The function of solder mask layer on the PCB Board.

September 20th, 2021

At last time, we shared a blog talking about Why most of the PCB boards are green? . Believe you’ve known the reasons for why most of solder mask colors are green.

Today, let’s share something about the function of solder mask on the Printed Circuits Boards.

The solder mask layer is designed mainly to prevent the PCB copper foil from being directly exposed to the air and play a role in protecting the PCB surface, which is also to prevent the area that should not be soldered from being soldered.

PCB Solder mask

As we know that almost all the PCB need to do the assembly, which need to go through the reflow soldering while the assembly, and solder mask plays an important role during control of the reflow soldering process.

Here is a summary for what solder mask roles played on the board:

(1) Prevent physical disconnection of conductor circuits on the circuits board;

(2) In the welding process, solder mask can prevent short circuit caused by bridging;

(3) solder mask can reduce copper pollution to the soldering trough;

(4) Print solder mask on the PCB can prevent insulation deterioration and corrosion caused by external environmental factors such as dust and moisture;

(5) Solder mask are with high insulation; it is possible to increase the density of the circuit.

Red solder mask

In terms of solder mask material, it must be used through liquid wet process or dry film lamination.

Dry film solder mask materials are supplied in a thickness of 0.07-0.1mm (0.03-0.04″), which can be suitable for some surface mount products, but this material is not suitable for PCBs with tighter pitches.

Why choose MCPCB rather than FR4 PCB for high power LED?

September 20th, 2021

Compared to conventional LED, high-power LED consume more electricity and require higher currents, but the heat generated in the end cannot be dissipated in time through the ordinary FR4 CPB. And there will be some failures when the heat from a LED is not properly removed, the LED’s light output is reduced as well as degradation when the heat remains stagnant in the LED package.

So if the PCB requires fast cooling, it’s better to use a metal base rather than a traditional FR-4 substrate. The typical LED MCPCB is a single circuitry layer copper foil which is bonded to a layer of thermally conductive dielectric material which is bonded to a thicker layer of metal like Aluminium or Copper base, the purpose of a MCPCB is to efficiently remove the heat from all topical IC’s (not just LEDs). Following are the comparison between FR4 PCB and MCPCB for your reference.

 

1 – Thermal Dissipation

FR4 has low thermal conductivity, typically around 0.3W/m.K, while MCPCB has higher thermal conductivity, ranging from 1.0-7.0W/m.K. MCPCB transfer heat 8 to 9 times faster than FR4 PCB, the dielectric layer must be very thin to create the shortest path from the heat source to the supporting metal plate, its thickness is normally between 0.003 and 0.006 inches.

As an example, consider that a test conducted on an MCPCB with integrated 1W LED showed how its temperature remained pretty close to the ambient temperature of 25°C, while the same power LED mounted on a FR-4 board reached a temperature 12°C higher than the ambient one.

2 – Better Strength and Stability

Since high power LED chips are usually assembled directly on the PCB, these LEDs can create stability and reliability problems for the circuit. Without adopting the right technique, heat dissipation can hinder the performance of electronic devices that operate at high power. The use of metal PCBs in these applications effectively solves this problem. In addition to ensuring a high durability, aluminum is very light, and adds strength and resilience to the printed circuit board without causing an increase in weight.

3 – Dimensional Stability

The size of a metallic printed circuit board remain more stable, as environmental conditions vary, than that of a PCB made with traditional materials, such as FR-4. Subjected to a heating process from 30°C to about 150°C, PCBs with metal layers (such as aluminum) have undergone a very small variation in size, ranging from 2.5% to 3.0%.

If you have other questions about MCPCB, welcome to contact us.

Ceramic PCB is suitable for UVC-LED

September 8th, 2021

Due to COVID-2019, UVC-LED is becoming more and more popular.

The wavelength of UVC-LED is 100-275nm, 265 nm is the best!

Why UVC-LED is becoming more and more popular?

Because UVC-LED has a lot of advantages for sterilization.

High efficiency: The UVC segment ultraviolet light emitted by UVC-LED generally kills bacteria and viruses within a few seconds.

Extensive bactericidal effect: UVC-LED can kill a lot of bacteria.

Safety and environmental protection (without mercury): The most obvious advantage of UVC-LED devices over traditional mercury-excited ultraviolet lamps is that the germicidal light source does not contain mercury or heavy metals, and is simple to operate, safer and more reliable.

