JPH10223681A - Method of depositing columnar plating in fine hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form columnar and straight bump electrodes at fine holes of a structure, by plating the inside of the fine holes with a liq. powerfully oscillated near the holes by an ultrasonic stirring at specified frequency. SOLUTION: A plating bath is not limited so long as it is not the type of corroding a substrate having fine holes and resist. An ultrasonic wave for stirring a plating liq. is set at 40kHz-1MHz and applied to uniformly diffuse the plating liq. in the fine holes and grows the plating straightly without laterally spreading even when the plating is over the height of the resist. If the frequency is less than 40kHz, the bubbles due to he cavitation are larger than the fine holes and hence cannot provide a sufficient stirring effect in the holes. If exceeding 1MHz, the stirring effect is poor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for depositing plating in the form of columns in micropores, and more particularly to forming a columnar bump electrode by plating micropores on a substrate having micropores. It relates to a possible plating method.

2. Description of the Related Art In recent years, higher performance and smaller size and lighter weight of electronic devices have been further promoted along with an increase in demand for mobile communication devices and computers, and accordingly, the mission of microelectronics technology has been increasing. Wire bonding has been used as a method of connecting LSI chips and external circuits, which has been performed since the birth of the semiconductor industry. However, as the integration of LSIs has progressed, higher functionality and higher capacity have been achieved. Accordingly, it has become difficult to cope with the wire bonding method due to an increase in the number of LSI terminals, miniaturization of electrodes, narrowing of wiring pitches, and the like.

Under such circumstances, as an electrical connection method replacing the wire bonding method, a flip chip method of connecting an LSI chip and a substrate via a bump-shaped electrode called a bump or TAB (Taped Automated Bonding).
The system has been adopted. Where the bumps are
It is formed by electroplating on a circuit conductor of an electronic circuit board, that is, in a fine hole portion of a substrate having fine holes. Since the place where the bump is formed is a fine hole on the resist coated on the laminated substrate, if plating is performed without stirring in this hole, the plating solution does not enter the fine hole and plating does not precipitate, so it is usually used. Is subjected to electroplating while stirring by bubbling or the like. However, stirring with a liquid flow or the like is not effective enough. When the plating thickness exceeds the height of the resist, the plating also grows in the edge portion in the lateral direction, so that mushroom-shaped bumps are formed, and the density of the pattern increases. This causes problems such as formation of bridges and difficulty in stripping the resist.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plating method capable of forming a columnar bump electrode by plating a fine hole portion of a substrate having fine holes. .

[0003]

Means for Solving the Problems The present invention has been made based on the finding that the above-mentioned problems can be solved by employing ultrasonic stirring at a specific frequency when plating is carried out in the fine holes. That is, according to the present invention, when plating is carried out in the fine hole, the plating is performed while vibrating the liquid near the object to be plated by ultrasonic stirring at a frequency of 40 kHz to 1 MHz. And a method for precipitating in a columnar form.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The plating bath used in the present invention is not particularly limited as long as it does not attack a substrate having fine pores and a resist. Gold, nickel, Sn-Pb alloy, Sn-Ag Any plating bath for depositing Pb-free solder such as Sn-Bi, Sn-Zn alloy or the like, indium or the like can be used. Specifically, for example, Japanese Patent Application Laid-Open No. 54-6953
No. 4, JP-A-7-138782 and the like can be used.

The substrate having micropores to be plated in the present invention includes, for example, a substrate having a coating of a metal such as copper, nickel, and chromium on a substrate of aluminum, alumina, glass, or the like. One having fine pores of a size is exemplified. The thickness of the substrate may be arbitrary,
Preferably, it is about 0.5 to 1 mm. The metal film is
Preferably it is about 1 to 50 μm. In the present invention,
More preferably, a substrate obtained by applying a resist on the above substrate is used. Here, examples of the resist include those described in JP-B-5-8203, JP-A-7-76565, and the like. The resist can be applied on the substrate by a conventional method, and the thickness of the resist is preferably about 0.02 to 1 mm. Here, the fine holes in the resist preferably penetrate to the substrate and the metal film.

