JPS60187090A - Method of coating gold for thickening ceramic substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method suitable for partially depositing a thick gold coating on a hemi-lamic substrate such as an IC board for small-sized electronic parts.

[Back mold of invention]

For small M electronic components and ceramic substrates on which semiconductors are mounted and integrated circuits are formed, there is a strong desire to uniformly form gold coatings of different thicknesses. The purpose of the gold coating is to provide good bonding, wire bonding, soldering, etc., but for cost reasons, it is customary to ensure the minimum different Au gland thicknesses that satisfy the respective characteristics. . In general, the gold coating method depends on the plating method such as electroless plating, # plating, electroplating, etc.
Cannot be made thicker than m. Therefore, it is used in combination with electroplating or electroless plating. Seven <
The following is a conventional technique for partially thickening a substrate.

Basically, gold with a thickness of 1 μm or more is formed by electroplating, and gold with a thickness of 1 μm or less is formed by electroless plating or electroplating. That is, -C is performed for only electric Au plating or for a combination of electric gold plating and electroless gold plating. but,
When applying thick partial gold using the Tomura plating method,
In order to provide a conductive part, a conductive tape was attached, and an insulating tape was applied to mask the unnecessary parts of the Au plating. This method has the following problems.

(1) The bonding tape peels off, and abnormal deposits occur frequently due to embedding of the metal paste, and unnecessary parts are also deposited.

(2) Mass production is poor and yields are low.

(5) Ceramic substrates with high-definition buttons have
Difficult to apply.

(4) If a thermal electrolytic gold plating step is included in the process, discoloration of the plating will eventually occur.

In addition, the following problems arose with the Pro-7 itself and the tamping liquid used in each process.

(5) Abnormal precipitation and uneven precipitation occurred during electroless Ni plating on W metallization.

(6) Adhesion between the plating layers was poor, causing blistering and peeling.

(7) In the above Pro-7, Guibond, Wirebond,
The properties such as solder wettability could not be fully satisfied.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gold coating method for partially thickening a ceramic substrate having a high-definition pattern, which eliminates the above-mentioned drawbacks of the prior art, has good mass productivity, and has a high yield.

[Summary of the invention]

In the present invention, after forming a nickle layer by electroless nickle plating on the base tungsten or molybdenum of a silver substrate, a layer of 1 to 5 μm in thickness is formed by electroplating with gold and a counterfeit layer of 0.05 to 0.3 μm. are formed in the same plane. In that case, since electroplating is used, an s-conductive paste for establishing electrical conductivity from the outside must be printed. Further, since thick gold and counterfeit metal are applied alternately, a resist is formed by printing to mask one part, and is removed after electroplating. That is, the features of the present invention are: a first electroless nickel plating step in which a first layer of nickel is formed on the base tungsten or molybdenum; a second layer of nickel is selectively formed on the first layer; 4'[4'[
2nd step of applying paste/resist; 3rd step of electrolytic Ni plating to form only the necessary parts on the first layer with the 2nd Ni layer: 1 to 5 μm thick coating on the 2nd layer of Ni is the entire 3rd step. I say no
Fourth step of 1-atm Au plating formed by ILwu plating: the conductive paste, the conductive paste for removing the resist/
Resist stripping fifth step; 4-conductor paste/4-conductor paste to cover the external leads and unnecessary parts thereof with an insulator to selectively form a counterfeit second layer on the first layer by electroplating;
Sixth step of resist coating; coat only the necessary areas on the first layer with 0.
2411. Electric Au plating seventh step of forming a second layer of counterfeit gold of 05 to 0.3 μm; conductive paste for removing a conductive paste, a conductive paste for removing a resist, an eighth step for removing a conductive paste/resist for removing a resist; and a ninth heat treatment step for heat-treating the plated metal layer in an inert gas.

