Properties of thick-film photoimageable inks for LTCC substrates
Miniaturization of electronic circuits is strongly associated with
miniaturization of conductive paths and pads. It also refers
to thick-film technology. Fabrication of details narrower than
150 μm by using of standard screen-printing is very difficult
task. There are few more precise techniques - for example
photoimageable inks method [1, 2]. It enables to create even
several-micrometers wide paths.
The inks prepared at Institute of Electronic Materials Technology
(ITME) were tested.
The compatibility between such inks and LTCC (Low Temperature
Cofired Ceramics) substrates was especially an object
of interest. The investigations were performed at Wrocław
University of Technology, Warsaw University of Technology
or Dresden Technical University. The path’s resolution, inks
shrinkage as well as chosen electrical and mechanical properties
(electrical resistivity, solderability, adhesion, shear resistance)
were determined.
Fabrication
The photoimageable films were made using standard screen-printing
combined with photolithography [3]. A special ink was screen-
printed onto the substrate (Fig. 1a). The investigated pastes
had good UV-resistance and using of UV-filters was unnecessary
[4]. However, they need large amount of radiation during exposing.
A proper photomask caused that only selected areas of ink
were polymerized by UV light (Fig. 1b). The Hibridas Exposure
Unit MA-4K were used. Remaining areas stayed unpolymerized
and it was possible to remove them in the next technological step
- spraying with proper developing solution (Fig. 1c). The Hibridas
Developer Unit SC-4K and ethanolamine solution were used. As
a result pattern from the photomask was transferred onto the substrate.
The last technological step was firing of achieved layer in
t[...]
Bonding technologies for 3D-packaging
Market drivers and requirements for performance pushed semiconductor
devices to scaled geometries, less power, smaller sizes
and lower cost. The scaling of CMOS structures “more Moore" will
not be able to meet the current and future demands of the drivers
due to the functional diversification of electronics, physical limits
of CMOS technology and growth of costs.System on Chip (SoC) and System in Package (SiP) both are
technologies which have the potential to continue the improvement
in performance, size, power, and cost of electronic systems
(see Fig. 1). Both technologies feature advantages and disadvantages
with respect to system integration.
SoC is a way to increase functional integration by including
sub-systems on a single chip which means large scaling but
increased design effort. For this, more than just digital functions
have to be incorporated into an integrated circuit design,
e.g. analogue-to-digital and digital-to-analogue conversion.
SiP combines multiple active electronic components of different
functionality, assembled in a single unit. This enables multiple
functions inserted into a system or sub-system with low
design effort but higher package size. A SiP may also integrate
passives, MEMS, optical components and other packages. [2]
The following approaches can be regarded as state of the art
of SiP technologies:
- Horizontal structures (Multi Chip Module as QFP, BGA or FCpackages)
- Stacked structures (PoP, 3D-integration with TSVs)
- Embedded structures (embedded wafer level packages
(eWLP))
Three-dimensional integration is an attractive way for bringing
together various functional blocks in a vertical fashion. Hence, the
reduction of package sizes leads to shorter signal and power interconnects
and results into lower signal propagation delay and power
consumption [3]. The advances of 3D-integration can also be
used for “More than Moore" approaches, where a heterogeneous
syste[...]