Method for producing copper tracks on insulating substrates

FIELD: producing copper tracks on insulating substrates.

SUBSTANCE: negative image of track is projected onto copper halide solution layer in organic solvent of substrate with the result that concentric capillary flow occurs in layer which transfers solution to illuminated sections of substrate wherein copper halide tracks remain upon solvent evaporation. These tracks are reduced to copper ones in hydrogen current at temperature sufficient to conduct reducing reaction.

EFFECT: facilitated procedure, reduced cost and copper consumption, improved environmental friendliness due to elimination of wastes.

1 cl, 3 dwg

 

The present invention relates to methods of forming copper tracks on dielectric substrates.

The known method of forming the copper tracks on dielectric substrates [1], in which the copper foil glued on a dielectric substrate, put a layer of photoresist. After exposure of the photoresist through the photomask with the image paths, clipping is photopolymerization. Solvent to remove unpolymerized photoresist from transmission sites. Because the solvent is valid only for the unpolymerized photoresist, the exposed areas of the photoresist, where he polymerizable remain on the copper foil. Copper with unprotected by the photoresist release sites in the acid solution. Then other solvent acting on the cured photoresist, but not dissolving copper, remove the cured photoresist. The result is a dielectric substrate with tracks of copper in the right places. This substrate serves as a template for a printed circuit Board, in which it is necessary only to drill holes for the pins of the radioelements.

Method [1] has several disadvantages.

First, this multi-way that not only increases the time of formation of the copper tracks, but also makes the process of formation expensive, since at each step processability special equipment. In addition to the basic operations of the method [1], described above, requires auxiliary operations such as the preparation of the copper surface by the application of a photoresist (grinding, washing, drying) [2], and rinsing and drying the substrate after each major operation to remove residual solvents and etching solution [1].

Secondly, for the method [1] requires various chemical reagents (photoresist, solvents, acids), which consume in large quantities, which increases the cost of production [3].

Thirdly, expensive copper is used is extremely uneconomical. It is known that at the final stage of manufacturing the printed circuit Board conductors and contact pads occupy no more than 25-30% of the surface, and the rest of the metal goes into the pickle solution [3]. For foil on both sides of the fiberglass with layers copper thickness of 50 μm, it is 1 kg of copper with 1 m2surface. For recovery of copper from spent pickling solution requires additional hardware and electricity costs of about 2 kW×h per 1 kg of the metal [4].

Fourthly, the method [1] is environmentally harmful. In the wastewater contains a large number of inorganic and organic substances, mainly oxides and hydroxides of the metals, and chemical waste from removal of photoresist [5]. Since the thickness f is toresist lies in the range of 25-60 μm, i.e. comparable with the thickness of the copper foil, the amount of waste from the processing of photoresist is comparable to the amount of waste from the etching of copper [3]. To meet modern environmental requirements, full utilization of the listed waste at the treatment facilities of enterprises is not possible [5]. The cost of operation of sewage treatment plants per 1 m2manufactured PCB, approaching total cost 1 m2foil copper, fiberglass and chemicals required for processing this square fiberglass [3].

The aim of the invention is to simplify and cheapen the process of forming the copper tracks on dielectric substrates, saving copper and elimination of waste in the process, i.e. the elimination of environmental pollution.

This goal is achieved through the use of concentration-capillary effect induced by non-uniform illumination of a layer of copper halide in an organic solvent, lying on a dielectric substrate.

Scheme of the proposed method is shown in figure 1, where 1 - lamp, 2 - condenser 3 - a banner with transparent patches on location tracks, 4 lens, 5 - layer solution of the copper halide in an organic solvent, 6 - borders, preventing the spreading of the solution, 7 - mean the food.

The essence of the method consists in the following. On a substrate applied a layer of a solution of copper halide in an organic solvent. This layer is projecting the image of the banner. In the irradiated areas of the layer due to heating, the evaporation rate of the solvent increases, which leads to the increase of the concentration of the halide of copper. Since increasing the concentration of the copper halide surface tension of the solution increases, then there are shear stresses directed in the irradiated areas. Under the action of tangential stresses arise fluid flow, which carry the solution from dark areas in light and form thus a negative transparency, i.e. the positive circuit. After evaporation of the solvent on the substrate remain on track from a halide of copper. The resulting track is reduced to copper in a stream of hydrogen at a temperature sufficient for reaction of recovery.

Figure 2 shows the track from the dibromide of copper (CuBr2), obtained on the glass substrate by direct projection lens Helios 44-M image M-shaped spiral bulb 100 watts per layer saturated by 70% at 20°With a solution of CuBr2in ethanol. The solution layer thickness of about 100 μm was on the surface of the glass size 2×2 cm strips limited livestock is A.

The track is formed as follows. Included lamp, under which the solution was collected in the irradiated areas, and waited for complete evaporation of the ethanol, to obtain paths of CuBr2. Then remove the strips of tape and put the backing track of CuBr2in the furnace, where the tracks have been restored to copper in a stream of hydrogen from the generator GW-4 at 350°C.

The thickness of the obtained copper tracks reached several tens of micrometers, and they had a continuous (i.e. conductive) structure. Figure 3 shows a plot of the reconstructed tracks, on top of which, for clarity, the dashed line shows the profile of the spiral filament lamp.

Thus, the proposed method has the following advantages. The process of obtaining the track consists of two steps is the formation of tracks from a halide of copper and restore them to the copper, in contrast to multi-stage process [1]. For the implementation of the proposed method it is enough to have such inexpensive equipment, such as an incandescent lamp, a condenser, a banner with the negative image of the tracks and the lens. All copper from a solution of copper halide in an organic solvent is used for forming the tracks, i.e. the formation of tracks is a waste, in contrast to [1], where 70-75% of copper goes into the etching solution, otkuda have to restore. In addition, no additional reagents (photoresist, solvents, acids, etc), which after a failover turn into toxic liquid waste, therefore the proposed method is environmentally friendly.

Sources of information

1. Fpolicy. Characteristics of modern technology printed circuit boards. http://www. fpgaletsky.ru/fpg/statj i_g/ops_galt.htm

2. The photoresist Photec H-W 240. http://www.rezonit.ru/pcb/articles/material/03/

3. Whatev, Namarti. Ecologically clean technology of printed circuit boards and large hybrid IC. http://www.chipnews.ru/html.cgi/arhiv/99_07/ /stat_29.htm

4. Splutter. The etching of printed circuit boards and the regeneration of the etching solution company ELO-CHEM. http://www.compitech.ru/html.cgi/arhiv/02_02/ /stat_124.htm

5. Sverakova, Sevkazenergo, Lchicine process of comprehensive utilization of copper-containing etching solutions from the production of printed circuit boards. // Journal of deposited manuscripts No. 5, may 2000. http://www.rezonit.ru/pcb/articles/technology/05/

The method of forming the copper tracks on the dielectric substrate, wherein a layer of a solution of copper halide in an organic solvent, lying on the substrate, projecting a negative image of the tracks, resulting in the layer occurs concentration-capillary flow, which brings the solution in the illuminated areas of the substrate where after evaporation of the solvent remain track of the halogen is Yes copper, which is then reduced to copper in a stream of hydrogen at a temperature sufficient for reaction of recovery.



 

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SUBSTANCE: negative image of track is projected onto copper halide solution layer in organic solvent of substrate with the result that concentric capillary flow occurs in layer which transfers solution to illuminated sections of substrate wherein copper halide tracks remain upon solvent evaporation. These tracks are reduced to copper ones in hydrogen current at temperature sufficient to conduct reducing reaction.

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