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Heavy Copper PCB and Extreme Copper PCB have been used in more and more power electronic products. Most commercial PCBs are manufactured for low voltage / low power applications, with copper weighing from 1 / 2 oz / ft2 to 3 oz / ft2 for copper wiring / planar applications. The weight of copper in heavy copper PCB is between 4 oz / ft2 and 20 oz / ft2. Copper may also weigh up to 20 oz / ft2 to 200 oz / ft2, which is called polar copper. Our discussion will mainly focus on heavy copper.

heavy copper pcb
heavy copper pcb

The construction of heavy copper pcb makes the circuit board have the following advantages:

  • It increases the bearing capacity of thermal stress.
  • The current carrying capacity increases.
  • The position of the connector and the mechanical strength in the PTH hole are improved.
  • In the case of no circuit failure, make full use of exotic materials to achieve their full potential (i.e. high temperature).
  • The product size is reduced by combining multiple copper weights on the same circuit layer (see Figure 1).
  • Heavy copper plated vias flow higher current through the plate and help transfer heat to the external radiator.
  • The on-board radiator is directly plated onto the plate surface using up to 120 ounces of copper.
  • On board high power density planar transformer

Heavy Copper PCB Function

Pcbogo is an experienced person, PCB manufacturers can develop and produce excellent high quality heavy copper PCB products. We can provide heavy duty copper PCB manufacturing services with 13 ounces of copper. Please check the functions in the table below:

FeatureCapability
MaterialFR-4 Standard Tg 140°c, FR4-High Tg 170°c
Min.Track/SpacingFor External layers:
4oz cu 9mil/9mil,5oz Cu 11mil/11mil6oz Cu 13mil/13mil,12oz Cu 20mil/ 32mil
For Internal layers:
4oz Cu 8mil/12mil,5oz Cu 10mil/14mil6oz Cu 12mil/16mil,12oz Cu 20mil/32mil
Min.Hole Size10mil
Max Outer Layer Copper Weight15oz
Max Inner Layer Copper Weight12oz
Board Thickness0.6-6mm
surface FinishingHASL lead free, lmmersion gold, OSP, Hard Gold,lmmersion silver, Enepig
Solder MaskGreen, Red, vellow, Blue, white,Black, Purple,Matte Black,Matte green
silkscreenwhite,Black
Via ProcessTenting Vias,Plugged Vias,Vias not covered
TestingFly Probe Testing (Free) and A.O.I.testing
Build time5-10 days
Lead time2-3 days

Application of Heavy Copper PCB

Needless to say, heavy copper pcb has been widely used in various electronic industries, such as heat dissipation, high power distribution, planar transformer and power converter. What’s more, there is a great demand for heavy copper PCB in computer, automobile, military and industrial control.

In addition, heavy copper PCB board is also used for other purposes:

  1. Power supply, power converter
  2. Automobile industry
  3. Welding equipment
  4. Power distribution
  5. Power line monitor
  6. Torque control
  7. Overload relay
  8. Protection relay
  9. Solar panel manufacturers, etc.

Heavy copper PCB Construction

Standard printed circuit boards, whether double-sided or multilayer, are manufactured by a combination of copper etching and electroplating processes. The circuit layer starts with a thin copper foil (usually 0.5 oz / ft2 to 2 oz / ft2), then etched to remove excess copper, and then plated to increase the copper thickness of the flat, wire, pad, and plated via. All circuits are laminated into a complete package using an epoxy based substrate such as FR4 or polyimide.

Boards containing heavy copper printed circuit boards are produced in exactly the same way despite the use of special etching and electroplating techniques such as high speed / step plating and differential etching. Historically, heavy copper features were created entirely by etching thick copper clad laminate material, resulting in uneven sidewalls and unacceptable undercutting. Advances in electroplating technology have allowed a combination of electroplating and etching to form heavy copper features, resulting in straight sidewalls and negligible undercutting.

Electroplating of heavy copper PCB enables the board manufacturer to increase the thickness of copper in the side walls of plating holes and through holes. Now you can mix heavy copper with standard features on a board (also known as PowerPoint). Advantages include fewer layers, low impedance power distribution, smaller footprint and potential cost savings. Generally, high current / high power circuits and their control circuits are produced on separate boards. Large amount of copper plating can integrate high current circuit and control circuit, so as to realize high density and simple circuit board structure.

Heavy Copper PCB Strength and Survivability

Circuit board manufacturers and designers can choose from a variety of dielectric materials, from standard FR4 (operating temperature 130 ° C) to high temperature polyimide (operating temperature 250 ° C). It may be necessary to use foreign materials in high temperature or extreme environmental conditions, but if the standard setting for circuit wiring and electroplating is set to 1 oz / ft2, will they survive in extreme conditions? The circuit board industry has developed a test method to determine the thermal integrity of finished circuit products. Thermal strain comes from various circuit board manufacturing, assembly and maintenance processes. The difference of CTE between copper and PWB laminates provides a driving force for the development of crack nucleation and circuit failure.

The increase in resistance indicates a decrease in electrical integrity due to cracks in copper circuits. The standard sample design for this test uses 32 plated through-hole chains, which have long been regarded as the weakest point of the circuit under thermal stress.

The TCT results clearly show that the failure rate is unacceptable no matter which board is used. A thermal cycle study of standard FR4 circuit boards with 8 to 1.2 million mils shows that 32% of the circuits fail after eight cycles (a 20% increase in resistance is considered a failure). The failure rate of PCB with heterogeneous materials is significantly increased (up to 3% after eight cyanate cycles), but the price is too high (five times of the material cost and 10 times of the material cost) and difficult to process. A typical SMT component must go through at least four thermal cycles before leaving the factory, and each time the component is repaired, another two thermal cycles may be required.

The use of heavy copper PCB will completely reduce or eliminate these faults. Plating 2 oz / ft2 copper on the hole wall can reduce the failure rate to almost zero (TCT results show that for standard FR4, after eight cycles, the coating is at least 250 mil, with a failure rate of 0.57%). In fact, the copper circuit is not affected by the mechanical stress exerted by the thermal cycle.

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