JPS58185794A - Activated palladium solution - Google Patents

Abstract

PURPOSE:To obtain an activated Pd soln. preventing excess deposition and defective adhesion, by adding a specified complexing agent to an activated Pd soln. contg. a water-soluble palladium salt and an alkali metallic hydroxide. CONSTITUTION:An activated Pd soln. of >=about 8pH is prepared by adding an alkali metallic hydroxide such as sodium hydroxide as a pH regulator to a soln. of a water-soluble palladium salt such as palladium chloride having about 5X10<-5>-10<-2>mol/l concn. expressed in terms of Pd<2+>. To the activated Pd soln. is added >=1 kind of complexing agent selected from ethylenediamine, propylenediamine and butylenediamine. The performance and reliability of electronic parts such as a tuner can be enhanced by using the resulting activated Pd soln.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an effective active material for attaching palladium to a batten made of metal such as tungsten or molybdenum on a ceramic substrate such as a tuner or an IC package using an electrochemical substitution reaction. This relates to chemical treatment liquids.

For the conductor pattern of the ceramic substrate, metals such as tungsten and molybdenum with good heat resistance and low thermal shrinkage are used.

Therefore, the lifting weight of NiSAu plating performed in the subsequent process, and the weight of palladium. Pentasexuality is an essential condition. That is, plating is impossible without activation of palladium.

It is also useful as a metal plating for palladium activation.

Conventionally, there are two types of activation: microtype and alkaline type. Banoteigu is a bath made of palladium chloride plus Ml).
However, in the case of chelating agents such as TA, cracks occurred between the tanks during the nickel plating process in the subsequent process.

That is, in the former bath, the surface of tungsten is oxidized to make it strongly acidic, and I-sound with palladium occurs.
, 2Y Kel plating caused uneven precipitation and poor adhesion.

On the other hand, with alkaline type gDT & bath, there was a problem that excessive precipitation occurred, palladium was deposited outside the baton, and nickel plating was deposited all over the ceramic. The purpose is to eliminate the shortcomings of -1° activation and to provide palladium activation*V which allows for good marking with good writeability without adhering to the outside of the ceramic substrate.

We investigated the matter thoroughly and found the following.

In other words, when the liquid Pl is lower than 6, tungsten becomes (1
), and if it is nobler than 6, the reaction of formula (2) W +5820 = WO3+6H++66--(1
)W +4H20=WO"r+8H++6e -(
2) occurs, and tungstic acid is formed.9, commonly understood.

Moreover, even if it is oxidized in the air and forms an oxide film, it is generally understood that at a pH higher than 6, the reaction of formula (3) occurs.

WOa 10HzO=WO"4 +2H" -(3)
-10,000 Since palladium has a yellower potential than tungsten, gold-dip palladium is deposited using equation (4). That is, a 11(Il! reaction occurs).

Pd”+26 − Pd (4) Therefore,
When the VPLPH is lower than 6, Kongo palladium will be deposited on the tungsten oxide film, and the density of the plating will be compromised and uneven deposition will occur.

Therefore, the alkaline type of palladium-activated V is better than the kneaded type. Furthermore, the alkaline type dissolves the cough that has already occurred, making it even more effective. On the other hand, palladium (
Although it is necessary to precipitate gold-palladium using the formula 4), this is only possible when the gold-palladium is present as palladium ions. Palladium ions exist only when the pH is lower than 1 when no chelating agent is present, and when the pH is lower than 1, hydrolysis occurs and colloids are produced (5).
Palladium oxide is formed by the reaction of formula (6).

Pd"+ H2O-PdO+2)1"-(s+)'
d” + 82(J −PdO2+4H+2e
-(61 Here, palladium is mixed between two parts. One is the palladium oxide produced, and this is nickel plating in the next process, which causes fine 1 #4 fine and uneven precipitation. One of the factors is the colloidal product of palladium, which is highly adsorbent and therefore adheres to areas other than the tungsten batten on the ceramic substrate.

For this reason, excessive precipitation of plating occurs. Therefore, in order to solve these problems, various chelating agents are added to the palladium accommodation solution.

The present invention is based on the discovery of an M-effective chelating agent for preventing the above-mentioned problems.

