What is glass PCB?
Glass Printed Circuit Board (PCB) is a flat circuit board made of glass fiber-reinforced epoxy resin, produced by screen printing copper foil on the surface of glass fiber-reinforced epoxy resin. Using pure copper foil as the metal layer has advantages such as high electrical conductivity, good thermal performance, and excellent mechanical strength. The metal layer can be used in high-voltage applications.
What materials are used to manufacture glass circuit boards?
The glass circuit board is made of two types of glass. One is a piece of glass, as needed. The other is UV photo resistance. UV photo resistance is used to convert light into electricity.
The glass circuit board has three layers: the foil made from copper, the chloride of iron, and a printout from OHP. These materials are glued together with special PCB glue.
Glass PCB material specification and features
Glass PCB material specifications and features are as follows:
Specifications
Features
●High thermal conductivity: The thermal conductivity of glass is 3-5 times higher than that of FR4 or other common substrate materials. It can be used for high-power circuit applications or heat dissipation requirements.
●Excellent electrical insulation: Glass has excellent electrical insulation properties that can meet the needs of different applications, such as high-frequency or high-voltage circuits. The thickness of glass PCB is generally thicker than FR4 PCB to ensure its good electrical insulation performance.
●Good mechanical strength: Glass has good mechanical strength, which can withstand bending, pressure, twisting, and even some impact load during the installation process because of its high elastic modulus (about 7 GPa).
Types of glass PCBs
There are many types of glass PCBs available on the market. Each type has its characteristics and applications.
Glass copper PCB
Glass copper PCB is the most common type of glass PCB. It is made of glass fiberboard and copper foil. The copper foil is printed with a layer of copper. The glass fiberboard comprises insulating materials such as glass wool, rock wool, etc.
Glass epoxy PCB has the same structure as glass copper PCB, but the insulating material is epoxy resin instead of glass wool or rock wool.
Transparent glass PCB
The structure of a transparent glass PCB consists of two sides: one has a layer of UV-cured photoresist that protects the surface. In contrast, the other side has no photoresist protection layer and allows light to pass through it directly. This type of transparent glass PCB can make transparent displays, which are widely used in mobile phones, tablets, and other electronic devices.
Glass fiber PCB (GFPC)
The GFPC uses glass fibers for reinforcement and has good electrical properties, thermal conductivity, and mechanical strength. This type of glass PCB has been widely used in industrial fields such as avionics and military electronics because it can support higher temperatures than ordinary boards and can withstand electromagnetic interference (EMI).
Printing glass PCB
Glass-printed circuit boards are commonly used in industrial applications for their durability and resistance to high temperatures; they can withstand temperatures up to 200°C without any degradation in performance or functionality.
Multilayer glass PCB
The multilayer glass circuit board is composed of high-quality epoxy resin with FR-4 circuit patterns, providing excellent electrical and mechanical performance. It is suitable for high-speed and high-density interconnections between components on the board.
Advantages of glass PCB
Glass PCB has the following advantages:
Impact resistance
Glass PCB has excellent toughness and strength, effectively resisting external impact. It is a better choice for rugged applications.
High-temperature resistance
Glass PCB has high thermal conductivity, which is good for heat dissipation. It can withstand high-temperature environments and operate normally without degradation.
Low-temperature coefficient
Glass PCB’s low-temperature coefficient of resistivity enables it to have stable electrical performance under various temperatures, thus making it suitable for multiple applications.
Low noise level
Because glass has no internal dielectric layer, its dielectric constant is very low, and its thermal expansion coefficient is close to zero. As a result, glass PCB has a low noise factor and a low impedance value that are advantageous for high-frequency circuits such as RF circuits, high-speed digital circuits, etc.
Applications of glass PCB
Glass PCB is a new advanced technology that replaces the traditional FR4 PCB. It has excellent electrical properties and mechanical strength. It can be used in many applications, including solar power equipment and systems, glass LED display screen, new-energy electrical and electronics devices and procedures, and optical instruments and devices.
New-energy electrical and electronics devices and systems: Solar panels, wind turbines, etc., use glass PCB for insulation. It prevents short circuits from occurring due to high voltage levels or high temperatures generated by these devices.
Optical instruments and devices: Glass PCB is a substrate material for optical devices such as lenses, cameras, and other similar equipment.
Solar power equipment and systems: solar cells, solar panels, and other components use glass PCB to make them more durable.
Glass LED display screen: The mobile phone’s touch screen is made up of glass. The LCD panel of TVs and monitors is also made up of glass PCB.
How to make a glass PCB?
Step 1: About the technique
Making Glass PCBs is quite different from the traditional method of making PCBs. In this technique, designers must expose the design on a glass plate with light and then etch it. The advantage of this method over other methods is that it can be used for mass production easily.
Step 2: Materials
This step requires the following materials to make glass PCBs:
●Glass Plate
●Copper Foil (1 oz) or Copper Clad Board
●Lithium Hydride Battery or Coin Cell Battery
●LED Light
Step 3: Preparing the circuit design
Prepare the circuit design for printing on a glass substrate. First, convert the circuit diagram into an image file (GIF or JPG) that can be printed on the glass substrate.
Step 4: Print the design
Print the design on a special film using a laser printer. Then place this film on the glass to create a negative image of the traces and pads.
Step 5: Gluing the copper foil to the glass
Apply the special glue to the copper foil and then place it onto the glass. The glue will help hold down any parts of copper foil that are not sticking to the glass.
Step 6: Applying photo resist
After that, a Photo Resist is applied over the top of all exposed copper foil areas. This material prevents light from exposing all areas of copper while still allowing light through its clear areas. The photoresist must be cured after application using UV light or heat to prevent further exposure to UV light which could cause damage to this material.
Step 7: Light setup
UV Light is a great way to expose PCBs. It’s inexpensive and easy to use, but the main drawback is that exposure takes around 10 minutes per side.
The exposure time can be shortened by increasing the intensity of the UV light source, but this increases the cost and complexity of your setup.
Step 8: UV-Vis absorbers
Another option is to use UV-Vis absorbers in combination with a bright white LED. This is a good solution if you want to do high-volume production because it’s fast — only a few seconds are needed for each side of the board.
Step 9: Develop resistance
The developer is then prepared by creating a baking soda solution. In the absence of baking soda, rinse powder can be used. Second, immerse the copper board in the developer for one to two minutes. Observe that the unexposed portions fly away after removing the copper board and washing it. Continue until all unexposed portions of the copper board have been removed and the resist tracks have cured.
Step 10: Clean and etch glass
Clean the glass with detergent and warm water, then etch the back with hydrofluoric acid. This will remove any grease or dirt on the glass’s surface and etch away some of its material. The etched area should be large enough to accommodate all of the components.
Final words: The future of glass PCBs
There is potential for a shift toward glass PCBs in the PCB industry. Rigid-flex PCBs were not widely used until recently. Rigid-flex PCB’s soaring popularity directly results from the growing need for dynamic stability in increasingly compact and high-performance electronic products.
Glass circuit boards will gain popularity when power consumption increases, and improved thermal dissipation is necessary for electronic products.