JPS60251296A - Method for plating fine pattern - Google Patents

Abstract

PURPOSE:To manufacture a printed circuit having a finer pattern by stirring a plating soln. by air blowing and cathode rocking so as to prevent the formation of a circular unplated part and burning. CONSTITUTION:When a fine pattern is formed on a substrate for a precision printed circuit by plating, a plating soln. is stirred by cathode rocking at >=1.0m/ min linear velocity in a direction parallel to an anode and air blowing at >=0.01m<3>/min flow rate per unit area (m<2>) of the bath. Thus, the formation of an unplated part probably due to bubbles or gaseous H2 on a fine circuit pattern in case of only air blowing is prevented, and burining due to reduced limiting current density in case of only cathode rocking is also prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fine pattern plating method applied to precision printed circuit boards and the like.

<Conventional technology> Photolithography has traditionally been frequently used to produce precision printed circuit boards, but the use of additive methods in particular allows circuit boards with high wiring density to be produced, and is considered to be a highly advantageous manufacturing method. It's coming. Incidentally, the wiring density of circuit boards has been increasing in recent years, and when attempting to form even finer circuit patterns by plating, the plating solution is generally stirred using air agitation or cathode locking. rocking the board) is performed.

<Problem> However, the cause cannot be clearly understood with air agitation alone.
A small amount of circular bonding, which is thought to be caused by air bubbles or hydrogen gas, may occur on the fine circuit pattern, causing the conductor to become thin locally, reducing the reliability of the circuit board, or in severe cases, causing the conductor to become thinner. The pattern is broken. Further, if the circuit board is simply cathode-locked in a direction perpendicular to the anode, as is generally done, the limiting current density will decrease and discoloration will easily occur. Therefore, the present inventors conducted intensive studies to solve the above problems by using air agitation and cathode locking in combination, and as a result, they arrived at the present invention.

<Configuration> That is, in the present invention, the angle of 1.0 in the direction parallel to the anode is
Cathode locking with a linear velocity of more than g/jlb and an air flow rate of 0.0I n1″/-i-/ at the unit bath liquid level
The present invention provides a plating method characterized in that plating is performed in combination with air agitation of r& or higher.

The present invention will be explained in detail below.

Air agitation and cathode locking performed in the present invention may be performed using conventional equipment, but the direction of cathode locking is horizontal to the anode. The reason for this is that in the direction perpendicular to the anode, it is difficult to remove bubbles or hydrogen gas adhering to the pattern and to obtain a pure velocity that does not damage the substrate. By using both air agitation and cathode locking in the horizontal direction to the anode, it is possible to prevent the occurrence of air bubbles on the fine circuit pattern that cannot be removed by air agitation alone, or the occurrence of stuck spots that are thought to be caused by hydrogen gas, and the cathode locking alone is not enough. This method makes it possible to obtain good plating with a wide gloss range by increasing the limiting current density, which tends to cause discoloration when the current density decreases. Air stirring amount is o, olrl/wi
g/r is preferably 1 or more, particularly 0.03 to 0.50-/
m/g, more preferably 0.05 to 0650♂/-/♂.

Further, cathode rocking is preferably performed horizontally with respect to the anode at a linear velocity of 1.01 rL/IIk or more, particularly 3.0-15.0 m/lk, more preferably 5.0 m/lk.
#15.0@/1w1n is preferable. Cathode locking 1. If it is less than OV-, it is impossible to completely remove the circular stuck portions on the circuit pattern that are thought to be caused by bubbles or hydrogen gas. In addition, the air flow rate is 0.01 m1
'/#! If it is less than #/ml', the critical current density also decreases, making it easy to cause discoloration.

By the way, if the air flow rate is too large, problems such as bending of the circuit board and splashing of the plating solution outside the bathtub will occur, so it is usually set to t, o d/h/rl or less.

In addition, if the linear speed of cathode locking is too fast, problems such as the circuit board coming off from the cathode jig are likely to occur, so normally 20. OTn/- or less.

The circuit board used in the present invention may be any commonly used circuit board. For example, a thin metal plate may be bonded to an insulating substrate on one side or both sides depending on the purpose, and a photoresist may be applied thereon. A resist pattern may be formed, unnecessary portions other than the conductor portions may be removed by etching, and then the resist may be peeled off. Alternatively, a resist may be formed on a thin metal plate in areas other than the circuit portion, plated using the method of the present invention, and then used in a method in which the thin metal plate is removed.

