Work at Tek
Tektronix, Inc work from 63-72
After two years as a utility man, my career at Tektronix took a turn that influenced the rest of my working years. That turn was becoming a technician in the 'Tube lab'. The Tube Lab was a small department within CRT R&D that built all the prototype CRTs for the design engineers. I spent two years in the tube lab and learned the processes that were used to prepare prototype CRT's. The CRT is divided into two basic components, an electron gun and a glass or ceramic envelope. The envelope was prepared with processes that deposited phosphor on the face, lacquered the backside of the phosphor, and laid down an aluminum mirror. The aluminum, besides being a mirror that reflected all of the light from the phosphor forward, also was the electrode to collect and discharge the bombarding electron beam. Another process was applying a conductive helix to the inside of the glass envelope that helped to shape the electron lens. These CRT's were basically the same as a TV tube except the deflection of the electron beam was done electrostatically as opposed to magnetically as in a TV tube. They were obviously also designed to deflect the electron beam at very high speeds and with very high precision. But it was another aspect of CRT's that intrigued me. Oscilloscopes were very popular tools of electronic design engineers used to observe different shapes and sizes of electric signals. The electronics of the 50's and 60's was in a transition from electron tubes to solid state devices (diodes, transistors) and was booming. The need to be able to capture and observe very fast electric pulses that came sporadically was the challenge and was done by attaching a camera to the oscilloscope and triggering the camera with the incoming pulse (signal). The signal was delayed with delay lines, allowing it to be displayed and photographed. But a Tek engineer named Bob Anderson had invented a concept of a storage CRT. The first generation was successful but was limited to relatively slow signals and the display was not bright enough to be viewed in a well lighted room. A group of process development engineers had been formed to develop techniques for improving the Anderson storage tube (called bi-stable storage). I applied for and got the job working in this group as a process technician. My first assignment was working on a storage tube that used a metal (gold) hexagon web to act as collector rather than the tin oxide used in the early storage tubes.
I will digress a bit to explain how the bistable storage CRT worked. It was made possible by Tektronix developing the ceramic envelope for CRT's. This was a challenge in itself since the electron gun depends on an ultra high vacuum (~10^-8 Torr) and ceramic is porous. However, the ceramic engineers at Tek mastered that challenge. The ceramic envelope consisted of a ceramic funnel and a glass faceplate attached with a glasseous material (frit) that could be melted in an oven and form the seal at a temperature below the melting point of the glass faceplate. For the storage tube, the faceplate was coated with a transparent conductor (indium tin oxide) before being sealed to the funnel. This tin oxide film acts as the collector. For storage, in addition to the primary electron gun in all CRT's, there were two flooding electron guns. The flooding electron guns continuously emitted low energy electrons (relative to high energy writing gun) that uniformly covered the entire target area. The following curve will be used to describe how this worked.
The target (surface of the phosphor on the faceplate) voltage was prepared by a series of pulses applied to the tin oxide until it came to rest at a potential below point A on the curve. Theoretically the flood electrons would drive the voltage back to the point where the secondary emission ratio is one, but in reality, the voltage was above zero and below Vo. The storage worked by the writing electron gun depositing a charge on the phosphor (dielectric) surface in the area it traversed or wrote. This electron gun operated at about minus 2000-3000 volts with respect to the flood gun cathode which was used as the reference for the system. So, a charge was deposited due to the secondary electron emission of the writing beam being much greater than one. i.e., a net of electrons was emitted and to be written the area needed to be charged positive above point A. This positive charge attracted the low energy electrons from the flooding electron guns and the written area was moved to point B because the secondary emission ratio of the flooding electrons was greater than one. Thus the 'written' phosphor was continually bombarded and charged to the potential (Vc) of the collector (the Indium/tin oxide layer in this case) and kept glowing. The unwritten areas remained at the potential just above zero and did not attract flood electrons and thus were dark. The potential on the Indium/tin oxide layer was selected to keep the written areas at a stable point (that is with secondary emission greater than one for flooding electrons). The stored image could be erased (target surface prepared) by pulsing the faceplate potential (Vc) high (which capacitively drove the entire phosphor surface positive) and bombarding the entire surface with flooding electrons until it was at one uniform potential and then pulsing it down until the secondary emission ratio was less than one (below Vo) and then ramping the potential up slowly enough so the flooding electrons kept the surface potential near zero. The two problems with this concept were: first it was slow, the writing gun had to charge the phosphor surface many volts to "write" it. Second, it was dim, both because the phosphor had to be a good dielectric and the most efficient phosphors at that time were not good dielectrics and because the flooding electrons which created the light from the written area were relatively low (100-200 volts) energy. These limits made the storage oscilloscope a niche product until the advent of the transfer storage tube.
