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What Is MLC
Multi-layer Ceramic (MLC) is the integration of highly reliable ceramic materials,
close tolerance processes and flexible design methodologies that are used to
produce interconnects for semiconductors and electronic systems. An MLC package
is a high-density electrical interconnection system in a single monolithic structure.
MLC packages are fabricated from stacked and registered circuit and dielectric
layers of a ceramic base which are sintered or "co-fired". The ceramic constituents
are formulated with organic binders and cast into thin (5- to 20-mil) sheets called
green tape. Vias are punched in the green tape and conductor material is screened
on to fill the Via holes. This process makes the electrical connection between layers.
The conductor pattern for each layer is then screen-printed onto the green tape,
interconnecting the Vias. Printed green tape layers are laminated using heat and
pressure and then fired in a controlled atmosphere furnace to sinter the ceramic and
metal into a hermetic composite. An overview of the MLC concept is shown in Figure
1 below. Chip components are mounted on the surface layer to create a completed
circuit.
MLC advantages over etched-circuit boards
- Consumes less space and weight.
- Higher performance due to shorter conductor paths closer component spacing for tighter thermal coupling better control of parasitics, and excellent component tracking.
- Simplified system design; reduced system cost due to simplified assembly.
- Higher reliability due to fewer connections fewer inter-metallic interfaces, and improved immunity to shock and vibration.
- Easier system test and troubleshooting due to pre-tested MLC functional blocks.
MLC advantages over custom monolithic ICs
- Lower non-recurring design and tooling costs.
- Ready accommodation of design modifications.
- Faster turnaround for prototypes and early production.
- Ability to intermix many different device technologies for increased design flexibility.
- Ability to rework allows complex circuits to be produced at reasonable yields and permits a certain amount of repair.
MLC advantages over plastic packages
- Higher thermal conductivity for enhanced power handling.
- Higher performance due to built-in shielding and transmission lines for controlled impedance.
- Higher density due to multiple conductor layers inter-connected by vias.
- High reliability due to inert nature of substrate.
- More flexible l/O options and add-on components.
- MLC advantages over conventional thick/thin-film hybrids
The decision to use MLC devices is the result of a selection process in which other
technologies such as thick-film hybrids thin-film hybrids, leaded plastic packages,
custom ICs and etched circuit boards are considered. Some comparative strengths
of MLC are:
- High reliability.
- High interconnect density.
- Excellent power handling capability.
- Accommodation of high l/O pin counts.
- Excellent electrical isolation.
- Good control of transmission line parameters.
 MLC Designs (PDF File)
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