Aluminum PCB

Metal Core PCB

KKPCB is a PCB technology that makes it possible to conduct heat out of the LED and into the atmosphere in a faster and more efficient manner. While the primary focus of KKPCB is the rapidly evolving LED market, there are other applications for which KKPCB is an ideal candidate.

The thermal conductivity assisted by the aluminium core in the circuit boards makes higher packing densities, longer operating times, and improved security against failure possible, such as for LED technology and for high power transistors.

The KKPCB promise is to reduce LED junction temperature allowing users to increase LED life, increase reliability, increase brightness, increase lumens per LED and reduce cost per lumens and that is a promise KKPCB definitely delivers on.

What is an IMS PCB?

IMS = Insulated Metal Substrate, It also called metal core pcb. A metal core printed circuit board (MCPCB) also known as thermal PCB, incorporates a metal material as its base as opposed to the traditional FR4, for the heat spreader fragment of the board. Heat builds up due to some electronic components during the operation of the board. The purpose of the metal is to divert this heat away from critical board components and towards less crucial areas such as the metal heatsink backing or metallic core. Hence, these PCBs are apt for thermal management.

Copper circuitry bonded onto an electrically insulated thermal dielectric layer, that is bonded to a metallic substrate.

• The insulating thermal dielectric is a special material, with good thermal conductivity; normally it is 8 to 10 times more thermally conductive than FR4.
• The dielectric is normally is made using a filling material that normally used aluminium oxide, aluminium nitride, boron nitride, magnesium oxide or silicon oxide.
• An aluminium metal base is perhaps the most common metallic base. It is suitable for drilling, punching and cutting.
• In most cases and IMS board reduced the need for heat sinks.

Metal core pcb and aluminum pcb Material considerations

Aluminum pcb Base metal

• Consider the application to choose suitable metal base

1.  For normal lighting application, can choose 1K (1100) and 3K (3003) serial Aluminium ;
2.  For Power application, can choose 5K (5052) serial Aluminium;
3.  For Rectification application (shaking environment), can choose 6K (6061) serial Aluminium ;
4.  Postfix name “H” means; Work hardening state to increase strength; “T” means after heat treatment; the first digital after “H” &”T” means degree; see next slide.

• Copper base, much better for heat sink;
• Stainless steel, good for electromagnetism shielding;

At KKPCB you can get aluminium core PCBs with a thermal conductivity of 1.0 W/mK to 8 W/mK. The aluminium core helps to distribute the selective heat of heat-intensive components and to make the heat development on the printed circuit board more homogenous. The rule of thumb for many high-power LEDs is: A 10° C lower junction temperature increases the lifetime by 10.000h.

For one-sided metal core PCBs, a heat sink and/or fan (active cooling) can be mounted directly on the aluminum (passive cooling).

Key points of fabricating aluminum PCB

(1) Machining

No burr is allowed in the hole edge after drilling on the aluminum substrate, which will affect the pressure test. It is difficult to mill the shape. And stamping shape, need to use an advanced mold, mold production is very skilled, as one of the difficulties of aluminum substrate.

After the shape is punched, the edge is required to be very neat without any burr and the solder mask on the edge of the plate is not damaged. Usually, the operation die is used, the hole is punched from the circuit, the shape is punched from the aluminum surface, the circuit board is up shear and down pull, and so on. After punching, the warpage of the board should be less than 0. 5%. 

(2) The whole production process is not allowed to scratch the aluminum base surface: the aluminum base surface will change color and blacken when it is touched by hand or by some chemicals, which is absolutely unacceptable.  Some customers do not accept the re-grinding of the aluminum base surface.  Therefore, it is one of the difficulties to produce an aluminum base plate without touching the aluminum base surface in the whole process. Some enterprises adopt a passivation process, others stick protective film before and after hot air leveling (tin spraying).

