Precision Guided Munitions (PGMs) incorporate an active guidance system within the munition to meet increasingly stringent mission requirements for lethality and collateral damage.  This active guidance system relies on highly miniaturized electronics modules. PGMs require the development of packaging techniques that allow electronics modules to withstand the high-g forces encountered during a gun launch. Honeywell’s deeply integrated Inertial Navigation System – Global Positioning System with Anti-Jam capability (INS-GPS/AJ) product has been baselined as the primary production of navigation, flight control, and mission computer for a major DoD weapons program.  Figure 4-1 shows a typical Inertial Measurement Unit (IMU) that is offered by Honeywell and the basic assembly components and printed wiring boards of an IMU.  The newer generation IMUs are more compact, lighter and offer better performance.  Currently, a Navy funded program is targeting the packaging aspect of newer generation IMUs.

A previous high-g packaging program, supported by the Office of Naval Research (ONR) and the Program Executive Office for Integrated Warfare Systems (PEO-IWS), focused on improving the manufacturing technology and supply base for MEMS-based IMUs for use in precision guided munitions.  This program developed guidelines that increase the capability for the Navy to address high-g electronics packaging issues.  Failures that occur during large scale qualification can be very costly from both an economic and a scheduling perspective.  This risk can be mitigated by the use of inexpensive tests to screen components for survivability.  A preliminary screening methodology was demonstrated in this program.  This methodology could be employed not only to evaluate the high-g performance of an alternate MEMS accelerometer under investigation in this program, but is also applicable to evaluating electronics packaging and materials for future Navy high-g applications.  The guidelines identify the packaging characteristics that are conducive to high-g survivability.

These guidelines were based on both a literature search as well as a Design of Experiments (DOE) study.  This DOE used a 20,000g screening drop test to demonstrate survivability of test vehicles that were designed with consideration of orientation, substrate material, component geometry, restraining materials such as underfills and encapsulants, and assembly fixturing.  The screening DOE was generated using the JMP statistical program from the SAS Institute that utilizes algorithms based on providing the optimized design space for a given number of runs. 

As initially proposed, this DOE incorporated studying the effects of factors such as the component type, component size, and orientation on the board, board substrate material, encapsulant, and underfill materials.  These factors were chosen on the basis of testing samples launched by an air gun assembly that simulated the force, rotational movement, and durational time of actual projectile systems.  Figure 4-2 shows a typical shock pulse used in this study.  By design, the shock tester can simulate 20,000g acceleration with very short pulse duration. The final report of this program includes the information of more than 30 electronic packaging failure modes that occurred at various stages of high-g shock tests.  It also includes information about the commonly used high-g shock tests, and the laboratories and groups that offer high-g testing and modeling services.

Currently, leveraging the US Army’s investments in the Common Guidance IMU, Navy ManTech has been collaborating with Army program offices and developed a program “High-g Packaging and Miniaturization of Electronics for Deeply Integrated Inertial Guidance Units”.  This program will study the packaging of the BG1930G and similar products from the point of view of assessing its survivability to different gun launch environments, as well as suggesting improvements to the design.  Another aspect of this program is the application of System on a Chip (SoC) technology to the discrete semiconductor approach used in the BG-1930G.  The SoC approach is to combine the mission processor, inertial sensor assembly interface, and several other electronics functions onto a single substrate.  Development and incorporation of SoC technology will effectively eliminate an entire printed wiring board from the product baseline.  It will also enable the achievement of aggressive average unit production pricing objectives, producibility, reliability, weight, and volume objectives mandated by other Joint Navy/USAF program applications and a specific Army application. 

As mentioned earlier, this program will be built on the BG-1930 Deeply Integrated Guidance and Navigation Unit that Honeywell Aerospace has developed under other Army contracts.  Under this ManTech effort, the Mission Processor Board will be converted into a SoC using multi-chip packaging technology to meet a less than 300 mm2 form factor.  A multi-chip module package that combines the BG-1930 mission processor, field-programmable gate array (FPGA) and corresponding electronics functions on a single substrate, along with RAM and flash memory into a package will be developed in this program.  The major tasks in this program include: package concept design, package design implementation, SoC design integration, timing analysis of the design, prototype fabrication, high-g testing, and system integration.  This program also includes a MEMS sensor evaluation, a high-g packaging materials evaluation, and static and dynamic high-g shock modeling.  The high-g testing includes a board level centrifuge and shock plate testing.  In addition, Ballistic Rail Gun testing will be conducted with both non-functional units and functional SoC units. 

This program is managed by the EMPF with Honeywell International as the major sub-contractor. Penn State Applied Research Laboratory, US Army Picatinny Arsenal, and the PEO-IWS are also members of the program team.