SOLDERING

Radio Record, Volume I, Issue 2, 29 July 1927, Page 14

SOLDERING

SOME USEFUL HINTS Probably many home constructors are satisfied at first. to attempt to get through without soldering joints in their sets. But twisted wire joints may 80 a long way towards impairing the efliciency of the receiver, and soldering is really quite a simple and easy process to master, and once learnt, there will be no desire to risk noisy reception by letting joints go unsoldered. . The ideal soldering tool is the electric soldering-iron, as it keeps at an even heat, and is not made dirty by heating in a flame. ‘The copper-bit is perhaps the most usnal implement, and is capable of doing good work if prtoperly handled. Some joints may be more readily made with the assistance of a jeweller’s blowpipe (costing about is.) in conjunction with a flame of methylater spirits on cotton wool contained | in a‘small receptacle such as the lid of a metal shaving soap container. Inthis method the joint is cleaned and fluxed and a suitable blob of solder laid on and heat is applied by directing the flame of the spirits upon the joint by means of the blowpipe, actuated by the operator’s breath. Whichever method of heating is employed, the parts to be joined must be made mechanically clean, the heat must be ainple to melt the solder easily, and if a bit is used it must be kept in a properly tinned conditien. Flux must not be used too lavishly, and surfaces to be soldered must not be handled once they have been cleaned. By mechanical cleanliness is meant absence of all matter or conditions inimical to the success of the operation of soldering, for example, tarnish or oxidisation, grease, sooty deposits, ete. fhe presence of such matter in even minute quantities is sufficient to cause partial or complete failure in soldering, so that every surface to be worked ‘should first of all he cleaned cither with aney cloth, glass paper, or a smooth ile. It is unwise to assume that already tinned surfaces, such as those of tinned Wire, tags, e¢tc., do not require any cleaning. ‘The cleaning in these cases may, however, be confined to rubbing witlt a cotton rag on which a little flux has been smeared, though if they are badly tarnished the emery cloth should he brought into use. Certain means sometimes used for heating the bit are totally unsuitable for the purpose. A coal fire is one. Gas is not good, not only because it contains too many sooty impurities and oxidising agents, but also because its heating qualities are too great to be readily regulated for the purpose in hand. ; The most suitable and agent to use is undonbtedly a methy-lated-spirit flame, in which the bit can

usually be left for quite a considerable period withont raising its temperature sufficiently to cause oxidisition of the tinned surface. Small spirit lamps, especially designed for soldering work, may be purchased at small cost. It is advisable to choose a make which includes a hinged support for the bit. — The ‘point relative to keeping the in a properly tinned condition is of such importance that the process of tinning will be briefly described and hints added as to the proper maintenauce. of that condition. Tinning is the process by which any surface (not only that of the bit) is covered with a coating of bright solder. To do this with a new bit. it or rather the copper portion (the bolt), should be . cleaned with emery cloth and the bit bronght to the proper temperature in the spirit flame. This is the case when the flame becomes tinged with a green | colour. ; " a Here a word of warning. Never dllow the tinned portion of the bit ‘or that portion about to be tinned to come into direct contact with the -heatirg flame, which should only be allowed to play upon that part of the bit- where the bolt is rivetted to the shank. Remove the bit from the flame, dip the end of the stick of solder into flux, and with it lielitly touch each of the’ bevelled surfaces. The solder will probably not run evenly, but will collect in ‘"‘blohs," so in order to spread it satisfactorily over the entire surface the bit should be wiped while still hot on a cotton rag on which a small quantity of flux has been smeared. The operation is then . finished, and it will be seen that the business portion of the hit is compietely covered with a bright coating of "tin." Keep the bit well "tinned." This is the condition of the bit which it is necessary to maintain if quick, clean, and firm joints are to be effected. Should by any chance the tinned surface become dull {that is oxidisd), or otherwise mechanically dirty, the bit should be heated and wiped thoroughly on the cotton rag already referred to. In some cases where the bit has’ got into a particularly bid condition, it may be necessary to have recourse to a file to remove the @ntire existing surface, The bit must then be 1zetinned in the nanner described. . The rag already twice mentioned requires a short note to eniphasise the necessity of its consisting of vegetable fibre, such as cotton, and not of animal fibre, sucli as wool, which, owing to the quantity of grease and other carhon it contains, soon ruins the surface of the bit for soldering purposes The remaining points can be dealt with in a few words. Oxidisation, as can readily be inferred from what has already been written, is the main enemy of successful soldering. This vndesirable condition is usually the result of over-heating, althongh it also’ follows from exposure to the atmosphere for any length of time and it is mainly to counter its effects that flux is used. That is no excuse, however, for an improper use of this invaluable material. It shonld be remembered as an axiom that the slightest touch of flux properly applied in the right place is of far more value than wholestle and indiscriminate smears. ' Square-tinned wire has matty advantages over the round variety as far as ease of soldering is concerned. It is important to remember, ‘however, that in order to effect really sound joints at least three adjacent surfaces of square wire should be cleaned preparatory to applying the solder so that the latter mav flow readily all ronnd the actual surface to be joined.