Heavy Copper PCB

 

Heavy Copper PCB is the PCB with 4 oz or thicker copper weight on each layer. 4 oz heavy copper PCBs are most commonly used in commercial products. The copper concentration can be as high as 200 ounces per square foot. Heavy Copper PCBs are widely used in electronics and electrical circuitry where high power transmission is needed. Furthermore, the thermal strength offered by these PCBs is perfect. In many applications, especially electronics, the thermal range is of vital importance since high temperature is devastating for sensitive electronic components and badly affects circuit performance.

The heat sinking capacity of Heavy Copper PCBs is much higher as compared to 1oz PCBs. Heat sinking is vitally essential for the development of a robust and durable circuit. Poor handling of heat signals not only affects electronics performance but also shortens the life of circuitry.

 

 

As the electronic industry evolves, the demand for heavy copper PCB continues to increase. Printed circuit boards are the heart of the electronic industry. These boards play a vital role in the production of electronics. Heavy copper PCB is the most recent trend in the PCB industry, especially in power supply industry.

Heavy copper has its unique advantages which is useful in several applications due to its properties.

 

 

What is Heavy Copper PCB?

 

Heavy copper PCB is a circuit board with a copper thickness that is ≥ 4oz per sq. ft in its outer and inner layers. What makes a circuit board classified as a heavy copper PCB is its thicker plating. During the production of heavy copper PCB, copper thickness is enhanced through plated holes and sidewalls.

For instance, when a PCB has 2 ounces of copper per sq. ft thickness, it is a standard PCB. However, if it has more than 3oz of copper, it is a heavy copper PCB. Heavy copper PCB is considered a reliable wiring option. Heavy copper PCB is different from extreme copper PCB which features within 20 oz to 200 oz per sq. ft.

The extra copper thickness allows the board to conduct more current. Heavy copper PCB has strong mechanical power in the plated-through-holes and connector sites. This type of PCB is also known as thick copper PCB.

 

 

What is Heavy Copper PCB advantage?

 

Heavy copper PCB has a lot unique advantages. It has got some unique features that make it an ideal option for high-end applications. Let’s discuss some of the advantages of this PCB;

Great thermal distribution: Due to its copper-plated vias, this PCB offers high thermal resistance. Heavy copper PCBs are used in applications that demand high speed and high frequency. You can also use this PCB at harsh temperatures.

Mechanical strength: Heavy copper PCBs have strong mechanical strength. Heavy copper PCB will guarantee m the electrical system durable and robust.

Good Conductor: Heavy copper circuit boards is a good conductor. They are utilized in the production of electronics due to this feature. They help to link various boards together. These boards can transfer current.

Onboard Heat Sink: Heavy copper boards offer an onboard heat sink. With these boards, you can achieve effective heat sinks on mosaic surfaces.

Excellent Dissipation: Heavy copper PCBs are ideal for large components with a high loss of power. These PCBs prevent overheating from occurring in electrical systems. They dissipate excess heat effectively.

Supports exotic material: Heavy copper helps to protect and enhance exotic material. Exotic materials are sometimes used for designing electronic components. An extreme temperature may need an exotic material. Heavy copper boards end circuit failures because they use an exotic material to its full capabilities.

How is Heavy Copper PCB Fabricated?

For the fabrication of heavy copper PCBs, plating and etching is the main procedure.

Using the normal etching techniques for the fabrication of heavy copper PCBs isn’t ideal. Normal etching methods produce over-etched margins and edge lines that are uneven. PCB producers now use advanced etching and plating methods to achieve straight edges.

During the fabrication process, heavy copper PCBs are electroplated. This will help thicken the walls of PTH on the PCB. With this technique, the layer count shrinks and the impedance distribution reduces. When PCBs are exposed to several cycles during the manufacturing process, the plated holes can become weak.

