Electronic Design

The Art Of Solder-Tacking: Six Laws

All professions have artistic elements. The attorney masters the sly innuendo and the subtle suggestion to the jury, the surgeon deftly knots the stitch, the dentist undercuts the filling, and the most adroit electronics engineer knows the art of tacking.

Although many seek to proceed from notebook design directly to production, this practice is all but extinct, lost in the company failure statistics. We thus have the breadboard, the artistic masterpiece of electronics. The breadboard stands as the EE's sole remaining bastion against regimented conformity in these days of plug-in modules; his sole opportunity for exercise of the creative, artistic urge; his single link to a happier and more relaxed era. As a timely and highly significant contribution to the art, this article presents Johnson's Six Laws of Tacking.

LAW ONE: Never twist. Although an EE might naively (and even smugly) believe that at least some component values have been calculated correctly and won't change, such belief is foolhardy. This can be demonstrated in a breadboard by twisting together any two component wires and soldering. It is a fundamental law that when this is done, at least one of the components will change during the inventing process. So never twist.

LAW TWO: Never cut. The economy minded prefer to use components over and over again. Using parts from the Private Collection also avoids renewing battles with the purchasing department, stock room clerks, inspectors, value analysts and others. The extent to which re-use is possible depends on two factors: the length of the lead and how much overheating has occurred. The two factors are not independent; for the shorter the lead, the more heat from soldering. Again, simple demonstration can prove another fundamental truth: cut the lead off any component and leave just enough to solder it into the circuit. One will see that inevitably, this component is precisely the one that must be changed, thereby leaving a useless component with leads too short to use the next time. So, never cut.

LAW THREE: Avoid parallelism. Three-D circuits are the ultimate in electronic artistry; one can always follow the leads, make contact with probes, test leads and soldering iron, and there is less mutual magnetic and capacitive coupling when wires are skewed rather than parallel. The best breadboard circuits expand outward in a geometrically spherical fashion akin to a galactic nova. Thus, no two components or wires should ever be parallel.

LAW FOUR: Always use old solder. Shiny, new 60/40 solder is attractively packaged in handy dispensers, and the temptation is strong to use it. Unfortunately the dispenser can never be located among the pile of used components, tools, and test leads on the bench. One, therefore, develops the habit of picking up bits of old solder from the bench with the tip of one's iron and using this for tacking. This helps to keep the bench clean, saves money on solder, and avoids the splatter of resin.

LAW FIVE: Never tack more than two wires. When more than two wires are to be tacked, there is a problem. When the EE goes to tack the third wire, the others ungratefully fall apart. Without violating Law One (never twist), the recourse is to tack each succeeding component further up the lead of its neighbor. This is of assistance in satisfying Law Three as well, as there will be more rapid geometric expansion of the circuit.

LAW SIX: Stop at 14 changes! Statistics show that 78.2% of all engineering is done on the production line and after delivery. In these cases, the engineer must cope with an etched-circuit breadboard. Here, one has the annoying problem of tacking components as fixes for the defect without heating the board so much as to loosen the copper. Painstaking research by the author has disclosed that with the soldering iron operating at precisely 93 V, it is possible to tack a component on an etched board and remove it a total of 14 times, provided that Law Three (use old solder) has been obeyed. Beyond this point, one of two things will happen: the component becomes overheated and changes its value, thereby probably correcting the defect; or the copper separates from the board, so one can blame the etched-circuit board maker.

A corollary: If what goes up must come down, what is tacked must be untacked. One untacks to change a component, and, of course, when he is satisfied with the design—to save the components for his Private Collection. One simply touches the iron to the joints, and the breadboard flies apart like a mainspring. In fact, this is the test of a really good breadboard—every tack should fly apart by itself when touched by an iron. The only precaution in untacking is to leave enough old solder on the leads so they can be tacked again without violating Law Four. (Electronic Design, July 19, 1961, p. 176)

Despite being a deeply technical magazine, Electronic Design still has a place for the lighter side of engineering. Our thanks go to R.W. Johnson, consulting engineer, Anaheim, Calif., for submitting this insightful article back in 1961.

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