As I stated earlier, after a couple of years in the Tube Lab I moved into the Process Development Group as an Engineering Assistant and worked on development for a new storage tube. The project manager was Pierre, an engineer from France. The innovation for this CRT was using a hexagon thin film gold matrix on the glass faceplate rather than the solid transparent indium/tin oxide layer as the conductor/collector. The phosphor was the conductive but more efficient P31 photographically deposited in the bare areas within the hexagon matrix with the gold thin film acting as the photo mask. The trick was to get the solution of photo sensitive Poly Vinyl Alcohol and phosphor to stay in the clear areas and wash out over the gold hexagons so the gold would act as a collector for emitted electrons. I was assisting the process engineer and his process for clearing the gold after the exposure was to manually move the faceplate under a faucet and visually determine when it was cleared enough. There were problems with uniformity and repeatability and I seemed to have an innate sense of what would work in manufacturing and what wouldn't. This wouldn't! In my spare time, I built and experimented with a rinsing device that allowed the water to come out in a broad, thin layer like a waterfall and the faceplate was rotated under it with a motorized lazy Susan device that had been made for applying photo resists. It worked pretty well but the process engineer wasn't interested. So, I drew up a sketch of the device and showed it to Pierre. He was impressed with my innovation and furious with the process engineer. The technique was further refined and became the standard in manufacturing. The storage tube turned out to be not that big of an improvement and it never went anywhere and neither did Pierre. A year or so later he was out of Tek and off on some scheme to pressure treat fence posts in eastern Oregon.
Norm Winningstad worked at Tektronix in the late 1960's and he was one of the leading thinkers about where computers were going. He was one of the first ones to envision personal terminals where each engineer had access to the computer from his desk. The problem was how to save the information at each terminal while the computer was serving others. Norm thought the bistable storage CRT offered a solution and he formed a team in 1967 (which I was part of) to develop a large (11") storage CRT and build it into a monitor for his envisioned terminal. The project was successful and the monitor's acceptance was slow but over a period of several years became very profitable. What Norm had not envisioned was the potential in MOS memory which has continued to expand with device density increasing some 2X per year since the late sixties. MOS memory became cheap enough to solve the storage of information problems and large central computers with many terminals reigned until the dawn of the personal computer in the eighties. Norm, as had Noyes at Fairchild, lost his support in Tektronix management and went off and started up several successful companies including Floating Point Systems.
