SU780237A1 - Method of manufacturing laminated printed circuit boards - Google Patents

Description

(54) METHOD OF MANUFACTURING MULTILAYER PRINTED

Fee

one

The invention relates to the field of radio electronics and can be used in the manufacture of multilayer switching printed circuit boards used in electronic and electronic computing.

A known method of manufacturing multilayer printed circuit boards involves applying a masking coating to double-sided foil-insulated dielectric, obtaining a topology of a pattern of conductors and contact pads by etching the foil, obtaining joints between layers by galvanic metal buildup in vias. Double-sided printed circuits are separated by thin pads and fixing rods are soldered into the vias.

The disadvantages of this method are the increased complexity of manufacturing multilayer printed circuits due to the large number of soldered locking rods, their low reliability due to the large number of rations and the increased thickness of the rations, the inability to automate the manufacturing process, the difficulty of creating a universal tooling.

There is also known a method of manufacturing multilayer printed I-boards, including the implementation of fixing holes in individual plates (foiled dielectric, patterning of connecting conductors and contact pads by galvanic deposition of metal, deposition of metal epoxy composition 10 on the pads, aligning the plates

the holes, their connection at the contact pads under pressure at elevated temperature 2.

With this method, a special operation is needed to form an additional element, for example, a through-hole or a jumper for commutation of parts of the printed circuit located on opposite sides of the dielectric base. The lintels and the through plated holes provided by the method are unreliable. Voltage concentrations are formed at the metal-to-metal transitions in the hole, so there are gaps in the conductive layer under mechanical loads. Another reason for the unreliability of switching, which is tangled in this way, is that if there is excessive pressure in the process: the assemblies will push the balls through the foil layer, which will lead to a violation of the switching in the circuit. The contacts obtained in this way produce a large contact resistance, since it is technologically difficult to manufacture exactly the same metallic spherical particles.

The aim of the invention is to increase the reliability of interconnects of printed circuit boards.

The goal is achieved by the fact that in the method of manufacturing multilayer printed circuit boards, including making fixing holes in separate plates, forming contact areas on the surface of the plates by selectively electroplating the metal, forming a pattern of connecting conductors, aligning the plates through the fixing holes and connecting them along the contact areas, the formation of the pattern of connecting conductors is carried out by superficial and deep anodizing of the plates, and the connection Astin pads on cold welding is carried out under pressure, after which the plate package is sealed by soldering socket surfaces.

Anodized metals such as aluminum, tantalum, titanium, niobium, and hafnium can be used to manufacture multilayer printed circuit boards by this method.

The scheme of the method is shown in the drawing.

A multilayer printed circuit board is manufactured from separate metal blanks, which are processed simultaneously. Initially, fixing holes 2 are formed in the plates 1, which are necessary to align the printed circuit boards into a package. Then, a protective pattern of contact pads is formed on the plates by applying photoresist 3, for example, by photolithography. Then contact pads 4 and technological edge, 5 are formed by selective galvanic metal deposition. Thereafter, surface anodization of the plates is carried out to obtain a thin surface layer 6 of metal oxide. Then by deep anodizing, conductors-7 and insulating areas 8 of metal oxide are formed. The finished printed circuit boards are aligned on the fixing holes 2 and are connected mechanically and electrically by cold welding under pressure. Thereafter, the pack of printed circuit boards is sealed on the end surfaces by soldering.

An example of the method.

And aluminum ribbons of thickness 0, 20, 3 GLM cut down the plates with the technological allowance on the perimeter. OrynpoMefiKO with cutting out carry out the drilling of the fixing holes. The resulting plates are degreased, washed and dried before applying the photoresist, which is applied on both sides of the plate. Exposure and display are also carried out with two

Toron at the same time. After these operations, there is a pattern of contact pads and technological on the plate.

The entire technological advancement is not protected by a photoresist. A plating operation is carried out using a galvanic accumulation plate in ACIDS: nitric and hydrofluoric to remove the oxide film. The galvanic coating includes the deposition of copper with a thickness of about 60 microns and on top of it nickel with a thickness of 5-10 microns. After removing the photoresist, protruding contact pads and a technological edge are on the plate.

