Tape Transfer Process

Pin Registration Alignment System for Screen Printing and Stacking
There are two domains in which alignment must be provided in this process. The first is the position of the printed pattern relative to the tooling holes. The second is the position of the printed patterns relative to each other on a layer to layer basis.

The first alignment (conductors relative to tooling holes) is used to establish the position of the printed features within the bar. This allows the bar to be cut without going through an exploration process to find the position of the cut lines. Cut lines can be provided for confirmation of alignment, but have been found to be unnecessary. This process has been used for many years and has been found to greatly simplify cutting while improving cutting yield. It also aids in assuring that all parts produced are of identical size. The basics of the approach are as follows:

1. Position of Conductor Pattern on Screen -
The conductor pattern must be placed on the screen so that it will print in the correct spot relative to the tooling pins. In most processes this is accomplished by exposing the screen with the artwork in approximately the right position and adjusting the screen once it is mounted in the printer. This means that the position of the parts within the bar is not known exactly. It must be discovered by trial and error. It will remain constant within a lot of bars made with a given screen set-up, but will change from lot to lot. To get the position of the cutting set up initially the first cut must be aligned with the exposed cut lines. To do this accurately, magnification must be provided. This works well enough, but requires expensive optics and video equipment. It is also very time consuming and makes doing short test runs difficult.

The method we prefer is to place the conductor pattern on the screen precisely so that its position in the build-up will be known accurately enough to allow cutting without set up adjustments. This is done by mounting a tooling bar on the screen frame. The bar has a "V" notch machined into it. The screen with its tooling bar is placed on a master plate which is equipped with pins positioned to match up with the tooling bar. One pin falls into the notch in the tooling bar. Another pin sets against the edge of the bar at the opposite end from the notch. This defines one, un-movable, position for the screen. When the artwork is made, the position of the tooling pins that align the screen are marked along with the conductor pattern. The relationship between the pins and the artwork is a constant that is shared by the printer and the stacker. This is defined in a master drawing that is used to generate all artwork and is provided as a part of the process package. Two master plates are provided. One is used by the screen maker who will use it to align the screen and artwork for exposure. The screen maker uses a fixture with a microscope to find the center of each reference mark on the artwork. Once the exact center of the mark is found, a .250" hole is made in the artwork. This is done for both holes. The art is placed on the pins in the master plate using these holes to align it for the exposure of the screen emulsion.

2. Aligning the Screen in the Printer -
This alignment method provides the opportunity to print the pattern in an accurately known position. To do this the screen must be positioned with a known relationship to the printing platen. This is done by providing pins in the platen which engage the tooling bar attached to the screen frame as the screen lowers during the print cycle. Since this is the same tooling bar that was used to place the image on the screen, once the platen with its tooling pins has engaged the bar/screen we know exactly where on the platen the print will be placed. We know where this spot is since we have defined it in our artwork and we define it physically on the platen with a second set of pins. These are the pins that the holes in the carrier tape engage during printing. 3. Establishing Accurate Registration in the Stack -
Once you can print the conductors with a known position relative to the tooling holes in the carrier tape, you can stack the layers with the position of the conductors known relative to the edges of the bar. The tooling pins of the stacker position the prints relative to the mouth of the die.

In the die is a tool steel build-up pallet which fits the die very closely. The sheets of ceramic with conductors are deposited onto the pallet. The position of the conductors are now known relative to the edges of the pallet. When the pallet comes out of the stacker it is mounted in the cutter by placing it in a nest of pins which pick up its edges. The cutter is calibrated in reference to these pins in its cutting platform. Therefore, since the pallet with the parts is positioned by these pins and we know where the cut lines are on this pallet, the cutter can be programmed to place its cuts at the positions where the cut lines are expected to be.