JPH05335722A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To acquire a manufacturing method of a printed circuit board which does not lower wiring density and does not require application of solder paste, etc. CONSTITUTION:A required circuit pattern including a surface mounting pad is patterned in a conductor layer surface 1a which is integrally formed in at least one main surface of an insulating substrate. An electrolytic solder plating layer 5 is applied and formed in the circuit patterning surface, and a required circuit pattern including a surface mounting pad is formed by selectively etching an exposed conductor layer using the applied and formed electrolytic solder plating layer as an etching resist. Then, a specified circuit pattern part is masked and the electrolytic solder plating layer excepting the masked region is removed. After the mask is removed, a solder flow-out preventing dam 7 is formed in a conductor layer pattern surface of the remaining and applied electrolytic solder plating layer. Thereafter, the remaining and applied electrolytic solder plating is made into eutectic solder by heating treatment and a solder resist layer is applied and formed in a specified circuit pattern formation surface including a surface mounting pad.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board having surface mounting pads.

[0002]

2. Description of the Related Art For the purpose of reducing the weight and size of electronic devices, the circuit mechanism has been downsized.
That is, a mounting circuit device (mounting circuit unit) in which required electronic components are mounted on the main surface of a printed wiring board is being widely put to practical use in various electronic devices. Development of printed wiring boards is also in progress. By the way, the following means are known as a method for manufacturing the high-density printed wiring board for surface mounting.

(A) As an etching resist, selective etching is performed by using an electrolytic solder plating layer, and the entire conductor circuit including the surface mounting pads is formed into a two-layer structure of copper (underlayer) and plated solder (upper layer). A method for manufacturing a solder-plated printed wiring board to be formed on.

(B) A solder resist is coated on the conductor circuit pattern other than the surface mounting pad region, and then hot air leveling is performed to selectively form a solder layer on the exposed surface mounting pad region surface. Forming method of hot air leveling printed wiring board (HAL
Law).

(C) Compared with the HAL method of (b) above, the thickness of the electrolytic solder plating layer is about 2 to 3 times, and after the circuit pattern is formed by selective etching of the underlying copper, the electrolytic solder plating is applied together. A method for manufacturing a printed wiring board, which is crystallized to form a circuit pattern whose surface is coated with eutectic solder (solder through-hole plating method).

(D) The formation of the conductor circuit pattern including the surface mounting pad is performed by applying an etching resist pattern, selectively etching and peeling the etching resist pattern to form the conductor circuit pattern into a one-layer structure of copper.
A method for manufacturing a pre-flux printed wiring board, wherein a pre-flux is coated on the surface not covered with the solder resist. (e) After forming a conductor circuit pattern including the surface mounting pad by selective etching and further coating the solder resist, pull out the power supply plating lead from the required surface mounting pad and place it on the required surface mounting pad surface. A method for manufacturing a partially electrolytic solder-plated printed wiring board, which selectively deposits an electrolytic solder layer.

[0007]

However, the above-mentioned method for manufacturing a surface-mounted printed wiring board has the following problems in practical use.

First, in the case of a printed wiring board obtained by the method of manufacturing a solder-plated printed wiring board of (a), when the mounting components are soldered together with the miniaturization of the conductor circuit (density of wiring), There is an inconvenience that a solder bridge is likely to occur in the conductor circuit (pattern) portion covered with the solder resist.

In the case of the printed wiring board obtained by the method for manufacturing a hot air leveling printed wiring board of (b), the occurrence of solder bridges is avoided because the portions other than the soldered portion are covered with solder resist. However, since the thickness of the hot air leveled solder (upper layer) is not uniform (it is virtually impossible to adhere to a uniform thickness), there is a disadvantage that defective soldering of mounted components easily occurs.

In the case of the solder through-hole plating method (c),
When the circuit pattern width is reduced to 150 μm or less, short circuits easily occur between adjacent circuit patterns, and the solder layer remains under the solder resist layer, which reduces the reliability of electronic component mounting and mounting. There is a problem of inviting.

