Tektronix Printed Circuit Boards 1969

a radio telescope here's a million light-years into space a satellite relays communications between the continents a space probe sends close-up pictures of the surface of the moon or the planets a walk in space a rendezvous high above the earth at 18,000 miles per hour intricate electronic equipments helps make these things possible as we expand our horizons the need for extremely reliable electronic equipment becomes more urgent circuitry becomes increasingly complex and space becomes more and more limited electronic computers require thousands of intricate circuits automated control equipment extremely complex but dependable and in a small space communications and broadcast equipment is becoming much more compact the consumer market has felt this trend and so has electronic instrumentation complicated high performance instruments such as these have been made possible through the use of solid-state devices constructed on text circuit boards the circuit board enables an engineer to design equipment that is more reliable more complex in much less space and for these reasons Tektronix incorporated the world's largest manufacturer of laboratory cathode ray oscilloscope is relying heavily on the use of circuit boards in the design of new equipment because of the high component density offered by the use of these boards it is possible to build more sophisticated instruments with greater versatility and reliability let's follow some of the techniques in the design and manufactures of high quality circuit boards of Tektronix this is where it begins with the engineers schematic diagram of the circuit to be built a transparent ruled grid is placed on a light table a piece of frosted drafting film is placed over the grid paper templates representing the components are aligned over this way as our determined for the interconnecting conductors of the templates are four times the size of the components they represent the intersection of any lines indicates a possible hole position on the finished board solid lines indicate conductor paths on the top side dashed lines indicate conductors on the bottom of the board you arranged and rearranged until you find the shortest path sometimes we're a component placement is critical it is not practical to make the layout directly from a schematic diagram in such cases the actual layout will be made and tried breadboard fashioned after this is working in the satisfactory manner the component templates will be positioned and conduction paths laid out to duplicate those of the breadboard when the layout is complete and all work has been checked against the schematic the mock-up is made another grid is placed over the penciled layout a frosted sheet of wrapping film is placed over his grid a black circle or pad is placed at each point where a hole is to be drilled in the board conductor paths are laid down with black opaque tape the top side of the board is done first the black tape will duplicate each of the solid pencil lines a separate four times mockup will be made for each side of the board on the second side the black tape will duplicate the dotted pencil lines this larger size makes layout easier and ensures greater accuracy slight errors in component placement will be reduced by four on the finished board a final check is made between the mock-up and the original schematic the mock-ups are placed on a copy camera to be photographically reduced now we have a photographic negative the actual size of the finished board prototype boards may be handmade at this point to verify the design and if everything checks okay steps will be taken to make the circuit boards in production quantities film positives are made from the negative they are carefully inspected from these silk screens will be made to be used in later operations a silkscreen actually contains no silk it is a fine woven stainless steel or nylon mesh all openings in the mesh are closed except where the conduction paths will be on the finished boards ink or chemical resistant material can be forced through the openings in the mesh this is the electrochemical building it was especially built to house all the electrochemical processes used to manufacture components for the oscilloscope that Tektronix manufacturing circuit boards is one of the major processes handled here the fabrication of circuit boards begins the raw material is a 13 by 20 inch sheet of glass epoxy 1/16 inch thick the thin sheet of copper laminated on each side we call this a flap the material has been manufactured to very rigid specifications and was carefully inspected on arrival to assure that it is of the highest quality notches and registration holes required in the manufacturing process are punched into the flats the first step is to drill all the holes this may be done in two different ways depending on the size of the production run for smaller runs it is done with a special drilling machine called a pantograph drill the drilling template was prepared from the original mock-up it is two times the size of the finished board the pantograph drill has a reduction ratio of two to one at each point indicated on the template a hole is drilled through six flats at a time the high-speed drill is solid tungsten carbide each color of the template indicates a different drill size you larger production of boards is best handled with a machine which is almost completely automated for heads 16 drill spindles control by numerical information on a punched tape 10 flat that's 2 stacks of 5 flats each are drilled at one time several boards are produced on each flat the numbers were flat and dependent on the size of the finished board the tape not only programs the exact position of each hole but it also determines which spindle or drill size will be used the holes will be accurately positioned within plus or minus 2 thousandths of an inch although the drilling machine operates almost entirely without attention the making of the programming tapes requires a great deal of operator skill a microscope pinpoints the exact position of each pole on a photographic negative this position is represented by a numerical code punched into the tape this tape will be used to control the exact position of each hole drilled as well as which drill spindle is used all the component holes are drilled now we will deposit a metallic conductive path through the holes the drilled flats are racked up cleaned and into him electroless copper bath here a catalytic deposition of copper takes place now this is not an electrolytic plating solution however a thin film approximately ten millionths of an inch will be deposited out of solution to all surfaces including the inside of the holes now this was our objective to place an initial deposit of copper in the holes to provide a conductive path for subsequent electroplating the next step is to put a resistive material