At this time, ~1969, the CRT R&D engineers at Tektronix were divided into three groups: A product design group under Chris Curtin which primarily designed the electron guns, a process development group under Roger Franklin which designed the storage targets and processes to fabricate them, and an advanced product development group that worked on farther out ideas. I had been in Roger Franklin's group for a couple of years developing the 11inch storage tube. One of the teams within the Advanced product development group was managed by Jon Reed. Wes Hayward was in this team and he was working on a high-speed storage idea that involved two targets: a standard bistable storage target on the faceplate and a high-speed target on an electroformed nickel mesh. Tektronix had developed the electroform mesh capability to build small copper mesh that could be formed over a domed graphite mold at high temperatures and these domed mesh were used to shape the field in front of the writing electron gun; a major breakthrough in electron lens design. The CRT development engineers had extended this electroforming technology to form large nickel mesh. Wes had demonstrated the transfer of the image from the high-speed target to the bistable target and had recorded some remarkable writing speeds. The high writing speed was achieved by maximizing the thickness and minimizing the density of a magnesium oxide target. However, the light output from the written areas on the bistable storage target was so dim the image could only be seen in a darkened room. Wes was interested in his research. Jon wanted an application that would be useful in Tektronix products. Jon and I were friends from before his meteoric promotion and he discussed with me his frustration with getting Wes out of research mode. Although I was also interested in advanced storage CRT concepts, I was basically practical and I proposed an idea for solving the light output problem by adding another mesh with the bi-stable target and using high energy flooding electrons to excite a conventional (non-storage) target. The high energy would come from the potential (several kilovolts) between the conventional target on the faceplate and the mesh with the bistable target. The downside was that it was frighteningly complex from both the design and the fabrication point of view. It required the development of a bistable storage target on a mesh and extending Wes's transfer to a mesh-to-mesh transfer. I fleshed out the idea as much as I could before I proposed it to Jon. I don't know if Jon was convinced or just desperate but he offered me a position as engineer in his group to develop the idea (without engineering pay of course).
I faced some serious technical challenges. No manufacturable way had been developed for mounting the mesh inside the CRT. Wes, for his experiments, had the mesh attached through the wall of the ceramic funnel with frit (a solution that when baked became like glass and was used to join ceramic pieces together). But this was not a vacuum tight seal suitable for lifetimes of CRTs. The process for the low-density magnesium oxide (fuzz) was a kluge which had no controls and which produced, on occasion, targets with small areas that Wes could use for his research. The prototype CRT's Wes was using had to have a Gauss gauge attached which could be used for continual small volume pumping to maintain the required vacuum of about 1X10^-8 Torr. I had one technician working with me and she was an excellent operator and had been promoted to technician for her broad operator skills although she had no technical education.
The problem of the mesh mounting was assigned to Mike Keegan in Roger Franklin's group. He was given the charge of developing the mesh mounting to be used on both the transfer storage CRT that I would develop and a transmission (variable persistence) storage CRT that was being developed in Roger's group. This solved the problem for the long term but would not be done in time to solve the problem for the prototype CRT's I needed. This left the development of the two targets and testing of prototypes. I did the guidance of the technician in developing the high-speed target and both the guidance and the work of developing the bistable target as well as having prototypes built which I tested.
The development of the high speed (fuzz) target is described in detail for anyone interested in report 007 which is linked below. Here I will give a brief summary:
Basically, we had to put controls in place to control thickness, density and uniformity. We then had to optimize the parameters. I provided the direction and the technician did the work. The process was essentially subliming magnesium in a partial vacuum of helium and oxidizing it in a controlled air bake. One of the early setbacks was the technician was using an Electrolux vacuum cleaner to clean out the deposition chamber which became coated with low density magnesium. In the vacuum cleaner this formed dust and exploded, blowing out both ends of the vacuum cleaner up but not hurting anyone. We developed a vacuum in house that filtered out the MgO by bubbling the airflow through water to avoid the explosion. The technician's nerves eventually settled and she continued working on the development.
Tek Report 007
I did the development of the bistable target on a mesh. This needed to be a good dielectric (high density) but with short paths from the dielectric surface to the mesh which was to act as collector of secondary electrons. I did not keep a copy of the report written on this and have forgotten which target we ended up with. Some things I experimented were: electrophoretic deposition of magnesium oxide and silicon dioxide. Spraying these materials. I do remember that one of the electrophoretic depositions would look under the microscope like cracked mud flats and that was a good way to get the short paths to the mesh. I think we went into manufacturing with electrophoretic deposited silicon dioxide, but time is the minds enemy and I am not sure anymore.
