One PCB is increasingly being used by spacecraft and satellite avionics to integrate K-band RF, a high pin count, extremely deep submicron digital, the GSPS analogue, including high-current, low-voltage power distribution. The layout, design, and a PCB’s construction, the choice of an appropriate dielectric material, layers present in the stack up as well as their distribution, floor planning, and the shape and size of ground/power planes, routing, component placement, trace geometry, as well as grounding strategy are all factors that must be taken into account.
Physical board innovations are becoming more common, such as low-inductance capacitance, planar antenna, and embedded passives topologies. The actual manifestation as well as implementation of this design determines how well that most space electronics subsystems work; the Circuit board has become so essential that we frequently forget that it’s widely regarded as a component; just like all the parts, they have to be chosen with respect to the specifications in order to get the necessary performance.
What is a Space PCB?
A particular kind of circuit board used in the planning and building of spacecraft is known as the space PCB. The mechanical, electrical, and thermal qualities of this PCB are typically excellent.
In particular, stronger circuit boards than those required for the majority of ordinary electronic devices are required for the aerospace industry. For instance, numerous control towers, aircraft, satellites, as well as space shuttle components must be extremely dependable when operating in high-pressure and temperature environments.
Because space equipment will be subjected to significant vibration and shock, mechanical abuse must also be taken into account. Due to this, some PCBs might have to be modified to withstand these challenging circumstances.
Because the radiation levels in space seems to be higher compared to those on Earth, radiation is yet another aspect where space equipment should have the ability of handling. The boards must therefore be built to withstand intense radiation levels which can harm spacecraft.
To shield the aforementioned electronics against radiation, engineers may utilize a few specific parts or materials. Additionally, components would be made smaller than usual to ensure fewer units would be vulnerable to the detrimental effects of radiation.
Properties to Consider When Choosing Circuit Materials for Space PCB
Rogers Corporation has created a variety of circuit materials that have low outgassing properties for use in different applications of space PCB, including several varieties of the circuit materials for RT/duroid, that are usually based on the PTFE having inorganic materials (filler) like ceramic and glass materials, as well as temperature-stable series hydrocarbon circuit materials.
The Dielectric Constant
The effect of the significant temperature variations that can occur within a satellite or spacecraft as well as how the temperature swings might change the properties of the PCB material, including its DK – dielectric constant, are two additional issues for electrical circuits present in space.
Dielectric Constant’s Temperature Coefficient (TCDk)
The dielectric constant’s temperature coefficient can be used to compare the viability of various PCB materials to serve space-based applications. This PCB metric effectively quantifies how much the material’s Dk alters in response to significant changes in the operating temperature (that could be somehow large when in space).
The ideal TCDk values for PCB materials aimed for space-based applications would be zero. Maintaining continuous impedance matching for the active circuits, like amplifiers, as well as passive circuits like antennas under the always changing space’s operating conditions requires stable Dk.
Coefficient of Thermal Expansion (CTE)
One way to assess materials’ expectations for the dependability of the PTHs over a wide range of operating temperatures is to compare them using the PCB metric known as the CTE or the coefficient of thermal expansion. To reduce stress in-between the conductor and dielectric as a result of temperature variations, the coefficient of thermal expansion of the PCB’s Dk is frequently closely matched with that of copper conductor.
The projected reliability of these PTHs over the temperature is determined by the CTE of the z-axis PCB; ideally, the CTE inside the z direction of the circuit material was already engineered for minimum dimensional changes present in the PTHs of the PCB across the large temperature space extremes.
Temperature sensitivity
The ability to compare the capabilities and abilities of various circuit materials in dissipating heat into space is made possible by the measurement of the thermal conductivity of the PCB. Also, for the passive and active circuits present in space, any loss could be an issue, as it is measured by the dissipation factor of the PCB that has to be very low when choosing your circuit material that works best for a minimal loss.
