Issue link: https://iconnect007.uberflip.com/i/1473479
92 PCB007 MAGAZINE I JULY 2022 years, started working on optical alignment. He needed a method to hold layers together, so he looked at eyelets (rivets), hot heads, ultrasonic, and induction. Aer months of development, he settled on induction and came up with a scheme to "weld" the many inner layers together rather than use the com- mon rivets or plate pins. is has evolved to where welds can be located to interior spots on the I/L core. e pinless systems, with inner layer welding are also available for traditional pin layup. Process of Operation e process of using optical alignment is sim- ilar to manual layup, only more accurate and faster, with checks to ensure material order and orientation. e process is shown below: 1. Place the lower lamination plate in posi- tion on the layup table and begin layup as usual up to the first separator plate. 2. Aer placing the first separator plate in location, place the untooled copper foil (this foil will be outside layer n). 3. Next place the untooled prepreg (this is all the prepreg between layers n-2 and n-1). 4. Place the prepreg along the two perpen- dicular laser layup lines (Figure 3). 5. Continue placing material up to layer (core) 1 and 2 then activate the welding head. 6. Place the welded package along the two perpendicular laser lines. e welded package consists of layers 2 to n-1 with all the associated prepreg welded in place between all the layers. 7. Place the untooled prepreg (this is all the prepreg between layers 1 and 2). 8. Place the untooled copper foil (this foil will be layer 1). 9. Place the next separator plate and repeat the process for the entire book. e inner layers must first be prepared with the corresponding fiducial targets on top and bottom side for the optical alignment (Fig- ure 3). e prepreg has no need for any hole/ punch. e inner layers must have weld cou- pons etched in the reserve zones on both top and bottom sides (Figure 3), and can be placed anywhere along the edges of the lamination plate or inside the image area. e use of fiducial targets etched in the lay- ers to align through image processing via CCD cameras is the critical alignment step. is pro- cess results in lower manufacturing and main- tenance cost due to the elimination of the pins, bushings, and tooled separator plates on the lamination process. In today's best fit on pin lamination tech- nology guarantees around 75 µm for layer-to- Figure 2: Tolerances associated with pinning systems 2 .