Small size, flexible design, easy installation: UVC-LED devices are small in size, and the sterilization device is flexible in design. It can be used in small spaces where traditional ultraviolet mercury lamps cannot be used. It is more in line with the future development trend of high efficiency, small size and integration.

Why ceramic PCB is suitable for UVC-LED?

Because UVC-LED is sensitive to heat.

Due to the low external quantum efficiency (EQE) of UVC-LEDs, only about 1-3% of the input power is converted into light, while the remaining 97% is basically converted into heat. If the heat cannot be dissipated in time and the LED chip is kept below its maximum operating temperature, it will directly affect the service life of the chip, and it may even be unusable.

Due to the small size of UVC-LED, most of the heat cannot be dissipated from the surface, so the back of the LED becomes the only way to effectively dissipate heat. After years of development, UVC-LED is basically based on a flip-chip solution with a high thermal conductivity aluminum nitride substrate. Aluminum nitride (AlN) PCB made by Best Technology has high thermal conductivity (thermal conductivity 180 W/(mK) ~ 260 W/(mK)), which meets the needs of high heat dissipation of UVC-LED and effectively extends the service life of UVC-LED.

Please feel free to contact sales@bestpcbs.com to know more about ceramic PCB for UVC-LED.

Ceramic PCB for UVC LED
AlN Ceramic PCB

Why most of PCB boards are green?

August 24th, 2021

You may have found such a situation, most of the PCB boards are with green colors, while other colors are relatively rare to see, do you know why?

As we know that the Printed Circuits Board consists of Solder Mask Layer, Silk screen layer, solder PAD, Copper traces, surface finishing and other parts, etc.

Among them, the solder mask refers to the part of the PCB that is covered by oil. Since most PCB boards use green oil, the part of the green oil that can be seen on the board surface is the solder mask, which play an important role during the reflow soldering process.  

green solder mask

Then why are most of the PCB boards green? The main reasons are as follows:

  1. Green is less irritating to the eyes. We all know that green is good for the eyes and can resists fatigue. So when the PCB board with green solder mask, relative production and maintenance personnel are not prone to eye fatigue when staring at the PCB board for a long time, and it is less harmful to the eyes.

2. Cost for Green oil is lower. Since green is the mainstream in the production process, the purchase of natural green oil will be larger, and the purchase cost of green solder mask will be lower than other colors. At the same time, using the same color oil in mass production can also reduce the replacement cost.

  • When the board works on the SMT soldering process,  it needs to go through the process from Tinning, post soldering and final AOI inspection. These processes all need to be optically positioned and calibrated. The green background color is better for the recognition of the instrument.
PCBA AOI testing

Okay, now, do you understand why most of PCB boards are with green colors?

Though we know green is the most common one, but other colors such as red, yellow, blue, purple, black or some other colors are okay for us to make.

solder mask colors

If you have PCB board with a special color want to make, please contact us and we will try best effort to meet your request.  

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

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

Baking Time & Temperature Standard of MCPCB

August 17th, 2021

After manufacturing the Metal Core PCB, there is a shelf life, once the shelf life has passed, we need to bake the bare board before assembling the components, otherwise the MCPCB is prone to burst when the SMT line is produced. There are industry specifications for both how long MCPCB can be stored and how long they can be baked.

MCPCB Control Standard

  1. Unpacking & Storage
  2. If the packing bag is sealed, and the manufacturing date is within 2 months, it can be directly used before assembly.
  3. The manufacturing date is within 2 months, and the unpacking date must be marked after unpacking.
  4. The manufacturing date is within 2 months, and it must be assembled and used within 5 days after unpacking.
  • Baking Time
  • If unpacked for more than 5 days within 2 months of the manufacturing date, bake at 120±5°C for 1 hour
  • Two months after the manufacturing date, baking at 120±5℃ for 1 hour before assembly.
  • Two to Six months after the manufacturing date, baking at 120±5℃ for 2 hours before assembly.
  • Six to Twelve months after the manufacturing date, baking at 120±5℃ for 4 hours before assembly.
  • The MCPCB after baking must be used up within 5 days (put into IR REFLOW), and unused board must be baked for another hour before assembly.
  • Over half one year after the manufacturing date, bake at 120±5℃ for 4 hours before assembly, and then send it to the production line to do HASL_LF before using.
Baking Machine

Preservation & Baking Standard for in different regions

The specific storage time and baking temperature of MCPCB are not only related to the production capacity and production process of manufacturer, but also have a great relationship with the region.

