Metal working – Method of mechanical manufacture – Electrical device making
Patent
1995-03-06
1998-03-24
Vo, Peter
Metal working
Method of mechanical manufacture
Electrical device making
29830, 29847, 1566431, 174262, 216 18, 427 97, H05K 342, H05K 346
Patent
active
057298971
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is in the field of the manufacture of printed circuit boards and relates to circuit boards, foil circuit boards and metal-clad laminates for foil circuit boards with structured or patterned coverings and with plasma-etched interfacial connections and it relates to a photochemical method for the manufacture thereof.
BACKGROUND OF THE INVENTION
In the manufacture of thin, multilayer foil printed circuit boards constituted by insulator layers and conductor layers, hitherto a large number of separate structuring or patterning operations have been carried out by photochemical processes. Thus, for the structuring of interfacial connections in insulator layers firstly prepared interfacial connections are structured, whereby subsequently at the position thereof the interfacial connections are plasma-etched and plated on. However, current paths and pads are directly photochemically structured in electrically conductive layers. Finally, the photochemical structuring of the covering takes place in subsequently applied, protective resist coatings on surfaces of foil circuit boards.
Such structuring or patterning operations take place according to known, proven photochemical processes, which are widely used in electrical engineering. They are used successively and as multistage production processes suffer from the main disadvantages indicated hereinafter.
The more structurings are required, the more expensive the manufacture. For each of these structurings photomasks must be produced and accurately positioned. In addition, photoresist coatings must be applied to the intermediate product for producing foil circuit boards and then removed again.
The more structurings are required, the lower the efficiency or yield. The total yield of several sequentially performed production processes is formed from the product of the individual yields and the wastage of each process limits the yield of all the following processes.
The more structurings required, the greater the additional manufacturing costs. The potential physical and electronic possibilities of the photochemical processes used are consequently restricted by the large number of structurings performed. The restrictions are given below.
The manufacturing tolerances have a restricting effect. Thin, multilayer foil circuit boards with thicknesses below 100 .mu.m and interfacial connections with a diameter below 100 .mu.m must, in the case of several exposures with different photomasks, have certain manufacturing tolerances for all these structurings, which rapidly reach the order of magnitude of the structures.
The thicknesses of the current paths and the interfacial connections are restrictive. Following a structuring of the preworked interfacial connections, they are plasma-etched and plated on galvanically, e.g. with copper. The resulting interfacial connections deteriorate the dimensional stability of the overall foil circuit board, because electrodeposited metal coatings are not stress-free. The galvanic plating on also leads to an increase in the thickness of the top metal foil of the foil circuit board. The thicker the metal coating, the more difficult it is to chemically etch it. The physical advantage of very small dimensions on film circuit boards is limited in this way, as is the electronic advantage of thin current paths.
Finally, the photochemical structurings of coverings on circuit boards and foil circuit boards are restrictive. For producing very fine structurings in resist coatings with sharply contoured edges advantageously application takes place of photosensitive solder resists or photosensitive solder resist foils. The solder resist can be applied by means of various methods such as printing on, rolling on, pouring on, electrostatic spraying, electrophoretic deposition, etc. and is predried. The solder resist foil is laminated on by means of a vacuum coater. The structures in these coverings are transferred by means of a photomask having a high pattern definition of 20 .mu.m. The high installation costs for the
REFERENCES:
patent: 4277321 (1981-07-01), Bartlett et al.
patent: 4720322 (1988-01-01), Tiffin
patent: 4840093 (1989-06-01), Florgello et al.
patent: 4985990 (1991-01-01), Cronin et al.
patent: 5108553 (1992-04-01), Foster et al.
patent: 5227013 (1993-07-01), Kumar
patent: 5386627 (1995-02-01), Booth et al.
Hara Koji, "Manufacture of Flexible Printed Wiring Board", Patent Abstracts of Japan, Publication No. JP3206682 dated Sep. 1991, appl. No. JP00002678 dated Jan. 1990 (Sumitomo Electric Ind. Ltd.).
Martinelli Marco
Schmidt Walter
Dyconex Patente A.G.
Farley Walter C.
Vo Peter
LandOfFree
Method of manufacturing multilayer foil printed circuit boards does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing multilayer foil printed circuit boards, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing multilayer foil printed circuit boards will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2280551