LTCC PROCESSING INSTRUCTIONS For Ferro A6 and L8 Tape

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1.5 FILL VIAS STENCILS At Ferro Electronic Materials, 3 mil thick brass stencils are used on an AMI printer, MP9156, to fill vias. The brass is punched on a Ushio MP7150 punch using tight tolerance dies with 5μm clearance and brass bottomed strippers. The brass is lightly oiled before punching and usually is punched twice to ensure good cone-free holes. The punched brass is mounted in a 12” x 12” frame on a stainless steel 325 mesh screen. First, the brass is cut to size and glue is spread on one side around the edge of the brass in a band about 1/2-inch wide. The brass is then pressed into the center of the bottom of the screen and weights are put on the screen to ensure good contact of the brass and screen while the glue dries. After the glue has dried, the screen mesh is cut away from on top of the stencil. Some thin tape, such as Scotch tape, can be used to smooth the cut edge of the screen. PRINTER The printer used at Ferro Electronic Materials has a porous stone base through which a vacuum can be pulled. A backing paper is always used between the stone and the tape layer. The printer parameters are important. These are: PRINTING Squeegee 90 durometer, diamond 3/8 inches. Squeegee Set in the squeegee “down position” with the screen removed. The printer Pressure stage with paper and tape in place is positioned under the squeegee and the squeegee pressure adjusted to 7.5 psi. Downstop This can be left open. Squeegee Set to 0.6 inches per second in both directions. Speed Print Mode Use print/print mode, i.e., print in both directions for each filling of vias. Vacuum Use 20-25 inches Hg. It is important that areas of the stone outside the tape and backing paper are covered to prevent vacuum leakage. Mylar can be used for this. Snap-Off With stencil in place, bring the screen slowly down until the vacuum just pulls it on to the stone with tape and backing paper on it. Then use this as zero set-point and make snap-off at 25 mils. Vias are filled using the print/print printer mode. After printing, the paper must stay in place beneath the tape during the drying stage to ensure good vias. So carefully lift the paper and tape together from the printer stone stage and place in drying oven. Dry for 30 minutes at 70°C. Then pull tape from the paper. Only a very minor amount of paste will remain on the paper. Via filling is typically accomplished using modified on or off contact printing with metal or plastic
ased stencils. A vacuum pull through is typically used on the printing stage, and backing paper is typically used for backing the film during the via filling operation. Purpose built bladder type via filling equipment may also be used with the FERRO Tape and Via fill paste systems. Precise via filling conditions will depend on the number, size and mix of vias to be filled, and should be determined experimentally. 1.6 DRY After completion of via filling the parts should be dried (backing paper still supporting the tape) in conventional drying ovens at a maximum temperature of 70°C for 20 to 30 minutes. 1.7 PRINT CONDUCTORS Conductors are printed onto the tape using conventional screen printing techniques and recommended screens (see individual product data sheets). Conductor prints may be dried in conventional drying ovens at a maximum temperature of 70°C for 10 minutes. 1.8 DRY Dry in conventional drying ovens at a maximum temperature of 70°C for 10 to 20 minutes. 1.9 PRINT RESISTORS All co-fireable resistors are printed onto the unfired tape using #325 screens. Target dried thickness is 25-28 μm. The resistors should be dried in conventional drying ovens at a maximum temperature of 70°C for 10 minutes. 1.10 DRY Dry in conventional drying ovens at a maximum temperature of 70°C for 10 to 20 minutes. 1.11 STACK LAYERS All layers should be inspected for visual acceptance and collated. 1.12 INSERTS FOR CAVITY FORMATION Some general guidelines are offered in “Ferro LTCC Handling and Design Recommendations.” These must be followed for best results. There are four principal types of cavity. 1. Cavity with vertical walls but closed at bottom. 2. Cavity with stepped walls, closed at bottom. 3. Through cavity.
Page 1: 1.1 UNREEL TAPE LTCC PROCESSING INS
Page 5 and 6: no metallization, etc. Only minimum
Page 7 and 8: L8 Tape Burn out & Firing Profile B
Page 9 and 10: LTCC DESIGN RECOMMENDATIONS 2.1 CON
Page 11 and 12: 2.2 GROUND AND POWER PLANES IC Bond
Page 13 and 14: 2.4 ELECTRICAL VIAS Electrical via
Page 15 and 16: Thermal Hexagonal Via Pattern: Six
Page 17 and 18: Resistor to conductor termination o

LTCC PROCESSING INSTRUCTIONS For Ferro A6 and L8 Tape

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