Also in the case of the printed wiring board obtained by the method for producing a pre-flux printed wiring board of (d), since the solder resist 3 covers the portions other than the soldered portion, the occurrence of solder bridges is avoided. However, before mounting the required electronic components, it is necessary to apply solder paste to the surface mounting pad surface by a printing method, etc., and if the surface mounting pads become narrower than about 500 μm,
It becomes difficult to apply the solder paste by printing, which is not suitable for mass production.

In the case of the method for manufacturing the partially electrolytic solder-plated printed wiring board of (e), it is necessary to pull out the power supply plating lead for each surface mounting pad covering the electrolytic solder plating layer, and therefore the wiring of the circuit pattern is required. There is a problem that the density inevitably decreases.

The present invention has been made in view of the above circumstances, and does not reduce wiring density and does not require solder paste deposition by printing when mounting electronic components.
An object of the present invention is to provide a method for manufacturing a printed wiring board suitable for manufacturing a printed wiring board capable of highly reliable surface mounting.

[0014]

A method of manufacturing a printed wiring board according to the present invention provides a required circuit pattern including a surface mounting pad on a conductor layer surface integrally formed on at least one main surface of an insulating substrate. A step of patterning, a step of depositing an electrolytic solder plating layer on the circuit-patterned surface, and a step of selectively etching the exposed conductor layer using the deposited electrolytic solder plating layer as an etching surface A step of forming a required circuit pattern including a mounting pad, a step of masking the formed circuit pattern portion including at least the surface mounting pad, and an exposed electrolytic solder plating layer other than the masked area are removed. And the conductor layer of the electrolytic solder plating layer remaining / adhered after removing the mask used for removing the electrolytic solder plating layer Eutectic process of applying or arranging / forming the solder outflow prevention function on the upper end area of the turn surface, and electrolytic solder plating remaining / deposited by heat treatment after arranging / forming the solder outflow prevention dam And a step of depositing and forming a solder resist layer on a predetermined circuit pattern forming surface including a surface mounting pad after performing the eutectic solder by performing the heat treatment. And

[0015]

In the method for manufacturing a printed wiring board according to the present invention, prior to the step of forming a required circuit pattern including at least surface mounting pads, the conductor layer for this circuit pattern is used as a common power supply lead. Then, after selectively forming an electrolytic solder plating layer on the entire surface of the circuit pattern, the resist used for forming the circuit pattern is peeled and removed. After that, the conductor layer not covered with the electrolytic solder plating layer is selectively etched, and then at least the surface mounting pad surface (region) is masked to selectively remove the unnecessary portion (region) of the solder plating layer. .. In other words, it is not necessary to separately take out the power supply leads corresponding to the pad surface and the through holes that are exposed for mounting and mounting electronic parts in the future, and the required electrolytic solder plating layer can be selectively deposited. Also, the electrolytic solder plating layer that contributes to the soldering of mounted electronic components is
While eutecticization (densification) is performed in a state where the flow to the circuit pattern surface that is connected is prevented, this eutecticization (densification)
After that, a solder resist layer is deposited and formed, so that highly reliable mounting becomes possible. In other words, a printed wiring board that can be configured with a highly reliable mounting circuit device is provided without reducing the wiring density, and even when the surface mounting pads have a narrow pitch of about 300 μm, the required solder layer is provided. Can be obtained.

[0016]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8 (a) to 8 (c).

Embodiment 1 FIGS. 1 to 7 schematically show an embodiment of a method for manufacturing a printed wiring board according to the present invention. FIGS. 1 to 6 are sectional views, and FIG. 7 is a plan view. It shows respectively. First,
Prepare a laminated board 2 for a printed wiring board in which copper foil layers 1a with a thickness of approximately 18 μm are integrally arranged (formed) on both main surfaces, and perform punching at the required locations (positions) to produce electricity. A hole 3 for making a special connection is formed (FIG. 1). Then, after forming a panel copper plating layer 1b on the surface of the copper foil layer 1a of the perforated laminated plate 2, if necessary, chemical copper plating treatment of thickening or thinning and electrolytic copper plating treatment are performed. , A dry film is laminated, exposed and developed to perform pattern masking 4, and a pattern copper plating process is performed to form a copper plating layer 1c having a thickness of about 25 μm on the exposed surface including the inner wall surface of the hole 3 for connection. Wear and form (Fig. 2).

