Printed circuit boards surround our everyday lives. Electronic circuits can be found in high-tech goods, computer tools, and home appliances. There are many types of PCBs and various methods to manufacture them as well. The conventional way to print a circuit is to design a copper-covered board and etch away the undesired copper. However, if you could build your own copper board, there are many creative possibilities. Like other types of PCBs, there is a note on glass PCBs.
What is a glass substrate?
Glass substrates serve as the foundation for a wide range of optical devices. For mirrors and lenses, glass blanks are ground, coated, and polished. Substrate glass is thermally stable and highly homogenous when used in transmission, with diameters ranging from microns thick to meters in diameter.
Glass PCB usually used in LCB, LED. We can make it with the raw material of glass. In the glass PCB, we have to transfer the circuit onto the copper board using a UV curable mask. UV curable masks provide perfect results even with narrower track widths. This is the technique utilized even in bulk PCB manufacturing. When exposed to UV light, a thin coating of UV curable etches resist hardens. This resistance is applied to the copper board and exposed to a UV light source through an opaque film containing an image of the circuit. The circuit design is cured on the resist film in this manner. The uncured film may be removed using a developer, and the circuit is ready to be etched. Don’t be misled by the term developer; it’s just a low basic solution, similar to baking soda that can remove uncured UV resistance.
UV resist films are classified into two types: positive and negative. When the developer is applied, the exposed portions of the photoresist remain undissolved while the remaining parts dissolve. The opposite of negative is positive. In this Intractable, I’m going to utilize a negative one.
The material used in glass PCB
There is the material that we have to use to make a glass printed circuit board:
- Piece of glass, as needed
- UV photo resistance
- Baking soda
- The foil made of copper
- Chloride of iron
- Printout from OHP
The layout of Circuit
After having the material, we need a layout of our circuit board that transferred to a clean sheet. This may be performed by printing the design on OHP paper. Create a schematic diagram of your circuit first. Then create the PCB layout. After that, using the auto-route tool, route the routes of your circuit. For a novice, this may seem to be a little complicated. But after a few lessons, you’ll be fine.
There are a lot of unnecessary words and component diagrams in the design. Only the tracks and pads are required for our purposes. As a result, after you’re satisfied with your design, isolate the pathways and pads layer in the layer pallet and export the monochromatic picture as a PNG. We utilize the harmful kind of photoresist, which means we must expose the resist to light in areas where we want to keep the copper. As a result, using the “white on black” option in the exporting window is required. It implies that it keeps the tracks and pads white on a black backdrop. OHP paper that is white stays transparent after printing.
The goal of the OHP print is to create a mask that prevents UV light exposure of the resist in undesirable areas. To do this, the black portions of the OHP print must completely block light. Otherwise, the light would pass through them. However, one layer of paint does not completely block light. As a result, three prints were aligned and bonded together to keep them stable.
Gluing the GLASS to the Copper Foil
Suppose you will use copper placed on glass you have to glue the copper on the glass. In the last steps, we must dissolve unnecessary copper using ferric chloride. Using thick copper foil increases the time required for the procedure. A thickness of approximately 0.05mm is ideal.
To begin preparing the glass, we must first clean it and the copper foil with rubbing alcohol. Otherwise, the copper will cling to the glass. After washing, apply a generous quantity of adhesive on the glass and distribute it evenly. Then press hard with the copper foil. Make sure there are no air bubbles between the glass and the copper foil. Next, squeeze the copper foil to remove the extra adhesive. Allow it to cure thoroughly.
Using Photo Resist
First, cut a piece of the necessary size. The photoresist comes with two clear coverings that cover both sides. The photoresist substance is abrasive. When the cover is removed, it is elementary to attach to the copper board. As previously stated, the resist film has two covers. To adhere to the photoresist, we must first remove the cover. To do this, we may apply two pieces of scotch tape to the top and bottom of the resist film. It is possible to remove a cover by removing such tape pieces. Then, gently put the exposed side of the copper on the copper. Gently press the photoresist to ensure that they have firmly adhered. Make sure there are no air bubbles between the photoresist film and the copper.
Modify the Exposure to Light Setup
After applying the photoresist, we must now create the setting. Please take a look at the OHP printout that we previously created. Place it on top of the copper board. Make sure that the print is placed on the right side. If not, the whole print may be mirrored. Then, put a piece of glass to verify that the OHP print well adheres to the copper board. To keep the arrangement stable, I’ve added two clips. It is now time to expose to light.
We must now expose the setup to light. You have the option of using an artificial UV source. UV light may be obtained from bright sunlight. A 5-minute exposure to sunshine will be enough. Maintain the stability of the whole configuration during the exposing process. That’s where clips come in handy.
After 5-7 minutes, remove the setup from direct sunlight and dismantle everything. You should be able to see the print has dried somewhat on the resist.
Create the Resistance
On top of the resist, the film is another layer of cover. We must also eliminate it to improve it. Remove the lid once again with the assistance of scotch tape. Make a solution with some backing soda. Any simple solution would suffice. If you can’t locate backing soda, rinse powder will do the trick. Anyway, once you’ve made the developer (backing soda/rinse powder solution), dip the board and set it aside for a minute. Then take it out and gently wash it. You should be able to observe the unexposed portions being rinsed away. Repeat the procedure until all of the exposed parts have been rinsed away. Lastly, you’ll have a copper board with cured resist tracks.
Take some ferric chloride powder and dissolve it in approximately 150ml of water. The solution should be black. If necessary, add additional ferric chloride. After preparing the solution, immerse the copper board in it. Shake the board often to ensure effective etching. After around 10-15 minutes, all undesirable copper should be eliminated from the remaining pathways.
The resistance over the copper pathways may be removed using acetone or warm water. Making a PCB on glass may not provide any electrical benefits. However, these kinds of circuits manufacturer may be used for a variety of applications where transparency is required. A led set on this kind of track, for example, might be fantastic.
Advantages of glass PCB
The glass substrate has distinct advantages in terms of flatness, transparency, deformation, heat resistance, tear resistance, and so on; the deformation rate is very low when working at high temperatures for extended periods; the glass PCB can emit 360-degree luminescence, with an 80 color rendering index of 140lmw or more; it does not require a heat sink, and there is no light attenuation. Currently, glass PCB is extensively utilized in LED displays, solar panels, 3D printers, and other applications.