JPH0747727Y2 - Measuring device for oxide film on metal surface - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the amount of an oxide film on a metal surface and determining the degree of oxidation on the metal surface.

The present invention particularly relates to an apparatus for determining the degree of oxidation of the copper surface of a circuit board for soldering an electronic component to a circuit board of various electronic devices and predicting the solderability. And the applicant's earlier application for Japanese Patent Application No. 3
The present invention relates to an apparatus for measuring an oxide film by the method of Japanese Patent Application No. 298413.

[0003]

2. Description of the Related Art In recent years, in various electronic devices, electronic parts have been mounted on a fine circuit pattern with high density and soldered. In such a circuit board, it is necessary to surely wet the surface of the circuit pattern with solder, but if the surface of the copper forming the circuit pattern is oxidized, the wettability of the copper surface with solder is poor. And the solderability deteriorates.

On the other hand, it is inevitable that the circuit board is left in the air for a certain period of time after the manufacture of the circuit board and before mounting the electronic parts, during which the copper surface of the circuit pattern is oxidized.

It has been attempted to delay the oxidation by forming an anti-oxidation coating, but this is not very complete and it is preferable to know the degree of oxidation of the copper surface before soldering.

From this point of view, the applicant, as a method for measuring an oxide film on a metal surface, uses a metal material as a cathode and sweeps twice by potential-controlled electrolysis to electrolytically reduce the metal material,
A method for judging the degree of oxidation of a metal material from the difference in the amount of electricity in the two sweeps was invented, and Japanese Patent Application No. 3-29841.
Filed as No. 3.

Since this method can determine the degree of oxidation in a short time and corrects the effects of hydrogen generation and dissolved oxygen during electrolysis, the oxide film can be accurately determined by a simple operation. This is an extremely excellent method.

[0008]

By the way, as a concrete method in the specification of the above-mentioned application, a method of subjecting a test piece of a metal material to measurement and dipping this test piece in an electrolytic solution to electrolytic reduction is described. However, it is not always appropriate as a method for directly determining the degree of oxidation of the surface of the circuit board of the electronic device as described above.

That is, if the above method is applied to the circuit board, a large circuit board must be immersed in the electrolytic solution as it is, the measuring equipment becomes large and the operation becomes complicated.

Further, depending on the method of dipping in the electrolytic solution and the circuit pattern, it is difficult to make the area of the portion of the circuit board to be tested constant, and it is difficult to obtain an accurate measured value.

The present invention has been made in view of the above circumstances, and an oxide film can be easily measured on a circuit board, and the area is always constant regardless of the size of the circuit board or the circuit pattern. It is an object of the present invention to provide a device capable of measuring and measuring an accurate value.

[0012]

Therefore, the present invention provides a sealed internal
At the bottom of the body that encloses the electrolytic solution in the internal space,
Can be held by its surface tension and has a predetermined surface
A small opening having a product is formed, the counter electrode and the reference electrode are immersed in the electrolytic solution by penetrating the vessel wall of the body, and a supply pipe for supplying the electrolytic solution from the outside through the vessel wall of the body is attached. A device for measuring an oxide film on a metal surface, characterized in that

The present invention is suitable as a device for measuring an oxide film on the surface of metallic copper of a circuit board of an electronic device, but the measurable metal in the present invention is not limited to copper, but chromium, iron, It is also applicable to metals such as cobalt, nickel, zinc, silver, cadmium, indium, tin, gold and lead.

Further, it is not limited to pure metal, but tin-
It is also applicable to alloys such as lead alloy (solder), copper-zinc alloy (brass), nickel-iron alloy (permalloy), tin-zinc alloy, nickel-cobalt alloy.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a body. The container body 1 is formed by sealing an upper portion of a cylindrical body 2 made of an insulating material such as glass with a stopper 3, and a lower portion of the cylindrical body 2 is narrowed down to form a small diameter portion 4. A small opening 5 is formed at the lower end of 4.

The small opening 5 is an opening having a predetermined area, and it is suitable that the small opening 5 has a circular shape with a diameter of about 3 to 6 mm. And the inner space of the body 1 is sealed,
Only the small opening 5 communicates with the outside.

