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Technology, Innovations & Flutemaking

Miyazawa and Advanced Soldering Technology

This article deals with the variety of silver solders, gold solders and brazing alloys that Miyazawa uses, and the innovative way they are utilized to fuse our different metals and exclusive alloys together.

In years past, many manufacturers used soft solder comprised of lead and tin to solder toneholes as well as lip plates and ribs to the tubes of the flute. There is one advantage to this: It requires a relatively low melting temperature of about 355 degrees Fahrenheit, which means it will flow quite easily. This insures that the tube will not be annealed, or softened, as happens when precious metal tubes reach about 930 degrees Fahrenheit. This is where the benefits of soft soldering end.

The primary problem with soft solder is lack of strength. A soft solder bond is relatively weak compared with the modern solders and brazes that Miyazawa uses. A soft solder bond has the strength of about 5000 to 7000 PSI (pounds per square inch) while the hybrid silver solder that Miyazawa uses has a strength of 21,000 PSI, and silver braze has the strength of 65,000 PSI.

Another problem relates to the actual content of the solder. Lead is one of the densest and heaviest elements on earth, and when used in such a critical area as the tonehole, it has a tendency to "deaden" or "dampen" the sound of the flute. This is often mistaken as being a "dark" sounding instrument but in many circumstances makes the instrument difficult to resonate, and may produce undesirable resistance.

A more long term problem is that lead deteriorates over time, a problem exacerbated by moisture. This deterioration causes leaks in the solder between the flute tube and the tonehole, and has been the cause of much frustration for the performer as well as the repair technician. (Note: when doing repairs on an older instrument, be sure to check the toneholes for leaks.)

From the standpoint of clarity, response and lushness of tone, one of the most important decisions to be made in flute manufacturing is that of the solder to be used on the toneholes. Miyazawa uses a hybrid solder instead of a silver braze. As mentioned previously, hybrid silver solder has 3 times the bonding strength of soft solder. So why not use a silver braze instead, which has a bonding strength 3 times that of the hybrid silver solder? The answer is simple; tone quality and tube integrity.

Silver tubes are annealed, or softened, at a temperature of 930 degrees Fahrenheit. Hybrid silver soldering requires a temperature of only 450 to 535 degrees Fahrenheit, while silver brazing requires a temperature of 1200 to 1290 degrees F. The tubes glow red under these temperatures, and annealing occurs.

Why does Miyazawa go to these lengths to avoid annealing the flute tubes? There are two reasons. The first reason is that the high temperatures associated with silver brazing change the molecular structure of a silver or gold tube, particularly on the top side of the flute where the heat is directed. This means that the molecular structure of one side of the tube is different from the other side, making the tube composition inconsistent. When annealing occurrs, the metal is softer. This makes for a less rigid and slightly malformed tube. With this softness, the response of the flute slows down. The harder a tube is, the faster the notes respond.

Points of Interest About Soldering and Brazing

With some soldering jobs, Miyazawa uses a computer-monitored microwave energy instead of a flame. This is for more precise temperature control, achieving a temperature accuracy range within one degree Fahrenheit. This is significant since it prevents the metal from being heated up any hotter than it needs to be for the shortest time possible. This helps to maintain the integrity of the parts being soldered and also reduces the stresses that high temperatures can introduce into metal. This technique is used with excellent success on the key mechanism and the lip plate/chimney, both of which are silver brazed.

  • Solders and brazes match the color of the flute mechanism, toneholes, and tubes. Miyazawa uses a variety of gold solders and brazing alloys depending on the karat of gold being joined and strength of the bond required.
  • Unlike most manufacturers, Miyazawa key cups have an integrated spud (what the screw that holds the pad in is screwed into). No soldering is required since the spud is machined or milled out of the same piece of metal as the key cup, and a flat inner key surface is achieved. This is important because the pads and pad cups are subjected to a lot of moisture which accelerates the deterioration of the lead in soft solder typically used in traditional flutemaking.

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