Design Capability


Reinforcement refers to the optimal design, selection of high-quality materials, and process decisions for various factors that affect the performance of the equipment (such as system structure, electrical characteristics, mechanical physical structure, etc.) from the electrical and structural aspects to meet the environmental conditions of electronic equipment. Corresponding technical guarantee measures. Reinforcement is divided into congenital type and acquired type.

Reinforcement refers to the optimal design, selection of high-quality materials, and process decisions for various factors that affect the performance of the equipment (such as system structure, electrical characteristics, mechanical physical structure, etc.) from the electrical and structural aspects to meet the environmental conditions of electronic equipment. Corresponding technical guarantee measures. Reinforcement is divided into congenital type and acquired type.


The congenital type is also called full (internal) reinforcement, which has a long development cycle and high cost; the acquired type is a redesign of mature commercial technology or products according to a certain level of environmental boundary conditions. It is also called external reinforcement, that is, COTS reinforcement. technology. Such as liquid crystal display series, ruggedized network switches, etc., are all secondary designs using excellent commercial motherboards or industrial-grade motherboards. It not only has a good cost-effectiveness ratio, but also can absorb (transplant) the latest commercial technology achievements that are rapidly developing into the research and development in a timely manner. Therefore, COTS technology has become the mainstream of reinforcement design.

 

Why do we need reinforcement design
General electronic equipment environmental conditions refer to the integration of all external influence factors experienced by the equipment in its production, storage, transportation and use. According to the physical, chemical, and biological characteristics of various environments and their failure mechanisms on electronic equipment, they can be divided into the following categories:
Climate environment: temperature (humidity), wind, rain, snow and frost, condensation, sand dust, salt fog, etc.;
Mechanical physical environment: vibration, shock, collision, drop, swing, stress, vibration, noise, etc.;
Electromagnetic environment: electromagnetic fields, electromagnetic pulses, lightning, static sparks, solar radiation, nuclear radiation, etc.;
Chemical environment: corrosive atmosphere, acid, alkali, salt, etc.;
Biological environment: molds, microorganisms, etc.

 

Vibration and shock
The mechanical and physical environment faced by electronic devices is complex and changeable. Will be subjected to various forms of mechanical force such as vibration, shock, swing, and overturning. The most harmful ones are vibration and shock. It will cause two forms of damage:
1) Electronic equipment produces resonance with larger amplitude under the action of a certain excitation frequency;
2) Long-term vibration or repeated shocks may cause fatigue damage to the equipment structure.

 

Thermal environment
The thermal environment includes two aspects: one is the harsh natural environment of the atmosphere; the other is the high heat flux density brought about by the high density and miniaturization of the enclosed electronic chassis (cabinet), such as the thermal power of the components of the printed board and the power module Consumption is the main heat source. According to the information, the high temperature of the desert once caused the radar screen on the launch frame to become blank from time to time. The reason is that the reinforced computer in the air-conditioned tank failed due to high temperature and the electronic circuit was burned. Therefore, improper handling of thermal design is one of the main reasons for the failure of electronic equipment.

 

Electromagnetic environment
With the extensive use of electronic equipment on ships, the electromagnetic environment is complex, the density of electromagnetic signals is high, and the frequency domain is wide, so electromagnetic interference (EMI) problems are very serious. Its composition must meet three conditions: the interference source, the interference path, and the response of the interfered object (sensitive equipment). These interferences should be eliminated or suppressed to a minimum, otherwise the equipment or system will not be able to complete its functions effectively and harmoniously.