The fabrication of heavy copper PCBs has its limitations which include;

• The etching process increases the cost
• The etching process requires a huge amount of copper to be removed
• It is hard to fabricate finer lines and thick copper traces
• Heavy copper traces make the surface uneven

 

Methods for Fabricating Heavy PCBs

 

 

Manufacturers utilize different techniques for fabricating heavy copper PCBs.

Embedded copper method: This method fabricates heavy copper PCB using a flat surface. Here the heavy copper is inserted within the prepreg resin. The thickness of the resin determines the thickness of the copper.

For instance, the fabricator begins with a 6-mil laminate and a 1 0z copper clad. Then the copper clad is covered with a photoresist. After this, a 5-mil laser beam is used to cut the circuit pattern from the side of the laminate. The laser has to cut via the laminate to the copper foil. If the laser is controlled, the fabricator can prevent the copper foil from damage.

The fabricator positions the laminate into a plating tank to electroplate. The copper plating produces about 6 mil plating thickness after filling the laser cut groove on the laminate.

Blue bar method: The blue bar method involves inserting thick copper bars into circuit boards. This method saves the material and reduces the weight of the PCB. During the fabrication process, the resin flows into space within the copper traces, this helps to achieve an even top surface.

Fabricators must pay attention to the level of copper fill between inner layers when it comes to multilayer boards with heavy copper layers. Low levels of fill and low levels of resin can lead to resin hunger.

Difference between a Standard PCB and Heavy Copper PCB

Standard PCBs can be produced with copper etching and plating processes. These PCBs are plated by adding copper thickness to planes, traces, PTHs, and pads. The amount of copper used in the production of standard PCBs is 1oz. In the production of heavy copper PCB, the amount of copper used is greater than 3oz.

For standard circuit boards, copper etching and plating techniques are utilized. However, heavy copper PCBs are produced via differential etching and step platting. Standard PCBs perform lighter activities while heavy copper boards perform heavy duties.

Standard PCBs conduct lower current while heavy copper PCBs conduct higher current. Thick copper PCBs are ideal for high-end applications due to their efficient thermal distribution. Heavy copper PCBs have better mechanical strength than standard PCBs. Heavy copper circuit boards enhance the capability of the board in which they are utilized.

Other features that make thick copper PCBs different from other PCBs

Copper weight: This is the main characteristics of heavy copper PCBs. Copper weight refers to the weight of the copper used in a square foot area. This weight is usually measured in ounces. It indicates the copper’s thickness on the layer.

Outer layers: These refer to the external copper layers of the board. Electronic components are usually bonded to the external layers. The external layers begin with copper foil which is coated with copper. This helps to increase the thickness. The copper weight of the external layers is preset for standard designs. Heavy copper PCB manufacturers can alter the weight and thickness of the copper to suit your requirement.

Inner layers: The dielectric thickness, as well as the copper mass of the internal layers, is predefined for the standard projects. However, the copper weight and thickness in these layers can be adjusted based on your needs.

Applications of Heavy Copper PCB

Heavy copper PCB offers some outstanding features that make it ideal for certain applications. This type of PCB is used in military and defense applications. The demand for heavy copper PCBs has been increasing over the years. This is because these PCBs are used in several applications such as;

• Rail traction systems
• UPS systems
• Solar power converters
• Nuclear power industries
• Automotive industries
• Torque controls
• Power line motors
• Welding equipment
• Military equipment
• Safety and signal systems
• Protection relays

Conclusion

Heavy copper PCBs are produced via etching and plating methods. The major aim in the production of this PCB is to add copper thickness through sidewalls and plated-through holes. Heavy copper PCBs have several advantages which some engineer have to choose heavy copper PCB for their products.

Due to their outstanding features and benefits, they can meet your electrical requirements. These circuit boards will always dissipate heat generated due to heavy currents conduction. Electronics using heavy copper boards have been in use for a long time. Heavy copper can carry high currents. These boards will continue to meet the needs of various applications.

High power circuit wirings can be developed using Heavy Copper PCBs. Such a wiring mechanism offers more reliable thermal stress handling and offers fine finishing while incorporating multiple channels on a single layer of a compact board.

