The manufacture of certain types of multi-layer circuit boards involves laminating a plurality of board layers, each of the layers having circuit patterns on both major surfaces thereof, into an interleaved structure with dielectric bonding layers. Such a laminating operation is typically a thermo-compressive operation. The laminated panels or blanks are further processed into multi-layer boards by such operations as, for example, drilling and metallizing via holes, and photo-lithographically defining circuit patterns in outer foil sheets of such blanks.
The laminated blanks and the completed multi-layer circuit boards exhibit a tendency to warp over a period of time. However, a drying operation included in the manufacturing process after the laminating step and after any subsequent wet treatments stabilizes the laminated structure sufficiently to eliminate any perceptible amount of warping. However, during the drying operation itself, the blanks need to be weighted down to retain their shape.
Thus, in accordance with existing techniques, a plurality of the blanks are loaded in stacks onto flat support surfaces in the form of shelves of a rack referred to as a baking rack. Each of the stacks of laminated blanks is then weighted down by a flat, distributive weight plate, which an operator places on top of each of the stacks in the rack. The rack, which is typically equipped with wheels or casters is then rolled into a room-size treating chamber, such as a baking oven.
Problems have been experienced in the past in that operators have been exposed to the possibility of injury while they lifted the weights onto the stacks, particularly while they lifted the weights to the uppermost shelves of the rack. Also, an oversight of an operator to weight down a stack of circuit board blanks prior to placing the rack into the baking oven causes such blanks to warp and renders the blanks useless.