A flange 6 is formed on the outer periphery of the lower end of the small diameter portion 4, and a packing 7 made of an elastic material such as rubber is attached to the lower surface of the flange 6.

An electrolytic solution 8 is enclosed in the body 1,
The small opening 5 is held by the surface tension of the electrolytic solution 8 and the electrolytic solution 8 does not flow out of the container 1. In addition, the small opening 5 does not allow the electrolytic solution 8 to flow out of the body 1,
It must be large enough to be retained by surface tension.

The electrolytic solution 8 is a solution of a supporting electrolyte dissolved in water or an organic solvent, and examples of the supporting electrolyte include lithium chloride, sodium chloride, potassium chloride and lithium bromide.
Sodium bromide, lithium hydroxide, sodium hydroxide,
Potassium hydroxide, lithium perchlorate, sodium perchlorate, sodium acetate, ammonia and the like can be used. Moreover, these can also be mixed and used.

Although the concentration of the supporting electrolyte varies depending on the measuring conditions, it is often appropriate that the concentration is about 0.1 to 1M.

Reference numeral 9 is a counter electrode, and 10 is a reference electrode, each of which is attached by penetrating the stopper 3, and the electrolyte 8
Is soaked in. Reference numeral 11 is a supply pipe for the electrolytic solution 8, which is attached through the stopper 3 and is connected to a pump (not shown) via a tube 12.

A circuit board 13 has a circuit pattern 15 made of metallic copper on the surface of a plastic base 14. 16 is a working electrode used with the device of the present invention.

[0024]

Next, the method of using the present invention will be described.

FIG. 2 shows a circuit board 1 using the device of the present invention.
3 shows a state in which an oxide film on the copper surface of the circuit pattern 15 of No. 3 is measured.

A potentiostat 17 includes a voltage control circuit 18 and a current measuring circuit 19.

The voltage control circuit 18 is connected to the voltage sweep circuit 20 and controls the potential difference between the reference electrode 10 and the working electrode 16 by the voltage swept by the voltage sweep circuit 20.

The voltage sweep circuit 20 changes the voltage smoothly by using a personal computer or the like, and the potential of the working electrode 16 with respect to the reference electrode 10 is −.
It is designed to sweep from 0.4V to 2.0V.

The current measuring circuit 19 measures the current flowing between the counter electrode 9 and the working electrode 16, sends the measurement result to the current display circuit 21, and causes the display device 22 such as a display or printer to It is designed to display the change in current associated with the voltage sweep.

In order to use the device of the present invention, first, the plug 3 is removed from the cylindrical body 2, the small opening 5 is closed, and the electrolytic solution 8 is injected into the cylindrical body 2, and the counter electrode 9 and the reference electrode 10 are filled. And supply pipe 11
The cylindrical body 2 is closed by the plug 3 attached with, and the small opening 5 is opened. The device of the present invention is now ready for use.

Then, a pump (not shown) is operated to supply the electrolytic solution 8 from the supply pipe 11 through the tube 12.
The liquid is gradually injected into the container 1 so that the electrolytic solution 8 slightly protrudes from the small opening 5 due to surface tension as shown in FIG.

In this state, the circuit board 13 is positioned below the body 1 and the body 1 is moved downward to press the packing 7 against the surface of the circuit pattern 15.

On the other hand, the working electrode 16 is brought into contact with an appropriate portion of the circuit pattern 15 which is electrically connected to the portion where the body 1 is pressed.

As a result, the circuit pattern 15 has the small opening 5
Contacting the electrolyte 8 only within the area of the
6 is connected to 6 and participates in an electrolytic reaction as a cathode facing the counter electrode 9 and the reference electrode 10.

In this state, the voltage sweep circuit 20 is operated to sweep the potential of the working electrode 16 from -0.4V to -2.0V by using the working electrode 16 as a cathode and the reference electrode 10 as an anode. As a result, the oxide on the surface of the copper is electrolytically reduced in the portion of the circuit pattern 15 that is in contact with the electrolytic solution 8.

The change in the current between the counter electrode 9 and the working electrode 16 caused by the electrolytic reduction is measured by the current measuring circuit 19, and the result is displayed by the current display circuit 21 on the display device 2.
Display by 2.