Heavy Copper PCBs are widely used in various products as they provide multiple features for improving circuit performance. These PCBs are widely used in high power equipment such as transformers, heat sinking, power inverters, military equipment, solar panels, automotive products, welding plants, and power distribution systems.

Heavy Copper PCB generally need to adopt a special pressing procedure. It involves the use of multiple PP fillings to meet the required filling during the pressing process. The pressing involves high pressure and a large flow of glue. There are empty areas in the heavy copper PCB in each layer of the inner layer pattern; there is no copper in the open area. Also, the edge of the plate is designed with a single air guide groove.

Due to the high pressure, the amount of PP glue passes very easily, and the air guide grooves are lost. This causes the thickness of the board in the open area to be too thin. The board’s overall thickness is extremely large, which causes the film to be not tight during the subsequent processing of the outer layer, ultimately causes the product to be not useable.

The priority is to reduce the flow of glue in the open area and prevent the open area’s thickness from being too thin. This is an urgent problem to be solved in the production process for such heavy copper PCB .

 

How to solve issue of the uniform thickness in the production of Heavy Coppy PCB

 

1. This is amethod for manufacturing a heavy copper PCB with uniform thickness.Each inner core plate of the heavy copper PCB is provided with a copper-free open area at the same position, which includes the following steps:

• Cut the material to obtain the inner core board. Through the inner layer pattern and etching process, the inner layer lines are made on each inner core board, and some copper PADs are staggered on the edge of the open area of each inner core board. Made each inner layer board.
• The inner layer board and the outer layer copper foil are pressed together by the prepreg to make a multi-layer production board.
• Post-processing the multi-layer production board according to the existing technology to obtain a thick copper board.

2. The method for manufacturing a heavy copper PCB with uniform thickness according to claim 1, wherein the copper PAD in step S1 has the same shape and size, all of which are round, oval, diamond, or square.

3. This is a method for manufacturing thick copper plates with uniform thickness according to claim 2. The radius of each copper PAD is R, and at least two rows of circular shapes are provided on the edge of the open area of the inner core plate. The copper PADs in each row are arranged equidistantly along the long edge of the board. The center distance between two adjacent copper PADs is any two adjacent copper PADs in each row.

The bottom copper PAD is called the bottom copper PAD. The copper PAD between the bottom copper PAD is the corresponding vertex copper PAD. The center of each bottom copper PAD and the corresponding vertex copper PAD are connected to form an isosceles right triangle.

4. A thick copper plate with uniform thicknessiscomprised of at least one inner layer core plate. Each inner layer core plate is provided with a copper-free open area and at the same position, characterized in the open area of the inner layer core plate. Several copper PADs are staggered on the edge of the board.

5.The heavy copper PCB with uniform thickness according to claim 4, wherein the shape of the copper PAD is a circle, an oval, a diamond, or a square.

6.The heavy copper PCB with uniform thickness according to 5, each copper PAD has a radius R, and at least two rows of circular copper PAD are provided on the edge of the inner core plate’s open area. The copper PADs in each row are arranged equidistantly along the long edge of the board. The center distance between two adjacent copper PADs is any two adjacent copper PADs in each row;

they are called bottom copper PADs. Adjacent rows are located on the bottom side. The copper PAD between the copper PADs is the corresponding vertex copper PAD. The center of the two base copper PADs and the corresponding vertex copper PAD centers form an isosceles right triangle.

 

 

How thick is the copper on a PCB?

 

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RayMing can produce more than 20oz of heavy copper PCB. However, special attention should be paid to the inner layer’s width and line spacing if the copper thickness exceeds 3 ounces considering the side corrosion factor.

