What are heavy copper PCBs?
Printed circuit boards lift contemporary thru etched copper tracks. The modern-day carrying capability of a copper hint can be multiplied through growing its width, however this is now not constantly practical. Another way to extend the cutting-edge carrying ability besides altering the width of the copper traces is to use heavy or thick copper. This incorporates extra modern-day and enhances effectivity with higher warmness management.
There are no particular policies that specify the quantity of copper to be used when fabricating heavy copper pcb boards. However, the PCB enterprise considers three or greater oz of copper on any circuit board layer as heavy copper.
Design issues for thick-copper boards
Copper thickness and width
PCB designers gauge the quantity of modern required and based totally on this they diagram their heavy copper boards. This includes choosing the proper copper thickness, width, and the most temperature upward jab the circuit board can withstand. The quantity of warmness a heavy copper board generates is proportional to the quantity of cutting-edge it carries.
How to pick the proper copper thickness
As cited earlier, the copper thickness is decided by using the modern-day passing via the conductor. The thickness of the board can be decided by way of a hint width calculator. It can calculate the three parameters that consist of hint width, present day capacity, and temperature rise. If any two parameters are known, the device calculates the third.
Current carrying capacity
As present day passes thru a copper hint its resistance inadvertently heats it up. The nearby warmness transition generates a energy that dissipates into the ecosystem with the aid of conduction and convection. The clothier have to calculate the most present day the hint can raise earlier than it reaches the proper temperature upward jostle of about 30°C. A thumb rule in the enterprise is that the inner layers can preserve solely 50% of the current-carrying potential of the uncovered traces.
Substrate of a PCB is some other aspect a fashion designer have to think about whilst designing heavy copper boards. Substrate substances vary from regular FR-4 cloth with operational temperatures of 130°C to superior substances with very excessive glass transition temperatures (Tg). The Tg of the copper and substrate cloth is very imperative for the reason that a excessive contemporary may additionally reason cracks and layer separation.
Coefficient of thermal growth (CTE)
Coefficient of thermal enlargement (CTE) is the charge of enlargement of a PCB fabric as it heats up. It is expressed in components per million (ppm) improved for each and every diploma Celsius that it is heated to. CTE between copper and the substrate fabric is additionally vital as thermal stress produced via excessive currents thru traces may also end result in the formation of cracks, in the end inflicting board failure.
Circuit board floor thickness can be accelerated via electroplating. It reduces the resistance of copper traces thru the enchancment of warmth conduction. Electroplating is additionally used via fabricators for PTHs to limit their thermal resistance. Resistance discount helps to dissipate warmness efficaciously thru the modes of warmness switch such as conduction, convection, and radiation.