in the areas which are not to receive additional plating now this is done by image screening the screen which in this case is stainless steel was made photographically from film positives of the original circuit board mock-up the resist now covers the entire surface of the flat except for the circuit paths the flats will be dried and the opposite sides screened it is necessary to know the number of square inches of surface to be plated in order that the proper plating current may be chosen fight transmitted by the photographic positive and picked up by a photoelectric scanner gives an accurate indication of the area of the resist a calculation will determine the current required we can now plate additional copper on all surfaces not covered with the resist this operation is known as pattern plating the back-and-forth motion forces the plating solution through the holes copper is plated on all the exposed conductor areas and through the drilled holes each hole becomes essentially a built-in eyelet the flats are now ready to receive the final plating in this case gold though other metals might be used they are clean and placed in an acid solution of gold salts a few millionths of an inch of metal is deposited directly from the solution this provides an initial non-porous deposit the flats are rinsed and moved to the final plating tanks dere an electric current will deposit an additional thicker layer of gold only the circuit areas are plated the rest of the flat is covered with the resist the final plate will protect the copper from oxidation and will also protect it from the etching solutions used later resist has served its purpose so it can be removed now we have the copper covered glass epoxy base with additional copper and gold in the areas which will serve as conductors this includes copper and gold through the holes now we want to remove all the copper except that which is to serve as conductors the etchant containing ferric chloride will dissolve copper but it has no effect on gold so the gold protects the under layer of copper from the etching solutions metals other than gold might be used if they would resist the etch protect the copper and be readily soldered we now have a flat or several circuit boards with gold-plated copper conductors this plating extending through the holes which will receive component leads a scrubbing completely cleans the plants of any chemicals or residue left from the plating process the metallurgical and the process control Laboratories are constantly checking the process before a new board goes into production many tests are conducted each process must be kept completely in control at all times tests must be made in the thickness of the metal deposited on the structure of the metal to assure that the plating is of uniform thickness but it is bonded properly to the layer below chemical tests physical tests electrical tests a board is cut in sections here is the cross-section of the metal plated through a hole this shows that there is an unbroken electrical path from one side to the other the thickness of the final layer is measured on this machine beta particles are directed at the point to be checked by measuring the reflections or back scattered radiation it is possible to accurately determine the thickness of the plate from these measurements the plating time and currents are verified and adjusted if necessary to assure the proper thickness and crystalline structure nomenclature is screened to the component side of the board's a special solder mask is screened to the bottom of the board this solder mask will prevent solder from adhering to any portion of the board except where it is desired this makes it possible to solder the boards by the flow solder method we will see this later in the assembly operation the flaps are shared into individual boards the boards are blanked out in a die this punches out large holes notches or corners they are routed to exact size square pins are inserted in many boards these will be used for solderless interconnections in the final assembly test terminals and eyelets are added where required some of the plug-in boards require that special connectors be attached this completes the manufacturing of the boards every board is given careful inspection hole size and the positions are checked with an optical comparator the boards are a packaged ready for component assembly this is the assembly area here the circuit components are mounted on the boards the component leads have been pre-cut and bent to the proper size and shape using sample boards as a guide the components are inserted into the proper places in the future the machine may replace many of these hand operations we are now ready to solder the components in place this is an automatic soldering machine the boards are in special carriers different carriers are used for each type of board nylon pins have been inserted in any holes which are not to receive soldered first they pass over a foam flux unit then over a hot plate to preheat them next over two waves of molten solder a pump keeps the hot solder flowing in this matter the solder mask prevents solder from adhering to any points other than those that should be soldered capillary attraction in the force of the solder wave pulls the solder up through the holes here we have an excellent electrical connection as well as a solid mechanical support for the component lead note the solder actually rising up through the holes completely wetting the leads and bonding them to the plated copper conductors flux residue is removed by an ultrasonic cleaning process the solder mask is not removed it has no effect on the operation of the circuit and it offers some protection to the surface of the board here is a perfect board every connection properly soldered and solder only on those places desired delicate components which should not be subjected to the flow soldering or to ultrasonic vibrations and cleaning solvents or parts that must be placed on the underside of the board are now added and hand soldered the boards receive a 100% visual inspection each board is tested under actual operating conditions it is installed in the special test jig which is actually part of an operating instrument it is checked to see that it is operating properly and that all controls and be adjusted within proper range the board is assembled into an instrument the solderless connectors are attached to the square pins on the board the oscilloscope is complete it is adjusted and calibrated these are precision electronic measuring instruments cathode ray oscilloscope instruments that are rugged and dependable complicated instruments but easily serviced if necessary compact instruments with thousands of parts and connections instruments of higher performance greater reliability and smaller size instruments made possible through the use of modern edged circuit boards you