Inner layer 3oz:line width/space 8/10mil	Out Layer 3oz:line width/space 8/12mil
Inner layer 4oz:line width/space 8/12mil	Out Layer 4oz:line width/space 9/13mil
Inner layer 5oz:line width/space 10/12mil	Out Layer 5oz:line width/space 10/14mil
Inner layer 6 oz:line width/space 12/14mil	Out Layer 6oz:line width/space 12/16mil
Inner layer 7oz:line width/space 14/16mil	Out Layer 7oz:line width/space 14/18mil
Inner layer 8 oz:line width/space 14/18mil	Out Layer 8oz:line width/space 16/18mil

 

 

Heavy copper PCB Design for Manufacturing (DFM)

1. The diameter of the plugged via hole requires Φ≤0.5m.
2. The difference should not exceed 0.1mm, for no more than two types.
3. Minimize the types of vias.
4. The copper hole minimum requirementis 20um. The averagerecommended size is 25um.
5. The metalized groove on the side of the board must extend into the board by more than 4mil.

Profile Tolerance:

L＜100 mm	100 ≤L＜300mm	300≤L
Tolerance	±0.15mm	±0.2mm	±0.25

1. The minimum milling groove width between veneers and process edgesis ≥ 1.6mm.
2. The minimum internal angle R≥0.8mm, if 0.5mm internal angle needs to be marked,
3. External angle R ≥ 1.0 mm.
4. V-CUT tolerance ≥±0.15mm, angle: 30°.
5. V-CUT knife jump distance: 8mm.

Delivery Panel Design

1. The orientation is stated in the drawing.
2. The connection is a V-carved connectionor physical connection;a stamped hole is not recommended.
3. It is recommended to provide CAD drawings for easy reading.

Circuit Layout Design

1. The orientation is stated in the drawing.
2. The connection is a V-carved connectionor physical connection;a stamped hole is not recommended.
3. It is recommended to provide CAD drawings for easy reading.

Copper Thick(oz)	3oz	4oz	5oz
Inner line space/width	6/8(mil)	9/10(mil)	10/10(mil)
Out layer line space/width	7/8(mil)	9/10(mil)	10/10(mil)
Vias ring width	6(mil)	8(mil)	8(mil)
Parts vias ring width	8(mil)	9(mil)	10(mil)
SMD Distance	10(mil)	12(mil)	12(mil)
Min copper Legend line	8(mil)	10(mil)	12(mil)

 

 

 

Circuit Layer Display

 

It is recommended that copper should be laid in blank areas as much as possible in the design. The design of plan A schematic is far superior to the design of plan B.

1. Avoid opening the window with solder mask to expose lines.
2. When SMD and MD need to make a green oil bridge, they must meet a certain distance.
3. Avoid opening half a window in the hole position.
4. For the sprayed tin plate, the plugged vias should be designed to be covered with solder mask on both sides.The plugged vias of the non-sprayed board should be designed for single-sided solder mask coverage.

Silkscreen Layer Design

Basic requirements for characters:

 

Legend line width	Legend width	Legend height	Silk 2 SMD	Silk 2 PTH	Silk 2 Rout	Silk 2   V-CUT
≥5mil	≥7time line width	≥7time line width	≥8mil	≥8mil	10mil	≥16mil

Note: Try to avoid placing characters between the substrate and the copper skin.

Withstand Voltage Drawing

Thick copper plates need to withstand voltage and inductance test drawings. Provide test equipment and magnetic cores when necessary.

 

 

Thick Copper Circuit Board Production Process of Double-Sided 450um Ultra

 

 

 

 

Heavy Copper PCB Instruction

 

 

	Specification requirements
A	The copper thickness requirement of the circuit is ≥450UM
B	The copper plating thickness in the hole is required to be ≥150UM
C	FR-4 inner core board does not contain copper; the requirement is 1.4MM
D	The Resin hole plug must be flat with the surface of the circuit without voids or bubble

2. Cutting Laminate

 

 

Specification requirements	Operating conditions
A	Copper Foil Thickness 2oz=70um	Choose 1.4mm base fr4 core,2oz copper lam
B	Fr4 core 1.4mm without copper
C	Cutting Tolerance ±1.0mm	Normal production with roller cutting machine