Next, the potential of the working electrode 16 is returned to -0.4 V, and again swept from -0.4 V to -2.0 V, and the change in the current between the counter electrode 9 and the working electrode 16 is measured by the current measuring circuit 19.
Is measured and displayed on the display device 22.

Since the oxide film on the copper surface in the circuit pattern 15 is completely reduced at the first sweep,
During the second sweep, electrolytic reduction of copper oxide does not occur, but only electric current is generated due to the generation of hydrogen gas accompanying the electrolysis and the influence of dissolved oxygen.

Therefore, by obtaining the difference in the change in current due to the two voltage sweeps, the effect of hydrogen gas generation and dissolved oxygen is corrected and only the quantity of electricity required for the electrolytic reduction of oxides is calculated. be able to. Thereby, the amount of oxide on the surface of the circuit pattern 15 within the area of the small opening 5 can be measured, and the degree of oxidation of the surface of the circuit pattern 15 can be accurately determined.

When determining the degree of oxidation of the surface of the circuit pattern 15 on the circuit board 13 according to the present invention, it is possible to measure a part of a pattern forming an actual circuit in an electronic device. Since the pattern may be damaged at the working electrode 16, the circuit board 13
It is preferable that a pattern for measuring an oxide film is formed in a part of the above, and the pattern is used for measurement.

Further, at unnecessary portions on the circuit board 13,
It is also preferable to provide a substrate portion that can be easily removed and to form a pattern for measuring an oxide film thereon. By doing so, the board portion is cut off before mounting the electronic component on the circuit board, and at the same time as the body portion is supplied to the component mounting step, the oxide film is removed only on the cut board portion. Can be measured.

[0042]

According to the present invention, the electrolytic solution 8 is enclosed in the body 1, and the counter electrode 9 and the reference electrode 10 are immersed in the electrolytic solution 8. Therefore, the small opening 5 is formed in the circuit board 13. By pressing on the circuit pattern 15 of No. 3, an electrolytic circuit is immediately formed with the circuit pattern 15 as a cathode and facing the counter electrode 9 and the reference electrode 10 through the electrolytic solution 8, and the oxide film is measured by voltage-controlled electrolysis. be able to.

The apparatus itself is compact, and it is not necessary to suspend the circuit board 13 itself in the electrolytic cell.
The measurement can be performed simply by pressing the body 1 against the circuit pattern 15 and bringing it into conduction with the working electrode 16, and the operation is extremely simple.

Further, since only the portion corresponding to the inside of the small opening 5 on the surface of the circuit pattern 15 comes into contact with the electrolytic solution 8 and is subjected to electrolytic reduction, the measured value is the size of the circuit board 13 or the shape of the circuit pattern 15. It is possible to always measure the oxide within a certain area without being affected by the above, and to obtain accurate results.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view of an embodiment of the device of the present invention.

FIG. 2 is a conceptual diagram showing a usage state of the device of the present invention.

[Explanation of symbols]

 1 Body 5 Small Opening 8 Electrolyte 9 Counter Electrode 10 Reference Electrode 11 Supply Pipe

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Atsushi Saito 1-2-1 Tsuruga, Nada-ku, Kobe-shi, Hyogo Inside Kobe University (72) Sadayuki Himeno 1-1-2-1 Tsuruko, Nada-ku, Kobe, Hyogo Kobe University (72) Inventor Toshiyuki Osaka 1-2-1, Tsuruga, Nada-ku, Kobe-shi, Hyogo Prefecture Kobe University (72) Inventor Hajime Katano 1-2-1, Tsurukko, Nada-ku, Kobe City, Hyogo Prefecture Kobe University (56) Reference Reference JP-A-63-285457 (JP, A) JP-A-1-156656 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. An electrolytic solution (8) is sealed in a sealed internal space.
At the bottom of the container (1), put the electrolyte (8) inside.
It can be held by surface tension and has a predetermined area.
To form a small opening (5) through which the counter electrode (9) and the reference electrode (1) penetrate the electrolytic solution (8) through the vessel wall of the vessel (1).
0) is immersed, and a supply pipe (11) for supplying an electrolytic solution (8) from the outside through the container wall of the container (1) is attached to the device for measuring an oxide film on a metal surface.