After that, the laminated plate 2 on which the copper plating layer 1c has been deposited and formed is immersed in, for example, a borofluoric acid-based solder plating bath, and the copper foil layer 1a of the laminated plate 2 is used as a power-feeding lead for electrolytic soldering. The exposed surface is plated to a thickness of 10
An electrolytic solder plating layer 5 having a thickness of about μmm or more was deposited and formed (FIG. 3). Then, the pattern mask 4 was peeled and removed (FIG. 4), and a desired circuit pattern was formed by a conventional means. That is, using the electrolytic solder plating layer 5 as an etching resist, the copper layers 1a, 1b, 1c exposed by the removal of the pattern mask 4 are selectively etched away, and the surface mounting is covered with the electrolytic solder plating layer 5. A circuit pattern including pads for forming is formed.

After forming the circuit pattern including the surface mounting pads and the like as described above, a photosensitive material such as a dry film is laminated by using a vacuum laminator or the like, and the electrolytic solder plating layer 5 is adhered and formed. In the circuit pattern, the area where the electrolytic solder plating layer 5 is to be left, that is, the surface mounting pad surface and the through hole (connection hole) 3 area peripheral surface are masked with a photosensitive material layer 6
Exposure-development is performed as shown in FIG. 5 to selectively remove the electrolytic solder plating layer 5 in the exposed portion (region). Then, the photosensitive mask 6 is peeled and removed, and then a fusing treatment is performed (FIG. 6).

In this embodiment, in order to prevent the electrolytic solder plating layer 5 from flowing out during the fusing treatment, as shown in a plan view in FIG. 7, the end of the remaining electrolytic solder plating layer 5 is adhered. A dam 7 for preventing solder flow is previously formed by, for example, a printing method in an edge portion, in other words, in a boundary area with a circuit pattern connected to the surface mounting pad area covered with the electrolytic solder plating layer 5. In this way, after forming the solder flow preventing dam 7 by printing / deposition, a so-called fusing treatment is performed to fluidize or soften the remaining / deposited electrolytic solder plating layer 5 to thereby form a eutectic crystal.・ Be uniform. In this fusing process,
In the formation of a circuit pattern including a surface mounting pad by selectively etching the copper layers 1a, 1b, 1c using the electrolytic solder plating layer 5 as an etching resist, the copper layers 1a, 1b, 1c are susceptible to side etching. The electrolytic solder plating layer 5 having a side surface protruding with respect to the copper layers 1a, 1b, and 1c in the circuit-patterned state flows along the formed circuit pattern surface and is uniformly distributed. It was in the form of coating.

After the fusing treatment, on the surface of the required area except for the area where the electrolytic solder plating layer 5 remains and is adhered,
A so-called solder resist is coated. Then, the required external processing and electrical inspection are performed, and, for example, 300
Thickness on the surface mount pad surface of μm and 250μm pitch
A printed wiring board having a uniform solder layer of 10 μm or more and suitable for surface mounting was obtained.

Example 2 In the example of the embodiment schematically illustrated in FIGS. 1 to 7, the copper foil layer 1 surface of the punched laminated plate 2 (see FIG. 1) is thickened or if necessary. Panel copper plating layer after thin chemical copper plating and electrolytic copper plating
After forming 1b, a dry film is laminated, exposed and developed to perform pattern masking 4, and a region forming a circuit pattern connected to the surface mounting pad region is formed, for example, as shown in FIGS. ) Is patterned so as to form a non-linear shape. The copper plating layer 1c having a thickness of about 25 μmm is deposited / formed on the exposed surface including the inner wall surface of the connection hole 3 by the subsequent copper plating treatment (see FIG. 2), and the copper plating layer 1c is deposited / formed. Laminated board 2
Electrolytic solder plating treatment, thickness to exposed surface 10μmm
The electrolytic solder plating layer 5 was formed to a certain degree or more in accordance with the case of Example 1 (see FIG. 3).

