The packaging technology of leadless components on ceramic circuit boards
has been demonstrated to be sensitive to process control and the
use of materials of consistent characteristics. The relative newness of the
technology means that limits on the many operating "windows" are not well
established, resulting in more critical reliance on tight design, materials,
and processing controls.
Specific reliability and quality problems that have been
encountered, and the means to resolve them, are summarized below with a brief
comment on each.
• Solder fatigue
Mitigated by matched TCE between LCC and board, and use of a
heavy "window frame" on the LCC package to constrain thermal strain.
• Mounting pad failure
Control the exposure time and temperature to which the pads are
• Bowing and cracking of ceramic blanks
Control through initial flatness, materials and process controls
(especially firing temperature), and careful handling.
• Brittle copper trace
Results from large grain size or improper sintering of copper
(embrittlement is not a problem with noble metals). A temperature cycling
screen is recommended for all fabricated boards.
• Dielectric porosity
Only copper thick film MIBs reflect this problem due to gases in
the dielectric paste. Paste improvements continue, but conformal coating is
recommended to improve moisture resistance.
• Cracked dielectric
Nitrogen-fired dielectrics are subject to cracking in the
vicinity of vias due to shrinkage of the via fill material during firing. The
keys to avoidance are use of staggered vias and minimization of via size.
Controlled in air-fired noble metal materials by paste quality
control and proper furnace atmosphere control. In copper (nitrogen-fired)
systems, blistering has been effectively reduced by dielectric paste
modification and improved furnace design.