 Next, the plates are superficially judged from two sides in an electrolytic field. Sulfuric acid is used as the electrolyte. At solution temperature

155 + 24-C and a voltage of 12-28. At the time of anodizing, it is 20-45 mn. . The thickness of the oxide film formed on the plate surface is 2535 microns.

Plates subjected to surface anodization, prom1) are thawed with hot water and dried. A photoresist is applied to the surface on both sides and exposed. After the appearance, a topological pattern of the conductors is obtained,

closed with photo photoresist. The plate is subjected to through anodization in an electrolytic bath. Sulfuric acid is used as an electrolyte. At a temperature of O-SPC solution

and a voltage of 80-120 V anodizing time of 80-90 minutes.

After thorough anodization, the plgstins are washed in hot water and dried. The plates obtained in this way have switching conductors separated by an insulating layer of oxide and coated with a layer of aluminum oxide. Next, the plates are assembled at the fixing holes. M and connected to the contact pads by cold welding with pressure. The pressure force is chosen when welding is equal to 10-20 kg / cm. When welding on the contact pads, a micro gap is formed between the plates.

The final step in the manufacture of multi-layer printed circuit board is the connection along the perimeter of the plates by means of a folder on the end surfaces.

This method makes it easy.

Claims (2)

fabrication and installation of interconnects of printed circuit boards due to the following factors. - The number of technological operations is reduced due to the simplification of fabrication (the interconnection elements of the boards. The conductors in the board and the elements of inter-board commutation are one whole, there is no abrupt transition between them, therefore there are no mechanical stresses that break the commutation and transitional resistance. The method allows fabrication of plates operating at high current densities, since: the conductive layer can be made of any thickness, therefore the PO can vary over wide limits; the method provides x A good heat sink, since metal oxide conducts heat like the metal itself or even better, moreover, metal oxide is a better electrical insulator than the dielectric base of printed circuit boards, therefore, with that thickness, electrical protection in the boards is better in this way. increased reliability under the action of cyclic mechanical loads due to the effect of structural damping. Since the boards in this method are mechanically and electrically connected only by cold welding with pressure on the contact pads, the effects of cyclic mechanical loads (vibrations) on the oxide-coated surfaces of the boards will be micro-displacements relative to each other, while the energy of mechanical vibrations will be extinguished due to friction. Since the board is multilayered, the total surface over which friction occurs is large enough, and the mechanical energy that could destroy the interconnects is extinguished, the transition into thermal energy, which, with good heat removal, does not impair the reliability of the boards. ino пet: increase-reliability of interconnections of printed circuit boards, especially for equipment operating under the conditions of manufacture; reduce the production cycle by using a parallel sequential production process: 1 production and simplification of individual operations; reduce the cost and complexity of manufacturing multilayer printed circuit boards by reducing the duration of the process; In view of simplicity, the method can be easily automated, which will increase production efficiency and improve the quality of the equipment produced. The invention method of manufacturing multilayer printed circuit boards, including the implementation of the fixing holes in individual plates, the formation on the surface, contact plates of the contact area by selective galvanic deposition of metal, the formation of the pattern of connecting conductors that, in order to increase the reliability of the interconnections of printed circuit boards, the formation of the pattern of connecting conductors is carried out by Surface and deep anodizing of the plates, and the connection of the plates on the contact pads is carried out by cold welding under pressure, after which the plate pack is sealed on the end surfaces by soldering. Sources of information taken into account in the examination 1. French patent number 2106903, cl. H 05 K 3/00, 05.05.72. 2. Patent SSL No. 3795047, cl. H 05 K Z / Zb, 03/05/74 (prototype). “:. and .r: x: "-:"; vbi ieees .titivisw; ; : wax: and  About "gays" "" ";"; rk 5:%; 5 "X"; 5 "yes to PG I / X1 / Jb IGH I Well in 1zht {КЯМ ів1 кт пЖ1 GL