3. First Copper Plate Thickening

 

 

	Specification requirements	Operating conditions
A	Surface copper plating thickness ≥150UM	18ASF current density plating time is 80MIN plating six times
B	The deviation of copper thickness uniformity on board surface is within 20UM	The electroplating of the rotating transposition pinch point is divided six times to evenly distribute the current trend and the thickness of the coating

4.Outer Layer Drilling

 

 

Specification requirements	Operating conditions
A	Accurate positioning is required	Stack: 1PNL/1 stack
		Drill life: Φ 3.2mm diameter 100 holes, Φ 1.0mm diameter 500 holes/tool
		Drilling speed: 3.2mm Φ 0.4m/min, 1.0mm, Φ 0.8m/min
		Spindle speed: 3.2mm Φ 23krpm, 1.0mm Φ 55krpm
		Tool return speed: 3.2mm Φ 12m/min, 1.0mm, Φ 15m/min

 

 

 

5.First Circuit Etching

 

 

 

	Specification requirements	Operating conditions
A	No OS (open and short circuit), line width tolerance is controlled within ±15%	Film pressing speed: 1m/min Film pressing temperature: 105℃
		Film compensation: the original film is not compensated
		Alignment accuracy: CCD automatic alignment accuracy 3mil
		Exposure energy: 8 grids = 40mj
		Etching speed: 1m/min once +2.5m/min once, the machine has been etched twice

 

6.One-Time Resin Printing Plugging

 

 

 

 

	Specification requirements	Operating conditions
A	The resin ink filling must be flat with the circuit surface without voids, bubbles, or copper on the ink surface	Net yarn T number: 35T
		Screen open compensation: unilateral compensation 15mil
		Scraper angle: 21 degrees
		Printing speed: 1.2m/min
		Printing speed: front scraper 1.2m/min, oil return knife 1.0m/min
		Squeegee pressure: 7.5kg/cm2
		Number of printing knives: 8 knives repeatedly
		Baking parameters: 75℃ for 30 minutes 150℃ 60 minutes

 

7.Grinding Board

 

 

 

	Specification requirements	Operating conditions
A	No resin ink residue is allowed on the circuit surface	Use 320 grit sandpaper for uniform sanding, and sand all the resin ink remaining on the surface of the circuit.

8. One-Time Immersion Copper

 

 

 

	Specification requirements	Operating conditions
A	A layer of copper metal is evenly deposited and distributed on the surface of the circuit copper layer and filling resin	In heavy copper production, the glue is not removed, and the others are made according to normal production conditions.

 

9.Second Copper Thickening

 

 

 

	Specification requirements	Operating conditions
a	Surface copper plating thickness ≥100um	18ASF current density plating time is 80min plating four times
	The deviation of copper thickness uniformity on the board surface is within 15um	Plating with four rotating transposition grips to evenly distribute current trend and coating thickness

 

10.Second Circuit

 

 

	Specification requirements	Operating conditions
A	No OS (open and short circuit), line width tolerance is controlled within ±15%	Film pressing speed: 1m/min Film pressing temperature: 105℃
		Film compensation: the original film is not compensated
		Alignment accuracy: CCD automatic alignment accuracy 3mil
		Exposure energy: 8 grids = 40mj
		Etching speed: 1m/min once +3.5m/min once; the machine has been etched twice in total

 

11.Secondary Resin Plugging

 

 

 

	Specification requirements	Operating conditions
A	The resin ink filling must be flat with the circuit surface without voids, bubbles, or copper on the ink surface	Net yarn T number: 35T
		Screen open compensation: unilateral compensation 15mil
		Scraper angle: 21 degrees
		Printing speed: 1.2m/min
		Printing speed: front scraper 1.2m/min, oil return knife 1.0m/min
		Scraper pressure: 7.5kg/cm2
		Number of printing knives: 8 knives repeatedly
		Baking parameters: 75℃ for 30 minutes 150℃ 60 minutes

 

12.Second Drilling