JPH06270571A - Metal mask - Google Patents

Abstract

PURPOSE:To achieve improvement of hardness of a metal mask, the highly accurate printing of cream solder due to metal squeezing and the enhancement of the life of the metal mask and preventing the clogging of the aperture parts of the metal mask, in the metal mask used when an electronic part is mounted on the printed wiring board of welfare electronic machinery. CONSTITUTION:Potential difference is applied across a nickel-cobalt plating soln. 1 having 8-10wt.% of cobalt added thereto and a substrate 2 to precipitate a nickel-cobalt alloy on the substrate 2 to obtain a metal mask having hardness equal to that of a stainless steel mask. A silicon molecule is chemically adsorbed on the surface of the nickel-cobalt alloy 3 to increase the contact angle of the surface of the alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the miniaturization and weight reduction of consumer electronic devices and the miniaturization of components on printed wiring boards.
The present invention relates to a metal mask used for surface mounting and used for printing cream solder during mounting.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size and weight,
Printed wiring boards and electronic components are also being miniaturized and highly densified, and are being surface-mounted. Therefore, when mounting an electronic component, a metal mask is necessary to supply an appropriate amount of cream solder to the printed wiring board only in a necessary portion.

Since the opening of the metal mask becomes smaller along with the miniaturization of electronic parts, the substrate 2 to be an electrode is formed by attaching a resist to the nickel plating solution 6 as shown in FIG. Then, by applying a potential difference between the nickel plating solution 6 and the substrate 2 by the voltage source 4, the nickel metal 7 is grown on the substrate 2, the current density is adjusted, and the nickel metal 7 having a target thickness is produced.
It was used as a metal mask. FIG. 6 shows a sectional view of the solder printing state.

The cream solder 11 is applied to the metal mask 8, and the squeegee 9 pushes the cream solder 11 into the opening of the metal mask 8 to print the cream solder 11 on the printed wiring board 10.

[0005]

However, since the material of the metal mask as described above is nickel,
The surface hardness of the material made by etching is lower than that of the metal mask made of stainless steel, and when cream solder is printed using a metal squeegee made of phosphor bronze, the surface of the metal mask is scraped and the corners near the opening are scraped. As a result, good solder printing becomes impossible and the life of the metal mask is shortened.

Further, when printing is performed by using a urethane squeegee made of rubber having a high hardness instead of a metal squeegee in consideration of life, there is a drawback that the printed cream solder is scraped off by the urethane squeegee.

Further, when the components mounted on the printed wiring board are made smaller and the pitch is made finer, the openings of the metal mask become thinner, and the solder mask causes the openings of the metal mask to be clogged.

In consideration of the above points, the present invention has an object to improve the surface hardness of the metal mask so that the metal squeegee can be used, and to prolong the life of the metal mask. Further, the present invention provides a metal mask which solves clogging of the opening by surface-treating the metal mask.

[0009]

In order to solve the above problems, the present invention provides a nickel-cobalt alloy by adding 8 to 10% by weight of cobalt to a nickel plating solution when a metal mask is produced by plating. The surface hardness of the metal mask is increased by producing the metal mask with.

Further, by adhering silicon-based molecules to the surface of the metal mask, the contact angle of the surface is increased,
It prevents the adhesion of cream solder.

[0011]

The metal mask of the present invention has a surface hardness equivalent to that of a stainless steel plate, has a long life, can print cream solder with a metal squeegee, and controls the amount of printed solder with good reproducibility. be able to.

According to the surface-treated metal mask, the cream solder can be printed on the printed wiring board without clogging because the cream solder does not adhere to the opening of the metal mask.

[0013]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of a method for producing a metal mask of the present invention. Nickel-cobalt plating solution 1
When the substrate 2 is placed in the container in which is placed and a potential difference is applied between the nickel-cobalt plating solution 1 and the substrate 2 by the voltage source 4,
The nickel-cobalt alloy 3 is deposited on the substrate 2. The voltage, current and time of the voltage source 4 are adjusted to deposit the nickel-cobalt alloy 3 to the target thickness.

After the deposition is completed, the nickel-cobalt alloy 3 is removed from the substrate 2, a frame is attached, and the metal mask is used for cream solder printing.

