SU962337A1 - Method for electrochemically depositing copper - Google Patents

Description

one

The invention relates to the deposition of electroplated coatings, in particular copper, and can be used in the radio industry, in particular, in the processing of copper foils used in the production of foil dielectrics for printed circuit boards.

In the modern production of foiled dielectrics, various types of processing of copper foil, Q and Q are used to improve the adhesion of the foil-dielectric compound.

The known method of electrochemical treatment of copper foil consists in the sequential deposition of copper and copper oxide at a current density of 8–27 A / dm for 5–50 s and of a copper layer at 2.1–16 A / dm for 15–6 OIO s from copper sulfate electrolyte L1 J.20

However, this method of treatment allows to increase the adhesion of the foil to dielectrics by no more than a fold compared to untreated foil.

goy In addition, the presence of copper-like particles in the deposited layer leads to the appearance of undercutting during the processing of the foiled dielectric used in the manufacture of printed circuit boards.

Closest to the proposed by the technical essence and the achieved result is a method of electrochemical deposition of copper in potentiostatic conditions. The deposition is carried out from cyanide electrolyte.

The disadvantage of this method is that smooth, uniform precipitations of copper are deposited, which have very little adhesion to the dielectric applied to it in the manufacture of the foiled material.

The purpose of the invention is to increase the adhesion of the dielectric film with a copper coating by increasing the roughness of the latter and increasing the resistance to etching. This goal is achieved by the fact that the process is carried out for 6–15 s with non cathode overvoltage in odd pulses 500–620 mV, then 15–60 s in even at 80–200 mV, and the number of pairs of pulses is 6–12. To increase the resistance to cracking, a 0.03-0.1 µm thick layer of tin is applied to the copper coating. The choice of these overvoltage parameters and pulse durations is due to the fact that when copper coating is removed using electroplating parameters below the upper limits, the adhesion value decreases due to insufficient development of the surface of the sediment, and deposition using the parameters above the specified limits falls due to the reduction in the strength of adhesion of the deposited sediment to the body | The adhesive strength of adhesion with the dielectric of copper foil, by the processing proposed by the method, increases by 12–19 times in comparison with the untreated foil. Podravlivanie as confirmed and attempts at galvan resistance, performed according to the method according to 10316-87, is absent. The adhesion strength of the foil with the dielectric noche of such tests does not change. Example 1. Copper foil is treated by an electrochemically proposed method in a bath of composition, g / l: CuSO - 40 H S04200 is made of electrolytic copper. Bath temperature is 18-20 C. Electrolyte flow rate1, 4 m / min Foil adhesion to dielectric, type of FTS cheese (raw foil 30 GS / 3 mm at different electric modes, evaluated with delamination force (3 mm wide strips of foil produced at an angle EO), is given in Table 1. Example 2. Copper foil, worked analogously to Example 1, is coated with a layer of tin from the bath of the composition, g / l: Nn2.Sn (OH) (, inn NaOHefioB15 Bath temperature 70 -80 ° C. Cathode current density2-3 A / dm. Then, tests for galvan-resistance according to GOST 10316-78 were carried out. This is not observed. The magnitude of the adhesion of the foil to the dielectric is measured analogously to Example 1 (Table 2). The choice of optimal parameters is illustrated in Table 3. The copper is deposited in the bath as in Example 1. The calculated thickness of the resulting copper coating is 2, k-, 2 µm. The increase in the number of copper layers over the specified one, leading to a decrease in the layer thickness to less than 0.05 µm, or the deposition of less than 12 layers of copper (p 6), leading to an increase in the layer thickness to a value exceeding 0.1 µm, does not allow to obtain precipitation with a sufficient degree New developed surface. In the first case, this is due to insufficient surface development during odd pulses, and in the second, due to strong geometric alignment in even pulses. The test results are presented in Table. . The possibility of using zinc, nickel and tin to increase the resistance to etching of copper foil was investigated. These metals were chosen on the basis of their high chemical affinity for polar polymers, which include epoxy resins, and also on the basis of their good micro-scattering ability. The test results are given in Table 5. The thickness of the tin, zinc and nickel layers is 0.1 µm. Tests for galan-resistance carried out according to GOST 10316-78. Roles; in tin coating less than 0.03 µm does not ensure complete closure of the entire surface of the copper deposit (the microprofil wells may remain uncovered). A coating with a thickness of more than 0.1 µm can help reduce surface development due to the geometric alignment effect. Using the proposed method of electrochemical processing of copper foil provides an increase of 1.3-1.8 times compared with the known

, 59623376

adhesive strength due to the connection of various etching solutions in nenil copper foil - a dielectric foil during the processing of girovanny materials for printed circuit boards, which significantly improved, as well as stability, the quality and reliability of adhesive bonding to impact-5 circuits on printed circuit boards.

Table 1

600

Obtained by the mode of example 1

Covered with a layer of tin TO / 11ZINOM, micron

table 2

15

Partial cohesive dielectric failure

600

Obtained by the mode of example 1

Covered by a layer

600-700 600-700 O tin

Tables ak

Partial cohesion dielectric destruction

Cohesive dielectric failure

The magnitude of the adhesion of the foil to dielectric type FCS ,.

Baseline

560

zinc

90

nickel

Claims (2)

Invention Formula  1, Method of electrochemical deposition of copper in potentiostatic conditions, mainly from sulfuric acid J5 electrolyte, characterized in that, in order to increase the adhesion of the dielectric film with a copper coating by increasing the roughness of the latter, the process is carried out in 6-15 seconds with the cathode voltage in odd pulses is 500620 mV, then s in even pulses at 80-200 mV, and the number of pairs of pulses is 6-12. Note GS / 3 mm After being tortured 39 Partial cohesive dielectric failure ten Adhesive bond 2. A method according to claim 1, about tl and h a roll, and so that, in order to increase: no resistance K under-etching, a layer of tin 0.03-0.1 μm thick is applied to the copper coating. Sources of information taken into account G. US patent ff 32931Q9, cl. I6t - l66, pub. 1966. 2. Brilliant and combined metallic coatings. Workshop materials, vol. 2, M., MLNTI them. Derzhinsky, 1967, p. 93-97.