In the present invention, the above-mentioned substrate is used as a cathode, and platinum or a metal having the same composition as plating is used as an anode.
Electroplating is performed at ６０60 ° C. for 30 to 500 minutes to deposit the plating in a columnar shape in the fine holes in the substrate. here,
In the present invention, the setting conditions of the ultrasonic wave used for stirring the plating solution are set to a frequency of 40 KHz to 1 MHz (preferably 100 to 500 MHz).
KHz). Stirring frequency 40KHz
By using ultrasonic waves of ~ 1MHz, the plating solution is diffused uniformly in the micropores, and even if the plating exceeds the height of the resist, it does not spread horizontally and grows straight. is there. If the frequency is lower than 40KHz,
The bubbles generated by the cavitation phenomenon are large with respect to the size of the micropores, and a sufficient stirring effect cannot be obtained even in the pores.
In addition, uniform agitation cannot be performed because the interval between the standing numbers is long. On the other hand, when the frequency exceeds 1 MHz, the stirring effect is weakened. In addition, since the ultrasonic wave has a standing number, 40 KHz to 1 MHz
It is preferable to swing the plated product even during the period. The swing of the wave by the ultrasonic wave can be easily performed by using a cathode rocker. In the present invention, the plating is carried out using a direct current at a current density of 0.1 to 5 A / dm ² and a current of 30 to 30 A / dm ² .
It is good to perform for about 500 minutes. However, in the present invention, the plating can be deposited in the fine pores in a columnar shape by the above-described characteristic stirring even by electroless. Examples of such a plating bath that can be used for electroless are, for example, JP-A-5-295556 and JP-A-6-332.
No. 55 and the like.

Next, the present invention will be described with reference to the accompanying drawings. According to the plating method of the present invention, as shown in FIG. 1, a resist 3 on a copper film base 2 provided on a substrate 1
A columnar plating 4, that is, a bump electrode is formed in the micropores, but according to the method of the comparative example having no feature of the present invention, as shown in FIG. 2, a mushroom-shaped plating 5 is formed. You.

[0008]

According to the method of the present invention, a columnar, that is, a straight bump, rather than a mushroom-like or mushroom-like projection can be easily formed in a fine hole portion of a substrate having fine holes. Next, the present invention will be described with reference to examples.

[0009]

【Example】

Example 1 Coating with an epoxy-based resist (film thickness 50 μm)
Immersed in a tin-lead alloy plating bath described below using a substrate having a large number of micropores as a cathode and a tin-lead alloy as an anode at a temperature of 25 ° C. 1.0 A / dm ² while performing ultrasonic stirring (100 KHz)
Plating for 200 minutes at a current density of Sn / Pb = 75/2
The straight bump plating No. 5 of 100 μm was obtained. Tin-lead alloy plating bath composition stannous sulfate 32 g / l lead oxide 20 {sodium gluconate 120} EDTA-2Na 70} additive 10 ml / l (W-1110S manufactured by Dipsol) water balance pH 6.0 (PH adjusted with ammonia water)

Example 2 The procedure was performed except that plating was performed at a current density of 2.0 A / dm ² for 100 minutes while performing ultrasonic stirring (400 KHz) at a temperature of 25 ° C. using the following tin-lead alloy plating bath. Plating was performed in the same manner as in Example 1 to obtain 100 μm of straight bump plating of Sn / Pb = 50/50. Tin-lead alloy plating bath composition stannous sulfate 56 g / l lead oxide 10 グ ル コ glucono δ-lactone 120 〃 DTPA 70 添加 additive 10 ml / l (W-1110S, manufactured by Dipsol Corporation) Water balance pH 6.0 ( PH was adjusted with ammonia water)

Example 3 The following procedure was carried out except that plating was carried out at a current density of 1.0 A / dm ² for 200 minutes while performing ultrasonic stirring (400 KHz) at a temperature of 25 ° C. using the following tin-lead alloy plating bath. Plating was performed in the same manner as in Example 1 to obtain a straight bump plating (100 μm) of Sn / Bi = 95/5. Tin-lead alloy plating bath composition Stannous oxide 30 g / l bismuth oxide 2 {methanesulfonic acid 75} Gluconolactone 150 EDTA 60 Additive 20 ml / l (IE0428S manufactured by Dipsol Co.) Water Balance pH 4.0 (pH adjusted with ammonia water)

Example 4 The following tin-silver alloy plating bath was used at a current density of 2.5 A / dm ² while ultrasonically stirring (100 KHz) at 20 ° C.
Plating was performed in the same manner as in Example 1 except that plating was performed for 0 minutes, to obtain straight bump plating (75 μm) of Sn / Ag = 97/3. Tin-silver alloy plating bath composition stannous oxide 30 g / l silver oxide 1.2 メ タ ン methanesulfonic acid 150 〃 water balance additive 60 ml / l (IF0729S manufactured by Dipsol Co., Ltd.)