  1. For areas with heavier humidity, the MCPCB must be used up within 24 hours when exposed to the air, otherwise it is easy to oxidize. After normal opening, it is best to use it up in 8 hours.
  • For areas with a relatively dry climate, the preservation time of PCB will be longer, and the baking time can also be shorter. The baking temperature is generally 120±5℃, and the baking time is determined according to the specific situation.

The MCPCB with OSP or Gold Immersion has a shelf life of 6 months after packaging, and it is generally not recommended to bake for MCPCB with OSP.

PCB board with SMT

If you have other questions about MCPCB, welcome to contact us.

Why use ceramic circuit boards

August 11th, 2021

With the continuous upgrading and optimization of electronic products, the PCBs as the carrier of components have also been continuously improved, and ceramic circuit boards have appeared. So, compared with traditional glass fiber (FR-4), aluminum-based and copper-based, what’s the advantages of ceramic PCB?

1. Stable flatness

Ordinary PCB is usually made by bonding copper foil and substrate, and the substrate material is mostly glass fiber (FR-4), phenolic resin (FR-3), aluminum-based, copper-based, PTFE, composite ceramics and other materials. The mixture is usually phenolic, epoxy, etc. Due to thermal stress, chemical factors, improper production technology and other reasons during PCB processing, or due to asymmetric copper paving on both sides during the design process, it is easy to cause the PCB board to warp to varying degrees.
The ceramic circuit board is hard with good heat dissipation performance, and low thermal expansion coefficient. At the same time, the ceramic circuit board is bonded to the base material by magnetron/vacuum sputtering. The bonding force is strong and the copper foil will not fall off. High reliability, thus avoiding the

2. Large current carrying capacity:

100A current continuously passes through the 1mm 0.3mm copper board, and the temperature rise is about 17℃; 100A current continuously passes through the 2mm 0.3mm board, and the temperature rise is only about 5℃.

3. Thermal conductivity:

The thermal conductivity of alumina can reach 15~35, and that of aluminum nitride can reach 170~230. Because in the case of high bonding strength, its thermal expansion coefficient will be more matched, and the tested tensile value can reach 45 MPa.

4. Thermal conductivity:

The thermal conductivity of the high thermal conductivity aluminum substrate is generally 1-4W/M. K, and the thermal conductivity of the ceramic substrate can reach about 220W/M. K depending on its preparation method and material formula.

5. Low thermal resistance:

The thermal resistance of a 10×10mm ceramic substrate is 0.63mm thick. The thermal resistance of a ceramic substrate is 0.31K/W, the thermal resistance of a 0.38mm thick ceramic substrate is 0.19K/W, and the thermal resistance of a 0.25mm thick ceramic substrate is 0.14K /W.
 

6. Good insulation performance, high pressure resistance, protection of personal safety and equipment, strong bonding force, bonding technology, copper foil will not fall off, high reliability, stable performance in high temperature and high humidity environments.

7. Stable high-frequency performance, AK and DK values are lower than its PTFE, in line with ceramics.

In summary, with its advantages, ceramic circuit boards have been used in high-power power electronic modules, solar panel components, high-frequency switching power supplies, solid state relays, automotive electronics, aerospace, military electronics, high-power LED lighting products, and communications Antennas, automotive sensors, refrigeration sheets and other fields are widely used.

DSC-1135
DSC-1186

What kind of test for Coil Printed Circuit Board?

August 11th, 2021

In year 2019, one of our US customers asked us, Marina can Best Technology make a Coil PCB (Printed Circuit Board) with FR4 material? Yes, of course, we can make different kinds of PCB for our customer, included for the Coils PCB, which currently is widely used for wireless charging and antenna products. Please see the following Coils board from Best Technology.

The manufacturing process is same as other PCB manufacturing process, and just make sure the etching process and pay attention for the etching tolerance of the coils trace. And when coils PCB board finished, do you know what kind of test need to do to check the functional of Coils boards?

Today I would like to share how Best Technology test Coil PCB board. Everyone knows that we check the quality of PCB board with Flying probe tester, as the production efficiency is extremely low and the inductance and capacitance cannot be accurately measured. In this way, we need to use LCR meter to make verify the inductance and capacitance. See the LCT meter as following.

Best Technology chooses the digital meter LCR Meter to test the impedance characteristics of the coil. From the LCR tester you know see two numbers, one for inductance and another for resistance.

