Standard Electronic Module Research Articles

Experimental Thermal Contact Conductance of Electronic Modules

The Standard Electronic Module, format E, (SEM-E) is extensively employed in navigation, control, tracking, guidance, and communications electronics. Thermal resistance of the junction between the guide rib of the SEM-E frame and the liquid-cooled chassis card rail to which the module is clamped is a principal contributor to overall thermal resistance in the heat rejection path. High resistance causes excessive operating temperatures and failure rates. The currently used configuration employs anodic coatings on contact surfaces and segmented wedge clamps to secure modules to the chassis. In the present investigation, the thermal performance of alternative configurations utilizing nickel and silver platings instead of the anodic coating on card rails and pneumatic bladder clamps instead of wedge clamps is experimentally determined. These results are compared to previously obtained results for the baseline condition. Results indicate that nickel and silver platings and bladder clamps provide no enhancement in performance in an ambient air environment (in which surface vessels and submarines operate) compared to anodic coatings and wedge clamps. In a vacuum environment (approximating operational surroundings for high-altitude aircraft and spacecraft), nickel plating increases junction thermal resistance by 300%, silver plating reduces resistance by 25-33%, and bladder clamps decrease resistance by 25-40%.

An Overview of Navy Composite Developments for Thermal Management

This paper reviews: (1) Navy sponsorship of pitch graphite fiber development, and (2) assesses the impact of the high thermal conductivity fibers on future Navy applications. Navy exploratory development programs (6.2) have revealed potential applications in advanced systems for graphite fiber reinforced composites: (1) electronic packaging, (2) satellite radiators, and (3) elevated temperature applications such as missiles. Thermal management in these applications can be improved through the development and use of high thermal conductivity graphite fibers. In electronic packaging, the thermal planes that conductively cool the Standard Electronic Module, Format E (SEM-E) printed wiring board require both high thermal conductivity and thermal expansion matching. For satellite radiators, the graphite fiber reinforced metals offer a zero coefficient of thermal expansion, with maximum specific modulus. The joints between titanium missile structures and their ceramic nose cones require thermal expansion control, but high thermal conductivity is also a distinct advantage. Pitch graphite fibers are now available with a thermal conductivity of 1000–1100 W/mK and a modulus of 130–140 msi. Significant growth toward the theoretical thermal conductivity of graphite, at 2400 W/mK, is possible. The benefits of these fiber properties are shown for applications that are either thermal expansion or thermal conductivity dependent.

A quantitative technique to analyze materials trade-off for SEM 'E'

The standard electronic module (SEM) is defined by a Department of Defense specification designed to optimize electronic module materials and designs for the military, as well as to reduce system life cycle cost through standardization of design and test requirements. The size of the module is defined by its format designation. For example, the E format specifies a substrate dimension of 133 mm (5.25 in) by 152.4 mm (6 in). However, the specification does not define the materials composing the substrate, leaving material specification to the module designer. The performance requirements for SEM E are evaluated using a technique called multiattribute utility analysis (MAUA). This technique has been employed in a wide range of engineering problems in general, and materials specification problems in particular, and its application to this problem yields rich insights into the critical elements of materials selection for the SEM E application. >

A Generic Controller Card Set

ABSTRACTThis paper addresses the design of a generic controller card set (GCCS) which conforms to the Multibus II protocol. The GCCS design meets Navy Standard Electronic Module (SEM) format “E,” and consists of eight “building block” cards. Configuration flexibility permits the GCCS to perform many controller applications. The eight modules are: a central processing unit (CPU) card, controller card, central services module (CSM), analog to digital (A/D) card, digital to analog (D/A) card, discrete input and output (I/O) card, random access memory (RAM) card, and erasable programmable read only memory (EPROM) card. Each card contains both on‐line and off‐line built‐in‐test (BIT), which aids in fault diagnosis.