Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Reexamination Certificate
1997-01-06
2001-02-06
Pianalto, Bernard (Department: 1762)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C427S096400, C427S282000, C427S288000, C427S290000, C427S436000, C427S555000, C427S596000, C428S220000, C428S332000, C428S337000, C428S480000
Reexamination Certificate
active
06183839
ABSTRACT:
The present invention concerns a stencil for the depositing and gauging of more or less thick, point-base coats of a viscous product.
This invention falls within the technologies of surface mounting of electronic components on printed or microelectronic circuits.
In electronics manufacturing, the coating of so-called thick layers, namely solder paste and glue, are done by means of a syringe or serigraphy. The coating by syringe is a risky process of a limited output. The precision of its markings, the duration of the operation, and the slenderness of the lines and networks made, make this first operation unusable for current industrial applications.
Although paste and glue can be coated by liquid distribution equipment, the preferred method is serigraphy through a screen, by using a metal screen or stencil manufactured by chemical cutting, laser cutting, or electroforming. These three methods are satisfactory for dimension of up to 300 micro-meters, but smaller dimensions are required.
The use of a stencil, through which is deposited a product, cream or solder paste, which then form the desired contact soldering pins, is the most prevalent industrial procedure.
Three types of stencils are known today: the woven metal cloth of serigraphy, the polyester woven cloth of serigraphy and the metal stencil. Their technical qualities are determined depending on their efficiency or percentage of opening, tie off contact, and the force of tension applied.
The efficiency corresponds to the degree of sealing of the stencil holes which is a function of the presence of wires/fibers in the case of a woven stencil.
The off-contact is the angle that can be formed by the stencil with the support surface in working position when the squeegee is being supported. The greater the angle, the better is the extraction of the viscous product of the stencil. Obtaining an off-contact presupposes a considerable tension force of the stencil and a good coefficient of elasticity.
Depending on the off-contact, the metal serigraphic cloth is not as good as the polyester serigraphic cloth and better than a metal stencil.
For efficiency and tension force, the polyester serigraphic cloth is not as good as the metal serigraphic cloth, which in turn is not as good as the metal stencil.
The method and means of machining the stencils determine also the quality of the deposits as will be explained later.
The present invention remedies those drawbacks by presenting a means of applying thick coats by the use of a stencil made of a uniformly consistent solid sheet of a pliable and stretchable synthetic material bored by a cutting means in conformance with the deposits to be made.
Such stencils have been used.
Patent GB 2054462 uses such a stencil to mask out metal with a view to an electrochemical etching, hence a removal of metal and not a depositing of viscous product.
U.S. Pat. No. 3,981,237 uses such a stencil for ink printing on textiles, the stencil or mask being mounted on a rotary drum.
The purpose is different in the present invention, which aims to deposit and to gauge viscous products.
The invention is characterized essentially by a stencil for the depositing and gauging of more or less thick, point-base coats of a viscous product, the product being gauged by means of said stencil of a uniformly consistent solid sheet made of a pliable and stretchable synthetic material with transfer bores in conformance with the surface of each one of the points to be made, the size of said bores, in relation to the thickness of the sheet, making it possible to gauge the product amount to be deposited and to control the height of the deposit.
According to another feature of the invention, the stencil bores are round in shape.
According to still another feature of the invention, the bores are made by mechanical means. The stencil is preferably made of a sheet of polyester or a similar or equivalent synthetic material.
The present invention concerns also the stencil, as a device, which the process is meant to embody.
To remedy the problems found with a serigraphic screen made of polyester or metal cloth and a metal stencil, the present invention proposes to use a cloth made of polyester material or the like; however, this cloth no longer consists of fibers/wires but is a solid sheet in itself. This solid sheet made of polyester is mechanically bored at the desired places. Owing to the fact that the polyester cloth is solid, it admits of tension forces greater than those with wire mesh cloths and at least equal to those with metal stencils.
REFERENCES:
patent: 3981237 (1976-09-01), Rhodes
patent: 4208005 (1980-06-01), Nate et al.
patent: 4359928 (1982-11-01), Blessington et al.
patent: 4379185 (1983-04-01), Smith et al.
patent: 4537647 (1985-08-01), Foster
patent: 4571864 (1986-02-01), Bopp
patent: 4704305 (1987-11-01), Berger et al.
patent: 4796560 (1989-01-01), Berger et al.
patent: 4910048 (1990-03-01), Sinclair
patent: 4981746 (1991-01-01), Matsuo et al.
patent: 5046415 (1991-09-01), Oates
patent: 5104213 (1992-04-01), Wolfson
patent: 5196317 (1993-03-01), Kulesza et al.
patent: 5220724 (1993-06-01), Gerstner
patent: 5265773 (1993-11-01), Harada
patent: 5314709 (1994-05-01), Doany et al.
patent: 5334815 (1994-08-01), MacNaughton et al.
patent: 5347925 (1994-09-01), Holderegger
patent: 5360665 (1994-11-01), Sato et al.
patent: 5458949 (1995-10-01), Komiyama et al.
patent: 5475048 (1995-12-01), Jamison et al.
patent: 5532439 (1996-07-01), Watanabe et al.
patent: 0593050 (1994-04-01), None
patent: 2054462 (1981-02-01), None
patent: 63-222496 (1988-09-01), None
patent: 7-81027 (1995-03-01), None
“Adhesive Applied at a Single Stroke”, 2 page Product brochure, DEK, distributed Sep. 19, 1996.
A. Hobby, “Screen Printing Adhesive—The Complete Solution”, DEK Printing Machines Ltd., UK, (Oct. 25, 1996) (13 pages).
“Technology Insight Pump Printing” TM, Electronics Manufacture and Test, Sep. 1996, page 18.
Miranda, R., et al, “Application of Conductive Adhesives to SMT PCB Assembly”, pp. 761-769 of Proceedings on Factory Automation and Information Management, Limerick, Ireland (1991), (No Month Avail.).
R. Hudson, “Automatic Screen Printing,”, Printed Circuit Assembly, Aug. 1988, pp. 24-29.
A. Duck, “Dispensing SMD Adhesives: Rotary Pump Technology vs. Stencil Printing Technology”, EMI (May/Jun. 1996), pp. 17-19.
Rico Micro Electronics, “High Quality Mask for Solder Printing for Wiring Board”, Nikkan Kogya Shimbun, Jan. 18, 1995, 1 page.
8 pages product literature for E-Fab tm XL. “Electroformed Stencil”, AMTX, Inc., variously dated as No Month Avail. 1994-Apr. 30, 1996.
Pianalto Bernard
Vidas Arrett & Steinkraus
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