Archive for the ‘SinkPAD’ Category

Why HASL Surface Treatment Is Not Suitable For Sink Pad MCPCB?

Thursday, January 12th, 2023

Sink Pad MCPCB is a special type of metal core PCB (short for MCPCB), the working principle is through the sink heat pad solder direct to the metal substrate (commonly copper or alumina substrate), so people also call it as Thermal pad MCPCB. Sink Pad MCPCB is popular recently due to its excellent heat dissipation and thermal conductivity. Since the copper is easy to get oxidation, coating a metal film is good for protecting the surface, such as ENIG, ENEPIG or OSP. Lead-free hot air solder leveling (HASL) also is a kind of surface treatment, but why we don’t suggest to apply it? Let me explain with you.

Why is HASL not recommended?

  • Substrate

From the substrate aspect, due to the HASL process is to first dip the solder on the circuit board, then dip the solder flux in the melting, and finally blow off the excess solder on the printed board with the hot compressed air in the air knife through the two air knives, at the same time to eliminate the excess solder in the metal hole, so as to get a bright, smooth and uniform solder coating. Since most of customers prefer choose copper substrate as the base material (Aluminum core sink pad PCB thermal conductivity only could be 235 W/m.k, while Copper core sink pad PCB thermal conductivity could reach to 400 W/m.k). However, copper base is much heavier than alumina core, during the hot air knife scraping tin process, the copper surface is easy to be scratched and get damaged to affect the poor appearance and a short circuit risk. This is one of the reasons why HASL is not suitable for Sink Pad PCB.

  • Structure

From the structure of the Sink Pad MCPCB, the LEDs Chip Thermal Pads solder contact to the copper substrate directly, no dielectric between LEDs heat out pads and the Metal core. As you can see the stack up as below, what Sink PAD PCB laminate is pure film, the adhesion is not very good, so there’s a risk of delamination if do HASL (lead free).

  • Chemical

From the chemical aspect, due to the HASL (lead free) has the process of return the film, the potion will react with the copper chemically, which will bring the poor coating and poor adhesion, so we don’t recommend to use HASL on the Sink Pad MCPCB.

Advances of the Sink Pad MCPCB

  • Thermal conductivity 235 To 400 W/m.
  • Super good heat dissipation
  • Power LED junction temperature
  • Longer LED life
  • Most economical direct thermal path solution
  • Direct thermal path
  • Different structure can be made according different design needs

When can we use Sink Pad MCPCB?

With so many kinds of PCB types, when and where can we use the Sink Pad MCPCB?

  1. The copper metal core has high density, strong thermal conductivity and carries heat effectively. That means, it is possible to dissipate the same heat using a smaller sink-pad MCPCB, as compared to regular MCPCBs. So it is suitable be used in small applications which need to apply in high temperature.
  2. Very popular with high power LED mounting, sink-pad MCPCBs with their thermoelectric separation structure, can minimize the lumens depreciation of the LED, thereby prolonging the life of the LED lamp. Sink-pad MCPCBs are suitable for mounting high-power LED lamps and COB packaged LEDs. Moreover, manufacturers can tailor the sink-pad MCPCB to match the different design requirement needs of any LED.

Best Technology is a professional Sink Pad MCPCB manufacturer for more than 16 years in Asia, we have strong engineering team and specialized sales team can provide most suitable solutions for your applications in a very short time. What we can provide not only include single layer Sink Pad MCPCB, we also can produce 2 layers, double layer and multi-layer Sink Pad MCPCB. View https://www.bestpcbs.com/products/sinkpad-board.htm to know our capability about Sink Pad MCPCB.

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Advantages of Sink-pads Copper Substrate in the Field of LED Products

Tuesday, August 17th, 2021

For LED packaging, the cooling performance of the substrate will directly affect the relevant performance of the LED. Due to the low thermal conductivity of the insulation layer, the overall thermal conductivity is generally only 2~5W / (m K), which often causes high working temperature, stability and life decline of LED. Therefore, it is necessary to know the advantages of sinkpad copper substrate.

Doule sided sinkpad of copper board
  1. From the perspective of substrate, the application advantages of copper substrate in heat dissipation.

The copper substrate is used in the field of heat dissipation, mainly because the sinkpad copper substrate has the following advantages: high density, strong heat dissipation ability, the circuit part and the contact part of the products to achieve zero thermal resistance, can effectively extend the life of the products. Large power, strong thermal bearing capacity of copper substrate, according to the actual work requirements of tin spray, gold precipitation, silver plating and other effective treatment, to ensure the effectiveness of the surface treatment.

  • From the perspective of production process, the application advantages of thermal power separation copper substrate in module thermal resistance and chip temperature compared with ordinary copper substrate.

Different LED models and modules cause different thermoelectric effects. When using the common copper substrate, the junction temperature of LED chip is 72.41 ℃. However, when using the sink-pad copper substrate link, the detection shows that: the junction temperature of LED chip is 48.72 ℃. When using the common copper substrate, the thermal resistance of the module is 4.24 ℃ /W. However, after the use of sink-pad copper substrate, the overall thermal resistance of the module was detected to be 2.13 ℃ /W. Due to the different material properties, the thermal resistance of the module thermometer at the bottom of the substrate was different.  

