I often wondered whether in today′s modern technology, myths and fairytales still have places at all. With the entire hullabaloo about fancy electronic design and analysis programs getting more and more musical names by the day, who would give common soldering on the production floor much thought?
Plain common soldering, whether by means of re-flowing, wave, hand soldering or intrusive soldering, is often treated as the Cinderella of the assembly process in electronics.
Many companies embarking on OEM or contract manufacturing realise the importance of having a recognised standard to work to. Where the ISOs come in handy with respect to the administration and organisation, they lack the technical detail of the end-product. Coming to the aid is one of the more well-known and universal standards like IPC. More about IPC later.
In the absence of affordable, technically-superior adhesives, solder will remain the major interconnect medium between components and substrates like PCBs or alumina substrates. It is not only amazing but basically frightening to see how many myths still exist and are being worked with, in many reputable and sizeable companies.
What is a myth?
To avoid misunderstandings, ill-defined words and concepts, let us look at what a myth is, and see if there are different sorts of myths. Myths are symbols that reflect a community's (electronic manufacturers, inspection authorities, QA and end users) unspoken assumptions, beliefs and theories of action:
'Symbols embody a community's view (or theories) about particular phenomena, which in turn explain behaviours exhibited by members of the community' (Frost & Morgan 1983).
'Symbolism revolves around shared meanings - patterns of beliefs, rituals and myths, which evolve through time and function as social glue, binding communities together' (Smircich 1983).
'Myths can also be defined as a dramatic narrative of imagined events, usually to explain origins or transformations of something. It also reflects an unquestioned belief about the practical benefits of certain techniques and behaviour that is not supported by demonstrated facts (Trice & Beyer 1984).
'Myths are often communicated through the telling of a story. Myths are devices of mind that have been used throughout time to provide explanations, reconcile contradictions, and help resolve dilemmas. However, myths have also been known to distort images and misdirect attention (Bolman & Deal 1984).
Dry joint?
This last myth mentioned above pertains, in particular, to electronic soldering techniques and the most common myth is better known as 'the dry joint'. It in fact distorts images and misdirects attention. The definition of 'dry joint' is nowhere to be found in the IPC-T-50G standard ‘Terms and definitions for Electronics’. Where dry film can be found, the definition of a dry joint excels in its absence.
Maybe IPC made a slip-up and forgot about this very commonly used 'term'? IPC used to be better known some 10 years ago by the name: ‘The Institute for Interconnecting and Packaging Electronic Circuits’. It is a large world-wide organisation with its base in the USA, but stretches from Vladivostok to Los Angeles. Literally hundreds of companies with thousands of members communicate, exchange and standardise issues in the field of electronic assembly. Once consensus is reached with respect to a new process or terminology, it is taken up in their manuals and standards. There is no way the popular 'dry joint' could have been forgotten or overlooked. So what is the case? We have to accept the unthinkable: it is not defined and does not exist.
Many operators, inspectors, trainees, engineers, CEOs, managers and others have been using it since World War 2. It should have ended there and then but it did not. It lives on like a myth in electronics. I have heard it everywhere in South Africa, being used by engineers, managers, directors of companies, operators and technicians. Worse, I have seen it once in a reputable company on their official ‘inspectors' fault sheets’. It read: ‘PCB001xxx, 5 dry joints, at R11, C23, IC2, TR3, and R3’. How do we fix something that does not exist?
When confronted, the classical answer is: ‘You know what we mean by dry joint’. No, I am afraid not, and neither does IPC know. It is a deeply-entrenched myth that has almost become a reality. The foregoing myth could be compared with the myth of Santa Claus or Father Christmas. Everybody talks about him, especially around Christmas time. His name is known worldwide, some children even believe in him, yet he does not exist.
The 'dry joint' has been too long with us now and it has taken on ramifications. It is so deeply entrenched that some engineers, technicians and operators even refuse to accept a trainer's word that it does not really exist. Is this problem endemic to South Africa? No, fortunately not. But this is small consolation and does not result in a positive feedback in the electronic assembly industry.
Meaningful feedback is needed to correctly address the many problems in the soldering assembly realm. By starting off with incorrect definitions will not help solving the problem.
A master trainer from a company previously known as 'The School of Soldering in Scotland, UK' told us the following story based on his worldwide travelling as an engineering consultant.
Quote: "The most widely spread myth is the dry joint. The dry joint has plagued our industry from the early valve days, where valves were voltage switching in the hundreds of volts at very low currents. The non-wetted solder connections give sufficient electrical contact for short periods and then rapidly degrade the signal performance of the circuit, commonly termed at the time as: noise. Noise was closely associated to the phenomenon recognised at the time as the dry joint. It should be noted that these troublesome connections were constantly being revisited by the soldering iron to reduce the circuit noise each time, giving shorter periods of operations.
The remarkable thing is that this terminology is surviving in the environment of the modern manufacturing facility. It is alive and well in the whole spectrum of companies, from the largest to the smallest. I have spent mesmerising days in some of the largest companies watching operators 'touch up' the mythical dry joints. The interesting thing when challenged was the diverse range of dry joints. There were dull ones, bright ones, gritty ones and plain old ones the operators did not like!" Unquote.
Does the above sound familiar in your company? I really hope not. But if it does, some basic and intermediate training would definitely be recommended. There are more myths and beliefs, some more subtle like the non-wetting and de-wetting. I hope to elaborate on these in later articles.
Finally, allow me to add one more experience I had last year with a reputable company in South Africa. A technician surprised that after 20 years he had to deal with the non-existence of a dry joint was unwilling to change to the proper IPC standards and definitions relating to real hands-on problems in the assembly area. He fell back on his previous incorrectly-learnt dry joint saga when he was employed by another reputable SA car manufacturer. There they really pushed the myths further by giving flying reindeer to Santa Claus and came up with the DRY JOINT as follows: D = Defective, R = repairable and Y stands for yield.
This is absolute nonsense. It is high time we dedicate some time to proper training in this industry.
About the author: Eddy Van den Wijngaerd, Pr.(Tech) Eng SA, Ind. Eng. (Belgium), CIT (IPC), has a 36-year background in the electronics industry and is currently a consulting engineer and IPC certified trainer for South Africa.
For more information contact Eddy Van den Wijngaerd, +27 (0)21 7125964, [email protected]
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