In the above, the first step of non-oxidizing Ni plating is to remove the tungsten or molybdenum of the heptadramic substrate by alkali treatment, and then to remove the tungsten or molybdenum using a palladium activation solution using triethylenetetramine as a complexing agent. This is a step in which palladium metal is deposited and then a first layer of Nl is formed by non-reactive NI plating. Among these, palladium activation has an extremely important function, and if its performance is inferior,
Deposition abnormalities (uneven deposition, deposition outside the pattern, etc.) occur in electroless NI plating. The Pd activation solution of the present invention has high performance and can prevent abnormal precipitation. 4. In the second step of applying conductive paste/resist, a conductive paste containing silver or copper foil and a resist containing polyester resin are respectively applied by printing and heated at a temperature of 60 to 100°0. death,
It is for drying. The conductive paste is used for conduction during electroplating, and it is necessary to cover it with a resist to prevent plating precipitation from occurring after application. In addition, it is necessary to cover the entire surface of the area that will not be electroplated in the next third and fourth steps with resist. Next, the third step of electric Ni plating is started.

This step aims to prevent plating stains that will occur in the subsequent fourth step and to improve the adhesion between electroless Ni and electrical Au. In particular, the flatness of tungsten and molybdenum metallization is poor, and there may be no problem.
Since there are pinholes in the plating film, it is easy for the plating solution to penetrate and cause stains. Electric Ni Meriki 3
By adding a thickness of ~10 μm, pinholes disappear. Subsequently, in the fourth step of thick electrical Au plating, a plating solution containing cyanide gold salt as a main component and adding a small amount of thallium salt is suitable. The crystals of the precipitated Au film are fine and the bonding properties are good. The thick gold plating is to satisfy the characteristics of die bonding, wire bonding, frit sealing, etc., and it is appropriate to provide the Au film thickness of about 1 to 5 μm.

Next, 4w, in the fifth step of removing the paste/resist,
Use Triclean as a peeling agent. The substrate formed above is immersed in trichlorethylene and irradiated with ultrasonic waves.

In particular, heating trichlorethylene is effective in improving its peelability, and boiling is preferable.

Through the above steps, a gold gland layer was formed.

On the other hand, the process of forming the fake gold film layer is performed after the sixth step.

Conductive paste/resist coating In the sixth step, external leads necessary for electrical Au plating to form a fake gold film are coated with a 411L base, and a resist, which is an insulator, is coated thereon. In this case, the thickness of the coated portion is mainly formed on the gold film. The method and conditions for applying the conductive paste and resist are the same as in the second step. Next, the thin layer is electrical Au.
Entering the seventh stage of matsuki. The plating solution is exactly the same as in the fourth step. The Au film thickness is approximately 0.05 to 0.5 μm, and soldering is performed to ensure the following characteristics. If Au becomes thicker than this, the alloy layer with the solder will not float and the dense layer will deteriorate. Then, in the eighth step of stripping off the conductive paste/resist, the conductive paste and resist are stripped off. The method is the same as the fifth step. As a result of the above, partial gold thickening was formed. In the final ninth step, heat treatment is performed.

This process improves adhesion by diffusion between the plating parts. It also maintains good solder wetness on the counterfeit gold film.

[Embodiments of the invention]

Hereinafter, explanation will be given according to examples.

EXAMPLE OF THE INVENTION A slam-shaped ceramic substrate shown in FIG. 1 was used. The inner circular pad must be made of counterfeit gold only, and the outer square bat must be made of thick gold.

The circular bats and the square pads are electrically connected through their inner layers, but there is no communication from one circular bat to the entire square bat. Therefore, it is necessary to cover the entire surface of the circular butt part with a conductive paste and conduct the electroplating from that part. Hereinafter, gold coating was carried out for partially thickening the ceramic substrate using the following steps 1 to 9.

In addition, the cross-sectional view in FIG. 2 shows a...ceramic substrate, 6
~J...The first to ninth steps are shown, respectively.