That is, conventional alkaline type activating liquids cannot completely solve the above problems.

The present invention will be described in detail below. - As the water-soluble palladium salt, palladium chloride, palladium sulfate, palladium nitrate, etc. can be used, but palladium chloride is mainly used for economical reasons.

Since the concentration of palladium salt is low, it is necessary to keep the concentration as low as possible.However, if it is low, palladium will be difficult to precipitate, causing plating, non-precipitation, and uneven precipitation.

The quality encountered is 5 x 10-5 to 10-22 as Pd.
+MO4/l.

The alkali metal hydroxide group is a PH adjusting agent, and sodium hydroxide, potassium hydroxide, and lithium hydroxide can be used, but sodium hydroxide, which is inexpensive, is mainly used. P of activation liquid
As shown above, H is preferably in the alkaline region, and it is better to raise the pH above 18μ from the viewpoint of causing a chelate reaction with the chelating agent.

The chelating agent that is important in the present invention is ethylenediamine (N
l2 0H20H2Nl2), probile/diamine (N
l2-CH2CHN) (20Ha) Butylene diamine (
Nl2 0H20HNl2 0H2CH2) and is a derivative of ethylenediamine.

These chelating agents cause a reaction of formula (7) with palladium ions (Pd2±4 coordination) to form a stable planar structure.

Pd”+2L ÷ Pd”L2 β2 = 2
6 (7) Here, β2 is larger than the chelating agent used in Japan (EDTA, glycine) as shown from the value of the chelate formation constant β2.

Therefore, hydrolysis of palladium ions can be prevented and the life of the liquid can be extended.

Examples will be explained below.

The sample for evaluation is shown in Figure 1. This sample has a tungsten metallized layer on a ceramic substrate in a positive shape (2,5
The objective was to reliably evaluate the degree of palladium adhesion, that is, the degree of uneven precipitation of plating.

Figure 2 shows the steps up to plating a ceramic substrate sample. In addition, the experimental tank was filled with liquids required for each process in a 500° beer pressure vessel, and the temperature was adjusted using a water path. Examples, that is, the evaluation results of the palladium activation liquid obtained with each composition are shown in Table 1.
This was confirmed by observation at Sakaki.

814 raw, Qi 7"τ-13<I%tlLζ ○ Qi two te 1 well both necks .

First, Examples 1 to 4, which will be explained from the examples of the present invention, are those in which the palladium ion rock f was used. The drop in palladium io causes the plating to precipitate and become warmer. That is, it can be seen that the km reaction with tungsten is difficult to occur.

Therefore, it is appropriate for the palladium to be at least 10 -6 M0t/. Examples 5 and 6 show examples in which palladium nitrate and palladium sulfate can be used in addition to palladium chloride as the palladium salt.

Further, Examples 7 and 8 are examples in which propylene diamine and butylene diamine can also be used as chelating agents, which are substituted derivatives of ethylene diamine and have almost the same production constant as palladium ion. In Examples 9 to 12, the molar ratio of palladium ion and chelating agent was changed.

When 2=1, complete chelation is not achieved, resulting in hydrolysis and excessive precipitation. Therefore, at least 1=1 or more is required.

Examples 13 to 16 are examples in which the liquid pH value was changed.

When the pH is lower than 7, uneven precipitation occurs. This is because the substitution reaction with tungsten has become difficult to occur. On the other hand, in the conventional examples of Examples 17 to 19, El)'1'A
With 1 glycine, there was excessive precipitation, and with hydrochloric acid, which is an acidic type, poor adhesion occurred.In addition, the present invention solves the conventional problems of excessive precipitation, uneven precipitation, and poor adhesion of plating. This has the effect of significantly improving the performance and reliability of electronic components such as tuners.

[Brief explanation of drawings]

Figure 1 shows a model sample of a ceramic substrate, Figure 2
The figure is a block diagram showing the plating process. 1...Tungsten metallized layer 2...
・Alumina insulation layer

Claims (1)

[Claims] In the palladium activation solution containing water-bathable palladium salt and alkali metal hydroxide, 1&
A palladium activation liquid characterized by the addition of a complexing agent of a class or higher level.