Why it is Important to Consider a Circuit Material Characteristics for Space PCB Boards
When selecting a Circuit board material that suites space, certain other qualities of the circuit material must be taken into account to assess a material’s mechanical and electrical stability in the harsh operating environment of space. Furthermore, space’s circuit materials may also have to be able to withstand corona fields of high voltage as well as vacuum conditions.
Some applications for space travel may require to withstand high voltage circumstances and be able to withstand high breakdown voltage.
Additionally, the capacity to dissipate heat inside a small space, like the limits of the spacecraft, might be advantageous for the tiny, dense circuits normally constructed for space and satellite applications.
Also, the RF or microwave circuits’ density for space keeps increasing since reducing weight is indeed a priority for any boards deployed in space-based devices and satellites.
Plated thru holes which operate in the vast temperature ranges, as well as space’s temperature cycling, are commonly utilized to connect the circuit layers. However, the PTHs’ long-term durability can cause worry.
Important Consideration for Designing Space PCB
Space applications require circuits that can function at very high temperatures and can withstand and absorb large vibrations and shocks. Due to the increased risk of a radiation exposure when operating during high altitudes, PCBs as well as other different electronic components has to be designed to withstand high levels of radiation for lengthy time periods without experiencing any harm.
The most common guidelines and recommendations for assisting a designer with any difficult but eventually rewarding task of creating a circuit board for different space applications is given below.
Provide excellent thermal management
Space PCBs must, as was previously said, offer exceptional dissipation of heat without the use of external heatsinks. Asides from heavy copper tech as well as the widespread use of a thermal vias, specialized solutions depending on the materials including FR408, Pyralux AP, as well as other types of metal components and materials can be used. This is also advised to extend the gap present between those parts in comparison to standard PCBs to ensure more space for the dissipation of heat.
Routing suggestions
PCB traces must be chosen to suit a size which has the ability to handle the largest current load so as to effectively dissipate heat in all working conditions. Angles on traces, as with circuits containing signals of high frequency, must be lower than 45°. This is to make sure that the sent signal is regular and uniform across that circuit. Also, separating the low-frequency electronic components from the high frequency ones will prevent any interference.
Utilization of heavy copper tech
Even during currents of high intensity, heavy copper tech provides a natural heat dissipation without requiring additional cooling systems. Many manufacturers suggest combining solutions of heavy copper with the installation of numerous thermal vias to further improve heat dissipation.
How to Choose a Space PCB Manufacturer
Probably the most difficult task is sourcing space PCB. However, the procedure will be clarified and made simple in this part.
Experience
Longer experience is typically linked to perfection. The creation of the space PCB falls under this as well. It is better to get your space PCB from vendors with more extensive industry knowledge. Experienced providers too are probably quite familiar with aviation sector regulations. So, you’ll be more than confident that you will get the bet space PCB that suits your needs.
Advancement in Technology
Technology is constantly changing. Innovations occasionally play a role. These developments guarantee that the manufactured goods are more dependable and efficient. They are made stronger by incorporating the advantages of earlier technology. Additionally, they build on the shortcomings of the earlier technology and profit from them. This results in improved products.
Warranty Space PCBs are pricey. They are constructed taking into account a variety of environmental factors that affect airplanes. You shouldn’t purchase such a pricey item without the need for a warranty.
Also, the manufacturer’s trust in the item he offers you is demonstrated by the warranty. Additionally, it pays you your money’s value if an abnormality appears within the allotted time. This helps in reducing losses from any source.
Shipping
Space PCB manufacturers ought to plan the logistics of shipping their goods. Not all the courier services out there can ship space PCBs due to their fragility. You ought to pick a service provider who can deliver the goods you requested.
Conclusion
All the electronic circuits which has to adhere to a specific IPC standard, including printed circuits to be used in space, must be developed from the start with the goal of achieving excellent electrical reliability, particularly under the most challenging and unusual working situations.