  • From the perspective of heat dissipation theory, for the ordinary copper substrate, the diffusion path of the heat flow is the line layer (copper foil) → thermal conductivity insulation layer copper base. The interface between metal and insulation has high thermal resistance and low thermal conductivity. In the sinkpad copper substrate, the convex platform and the base are actually a whole, and most of the heat will choose to spread through the metal, and only a small amount of heat is transmitted through the interface between the metal and the insulating layer, which greatly improves the thermal conductivity of the substrate.

According to the heat dissipation theory of LED, reducing the junction temperature of LED beads can effectively improve the light output efficiency of LED, enhance the performance stability of LED, and greatly extend the service life of LED module.  

Therefore, in LED products application, the choice of thermal separated copper substrate is the best choice.

single sided sinkpad of copper board

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Common Problems in SinkPAD Board Design

Thursday, June 17th, 2021

1. What is the SinkPAD Board?

Sink Pad Board, also called Heat Sink or DTP (direct thermal path), it’s an alternative PCB technology to the conventional metal core PCB providing direct thermal path solutions for high power LED. 

The thermal conductive PAD is convexity area of copper core/pedestal, so that the thermal PAD of LED can touch the convexity area of metal core directly, and then the heat of LED will be dissipated into the air much faster and more efficient than conventional MCPCB.

Heat Sink

2. If only the LED pad can be made as SinkPAD?

Of course no, the pads of other chips or components also can be designed as Sink PAD, one of the most common is the IC pad. In some designs, IC needs to pass through the large current and it will emit a lot of heat, it would be best to design its pad as a thermal conductive pad at this time.

SinkPad Board after SMT

3. What is the thermal conductivity of a SinkPAD ?

The thermal conductivity could be 235 W/m.k to 400 W/m.k.

4. Can we use SinkPAD technology for any LED packages?

No, it’s designed to be used with the LEDs which has electrically neutral thermal pad. Such as Cree XPL/XML/XHP/XPG/XPE/XPC/XTE/XBD, Luxeon Rebel & Luxeon M from Philips Lumiled, Oslon SSL & Oslon square from Osram, Nichia N219, Seoul Semiconductor Z5P / Z5M, Samsung 3535, Bridgelux SM4, etc.

5. What is the Manufacturing Process for the SinkPAD Board?

Manufacturing process is the same as conventional MCPCB, please click here to see the manufacturing process status.

Shinkpad

6. How does SinkPAD Board compare to Conventional MCPCB?

Conventional MCPCB uses a thermally conductive dielectric layer to bond circuit layer with base metal (Aluminum or Copper) layer. The key to thermal performance of MCPCB lies in its dielectric layer. Even though thermally conductive dielectric has higher thermal performance compared to normal FR4, it’s still a weakest link in the conduction thermal path.

SinkPAD Board approach overcomes this limitation, which provides “Direct thermal path”, the LED Chip can directly contact the copper substrate, there’s no dielectric between LED thermal pads and the metal base, then the thermal resistance is very small.

7. Can the aluminum be made as the base of Heat Sink?

Actually yes, however, regarding of current technical conditions, since aluminum or aluminum alloy cannot directly react with acid, the reaction process is too complex and difficult to control, which will increase the difficulty of etching the LED pad platform.

Considering the scrap rate, the process of etching LED pad platform with aluminum is more complex and the overall cost is higher, and the copper also dissipates heat much better than aluminum, so copper is generally used as the substrate for Heat Sink in our company.

Copper Substrate

8. Does SinkPAD Board require special PCB design?

No, we can use your existing MCPCB Gerber data.

Welcome to contact us if you have other questions about Sink Pad Board. 

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If only the LED pad can be made as SinkPAD?

Friday, September 4th, 2020

According to our earlier blogs about SinkPAD introduction,

we can know that the high power LED’s thermal pad can touch the convexity area of copper core directly, so the heat of LED will be dissipated into the air much faster and more efficient than conventional MCPCB, but if only the LED pad can be designed as SinkPAD?

This image has an empty alt attribute; its file name is Stack-up-s.jpg

Actually the pads of other chips or components also can be designed as SinkPAD, one of the most common is the IC pad. In some designs, IC needs to pass through the large current, so it will emit a lot of heat.

This image has an empty alt attribute; its file name is Contrast-images-s.jpg

In order to dissipate heat in time, some customers will directly design the IC solder pad as sinkpad to directly contact the copper base, so that the life cycle will be longer.

As you can see the following picture, it’s the copper layer after doing Etching, the area with blue film we normally named it as convexity, the thermal pad of IC will touch the convexity directly to achieve the purpose of dissipating the heat very fast.

This image has an empty alt attribute; its file name is Convexity-s.jpg

If you have other questions about SinkPAD, welcome to contact Tammy (Email:sales9@bestpcbs.com), she will prove you professional suggestions and solutions.

In the end, I’d like to share the manufacturing process of SinkPAD Board with you, please Click here: SinkPAD-Board-Manufacturing-Process-Best-Technology.pdf

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