Example 5 The procedure was performed except that plating was performed at a current density of 2.0 A / dm ² for 100 minutes using a tin-zinc alloy plating bath at a temperature of 25 ° C. while performing ultrasonic stirring (100 KHz). Plating was performed in the same manner as in Example 1 to obtain 100 μm of straight bump plating of Sn / Zn = 90/10. Tin-zinc alloy plating bath composition stannous sulfate 36g / l zinc sulfate 35 {ammonium citrate 100} ammonium sulfate 100} additive 8ml / l (gelatin) water balance pH 6.0 (pH adjusted with ammonia water)

Example 6 Using the following gold plating bath, coating was performed at a temperature of 40 ° C. while performing ultrasonic stirring (400 KHz) (film thickness: 5 μm).
Plating was performed in the same manner as in Example 1 except that plating was performed on the laminated substrate at a current density of 0.5 A / dm ² for 40 minutes.
0 μm straight bump plating was obtained. Gold plating bath composition Potassium gold cyanide 10 g / l Potassium dihydrogen phosphate 96 〃 Citric acid 24 カ リ ウ ム EDTA-cobalt potassium 2 二 Dipotassium hydrogen phosphate 80 〃 Water balance pH 4.5 〃

Example 7 Using the following electroless Ni-P plating bath, plating was performed for 5 hours at a temperature of 90 ° C. with ultrasonic stirring (100 KHz), and a Ni-P straight plate was formed on the same substrate as in Example 1. Bump plating (100 μm) was obtained. Electroless Ni-P plating bath composition Nickel sulfate 20 g / l Sodium hypophosphite 24 乳酸 Lactic acid 27 ２ Propionic acid 2 〃 Water Remaining pH 4.5 (pH adjusted with NaOH aqueous solution)

Example 8 Using the following electroless Ni-B plating bath, Ni-B was coated on a coated (5 μm-thick) glass substrate for 2 hours while performing ultrasonic stirring (1 MHz) at a temperature of 65 ° C. 10 μm of straight bump plating was obtained. Electroless Ni-B plating bath composition nickel sulfate 20 g / l DMAB 2 グ リ glycine 3 ア ン ammonium acetate 6 〃 water balance pH 6.5 (pH adjusted with NaOH aqueous solution)

Comparative Example 1 Same as Example 1 except that plating was performed at a current density of 1.0 A / dm ² for 200 minutes while stirring the liquid at a temperature of 25 ° C. using the following tin-lead alloy plating bath. As a result, mushroom-shaped bump plating was formed on the laminated substrate. In addition, there was variation in the plating film thickness between the location where the liquid flow hits and the vicinity thereof. Tin-lead alloy plating bath composition stannous sulfate 56 g / l lead oxide 10 〃 gluconolactone 120 〃 DTPA 40 添加 additive 10 ml / l (W-1110S manufactured by Dipsol Co.) Water balance pH 6.0 (ammonia PH was adjusted with water)

Comparative Example 2 The same tin-lead alloy plating bath as in Comparative Example 1 was used at a temperature of 25 ° C.
When plating was performed in the same manner as in Example 1 except that plating was performed at a current density of 1.0 A / dm ² without stirring, hydrogen was generated inside the fine holes, and the coating resist was peeled off. The plating was hardly deposited. Comparative Example 3 Tin-zinc alloy plating Using the following tin-zinc alloy plating bath, current density was measured while stirring at a temperature of 25 ° C using a cathode rocker.
When plating was performed in the same manner as in Example 1 except that plating was performed at 2.0 A / dm ² , hydrogen was generated inside the fine holes in about 10 minutes, and the plating was not deposited.

Tin-zinc alloy plating bath composition stannous sulfate 36 g / l zinc sulfate 35 {ammonium citrate 100} ammonium sulfate 100 # additive 8 ml / l (gelatin) water balance pH 6.0 (pH adjustment with ammonia water) Comparative Example 4 The same electroless Ni-B plating bath as in Example 8 was used at a temperature of 65
When plating was performed for 2 hours on a glass substrate having the same coating (thickness: 5 μm) as in Example 8 while performing rocking stirring at 0 ° C., the plating shape was mushroom-shaped projections.

Claims (2)

[Claims] When plating is performed in a fine hole, plating is carried out while vibrating a liquid near an object to be plated by ultrasonic stirring at a frequency of 40 KHz to 1 MHz. A method of depositing in columnar form. 2. The method according to claim 1, wherein a columnar bump electrode is formed in the fine hole of the substrate having the fine hole.