Next, the pattern mask 4 is peeled and removed, and the exposed copper layers 1a, 1b, 1c are selectively removed by etching using the electrolytic solder plating layer 5 as an etching resist (see FIG. 4), A circuit pattern including a surface mounting pad whose surface is covered with the electrolytic solder plating layer 5 is formed. In this way, after forming a circuit pattern including pads for surface mounting, a photosensitive material such as a dry film is laminated using a vacuum laminator or the like, and the circuit pattern in which the electrolytic solder plating layer 5 is formed is formed. , The area where the electrolytic solder plating layer 5 is to be left, that is, on the surface mounting pad surface or through hole (connection hole)
The peripheral surface of the three regions is exposed and developed so as to be masked 6 with the photosensitive material layer, and the electrolytic solder plating layer 5 in the exposed portion (region) is selectively removed (see FIG. 5). Next, the photosensitive mask 6 is peeled and removed, and then a required fusing treatment is performed (see FIG. 6).

In this embodiment, in the fusing process, as shown in plan view in FIGS. 8 (a) to 8 (c),
The edge area of the remaining / adhered electrolytic solder plating layer 5, in other words, the boundary area with the circuit pattern connected to the surface mounting pad area covered with the electrolytic solder plating layer 5 is bent or enlarged. It is made non-linear by formation and the like, and adopts a configuration for suppressing or reducing the flowability of solder. Therefore, even in the eutectic / uniformizing process by fluidizing or softening the electrolytic solder plating layer 5 in the fusing process, the electrolytic solder plating flows out to the circuit pattern surface to which electrolytic solder plating is not desired to be deposited. -Effectively prevented from wearing. That is, in the case of this embodiment,
Non-linear areas such as bent or swelled portions of the circuit pattern function as dams for preventing solder flow.

In this fusing process, a circuit pattern including a surface mounting pad using the electrolytic solder plating layer 5 as an etching resist was formed so as to project from the side surface concaved by side etching. The electrolytic solder plating layer 5 has a circuit pattern surface (including a side surface)
It had a form in which it uniformly flowed along with.
After the fusing treatment, a so-called solder resist is coated on a required area surface excluding the area where the electrolytic solder plating layer 5 remains and is adhered. Next, external processing and electrical inspection are performed to obtain a printed wiring board suitable for surface mounting, for example, where a solder layer with a thickness of 10 μm or more is uniformly formed on the surface mounting pad surface with a pitch of 300 μm and 250 μm. It was

Although the circuit pattern is formed by selective etching of the copper foil layer in the above description, it may be formed by selective etching of another conductive metal layer. Of course it does.

In the above embodiment, the electrolytic solder plating layer 5 is selectively provided on the surface mounting pad surface and through hole (connection hole) area. The electrolytic solder plating layer 5 may not be provided in the connection hole area when it is not used for connecting a lead terminal of a component, or in the circuit pattern including the surface mounting pad, the surface mounting pad portion is used together with the surface mounting pad portion. The electrolytic solder plating layer 6 may be provided in a region other than the pad for use.

[0028]

As described above, according to the method for manufacturing a printed wiring board according to the present invention, it is possible to easily realize a printed wiring board which can be mounted at high density without complicated operations and has a high wiring density. Obtainable. That is, first of all, prior to the formation of the circuit pattern by the selective etching, the selective etching conductive metal layer is used as a power supply lead, and the electrolytic solder plating layer is formed on at least the surface mounting pad surface. The operation is simplified because there is no need to install a power supply lead separately. The elimination of the power supply lead contributes to the reduction of the wiring density. Secondly, the electrolytic solder plating layer can be easily and surely prevented from flowing into an undesired circuit pattern region in the process of eutecticization and densification by so-called fusing treatment, so that reliability can be improved. It has a high surface mounting surface (surface mounting pad surface) or does not cause short circuit between adjacent circuit patterns, and retains and exhibits excellent functions. Thirdly, a surface mounting pad, for example, 3
It is possible to set a narrow pitch of 00 μm or less, and even in that case, an electrolytic solder plating layer with a thickness of 10 μm or more and a substantially uniform thickness is deposited, so the soldering function for mounting is sufficient. Holds and demonstrates.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a connection hole is formed in a surface of a copper foil-clad laminate in an embodiment of a method for manufacturing a printed wiring board according to the present invention.