I also did the testing of the first prototypes of mesh-to-mesh transfer storage CRT's that we built. The capability of the 'Tube Lab' was limited and so we could only fabricate one CRT every couple of weeks and we tried to get all the info we could out of each one. I spent a lot of time working out the mesh-to-mesh transfer wave forms and trying to understand what was happening. The results were amazingly successful. The writing speeds that Wes was able to get in small areas, we were able to achieve over the entire screen. The stored images were easily viewable in bright rooms. The oscilloscope designers were enthused about building a product that would make more than an order of magnitude increase in both stored writing speed and brightness.
For those with more than average scientific curiosity, I have included two reports I wrote about the Transfer Storage Tube (report 002 and 007). These were written during the transfer of the design from R&D to Manufacturing and were written as tutorials for manufacturing engineers and technicians. The original title of 002 was "A simplified explanation of the Transfer Storage Tube" but my counterpart in manufacturing engineering encouraged me to leave off the "Simplified"! Tek Report 002
The project was successful and the new oscilloscopes were featured in the internal Tektronix, Inc magazine, Tekscope and also in a short announcement of new products in Electronic Design.
note: Chris Curtin got his name on the credits for developing the Transfer Storage CRT although he had almost nothing to do with it. The electron gun was designed by an engineer in his group named Bo Janko. This leads to my discussion of patents etc. a little later in my story.
The Electronic Design article:
This project did the most to crystallize my thoughts on invention. It is extremely rare, probably never, that an idea comes to the inventor out of the blue. Inventions are merely extensions of what has come before and owe a great debt to those who invented the base of knowledge that came before. Further the inventor owes much to his coworkers with whom he discussed the concepts and who probably contributed many ideas that he eventually put together into a small extension. In this project, the only entirely new concept was to add a third mesh which was significant contribution in that it solved the fundamental brightness problem and allowed the usefulness of the transfer concept. The real contribution, however, was the development of these ideas. The low-density magnesium oxide (fuzz) idea was not mine but when I took over, it was being done in a lab environment (no controls, no repeatability, little understanding) just a desire for low density. Many of the process controls were innovative including the idea of using a laser at low angle through the mesh to control thickness. The conclusion is that inventions are a group achievement and the one with his name on the patent is just the one who made the last step. Secondly, the real work and greatest contribution is by the one who discovers how to build the device, the process development engineer. I was influenced a lot on this by a talk that was given to Tektronix CRT design engineers at that time by Walter Brattain, one of the original inventors of the transistor at Bell Labs. He was the process engineer of the group and I was particularly impressed with his humility.
The sixties were a breakthrough decade in electronics and during the last half I was keeping up with developments through both work, school and a lot of reading of technical magazines. In the early sixties, primarily at Fairchild Semiconductor, Noyes et al were developing the planar transistor technology (MOS) and toward mid-sixties the first multi transistor models were demonstrated and by late sixties (maybe early seventies) the first microprocessors and first charge coupled devices (CCD) were demonstrated and reported on. I particularly remember the first article I read where the author was touting CCD applications in video cameras and a litany of devices that I thought was overly exaggerated. It turned out it was probably understated. No one could have envisioned the revolution that was ushered in with these MOS devices. Even in the eighties, few recognized the revolution in photography. In a meeting in about 1985-86 in which we were discussing the future direction of inkjet printing, I made a pitch that we should focus on color since photography would eventually be digital and it would be huge to be able to print them on our printers. I was the only one in a group of about twenty of the leaders of our inkjet business who believed this at this time. In fact, Tom Haswell, the head of the inkjet business at that time, discussed it with me after the meeting and was interested if I really believed color was our future. Fortunately for inkjet in HP, one of the vice presidents of HP who Tom reported to, had the same idea of color I did and he had the power to insist.
Back to a little history of electronics in the sixties, Noyes had trouble convincing Fairchild Semiconductor that what they were working on was the future and that department of Fairchild was defunded and the key players let go or left. Noyes and several of his coworkers (including Andy Grove) formed another company and they had pretty good success – as Intel.
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