Cheaper Thick copper PCB board Manufacturing with Good Quality made by Hitech Circuits in China
Thick copper PCB is one of the commonly used materials in electronic engineering, which has excellent conductivity and mechanical strength, and is therefore widely used in various electronic devices. This article will introduce the definition, characteristics, and applications of thick copper PCB.
Thick copper printed circuit boards contain over three ounces of copper material per square foot, used to carry high current loads.
1、 What is thick copper plate? ——Definition and Standard Boundaries
Thick Copper PCB refers to printed circuit boards with copper foil thickness ≥ 2oz (70 μ m). In the industry, 2-6oz is usually referred to as conventional thick copper, and>10oz (350 μ m) is referred to as ultra thick copper. The core feature is to break through the current carrying and heat dissipation limits of ordinary PCBs by thickening the copper layer.
1. Copper thickness standard and conversion (industry standard)
Copper thickness specification (oz)
Corresponding thickness (μ m)
Core application scenarios
2oz
70
Medium current power board, industrial control
3oz
105
High current control board, new energy BMS
6oz
210
Energy storage system, charging pile power circuit
10~12oz
350~420
Extra large current industrial equipment, high voltage platform
15~20oz
525~700
Special military and aerospace equipment
Note: 1oz copper thickness is defined as 1 ounce per square foot of copper foil weight, approximately equal to 35 μ m, and is the standard measurement method in the PCB industry.
2. Core boundary with ordinary PCB
Ordinary PCB copper thickness is mostly 0.5~1oz (17~35 μ m), focusing signal transmission; Thick copper plates are centered around "power carrying", with copper layers serving as both conductive channels and heat dissipation structures, making them the core foundational components of high-power equipment.
2、 Core performance advantages of thick copper plate
A qualitative leap in current carrying capacity
Copper thickness is approximately proportional to current carrying capacity, under the same line width and temperature rise conditions:
1oz copper thickness (35 μ m) 1mm line width current carrying capacity of about 30A, only suitable for low-power logic circuits;
10oz copper thickness (350 μ m) 1mm line width can carry 100A+current, meeting the requirements of the hundred ampere level power path;
In extreme scenarios, the ultra thick copper plate (20oz) can stably carry peak currents of over 500A.
Core principle: As the cross-sectional area of the copper layer increases, the resistance significantly decreases (R=ρ L/S), reducing losses and heat generation in current transmission from the source.
2. The "built-in radiator" effect of heat dissipation efficiency
The thermal conductivity of copper is about 401W/(m · K), which is over a thousand times that of FR-4 substrate. The thick copper layer itself is an efficient heat dissipation channel:
The transverse thermal conductivity of 10oz copper foil is increased by 300% compared to 1oz, which can quickly diffuse the heat of power devices such as IGBT/MOSFET and reduce the hotspot temperature by more than 40 ℃;
The steady-state temperature of a 3-oz copper thick PCB is about 15 ℃ lower than that of a 1oz PCB, and it can meet the thermal management needs of medium to high power equipment without the need for an additional heat sink;
The large-area thick copper grounding layer forms a "heat sharing plate" effect, effectively avoiding device failure caused by local overheating.
3. Mechanical strength and environmental adaptability
The thick copper layer enhances the rigidity of the substrate, and the tensile strength of the hole ring is three times higher than that of ordinary PCBs. It can withstand vibration environments of>5Grms and is suitable for harsh scenarios such as automotive engine compartments and mining equipment;
The copper layer has strong bonding strength and can withstand over 1000 cycles of cold and hot shock at -55 ℃~150 ℃ (IPC-TM-650 standard), maintaining stability even in extreme temperature environments;
The large-area copper layer reduces grounding impedance, has excellent electromagnetic shielding effect, reduces EMI interference, and improves equipment electromagnetic compatibility (EMC) pass rate.
4. High voltage resistance and reliability
High quality thick copper plates can withstand high voltages above 10kV, pass 1000V DC withstand voltage tests (leakage current<10 μ A), and with high Tg substrates (≥ 170 ℃) and optimized creepage distance design (≥ 8mm), can meet the safety requirements of new energy scenarios such as 800V high-voltage platforms.
3、 Core manufacturing process of thick copper plate (difficulties and key controls)
The difficulty of processing thick copper plates far exceeds that of ordinary PCBs, requiring breakthroughs in the three core bottlenecks of lamination, electroplating, and etching. Each step requires precise control of parameters:
1. Compression process: No bubbles, high adhesion is key
Pre treatment: Thick copper foil needs to undergo alkaline cleaning (to remove oil stains) and dilute hydrochloric acid micro etching (to remove the oxide layer). High Tg substrates need to be baked at 120 ℃ for 2-4 hours to remove moisture;
Compression parameters: temperature 170~180 ℃, pressure 30~40kg/cm ² (ordinary PCB only 20~25kg/cm ²), vacuum degree ≤ 10Pa, to avoid bubbles between copper foil and substrate;
Testing standard: The adhesion between copper foil and substrate is ≥ 5N/cm, the diameter of bubbles is ≤ 0.2mm, and there is no more than 1 bubble per square decimeter.