(3) Overvoltage test: 100% high voltage test is required for the aluminum base plate of communication power supply.  Some customers require direct current, some require alternating current, voltage requirements are 1500V, 1600V, time is 5 seconds, 10 seconds, 100% printed board is tested. At any point on the board surface, such as dirt, holes, burr on the edge of the aluminum base, line sawtooth, bruise, etc., the insulation layer will lead to fire, leakage, and breakdown of high voltage resistance test. Pressure test board delamination, bubble, are rejected.

Specification for aluminum base PCB fabrication

1. Aluminum substrate is often used in power devices with high power density, so the copper foil is relatively thick. If more than 3oz copper foil is used, the etching process of thick copper foil needs engineering design line width compensation, otherwise, the linewidth will be out of tolerance after etching.

2. The aluminum base surface of the aluminum substrate must be protected with protective film in advance during PCB processing, otherwise, some chemicals will erode the aluminum base surface, resulting in appearance damage. And the protective film is easy to be damaged, resulting in a gap, which requires the entire PCB processing process must be inserted into the rack.

3. The hardness of the milling cutter used in the glass fiberboard Gong board is smaller than that in the aluminum substrate. The speed of production of fiberglass milling cutters is fast during processing, while the production of aluminum substrates is at least two-thirds slower.

4. Computer milling glass fiberboard can only use the cooling system of the machine itself, but the processing of aluminum substrate must be separately targeted at Gong head and alcohol heat dissipation.

Thermal conductivity of aluminum PCB

The thermal conductivity of aluminum substrate refers to the heat dissipation performance parameter of the aluminum substrate, which is one of the three criteria to evaluate the quality of aluminum substrate (thermal resistance and pressure resistance are the other two properties).

The thermal conductivity of the aluminum substrate can be measured by the tester after the plate is pressed.  At present, the high thermal conductivity values are generally ceramic and copper.  However, considering the cost, the aluminum substrate is recognized by most customers in the market.  The thermal conductivity of aluminum substrate is also the most concerned parameter.  The higher the thermal conductivity is, the better the performance is. The aluminum substrate is a unique metal-based copper clad laminate aluminum substrate, which has good thermal conductivity, electrical insulation, and machining performance.

Thermal conductivity, also known as thermal conductivity, refers to the physical quantity of a material’s thermal conductivity.  It refers to the heat (kcal) passing through 1 SQM area within 1H due to heat conduction when the vertical distance of isothermal surface is 1m and the temperature difference is 1 ℃. It is expressed in kW / M. H.  ℃.

If the substrate material is required to bear greater heat dissipation efficiency, the substrate material used should have high thermal conductivity (thermal conductivity). If the substrate material is required to be able to achieve the effect of thermal insulation, the lower the thermal conductivity of the substrate material used, the better.

How to check the quality of aluminum PCB is good?

1. Use tools to measure the size, dimensions, and specifications of aluminum substrates, the thickness, size, and shape of the board will directly affect the assembly of the finished product.

2. Make sure to check the thermal conductivity of the aluminum substrate, copper foil, plate thickness, and pressure resistance, which directly affect the performance of finished products and the cost of procurement.

3. The brightness and solder resistance oil of aluminum substrate. Usually, the surface of the aluminum substrate will be covered with a layer of ink, which is mainly used for insulation. If it is found that the surface of the aluminum substrate is not smooth, it is usually covered with less oil, which will lead to poor insulation effect of aluminum substrate.

4. The pad size of the aluminum substrate will directly affect the subsequent patch and line conductivity.

5. If the circuit is close to the edge of the board, we must pay attention to the withstand voltage problem of the aluminum substrate, especially for the purchasers who have requirements on the withstand voltage.

6. Substrate, this is very important.  When purchasing, we must select regular and large-scale manufacturers.  The incoming materials from these manufacturers are strictly inspected before they are put into production. Its product quality assurance. The aluminum substrate is not just a circuit, it is like a human blood vessel, determines the life of the product.

7. In the production process, regular aluminum substrate manufacturers should ensure the process quality of each process, especially in etching, whether the aluminum substrate is corroded by etching water determines how long the aluminum substrate you purchase can be used.