Printing method and printing apparatus

Details Printing method and printing apparatus Printing method and printing apparatus

2000-08-30

2002-09-24

Funk, Stephen R. (Department: 2854)

Printing

Stenciling

Traveling-inker machines

C101S129000

Reexamination Certificate

active

06453811

ABSTRACT:

The present invention relates to a printing method and a printing apparatus for filling a printing material into openings of a printing face of a body to be printed, and more particularly, to a printing method and a printing apparatus for applying paste, and to an apparatus for manufacturing circuit boards for electronic devices, etc.
BACKGROUND ART
Recently, circuit boards have been changed from single-face boards having circuits formed on one face, to double-face boards and multilayer circuit boards so as to achieve compact and high-performance apparatuses. Many of the boards adopted at present are advanced multilayered ones. In the meantime, a printing technique using a filling head, i.e., a squeegee is employed in order to press and fill a paste into openings such as via holes or through holes in these circuit boards, or to press and fill the paste into openings of a metal mask to form circuits on the board. A lot of conditions are involved in the printing technique, for instance, hardness of the squeegee, angle of the squeegee to a printing face, pressure of the squeegee to the printing face, filling speed of the squeegee to the openings of the printing face, etc. Even a slight error in setting of the conditions adversely influences the quality of printing films, and therefore the set conditions are adjusted based on experiences on the production line, thereby improving yields in the paste filling process and quality of products.
Some adaptations are also made to the aforementioned squeegee in the filling process. For example, the squeegee is improved in shape to have a flat, a sharp, or a curved contact face as the printing face. In one arrangement, a heater is built in the squeegee to heat the squeegee itself to a fixed temperature, thereby lowering a viscosity of the paste and increasing filling efficiency for the paste to the openings of the printing face.
The viscosity of the paste increases in proportion to an operating time of the squeegee. For stabilizing the viscosity, therefore, the paste is exchanged at a fixed time interval, or an organic solvent is added to the paste to adjust the viscosity.
Meanwhile, the amount of the paste filled into the openings, e.g., via holes and through holes, etc. or the openings of the metal mask is controlled and stabilized by filling the paste up to a surface of the openings.
An example of the conventional circuit board-manufacturing method will be described with reference to
FIGS. 13A
,
13
B.
FIGS. 13A
,
13
B respectively represent examples of a manufacturing method and a manufacturing apparatus for circuit boards in the filling process according to the conventional art.
In
FIGS. 13A
,
13
B,
300
denotes a metal mask placed on a base material
301
.
303
and
305
denote squeegees which move on the metal mask
300
while keeping touch with the metal mask
300
.
304
denotes a paste, and
302
denotes a stage. The base material
301
is disposed in touch with on the stage
302
. The metal mask
300
is arranged with a slight space above the base material
301
, onto which the paste
304
is supplied. The squeegees
303
,
305
located above the metal mask
300
can move in an up/down direction and in a printing direction of the squeegees
303
,
305
.
The paste is filled in the thus-constructed apparatus in a process described herein. The base material
301
is first set at a predetermined position on the stage
302
. A through hole
301
a
formed in the base material
301
is registered with a hole
300
a
formed in the metal mask
300
, and the metal mask
300
is set above the base material
301
. The paste
304
is supplied onto the metal mask
300
. The squeegees
303
,
305
are lowered to hold the base material
301
by pressing a predetermined pressure on to the material
301
. Thereafter, the squeegees
303
,
305
are moved in the printing direction to move the paste
304
on the metal mask
300
, thereby printing onto the base material
301
. The paste
304
is pressed and filled in the through holes
301
a
formed in the base material
301
in this manner.
In the above paste filling process in the conventional art, a filling shape or the filling amount of the paste
304
is greatly changed even by mechanical errors, resulting in blanking, insufficient printing, or similar filling failures. When the flat squeegee
305
shown in
FIG. 13B
is used, a contact angle of the squeegee to the printing face of the metal mask
300
or base material
301
is hard to fix and maintain. The amount of the paste filled in the through hole
301
a
varies greatly and is considerably difficult to control properly. This is an important issue. In the case of the square squeegee
303
as shown in
FIG. 13A
, the contact angle of the squeegee to the printing face of the metal mask
300
or base material
301
is easy to set. A front end part of the square squeegee
303
in touch with the printing face of the base material
301
is not sufficiently sharp, and consequently the paste
304
is left on the metal mask
300
or base material
301
. The front end part of the square squeegee can hold only a small amount of the paste
304
. This makes it necessary to frequently replenish the paste
304
, and thus deteriorates productivity. When a viscosity of the paste
304
is increased because of the evaporation of volatile components or when the paste of a high viscosity is used, considerably less paste is filled than if kept under the originally properly set conditions. In other words, the filling condition should be re-set during operation although this takes a long time. This is another issue. In the case where a heater is incorporated in the squeegee
303
,
305
, this arrangement merely lowers the viscosity of the paste
304
. This does not effectively influence the rolling or filling of the paste
304
and raises the necessity for setting and adjusting the conditions again. Poor productivity still remains as an issue.
The object of the present invention is therefore to provide a printing method and a printing apparatus whereby a sufficient filling amount of a printing material into openings of a body to be printed is secured in conformity with various filling conditions, to thereby improve yields, quality, and productivity for printing with the printing material.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a printing method for pressing and filling a printing material by means of a filling head to openings of a body to be printed, wherein a flow pressure of the printing material is kept roughly constant during printing of the printing material.
According to a second aspect of the present invention, at least either a contact angle of the filling head to a printing face of the body to be printed or the speed of the filling head can be changed in accordance with a change of the amount of the printing material in the above first aspect, thereby keeping the flow pressure of the printing material roughly constant.
According to a third aspect of the present invention, printing of the printing material can be conducted in the above first or second aspect while the filling head is supported at the side (first side) of a pressing face thereof in touch with the printing face of the body to be printed, thereby keeping the flow pressure of the printing material roughly constant.
According to a fourth aspect of the present invention, in any one of the above-described first-third aspects of the invention, a temperature gradient can be applied to the pressing face of the filling head so that a temperature of a part in touch with the printing face of the body to be printed is higher than that of a part away (second side) from the printing face of the body to be printed and the filling head, thereby keeping the flow pressure of the printing material roughly constant.
According to a fifth aspect of the present invention, in any one of the first through fourth aspects, a pretreatment material can be applied before the printing material is filled by the filling head into the openings at the printing f

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