How to get the electrical signals through the glass envelope?
One of the most critical parts of the nixie tube is called the stem. It is the part where the metal electrodes penetrate the glass envelope. If it is not manufactured perfectly, it can contain leaks along the electrodes that will eventually let the surrounding air enter the nixie tube and spoil the sensitive internal atmosphere.
All the mass-manufactured nixie tubes from the 70s use flat disc stems. A flat stem allows the nixie tube to be small and makes manufacturing easier and less expensive. The only problem is that the machinery needed to produce such stems is too complex. We had to develop something different as building such machinery was above our capabilities.
There was an older technology available.. a pinched stem.
Prior to the flat stems, vacuum tube manufacturers used pinched stems. A pinch stem can be found in incandescent light bulbs – which is an early kind of vacuum tube. This kind of stem doesn’t need such complex machinery, it can be made by hand with simple tooling. The disadvantage is that it takes longer to make and the final vacuum tube needs an additional base – but that was an acceptable compromise.
The decision to use pinched stems enabled us to begin the actual production.