As for the type of electrolytic plating, all usual types can be used, and copper is preferred from the viewpoint of conductivity and economy, but any other metal such as silver, gold, or nickel may be used. The types of plating solution are:
Silver cyanide baths can be used for silver plating, acidic or neutral alkaline baths can be used for gold plating, and nickel sulfate baths, sulfamino acid nickel baths, etc. can be used for nickel plating. Examples of copper electrolytic plating include copper cyanide plating, copper pyrophosphate plating, copper sulfate plating, and copper borofluoride plating.

The cathode current density may be under normal conditions, but when plating fine patterns, 3 A/d- or higher, especially 5 A/d- or higher.
d♂ or more, more preferably 8 A/d♂ or more, and 4- When the cathode current density is increased, thickening in the width direction is suppressed. The higher the cathode current density, the better, and pulse plating is also preferably used. The upper limit of cathode current density is determined by burnout.

Other electrolytic plating conditions may be carried out under normal conditions.

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

Examples 1 to 5 Polyimide film “Kapton” manufactured by DuPont, thickness 25
μm VC5μm thick copper foil manufactured by Bostic rXA-
564-4J Adhere using phenolic resin adhesive. Next, after drying, a negative resist "Microresist 747-110 cat J" manufactured by Eastman Co., Ltd. was applied to the copper surface so that the resist thickness became 3 to 5 μm. After prebaking, it was exposed to a high-pressure mercury lamp through a circuit pattern mask. The resist is then developed using a developer (Microresist Developer) manufactured by Eastman Kodak and a rinsing liquid (Microresist Rinse) manufactured by Eastman Kodak, followed by post-baking to form a resist in the form of a circuit pattern. Subsequently, the copper foil was etched away using a 50% solution of ferric chloride, and the resist was removed using "Resist Remover J-100J" manufactured by Nagase Kasei Co., Ltd. As a result, the film thickness was 5 μm s m 1.
A linear pattern with an array pitch of 150 μm was obtained. Next, using a birophosphate copper plating solution made by Barshaw Murata, the linear pattern was used as a cathode to create an air agitation amount Q, IQ.
m”/m tide, the cathode rocker was moved horizontally with respect to the anode at a linear velocity of 7.5 μm, and the current density was 5.o A/dn.
Plating was performed under conditions of r.

As a result, there was no discoloration or circular bonded areas in the copper wire pattern.

Furthermore, the linear speeds of the air stirring lid and cathode rocker were changed as shown in Table 1, and plating was performed on the same type of copper wire pattern as described above under the same conditions. The resulting pattern was examined for discoloration or for the occurrence of circular matte areas. The results are shown in Table-1.

Comparative Examples 1-2 Polyimide film “Kapton” manufactured by DuPont, thickness 25
Add 5μm thick copper foil to the μm one using Bostik rXA-5.
Adhere using 64-4J phenolic resin adhesive.

Next, a negative resist manufactured by Eastman Co., Ltd. [Microresist 747-110 cst J] was applied to the copper surface so that the resist thickness after drying was 3 to 5 μm, and after prebaking, it was applied using a high-pressure mercury lamp through a circuit pattern mask. It is exposed to light, developed with Eastman Kodak's developing solution "Microresist Developer" and Eastman Kodak's rinsing solution "Microresist Rinse," and post-baked to form a resist in the form of a -C circuit pattern. Next, the copper foil is etched away using a 50% solution of ferric chloride, and the resist is removed using Nagase Kasei Co., Ltd.'s "Resist Remover J-100J".As a result, the film thickness is 5 μm, width is 1.
A linear pattern with an array pitch of 150 μm was obtained. Next, using a birophosphate copper plating solution made by Barshaw Murata, the linear pattern was used as a cathode and the amount of air agitation was 0.00.
5 d71s/♂, cathode rocker linear velocity 7.57
71/m horizontally with respect to the anode, and the current density is 5. O
Plating was performed under A/d♂ conditions.

Although the copper wire pattern obtained as a result did not have a circular bonded area, it did cause some discoloration.Furthermore, the amount of air agitation and the linear speed of the cathode rocker were changed as shown in Table 2, and the above-mentioned The same type of copper wire pattern was plated under the same conditions, and the resulting pattern was examined to see if there was any discoloration or circular bonded areas. The results are shown in Table 2. *1: Using a magnifying glass, visually observe the pattern.
The presence or absence of a circular mesh attachment area was examined.

*2; Visually inspected the pattern and checked for discoloration 02-2 *12 *2 Both were investigated using the methods shown in Table 1.

<Effects> By performing plating according to the method of the present invention, circular bonded areas and discoloration do not occur, and as a result, printed circuits with finer patterns can be manufactured.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] Cathode locking with linear velocity of 1.0@/- or more in the direction parallel to the anode and air flow rate per unit bath liquid level of 0
, a method of fine pattern plating characterized by performing plating in combination with air agitation of OX yd/m/r1 or more.