Copper-Aluminium-Copper (CAC) and Copper-Steel-Copper (CSC) offer an aluminium steel separator with an impressive difference. It is sandwiched between two sheets of copper foil, which pre-seals the critical copper shiny surfaces from exposure to airborne particles and resin dust. During multilayer lamination, the copper foil releases from the aluminium/steel separator sheet and becomes the outer layer foil for the printed circuit board, above and below.
GOULD's proprietary process ensures that the copper surfaces are free of any particles or dents 5 μm or larger. The net result is consistently higher yields on high density, fine line and gold feature circuit boards. Costly manual handling and cleaning steps are eliminated, which reduces labor costs and improves cycle time and throughput during the lay-up process.
CAC/CSC is also the best and most economical solution for using difficult-to-handle free-standing thin foils like 5 μm and 9 μm (laser drillable) on high end multilayers.
Aluminium or steel separators are less than the half thickness of the conventional stainless steel press plates. This offers a significant capacity increase without capital expenditure.
CAC/CSC improves post-electrical test and final yields with the degree of improvement keyed to circuit density, line width, and line spacing. It ensures that critical copper foil surfaces remain free from foreign material and airborne particulate contaminates before and during lamination.
Reduction of lay-up time with less components to handle and no cleaning of the foils simplifies the lay-up process and reduces costs.
Because the foil is attached onto a rigid separator by glue lines the difficulties of handling are eliminated. Thin foils allow realization of fine lines and spaces as small as 50 μm as well as laser drilling. There is no need for differential etching with all the negative implications of reduced thickness uniformity.
The choice of aluminium or steel (high resp. low CTE compared with etched inner layers) minimizes thermally induced stress by CTE mismatches and improves dimensional stability at critical multilayer build-ups.
CAC/CSC is available with GOULD's proven and proprietary copper foils. The separator material is hardened (Alu) and chrome-plated (steel) to meet the demanding requirements of today's lamination and drilling processes. Thickness is 0.30 mm (CAC) and 0.22 mm (CSC). To reduce risk of image transfer depending on lay-up and lamination conditions CSC is available also with 0.49 mm steel.
The use of CAC and CSC can reduce inherent temperature differences in a lamination book due to its higher thermal conductivity and lower mass (see graphs below) and allows anincrease of the maximal load per daylight opening when compared with conventional lamination conditions. For best results, refer to GOULD's recommendations on lamination conditions.
The glue area is set in a range of 5 to 50 mm from the sheet edges. Glue adhesion is weakened by heat during processing and allows for easy seperation of the laminates after pressing.
|0.30 mm||0.22 mm||0.49 mm|
|Specific heat capacity||kJ/kg*grd||0.99||0.45||0.45|
|CTE (0...200°C)||10-6 1/grd||26.1||12.1||12.1|
|Elongation||%||> 10||> 16||> 18|
CAC and CSC sheets can be supplied in varying sizes with and without registration holes. Foils are available in thicknesses from 5 μm (0.148 oz/ft2) to 70 μm (2 oz/ft2).