By using the nickel-cobalt plating solution 1 in which cobalt is added to the nickel plating solution, the metal mask can be made of nickel-cobalt alloy instead of nickel metal. The hardness of the nickel-cobalt alloy 3 changes by changing the amount of cobalt added to the nickel plating solution. As an example, the result of measuring Vickers hardness is shown in FIG.

In the graph, the horizontal axis represents the amount of cobalt added and the vertical axis represents Vickers hardness. From the graph, the Vickers hardness increases as the amount of cobalt added increases. The higher the Vickers hardness is, the longer the life of the metal mask is, but the shape of the opening becomes unstable in solder printing. As an example, FIG. 3 shows the cross-sectional shape of the openings with 9 wt% and 14 wt% cobalt added.

FIG. 3 (b) is a view showing the sectional shape of the opening of the metal mask to which 14% by weight of cobalt is added. When the cream solder is printed with R on the printed wiring board side, the metal mask is used. The cream solder adheres to the printed wiring board side of the above or shifts from the copper foil 12, resulting in a solder bridge or other defective solder.

The opening cross-sectional shape shown in FIG. 3 (a) allows the amount of solder to be printed on the copper foil 12 with high accuracy without a straight cross-sectioned portion.

In this embodiment, the printability of cream solder,
Vickers hardness of stainless steel metal mask (340H
In consideration of V), the nickel-cobalt alloy is produced with the amount of cobalt added of 8 to 10%.

As described above, according to this embodiment, the metal mask is prepared by using the nickel-cobalt plating solution 1 in which 8 to 10% by weight of cobalt is added to the plating solution.
The surface hardness can be made equivalent to that of the stainless steel plate, printing with a metal squeegee is possible, highly accurate solder printing is possible, and the life can be extended.

(Embodiment 2) Another embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a view showing an example in which silicon molecules are adsorbed on the metal mask of the present invention. In the past, when printing cream solder with a metal mask, clogging was caused by the cream solder when the opening of the metal mask became small.

In this embodiment, nickel-cobalt alloy 3
The contact angle of the surface of the nickel-cobalt alloy 3 can be increased by adsorbing the silicon-based molecule 5 such as silicon or fluorine by chemical treatment on the surface of the nickel-cobalt alloy 3 and the cream solder is printed using the nickel-cobalt alloy 3 as a metal mask. In doing so, the opening of the metal mask will not be clogged with cream solder.

As described above, according to this embodiment, by adsorbing the silicon-based molecules 5 on the surface of the metal mask, the contact angle of the surface is increased, and the opening of the metal mask is prevented from being clogged with cream solder. can do.

[0026]

As described above, in the metal mask according to the present invention, it is possible to prolong the life of the metal mask by producing the metal mask with the plating solution containing 8 to 10% by weight of cobalt. Highly accurate cream solder printing with metal squeegee is possible.

By adsorbing silicon-based molecules on the surface of the metal mask by a chemical treatment, the surface contact angle of the metal mask can be increased and clogging of the opening of the metal mask due to cream solder can be prevented. Is possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a nickel-cobalt alloy deposition method used for a metal mask according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the cobalt content and Vickers hardness of a metal mask that is an embodiment of the present invention.

FIG. 3 (a) is an embodiment of the present invention in which the amount of cobalt is 9
Cross-sectional view of metal mask added with wt% (b) Cobalt amount which is one embodiment of the present invention is 14 wt%
Cross section of the added metal mask

FIG. 4 is a cross-sectional view of a metal mask on which silicon-based molecules are adsorbed, which is an embodiment of the present invention.

FIG. 5 is a schematic view of a nickel metal deposition method used in a conventional metal mask.

FIG. 6 is a sectional view of cream solder printing using a conventional metal mask.

[Explanation of symbols]

 1 Nickel-Cobalt Plating Solution 2 Substrate 3 Nickel-Cobalt Alloy 4 Voltage Source 5 Silicon Molecule 6 Nickel Plating Solution 7 Nickel Metal 8 Metal Mask 9 Squeegee 10 Printed Wiring Board 11 Cream Solder 12 Copper Foil

Claims (2)

[Claims] 1. A metal mask characterized by being prepared from a nickel-cobalt alloy by adding cobalt to a plating solution of 8 to 10% by weight. 2. The metal mask according to claim 1, wherein silicon-based molecules are adsorbed on the front surface, the back surface, and the opening of the nickel-cobalt alloy metal mask.