Channel: VintageTEK Museum

Views: 39,748

Keywords: Tektronix;, Oscilloscope

Id: 7weZ0TNRcuw

Length: 29min 56sec (1796 seconds)

Published: Sun Oct 30 2016

Reddit Comments

[u/hex00110]

My grandfather worked as a courier for a company that made these huge taped diagrams - i use to have a portfolio big leather case that had a few old diagrams of circuit boards I think for CAT construction equipment. — I’ve searched for that folio soooo many times when I visit home but can never find it.

I’d I ever do I’ll be sure to post pics and get hem framed

[u/Beerwithme]

That brings back memories for me, I've done that work 40 years ago. Many hours in the dark-room (before it had the other meaning) and drilling bare PCBs. Super dull work, but also strangely satisfying to go from large routed design to 5x smaller assembled and functioning PCB.

[u/DiamondCubeMiner]

Knowing that it's from 1969 the quality's amazing!

[u/orangenormal]

What a painstaking process. Thanks for sharing this. It’s truly incredible how far we’ve come.

[u/[deleted]]

Is it Morgan Freeman narrating the thing? lol

[u/Howie1962]

I got to design 100's of PCB in the 80's with a similar process. We didn't get to use artwork 4X size as we didn't have all that fancy camera gear. It was all done with 1X donuts and tape (Bishop Graphics) on film. We would make a 1X negative of the artwork by contact and then contact exposure to copper clad that was pre-coated with a resist. For us every board was hand drilled one board at a time.

Having this all in house meant we could come up with an idea in the morning and have a working board by the end of the day. (Or week depending on complexity.) All of our boards were single sided or double sided with no plated through holes. Any via was achieved via component leads and soldered both sides.

Fun times

[u/dekankur]

HCB - Handwritten Circuit Board

[u/GioDude_]

That was amazing to watch thank you.

1) I love the amount of detail goes into everything. The double and triple checking that had to happen so you didn’t forget to connect two things and reorder a board. 2) nobody is wearing mask or anything. Just the way it used to be done. 3) “in the future machines will place components for us” crazy to think now pick n place machines are so well known people are building them for home use.

[u/halfbreed_]

My old employer