50 years of wave solder
07 November 2006
How wave solder came to light
It's winter 1955, the cold chill has settled over south London, snow is on the way. Churchill has resigned to be replaced by Anthony Eden, James Dean died last month, aged 26, and On the Waterfront wins best picture award at the Oscars.
In a cold corner of Fry's Metals Foundry in Merton Abbey, Allan Barnes, a research scientist and Ralph Strauss, a flux chemist are huddled over a small pot of molten solder getting a heat while discussing Allan's latest invention. Little did they know at this time that they were about to make a breakthrough that changed the history of the assembly of printed circuit boards.
It all started on November 27th 1911; John Fry had been working for some years for Hallet and Fry, a family business owned in part by his father. The primary business was the smelting of Antimony, and some small interest in print metals. John was restless, he could see new opportunities to supply the printing industry, the formulation and control of the composition of these alloys was rudimentary, John new that bringing science and metallurgy to this industry could have a huge value.
He had been planning this for some time, for some three years previous he had been attending evening classes in Metallurgy and Chemistry at the Northampton Institute under the direction of Alfred Mundey, who was in charge of Chemistry and Metallurgy at the Institute.
On this November night John was returning from the Institute with Alfred, he met his wife on the way and all three retired to Lyons restaurant. Over a hot cup of tea John shared his vision for a new business, bringing metallurgy and science to the print metal business. His vision was well received, he received whole-hearted support from his wife and Alfred agreed to become Consultant Metallurgist for the new company. Fry's Metals Foundries was born. On July 1st 1912, John, after months of searching, took down the shutters on his premises at Holland Street. He had little money, no actual orders and a few tons of Lead, Tin and Antimony, and was almost unknown in the print industry. It was not a particularly promising start, John had doubts, was this a bold or foolish move? He knew that to improve the printing process he needed to understand more about the interaction of alloy composition with the process and the influence of impurities in the alloys. With this in mind he took the bold step of funding a young post-graduate to do research on the subject. Frances Weaver was interviewed and selected to undertake this work, this proved to be a fruitful collaboration, the output from this research was considered to be the definitive work on the subject and Frances was awarded a PhD. John Fry now had a firm knowledge base with which he could expand his business. This new knowledge combined with the co-operation of Alfred Mundey plus courage, perseverance and enthusiasm enabled Fry's to become known as technical experts in the printing industry.
Barnes and Strauss were getting some comfort from the heat of the solder pot, they knew that there was a better way to solder printed circuit boards and were determined to get a solution. They looked at the current process, placing components through holes in the PCB, dipping the bottom side in liquid flux and then dipping this assembly into a bath of molten solder.
At this time, 10 years after the end of WW2, many materials were still in short supply, rationing was finally ended this year. Petrol (at 22p per gallon) had been taken of the ration list a few years earlier, but still, rudimentary materials for building a solder machine were in short supply.
This dipping process was not working well, the static nature of the interaction of the solder and flux tended to cause flux to accumulate around the joints to an extent sufficient to deny access to the solder. Another problem was that the surface of the bath was covered with a film of oxide that had to be cleared away before each dip, the resulting soldered PCB's had a less than adequate electrical connection. They needed a way to present fresh moving solder alloy to the solder joints and do this in a way that was convenient for automated soldering.
Allan Barnes knew that a moving stream of solder was the answer and that day were about to try the latest incarnation of the solder nozzle to try to create the smooth non turbulent gently overflowing stream that they needed. Previous versions had been clumsy, Alan Barnes knew that the relationship between the dimension of the orifice, the pump speed, the static pressure and the back pressure was key to maintaining a smooth flow. They had found through experimentation that the crest of the wave could only remain flat and level if the nozzle had no increase in it's cross sectional area from the lower end to it's mouth to the nozzle thus avoiding eddies in the molten solder. This had required some careful and intricate design and fabrication. They had recently fitted a new flow straightener at courage, perseverance and enthusiasm enabled Fry's to become known as technical experts in the printing industry.
Barnes and Strauss were getting some comfort from the heat of the solder pot, they knew that there was a better way to solder printed circuit boards and were determined to get a solution. They looked at the current process, placing components through holes in the PCB, dipping the bottom side in liquid flux and then dipping this assembly into a bath of molten solder.
At this time, 10 years after the end of WW2, many materials were still in short supply, rationing was finally ended this year. Petrol (at 22p per gallon) had been taken of the ration list a few years earlier, but still, rudimentary materials for building a solder machine were in short supply.
This dipping process was not working well, the static nature of the interaction of the solder and flux tended to cause flux to accumulate around the joints to an extent sufficient to deny access to the solder. Another problem was that the surface of the bath was covered with a film of oxide that had to be cleared away before each dip, the resulting soldered PCB's had a less than adequate electrical connection.
They needed a way to present fresh moving solder alloy to the solder joints and do this in a way that was convenient for automated soldering.
Allan Barnes knew that a moving stream of solder was the answer and today was about to try the latest incarnation of the solder nozzle to try to create the smooth non turbulent gently overflowing stream that they needed. Previous versions had been clumsy, Alan Barnes new that the relationship between the dimension of the orifice, the pump speed, the static pressure and the back pressure was key to maintaining a smooth flow. They had found through experimentation that the crest of the wave could only remain flat and level if the nozzle had no increase in it's cross sectional area from the lower end to it's mouth to the nozzle thus avoiding eddies in the molten solder. This had required some careful and intricate design and fabrication. They had recently fitted a new flow straightener at the base of the nozzle to give a more laminar flow to the solder, and hoped that this would make the difference.
Ralph Strauss looked at the temperature gauge, now reading 250C, he nodded to Allan Barnes, it was time to switch on the pump. Allan gingerly switched on the motor and slowly turned the large black dial to increase the motor speed. The bright silver liquid surged through the nozzle extending two inches, hanging in the air before splashing back into the molten solder pot. Allan quickly turned down the dial and the solder settled into a smooth regular stream flowing evenly over both sides of the nozzle. All three look at each other, slowly taking in the sight in front of them - the wave solder process was born.
The first machine to be built had a gas fired melting pot and the board transfer mechanism was constructed from Meccano, the impeller for the pump was a three bladed stainless steel propeller from a motor boat engine this machine was sold to Plessey (radio receiver pioneers) for the grand sum of £197. Peter Offord, who wrote many technical articles, promoted this new soldering technology. Allan Barnes did endless trials and tests to show the capabilities of the technology and word gradually got around the industry.
Allan Barnes, Vic Elliot and Ralph Strauss applied for a patent for this new invention on Oct 3rd 1956 and this was granted on July 23rd 1958. This invention was to help start the revolution in Electronics by providing an efficient and economical method for the mass production of printed circuit boards. No patent was applied for in the US as at the time this was thought to be a difficult process.
Today there are around 75,000mt of solder alloy produced on an annual basis to feed the tens of thousands of wave solder machines in all countries across the world. All made possible due to the courage, perseverance and enthusiasm of three men, the teams that supported them and the culture imbedded in the company by the founder John Fry.
In 1943 Associated Lead Manufacturers (ALM) bought Fry's Metal Foundries. In 1977 ALM changed its name to Lead Industries Group Ltd (LIG) and then in 1982 LIG changed its name to Cookson Group plc.
Today the heritage of the wave solder process is carried by Cookson Electronics Assembly Materials who continue to bring innovation to the wave solder process through their Alpha branded soldering materials. The industry leading Lead-Free alloy SACXTM continues this tradition breaking the mold by delivering high yields and reliability at a lower cost.
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