FIG. 2 is a cross-sectional view showing a state in which an electrolytic copper plating layer is selectively provided in the embodiment example of the method for manufacturing a printed wiring board according to the present invention.

FIG. 3 is a cross-sectional view showing a state in which an electrolytic solder layer is provided on a copper plating layer that is selectively provided in an embodiment of the method for manufacturing a printed wiring board according to the present invention.

FIG. 4 is a cross-sectional view showing a state in which a pattern mask used when selectively providing an electrolytic copper plating layer and an electrolytic solder layer is peeled and removed in an embodiment example of a method for manufacturing a printed wiring board according to the present invention.

FIG. 5 is a view showing an embodiment of a method for manufacturing a printed wiring board according to the present invention, in which an electrolytic solder layer on a circuit pattern surface including a surface mounting pad formed by selective etching is masked to selectively remove the electrolytic solder layer. Sectional drawing which shows the removed state.

FIG. 6 shows a flow chart of flowing electrolytic solder layer remaining on an adherend in an example of an embodiment of a method for manufacturing a printed wiring board according to the present invention.
Sectional drawing which shows the state which the eutectic became uniform.

FIG. 7 is a flow chart showing the flow of the remaining electrolytic solder layer deposited in the embodiment of the method for manufacturing a printed wiring board according to the present invention.
Sectional drawing which shows the state which provided the dam for preventing outflow of an electrolytic solder layer at the time of eutectic uniformization (fusing process).

8 (a) to 8 (c) are schematic views showing another embodiment of the method for manufacturing a printed wiring board according to the present invention. Prevents the outflow of the electrolytic solder layer during uniformization (fusing treatment)
The top view which shows the circuit pattern example different from each other given to the circuit pattern part connected.

[Explanation of symbols]

1a ... Copper foil layer 1b ... Panel copper plating layer 1c ... Electrolytic copper plating layer 2 ... Laminated plate 3 ... Connection hole 4 ... Pattern mask 5 ... Electrolytic solder plating layer 6 ... Masking (photosensitive mask)

Claims (2)

[Claims] 1. A step of patterning a desired circuit pattern including a surface mounting pad on a conductor layer surface integrally formed on at least one main surface of an insulating substrate, and electrolytic solder plating on the circuit patterned surface. A step of depositing a layer, a step of selectively etching the exposed conductor layer using the deposited electrolytic solder plating layer as an etching resist to form a required circuit pattern including a surface mounting pad, A step of masking the formed circuit pattern portion including at least the surface mounting pad, a step of removing the exposed electrolytic solder plating layer other than the masked area, and a mask used for removing the electrolytic solder plating layer. After removal
A step of disposing / forming a solder outflow prevention dam on the upper end of the conductor layer pattern surface of the remaining / adhered electrolytic solder plating layer, and a step of disposing / forming the solder outflow prevention dam and then applying heat treatment to leave / remain. A step of converting the deposited electrolytic solder plating to eutectic solder, and after applying the heat treatment to form eutectic solder, deposit and form a solder resist layer on a predetermined circuit pattern forming surface including a surface mounting pad A method of manufacturing a printed wiring board, comprising: 2. A step of patterning a required circuit pattern including a surface-mounting pad on a conductor layer surface integrally formed on at least one main surface of an insulating substrate, and electrolytic solder plating on the circuit-patterned surface. A step of depositing a layer, a step of selectively etching the exposed conductor layer using the deposited electrolytic solder plating layer as an etching resist to form a required circuit pattern including a surface mounting pad, A step of masking the formed circuit pattern portion including at least the surface mounting pad, a step of removing the exposed electrolytic solder plating layer other than the masked area, and a step of arranging and forming the solder outflow prevention dam, A step of applying eutectic solder to the electrolytic solder plating remaining or adhered by heat treatment, and applying eutectic solder to the heat treatment And a step of depositing and forming a solder resist layer on a predetermined circuit pattern forming surface including the surface mounting pad, the conductor layer being selectively etched to form a required circuit pattern including the surface mounting pad. In the step of forming, the connecting area portion of the conductor layer pattern for leaving and depositing the electrolytic solder plating layer is formed to be non-linear to prevent the solder outflow in the eutectic soldering step due to the heat treatment. Printed wiring board manufacturing method.