(1) First step of electroless Niracle plating First, the hexalamic substrate was immersed in an alkaline degreasing solution to degrease the tungsten metallization.

fa) Degreasing solution composition and conditions NtLOH: 100yL, solution temperature: 60-90°C Immersion time: 10-20 minutes Then, after washing with water, it was immersed in a palladium activation solution.

(8) Composition and Conditions of Palladium Activation Solution After forming Ni plating, it was washed with water and dried with a dryer.

(2) Conductive Paste/Resist Application Second Step Using a printing mask (Tetron 200 Metshi), A4 paste was printed and dried.

Then, using the same mask as above, it was printed and dried.

(3) Third step of "tIL 1'Ji plating" Subsequently, the above sample was subjected to alkaline degreasing, hydrochloric acid treatment, and electroplating with Ni.

'1Ni plating liquid composition and conditions (4) Thick plating is the fourth step of electric Au plating Then, it was washed with water and plated with electric Au plating.

After plating, the sample was washed with water and dried with a dryer. (5) Conductive paste/resist peeling Fifth step The above sample was immersed in Tri-Crezi and irradiated with ultrasonic waves.

Through the above process, gold plating was formed.

(6) Conductive paste/resist Sixth step Conductive paste, resist and printing method using 1. Drying conditions are the same as in the second step.

(7) Thin/electric Au plating Seventh step The plating solution and conditions are the same as the fourth step.

However, the plating time was 0.5 minutes and the film thickness was 0.1 μm. Washed with water and dried.

181 4% paste/resist stripping Eighth step This was carried out in exactly the same manner as the fifth step.

Through the above process, a thick layer of gold-counterfeit metal was formed on the ceramic substrate.

(9) Heat Treatment Ninth Step The above sample was heat treated in methane for 460'0110 minutes.

〔Effect of the invention〕

As described above, according to the present invention, this was not possible with the prior art. We have created a process that can be applied to ceramic substrates with Mi@ patterns, has good mass productivity, and has a high yield. In addition, the film quality was also sufficient to improve bonding properties, soldering properties, and other properties.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the shape of a metallized button on a ceramic substrate, and FIG. 2 is an explanatory diagram showing a gold coating process for partially thickening the ceramic substrate of the present invention. 1-1...Tungsten metallized square pad 1-2...
...Tungsten metallized circular pad 2-1...Arm metallization 2-2...None/IIL solution Ni layer 2-3...Conductive paste 2-4...Resist 2-5...Electrical Ni Layer 2-6... Thickness is gold layer 1 2-7... Conductive paste 2-8... Resist 2-9... Gambling is gold layer. Figure 1

Claims (1)

[Claims] 1. In the gold coating method, partial thickness deposition on a lamic substrate is the first step of electroless niracle plating, which forms a first layer of niracle on the base tungsten or molybdenum;
Selectively form the second layer of Niracle on the layer and the third layer of Kintetsu by electroplating, and apply 24 conductive paste/resist at least on top of the necessary external leads and at least the top with an insulator. Process: Electrolytic NI plating to form only the necessary parts on the first layer with the second layer of Niracle.Third step: Three layers of 1 to 5 μm thick are formed on the second layer of Niracle by electrolytic gold plating. A fourth step of electrolytic gold plating to form; a fifth step of stripping the 4-electroconductive paste/resist to remove the 4-electroconductive paste and resist;
A sixth step of applying a conductive paste/resist to cover external leads and at least the top thereof with an insulator necessary for selectively forming a second thin gold layer on the first layer by plating; 0.05-0.5μ only on the necessary parts on the layer! 7th step of electrolytic gold plating to remove nO thin gold 2nd counterfeit; 8th step of conductive paste/resist peeling to remove the conductive paste and resist; heat treatment to heat the plated metal layer in an inert gas The partial thickness coating on the ceramic substrate is a gold coating method, which is characterized by including the ninth step.