21 to the surface of the substrate 1 (see FIG. 2D), a thick portion 2A that is a circuit forming portion and a thin portion 2B that is a concave portion is formed.
A copper foil layer 2 having one surface of the circuit forming portion coated with an etching resist 3 was bonded to the surface of the substrate 1. When the copper foil layer 2 is bonded to the surface of the substrate 1 made of polyimide or the like, polyimide in a solution state is applied to the etching resist stripping surface 21 by a casting method, and then the coated surface is reflowed from polyimide. The copper foil layer 2 may be bonded to the surface of the substrate 1 formed on the substrate. After bonding the copper foil layer 2 composed of the thick part 2A and the thin part 2B to the substrate 1, as shown in FIG. 3A, the copper foil layer 2 is exposed to an etching solution, and Similarly, the portion not covered with the etching resist 3 is etched from one side, and the other portion is dissolved and removed while selectively leaving the circuit forming portion covered with the etching resist 3 (see FIG. 3B). . At this time, the portion not covered with the etching resist 3 (the portion to be etched) is formed in a thin shape (thin portion 2B), and the etching time required for dissolving and removing the thin portion 2B is short.
Therefore, side etching of a circuit formation portion due to erosion of the etching solution can be suppressed. Finally, the etching resist 3 covering the circuit forming portion is peeled off, and a printed wiring board having the circuit 20 formed on the surface of the substrate 1 is obtained (see FIG. 3C). That is, in this embodiment, the etching resist 3 is coated on both surfaces of the circuit forming portion of the copper foil layer 2 having a uniform layer thickness, and the concave portion 4 is formed by etching the copper foil layer 2 from both surfaces. A copper foil layer 2 including a thick portion 2A which is a circuit forming portion and a thin portion 2B which is a concave portion (that is, a portion which is not a circuit forming portion) is prepared in advance. Then, one of the etching resists 3 covering both surfaces of the copper foil layer 2 is peeled off, and the peeled surface of the etching resist is bonded to the surface of the substrate 1. Then, the thin portion 2B of the copper foil layer 2 is dissolved and removed by etching again the copper foil layer 2 bonded to the substrate surface and covering the surface of the circuit forming portion with the etching resist 3 and finally the circuit forming portion. Then, the etching resist 3 coated on the substrate 1 is peeled off, and a printed circuit board having the copper circuit 20 formed on the surface of the substrate 1 is obtained. According to the present invention, unlike the conventional circuit formation in which a copper foil layer having a uniform thickness is etched from only one side, the copper foil layer 2 is etched from both directions to form a thin portion 2.
B, the copper foil layer 2 is bonded to the substrate 1 and then etched again to etch the thin-walled portion 2B to form the circuit 20, so that side etching due to erosion of the etchant is suppressed. Thus, a printed wiring board having a circuit with good circuit accuracy can be obtained. Further, since the copper foil layer undergoes a process of being etched from both directions, the processing time for the etching can be reduced to about half. Hereinafter, a method of manufacturing a printed wiring board according to the present invention will be described with reference to the flowchart of FIG. In the method for manufacturing a printed wiring board according to the present invention, the etching resist 3 is coated on both surfaces of the circuit forming portion of the copper foil layer 2 (step S1).
The copper foil layer 2 is etched from both sides by immersing an etching solution in a portion not covered with (Step S2), and a concave portion 4 is formed in a portion not covered with the etching resist 3 (Step S3). After obtaining the copper foil layer 2 to be the thick portion 2B (step S4), the copper foil layer 2
One of the etching resists 3 coated on both sides of the etching resist 3 is peeled off (Step S5),
The adhesive 6 is applied to the etching resist stripping surface 21 (Step S6), and the copper foil layer 2 is bonded to the surface of the substrate 1 (Step S7). Then, etching resist 3
The etchant is eroded again from the direction (circuit surface side) where the copper foil is coated (step S8), and the thin portion 2B of the copper foil layer 2 is removed.
Is dissolved and removed (step S9), and the etching resist 3 covering the circuit forming portion is peeled off (step S9).
10) Obtain a printed wiring board having the circuit 20 formed on the surface of the substrate 1 (Step S11) As described above, in the method of manufacturing a printed wiring board according to the present invention, a copper foil having a uniform layer thickness is obtained. After coating the etching resist on both sides of the circuit forming part of the layer,
A step of forming a concave portion by etching a portion not covered with an etching resist from both sides, and obtaining a copper foil layer including a thick portion that is a circuit forming portion and a thin portion that is a concave portion, After exfoliating one of the etching resists coated on both sides of the foil layer, a step of bonding the peeled surface of the etching resist to the substrate surface, and a step of bonding the etching resist peeled surface to the substrate surface and forming an etching resist on the circuit forming portion After etching the copper foil layer covering the thin portion by dissolving and removing the thin portion, and by removing the etching resist, a circuit is formed on the substrate surface, thereby suppressing side etching of the circuit forming portion. Thus, a circuit having excellent circuit accuracy can be formed on the surface of the substrate. Then, at the time of circuit formation, erosion of the circuit formation portion due to side etching is suppressed, so that the circuit surface is secured without being scraped, and as a result, a printed wiring board having a circuit suitable for mounting a semiconductor can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a method for forming a copper foil layer. FIG. 2 is an explanatory diagram of a method of attaching a copper foil layer to a surface of a substrate. FIG. 3 is an explanatory diagram of a method for forming a circuit on a surface of a substrate. FIG. 4 is a flowchart showing a method for manufacturing a printed wiring board according to the present invention. FIG. 5 is an explanatory view showing a method for manufacturing a printed wiring board according to a conventional technique. [Description of Signs] 1 Substrate 2 Copper foil layer 2A Thick portion (circuit forming portion) 2B Thin portion 3 Etching resist 4 Depression 5 Detachment suppressing resist 6 Adhesive

Claims (1)

Claims: 1. A printed wiring board in which a circuit is formed on a substrate surface by selectively leaving a necessary portion of a copper foil layer and etching another portion, wherein the layer thickness is uniform. After the etching resist (3) is coated on both surfaces of the circuit forming portion of the copper foil layer (2), a portion not coated with the etching resist (3) is etched from both surfaces to form a concave portion (4). A step of obtaining a copper foil layer (2) composed of a thick part (2A) as a part and a thin part (2B) as a concave part; and both surfaces of the copper foil layer (2) are coated. One of the etching resists (3) among the etching resists (3)
After removing the etching resist, the etching resist removal surface (21)
Bonding the copper foil layer (2) to the surface of the substrate (1), and bonding the copper foil layer (2) to the surface of the substrate (1) and covering an etching resist (3) on a circuit forming portion.
Forming a circuit on the surface of the substrate by etching the thin film (2B), and removing the etching resist (3) after dissolving and removing the thin portion (2B).