Testing methods were studied for severe estimation of solderability of electroplated metals. The vertical immersion testing method was found to be simpler and more reliable than horizontal one. The lower half of each specimen (25×25×0.25mm) was immersed into a sufficient volume of molten solder after flux treatment. A solution containing 25wt.% water-white rosin and 75wt.% isopropyl alcohol free from additives was used as the flux. The solder used was the normal 60%Sn-40%Pb alloy. Soldering temperature was kept at 230±1°C and specimens were immersed into the solder bath for 1±0.1sec. In order to obtain highly reliable data it was necessary to control the bath temperature and immersion time accurately. The solderability was classified into five grades from these three points of view: spreading area, wetting area percentage and appearance of soldered test panel surface. It was found that the testing method proposed here could distinguish even a slight difference in solderability due to very delicate variations in electroplating processes.

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Solderability is one of the important factors to select a metal coating which is to be electroplated on electronics parts. Not only solderability of a coating just after plating but also that after a long time storage should be discussed because solderability varies with the passage of time. Solderability of metal coatings was measured after various accelerated ageing treatments in order to select a suitable one by which the effect of a long storage on solderability was known in a short period. Accelerated ageing treatments examined were vapor treatment on boiling water, heat treatment, exposure in a SO₂-containing atomosphere and salt spray treatment. Vapor treatment is considered to be most suitable for severe estimation of solderability of a coating after storage because of its simplicity in procedure, its good reproducibility of results and its severe condition for deterioration of solderability. The solderability test after vapor treatment was able to discriminate even a very slight difference in solderability, which was not able to discriminate just after plating, such as difference between that of a tin-plated surface and that of solder-plated one.

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A study was made on electrodeposition of cobalt from cobalt ethylenediamine chelate solution for the purpose of investigating the stability of chelate on pH and the optimum condition in electrolysis. The results obtained were as follows: 1) Ethylenediamine (en) and cobalt ion (II) formed stable chelate compound of (Coen₃)²⁺ in a pH range 8.0-10. 2) Bright cobalt platings were obtained from chelate solutions of pH 3.0-5.0 by the addition of two addition agents, and cathodic current efficiency was found to be decreased. The optimum bath composition for bright cobalt plating was as follows: CoCl₂⋅6H₂O (CoSO₄⋅7H₂O) 0.05-0.20mol/l (0.1-0.3mol/l), en 0.15-0.60mol/l (0.3-0.9mol/l), HOCH₂C: CCH₂OH 0.05g/l, C₁₀H₆ (SO₃Na)₂⋅2H₂O 0.03g/l, pH 3.0-5.0, Temperature Room temperature, Cathodic current density 0.8-1.5A/dm². The cathodic current efficiency under the above condition was about 70-80%. 3) The cobalt deposits obtained from Co-en baths were of small grains in crystal structure, and the brightness apparently increased with increasing electrolysis time.

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An investigation has been made of the electrodeposition of copper from solutions of Cu(P₂O₇)₂^6- containing small amounts of ammonia. It is found that mixed complex ions, Cu(P₂O₇) (NH₃)^2- and Cu(P₂O₇) (NH₃)₂^2-, are formed at small concentrations in the solution, and hence the possible deposition reactions are:
Cu(P₂O₇)₂^6- Cu(P₂O₇)^2-+P₂O₇^4- Cu(P₂O₇)^2-+2e→Cu+P₂O₇^4- (Main) (1)
Cu(P₂O₇) (NH₃)^2-+2e→Cu+P₂O₇^4-+NH₃ Cu(P₂O₇) (NH₃)₂^2-+2e→Cu+P₂O₇^4-+2NH₃ (Secondary) (2) (2′)
The increase in cathodic current caused by addition of ammonia is attributed to the secondary reactions occuring parallel with the main reaction (1). The partial current of the secondary reactions was measured by using a rotating copper disc electrode and it was found that the current is proportional to the Cu(P₂O₇) (NH₃)^2-ion concentration. This indicates that, of the two secondary reactions, (2) is of much more importance. The mechanism of the reaction (2) is discussed in detail and also compared with the one reported previously for the solutions free from ammonia.

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Film thickness distribution of water soluble acrylic resin paints dip-coated on extruded aluminum shapes has been investigated, under stationary state, with some theoretical considerations. Test pieces were of bent plates having curved corners, radii of which varied with each specimen over the range of 0.02-0.2cm. Dip-coating was done with withdrawal speeds of 1.03 and 1.50cm/s. Values of Ca (Ca=μVw/σ) were 4.8×10^-3 and 7.0×10^-3, respectively, and values of Go (Go=R(ρg/2σ)1/2) were in the range of 0.08-0.79, where μ is viscosity, σ is surface tension, ρ is density of paint and g is gravitational acceleration. The following results were obtained by the above experiment. 1) A gradual decrease of film thickness from the plane portion to the corner was observed with the minimum value at the apex. 2) Film thickness at the corner (h″_th) can be caluculated theoretically by multiplying the thickness on plane portion (h_th) by a coefficient C′m, that is
h″th=C′m·hth=C′m[0.944Ca1/6(μVw/ρg)1/2] where C′m=1/2.4(Go-0.15)^0.85/1+2.4(Go-0.15)^0.85+0.5/(Go-0.15) Go=R(ρg/2σ)^1/2≥0.15
3) Residual coefficient (K) was found to be almost equal both at the bent portion and on the other flat surfaces if the painting conditions would be the same.
h″_ov=K·h″_th=K·C′m·h_th
whereh″_ov is the measured value.

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A modified Heisler's analysis using one dimentional unsteady state thermal conduction equation has been applied to the studies of temperature change of electrodes due to Joule's thermal effect. It was shown that temperature of the electrodes increases in the form (1-e^-kt) with time t and that the onset time of the steady state of the electrode temperature is affected by electrode geometries, hydrodynamic conditions, electrode materials and properties of electrolytes. Temperature increase of aluminum during anodizing was observed under stagnant and forced laminar flow conditions and the results were compared with the theoretical ones. Electrode temperature increase with time in these cases was in good agreement with the theoretical ones but the observed onset times were 1.5-2.0 times as long as the calculated values. Discrepancy between theoretical and experimental onset times has been discussed.

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