Final Machining of the Cold and NV Circuit Boards --------------------------------------------------- Date 26-Oct-2020 This note describes the final machining that is required for both the Cold and NV printed circuit boards. Two machining operations are need on both the Cold board and the NV board: - Cut the "Chip Trench" into the board at its center - Cutout the perimeter of the finished circuit board. This work is for Niyaz Beysengulov and Johannes Pollanen and is on Johannes account number GE100099 . I have 6 of both the Cold-Brd and NV-Brd. To start with lets work with 3 of each: 1 of each for setup and practice and 2 of each for finished usable cards. These are microwave circuit boards that are made with a special low loss circuit board laminate. This laminate is mechanically much softer and weaker than the normal G10 / FR4 printed circuit boards that one sees in typical equipment. The "zero, zero" of the coordinate system for both of these circuit boards is in their Center. Both of these circuit boards have 4 holes for 1/8" diameter alignment doll pins - one hole in each corner. - On the Cold board the doll pin holes are located 31 mm in both X and Y from the zero, zero Center of the board. - On the NV board the doll pin holes are located 11.5 mm in X and 16.5 mm in Y from the zero, zero Center of the board. Y is the long dimension of the NV board. Chip Trench: ------------ - The exact same shape and depth of chip trench needs to be cut into the Cold and NV circuit boards. This cut should be made with a 20 mil diameter end-mill. The details of this cut are shown in the attached drawing. - The depth of the cut is 20 mils below the top surface of the card. - All copper has been kept back 0.15 mm from the edge of the chip trench cut. Finished Card Perimeter Cutout: ------------------------------- - I assume that some setup will be needed to clamp down the center part of the card (i.e. the desired finished part of the card) while its perimeter is cutout. - Any of the holes in the center part of the Cold board may be used to pass screw through to hold down a disk shaped clamp if you want to do that. Clamping down the center part of the NV board may be more difficult. - The finished shape of the Cold board is a disk 56.00 mm in diameter. The ground plane copper has been held back 0.10 mm from the perimeter of this final cutout disk. I have placed a white silk screen line just inside the perimeter of this 56 mm diameter disk - so most of this line will probably remain on the finished disk after it is cut out. - The finished shape of the NV board is a rectangle 14.00 mm in X by 25.00 mm in Y with its corners rounded to 0.80 mm radius. Again the ground plane copper has been held back 0.10 mm from the edge of the finished card. I have placed a white silk screen line just inside the perimeter of the finished 14 mm by 25 mm rectangular card with rounded corners. Most of this line will probably remain on the finished NV card after it is cut out. Scratches on the Cards Please try to minimize scratching the surfaces of these cards. If scratches are necessary please try to put them on the back side of the card - the side without traces. Additional Drawings or Documentation I'm happy to answer any questions or make any addition drawings or documentation that you want to describe this work. Please Save Jigs and Machine Setups There may be more cards coming that will need final machining that is identical or very similar to the Cold and NV board so please save any jigs that you need to make and machine setups. I'm happy to store the jigs if you want me to. Please Save some Scraps Please save some of the larger pieces of scrap material after cutting out the perimeter of these cards. I would like to give some scrap pieces to Niyaz and Johannes so they can get a real feel for the mechanical properties of this microwave pcb laminate. Pictures of the Cards Still in the Panel If you want to study the layout of the cards to plan your work I have pictures of them still in the panel at: https://web.pa.msu.edu/people/edmunds/Cold_Brd/ Photos_Cold_and_NV/ Cutting the Individual Cards Out of the Panel I assume that you want to start the final machining work by cutting the individual cards (with their alignment pin holes) out of the panel. If you want I'm happy to do that on a flat clean bench with a straight edge and an exacto knife. Edges of Finished Cards I have no idea how well this microwave pcb laminate is going to cut. If the edges of the finished cutout cards are rough that is not a problem. I can clean them up with 400 grit paper or something like that. Schedule If we can have the finished cards in November that would be great. Thank you for your work to make these specialized circuit boards for their research. Dan Edmunds Phone: 884-5521 email: edmunds@msu.edu