CPU Core in the Industry’s Smallest Footprint
Both the ceramic and laminate versions achieve the industry’s
highest level of packing density, enabled by using double-
sided mounting assembly technique. The top side contains
PBSRAMs and passive components, and the bottom side has
P55C, 430TX and tag RAM. The ceramic version applies
existing wire bonding technology in twelve-layers built on
alumina ceramic substrate. Chips are mounted using Fujitsu’s
chip-on-board (COB) and regular solder reflow process for
SMT components. The ceramic version measures 42mm x
40mm. The laminate version is an eight-layer MCM using a
state-of-the-art thin-film “build-up” substrate technology (FR-
4 laminate). Chips are mounted using flip-chip technique, so
the MCMs combine the cost and performance advantages of
laminate substrate with the latest flip-chip technology. The
laminate version measures 44mm x 32mm.
The new MCMs address the rapidly-changing performance
objectives of OEMs for new generations of mobile computing
products, including small form factor, optimal heat
dissipation, and high reliability. The reduced size of the
MCMs allows OEMs to develop lighter and thinner mobile
products with system motherboards that are smaller, and less
expensive than current implementation.
Full-featured mobile computing products are the fastest-
growing segment of today's mobile computing markets.
Designers and OEMs require versatile, modular
solutions that optimize system
performance for a wide range of
frequencies, and cache sizes. These
MCMs enable OEMs to develop
motherboard designs to achieve quicker
time-to-market. The MCM architecture
‘decouples’ the high-speed interfaces
from the system motherboard, simplifying
the OEM design task by reducing
complexity and eliminating the need for
system redesign.
These MCMs represent the third generation
products and demonstrate Fujitsu’s continuing
excellence in developing cost effective mobile
computing solutions.
Electrical Specifications
The MCM requires four different power supplies, as shown
below:
• +V_CPUCORE: 2.5 V, for CPU CORE
• +V_CPUIO: 3.3 V, for CPU IO
• 3VS: 3.3 V, for 430TX and PBSRAM
• 3V: 3.3 V, for 430TX
When the processor is in “suspended mode”, +V_CPUCORE,
+V_CPUIO and 3VS go down to 0 V, while 3V power supply
remains at 3.3 V.
The MCM has ceramic multilayer capacitors, which along
with internal power plane structure, offer a very low power
supply impedance in high frequency range. However, the
MCM does not include “bulk capacitors”. Fujitsu
recommends using low ESR bulk capacitors, such as
Tantalum capacitors or “organic semiconductor capacitors”,
externally and placing them as close to the MCM IO
connector as possible, and connecting them using thick
copper traces. Placement of these bulk capacitors, though the
actual values of these capacitors depends on the specific
motherboard design requirements.
Supply voltage for CPU CORE and CPU IO may change for
future generations of processors. The MCM provides a set of
pins that indicate the +V_CPUCORE and +V_CPUIO power
supply voltages. Fujitsu recommends motherboard
designers to recognize these voltage levels and
change the voltage externally, if upgradeability
and compatibility are considerations factors in
the design.
Signal integrity analysis was performed. The
signals on the longest (89.5mm) and
shortest (12.5mm) traces were simulated.
The simulations were done using
SPICE models for SRAMs and
IBIS models for P55C
and 430TX. The
input signal had a
frequency of 66 MHz,
with a rise time of 1.5 ns.
Photograph courtesy of
Fujitsu PC Corporation.