After test each coils printed circuit board, we will make record at our paper to make sure every measurement data will meet for customer requirement.

Currently, LCR Meter only provides a single-channel test function, and can only test the impedance characteristics of a set of coils at a time. But this is the effective test method for Coil printed Circuit Board. But we believe we will buy more LCR meters to let the test coil board become quicker.

If you have any comments on the testing for Coil printed circuit board, you are welcome to send us query and we are happy to discuss with you. You can visit www.bestpcbs.com to know more about us. Thank you

The way to add the mouse bite on the PCB Panel #Bestpcb

July 31st, 2021

#Bestpcb #Best PCB

Maybe you’ve ever been recommended by your PCB manufacturer to add a mouse bite on the PCB edge?

But, what’s mouse bites?  Is it something about the Rat?

Of course not, it is kind of connection way for PCB Panel.

As you know, usually the Printed Circuits Boards are manufactured on a standard sized panel, and sometime, the panel will with sharp edges, and those sharp edges are often referred to as “mouse bites” and they are left over after depanelization.

mouse bite PCB depanelization Best Technology

Mouse Bites usually presented as row of tiny holes on the board edge, just like the half holes around a stamp, which to connect and allow those small boards in an array.

mouse bite stamp holes on the PCB edge

Here is the picture for you to see how the mouse bites presented on the Gerber drawing and what it is when it is finished.

Partial Effect drawing after Penalization: (the way of connecting bridge is used in the middle, this way can reduce the residue of burr in minimize)

Partial Effect drawing pcb panel
PCB panel mouse bite

Some People also called mouse bites as perforated breakaway tabs, it is designed for a better the purpose of the mouse bites is for a better grasp when mounted.

Here is the design rules if you need to add the mouse bites on your PCB panel.

  1. The distance between each single board need to arranged as 1.2mm and 1.6mm.
  • The distance between each holes need to be 0.2mm, the distance between holes center should be 0.75mm.
  • Need to add two rows, the mouse bites extend to 1/3 of the board, if there is a some circuits on the board edge, you will need to avoid it.
  • After adding mouse bites, the shapes of the two sides of the hole are connected, which is convenient for the production of gongs after work.

Here are some of our PCB with mouse bites for your reference.

mouse bite PCB Best Technology
PCB with mouse bit

If you want to add mouse bites on your PCB board, you are welcome to send us your request and we will help you make it on your PCB Panel.

How to make Panel for MCPCB?

July 16th, 2021

Regarding all Metal core PCB required panelization, which needs to take into account how the boards are connected. There are two main connection methods for panel: Double face carved V-shaped groove (V-CUT), and the long slot plus a small circular hole (commonly known as stamp hole), depending on the shape of the PCB.

  1. V-CUT

V-CUT is to draw a slot at the junction of two boards, where the connection of the boards is relatively thin and easy to break. Currently SMT Board is widely used, characterized with neat and level edges after separation, which is recommended as priority.

V-cuts are generally straight lines, and there will be no complicated traces such as curved arcs, so pay attention to be in a straight line when making the panelization. Please also note the following two points.

① The two sides of V-CUT line (top side and bottom side) require a no circuits area that is not smaller than 1mm, to avoid the damage circuits when separating.

② After cutting the V-shaped groove, the remaining thickness should be 1/4 to 1/3 of the total board thickness , which is not smaller than 0.4mm.

V-Cut
  • Stamp Holes/Mouse Bite

For irregular PCB boards, the shape of the board has curved corners, there will be many burrs if use V-cut. In this case the stamp hole connection would be the better choice.

  1. Panelization Rules:
  1. The spacing between the panel and the board is 1.2mm or 1.6mm.
  • The diameter of hole is 0.55mm, generally a row of 8 holes (Hole count depends on the design requirements, more holes can enhance the stability), the spacing of the two holes is 0.2mm.
  • The distance between the upper and lower rows of holes is 2mm, and 1/3 of the stamp holes enter the board. Pay attention to avoid the circuit on the edge of the board.
  • After adding the stamp holes, the shape of both sides of the hole need to be connected to facilitate the subsequent routing manufacturing.
  • The part picture after panelization.(Using the connection bridge in the middle, which can minimize the residual.)
Part Picture
  • The effect picture after panelization.
Stamp Holes

If you want to learn more about MCPCB design, welcome contact us.