 

Anti-vibration and shock design
A set of hierarchical anti-vibration design system from small to large, from inside to outside, from board level, module, cabinet to the whole machine is established, which not only has low technical cost, but also has remarkable anti-vibration effect. The basic design measures are nothing more than covering two points: one is to increase the rigidity and strength of the board-level or module box itself, that is, to increase the natural frequency. So that "innate" has good dynamic characteristics; the second is to isolate the source of vibration and shock. In principle, it is to install a matching vibration isolation buffer system for the whole machine.
With the deepening of the modular design concept, starting from basic units such as circuit boards, plug-in modules, and mainframes, we start with the strength and rigidity of the mechanical structure itself, and strengthen the weak links to make it have a certain "robustness". Sex". Through the configuration and potting of the components on the module board, the structural mode of the wall plate, the overall welding process of the cabinet, etc., its own anti-vibration ability is allowed or higher than the actual response value; and the assembled electronic cabinet will also be changed from The overall load, geometric center of gravity, environmental excitation frequency and other factors are comprehensively considered to configure the best overall vibration isolation buffer system. In order to finally obtain the system dynamic characteristics of the whole machine without resonance and low coupling.
Under certain circumstances, for high-precision modules, such as hard disks, optical drives, etc., because the internal read-write head positioning accuracy is extremely high, when the system's vibration isolation efficiency cannot meet the response indicators of sensitive components, the principle of secondary vibration isolation is required . However, it should be noted that the secondary vibration isolation is effective only when the excitation frequency has a small variation range. Otherwise, it will be counterproductive due to multi-level resonance. Therefore, the increased system freedom and the selection of vibration isolation parameters must be carefully analyzed and optimized during engineering design.

 

Thermal design
Heat dissipation is one of the important items of structural design. Its purpose is to reduce the thermal resistance of the heat transfer link, form a low thermal resistance heat flow path, so that the heat can be quickly transferred to the final radiator (usually the small environment around the device), so that the temperature of various power components or equipment Control within the specified value. Its technical scheme must meet two basic points: one is to limit the temperature of the equipment between a certain maximum and minimum; the other is to minimize the temperature gradient between various points in the equipment.
Conventional thermal design methods are very mature. The general design principle is: for components and printed circuit boards, the main focus is on good radiation or conduction heat dissipation after surface mounting; while the modular closed chassis cabinet strives for the circulating exchange of hot and cold air. For example, in the control cabin with air-conditioning system, the electronic cabinet or display console generally uses fans to achieve forced convection heat dissipation, which is economical and effective. In special environments, liquid circulation cooling can also be used for processing. However, its cost is high and its internal structure is complex. Here is a brief introduction to some of the new temperature control technologies that have been successfully applied in model engineering in recent years. For example, a new type of heat conduction plate designed with heat pipe heat conduction technology on a computer CPU module board for the first time improves the board-level heat dissipation efficiency and broadens the application of surface mount heat dissipation technology; and the reinforcement of a certain type of network switch uses phase change transmission for the first time Thermal technology reduces the temperature gradient between the motherboard chip and the environment to below 10°C, successfully solving the problem of low-resistance heat transfer inside and outside the high-power airtight cabinet.

 

EMC design
EMC's design measures are mainly targeted from three aspects:
Control the electromagnetic radiation of the interference source; suppress the coupling channel of EMI; enhance the anti-interference ability of sensitive equipment. Specific to the engineering design, it mainly covers several basic methods:
1) Good grounding. Grounding is the main method to suppress noise and prevent interference. Generally, single-point grounding is adopted at low frequency, and multi-point grounding is adopted at high frequency;
2) Shielding measures. In short, it is to surround the components, parts, circuits, cables (including wiring) or the entire system with a shield to prevent the interference electromagnetic field from spreading out or itself from external interference. In terms of the structure and process plan, start from the rational selection of structural plates, the correct lap process, the appropriate treatment of holes and gaps, and the optimized layout of cables;
3) Filtering technology. Filtering can effectively suppress the conduction coupling, which is one of the EMI propagation paths. Therefore, the selection and installation method of the filter in the structural design is particularly important. The interference path, coupling method, and degree of EMI are very complicated. Therefore, EMC is a key point in comprehensive reinforcement design, and it is also a difficult point in engineering applications.
In addition, with the development of weapon systems, electromagnetic pulses generated by electromagnetic bombs or nuclear explosions will pose a lethal threat to electronic equipment. In order to improve the wartime survivability of electronic equipment, including the shipborne command and control system, the strengthening of research topics on the electromagnetic pulse effect of equipment and its defense technology has also attracted considerable attention. Therefore, in view of the complexity of electromagnetic pulse defense technology and EMC, these will be areas that need further research in the future.