2. Electroplating thickening: Uniformity control is the core
For products that require an extra thick copper layer, further thickening is required through electroplating process:
Electroplating solution formula: copper sulfate (180-220g/L)+sulfuric acid (50-70ml/L)+additives to ensure uniform deposition of copper ions;
Key parameters: current density 1-1.5A/dm ², temperature 20-25 ℃, using air agitation and filter element filtration to avoid pinholes or nodules in the copper layer;
Accuracy requirement: The difference in copper thickness between different areas of the same circuit should be ≤ 10%. For example, the allowable deviation for a 3-oz copper layer (105 μ m) should be ≤ 10.5 μ m.
3. Etching process: Control side etching and residual copper
Thick copper foil has a long etching time and is prone to side corrosion (excessive corrosion on the side of the circuit):
Etching solution selection: Acidic etching solution of ferric chloride or copper chloride (concentration 38-42Be '), temperature 45-50 ℃, spray pressure 2.5-3.0bar;
Side corrosion control: By adding corrosion inhibitors or segmented etching techniques, the side corrosion amount is reduced to ≤ 10% of the line width;
Residual copper control: After etching, the residual copper rate is ≤ 0.1%, and the residual copper powder is removed by washing with a high-pressure water gun (0.8MPa).
4. Post processing: Ensuring long-term reliability
Cleaning and drying: Rinse 3-4 times with deionized water, dry in an oven at 80-100 ℃ for 15-20 minutes, ensuring that the moisture content is ≤ 0.1%;
Surface treatment: Nickel gold plating (nickel layer 5-10 μ m, gold layer 0.1-0.3 μ m) is used in automotive/industrial scenarios to enhance corrosion resistance, while OSP treatment is used in ordinary scenarios to reduce costs;
Full process testing: 100% AOI optical inspection, cross-sectional analysis, electrical performance testing (line resistance, insulation resistance).
4、 Typical application scenarios of thick copper plates (irreplaceable core areas)
Thick copper plates are a "must-have" for high-power and highly reliable electronic devices, with core applications concentrated in four major fields:
1. New energy and energy storage
Charging pile: power module, high-voltage distribution unit, requiring 6-10oz thick copper to carry high current fast charging;
New energy vehicles: OBC (on-board charger), BMS (battery management system), 800V high-voltage platform IGBT module, 12oz thick copper can reduce the temperature rise of the module from 65 ℃ to 42 ℃;
Photovoltaic inverter/energy storage PCS: DC-AC conversion circuit, 10oz thick copper to avoid copper foil melting caused by 200A+current.
2. Industrial electronics
Industrial power supply: Communication base station power supply, server power supply, 3-6oz thick copper ensures continuous and stable power supply;
Variable frequency drive/servo drive: high-power motor control, thick copper reduces power device temperature rise, extends equipment life;
Welding equipment: high current output circuit, thick copper layer to resist high-frequency thermal shock.
3. Special equipment
Aerospace: Electronic systems under extreme temperature changes (-40 ℃~150 ℃) and vibration environments require a copper layer bonding force of 1.8N/mm ²;
Military equipment: High voltage, high current special components, ultra thick copper (15~20oz) to meet strict reliability requirements;
Mining equipment: frequency converter in strong vibration and high dust environment, with thick copper substrate to enhance impact resistance.
4. Other high demand scenarios
Medical equipment: high-power therapy equipment, diagnostic equipment, thick copper ensures stable operation and electromagnetic compatibility of the equipment;
Rail transit: train power module, traction control system, suitable for high voltage and high current working conditions.
5、 Key points for selecting thick copper plates and guidelines for avoiding pitfalls
1. Core principles for selection
Select copper thickness based on current: choose 2oz for 5-15A, 3-6oz for 15-50A, 6-10oz for 50-100A, 10oz+for 100A and above, with a 20% safety margin reserved during design;
Select substrates according to the environment: High Tg FR-4 (Tg ≥ 170 ℃) is used for conventional environments, while polyimide or ceramic substrates are used for extreme environments;
Process selection based on reliability: High pressure scenarios require vacuum pressing+3D groove cutting technology, while vibration scenarios require thick copper filling process to enhance the strength of the hole ring.
2. Common misconceptions and pitfalls to avoid
Misconception 1: Thicker copper is better → Increasing copper thickness can lead to increased costs, limited wiring, and extended lead times (1-3 days more than regular PCBs). It is recommended to adopt a "locally thick copper" solution (only use thick copper for power circuits, maintain regular copper thickness in other areas);
Misconception 2: Neglecting line width matching → The larger the copper thickness, the higher the minimum line width/spacing requirement (such as 13mil/13mil for 6oz copper thickness), and it is necessary to confirm the process capability with the factory in advance;
Misconception 3: Neglecting heat dissipation design → Although thick copper has good heat dissipation, it still needs to optimize the copper layer layout (such as grid design, window opening rate of 30%) to further reduce temperature rise.
6、 Industry Development Trends
With the popularization of new energy and silicon carbide (SiC) devices, thick copper plates are developing in two directions:
Combination of ultra-high copper thickness and ultra-thin substrate: such as 12oz thick copper+0.2mm ultra-thin substrate, suitable for 800V high-voltage platform, power density increased to 50W/cm ³;
Integrated process innovation: The popularization of technologies such as vacuum resin plug holes and dynamic impedance compensation further enhances reliability in extreme environments;
Green manufacturing: The application of halogen-free thick copper and recycled copper foil has increased, complying with environmental standards such as RoHS and REACH.
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