3D Modeling (PCS – Printed Circuit Structures)
The PCB is a critical part of every electronic circuit. The shapes and sizes of the PCBs are conditioned by their application, working environment and the size constraints of the equipment to be manufactured.
Though with the existing technology we are able to use the x and y dimensions effectively, little has been done to utilize the z dimension. Today, 2.5D approach is widely used.
The 2D and 2.5D technologies have a few drawbacks.
Solid features are created and they have a good finishing. A resolution upto 0.001 per inch can be achieved but the research tools have achieved upto 0.0001 per inch resolutions.
Fused Deposition Manufacturing (DFM)
In this technique, a heated nozzle is used to remove plastic directly onto a surface. This process can then be repeated until a certain number of times to create a 3D structure, that we mentioned earlier. In this way, 3D layering can be obtained. The nozzle and the head is moved onto a moving platform and is coordinated with the flow of plastic metal. Like SLA method, the structures created by DFM also require the use of support structures that are water soluble.
The disadvantage of the method is it creates a porous structure due to extrusion of the melted plastic. The structures are not self leveling and contain air bubbles in the structures. This goes in contradiction to the concept of 3D structure.
This demerit of the process can be overcome by using high resolution prints and controlling overlapping parameters.
The finishing obtained by this method is rough and it needs to undergo additional processing to deliver a smooth finish.
The resolution is in the order of 0.005 inch but the structures produces are rigid which allow their usage for mechanical parts.
Printed electronics
This approach of printing is used to achieve printing on various substrates as cheap as vinyl. This technique is designed for fast and low cost printing to achieve small features. The different approaches in this class are:
1. Screen printing : This is well known in solar cell manufacturing industry. Screen with a set pattern is laid on top of the work material and is pressed to it. The resolutions can be as good as 100 micrometer with a throughput (the amount of material) of 50 m2/h. It has a capability to produce thick layers with a wide range of materials having different measure of viscosity.
2. Direct Digital Manufacturing (DDM): This requires ink jetting to be done on a substrate with a low viscosity ink. The ink particles have conducting and self adhesive properties. A throughput of around 100 m2/h with a thickness of around 0.0005 inches can be made.
3. Electroless plating: A metallic film is deposited on the substrate with the help of a chemical (reducing) agent. The process is slower than the electrolytic plating but the resolution achieved is higher and thin lines are obtained.
4. DP (Direct print methods) : A quill is dipped in the depositing material. The material sticks to the tip of the quill. This tip can then be moved over a substrate in 3 axes to produce a 3D print. It can produce a 14 nm line width and 5nm resolution in 3D patterns.
Major challenges and remedies
As the structure is getting smaller and smaller, the electromagnetic interference between the traces and components become a larger problem. This can be minimized with the use of anisotropic materials and spatially variant lattices.
Additionally, this method is still premature due to lack of development of required automation tools. Currently, 3D printing and DP method are used collectively to achieve objectives but a technology named Direct Printing Additive Manufacturing System (DPAM) is being developed to build a common automation tool to the above problem statement.
The PCB is a critical part of every electronic circuit. The shapes and sizes of the PCBs are conditioned by their application, working environment and the size constraints of the equipment to be manufactured.
Though with the existing technology we are able to use the x and y dimensions effectively, little has been done to utilize the z dimension. Today, 2.5D approach is widely used.
The 2D and 2.5D technologies have a few drawbacks.
- Ineffective utilization of z dimension.
- Limited data transfer capabilities.
- Harmonic effects due to impedance mismatching of materials.
- Magnetic reflections due to sharp turns of the conducting path.
The 3D printing technology will eliminate the use of epoxy, vias, soldering, wires, screws and bolts. The circuits are flexible enough to be be rolled into a cylinder with the circuit inside it. The structures can vary from being solid to porous to elastic depending upon the application of the product.
With the help of DFM (Fused Deposition Manufacturing) machines, printing can be done at home and converted into physical structures.
Go Green
The earlier practices of PCB manufacturing consisted of bulk materials - raw materials and rejecting the excess unwanted part to utilize. It resulted in a large amount of wastes. 3D or AM (Additive Manufacturing) is a process of accumulating successive layers of materials leaving little or no waste.
Selective Laser Sintering (SLS)
This is the first additive manufacturing process employed. In this, a thin layer of powdered material is placed on the work surface and a laser beam sinters the particles together by creating metal thin shapes. The surface is lowered and another layer is deposited on the existing layer. This process is repeated, which creates a 3D structure.
The 3D structure can be built with features and voids that cannot be achieved by subtractive process. The resolution of lines is around 0.005 inch and thickness of layer is 0.004 inch.
Stereolithography Apparatus (SLA)
This is a process similar to that of SLS but hardening of photosensitive resins is done here instead of sintering particles. Support structures are required if there are large gaps in the build. The support structures are temporary and can be dissolved in water later.
With the help of DFM (Fused Deposition Manufacturing) machines, printing can be done at home and converted into physical structures.
Go Green
The earlier practices of PCB manufacturing consisted of bulk materials - raw materials and rejecting the excess unwanted part to utilize. It resulted in a large amount of wastes. 3D or AM (Additive Manufacturing) is a process of accumulating successive layers of materials leaving little or no waste.
Selective Laser Sintering (SLS)
This is the first additive manufacturing process employed. In this, a thin layer of powdered material is placed on the work surface and a laser beam sinters the particles together by creating metal thin shapes. The surface is lowered and another layer is deposited on the existing layer. This process is repeated, which creates a 3D structure.
The 3D structure can be built with features and voids that cannot be achieved by subtractive process. The resolution of lines is around 0.005 inch and thickness of layer is 0.004 inch.
Stereolithography Apparatus (SLA)
This is a process similar to that of SLS but hardening of photosensitive resins is done here instead of sintering particles. Support structures are required if there are large gaps in the build. The support structures are temporary and can be dissolved in water later.
Solid features are created and they have a good finishing. A resolution upto 0.001 per inch can be achieved but the research tools have achieved upto 0.0001 per inch resolutions.
Fused Deposition Manufacturing (DFM)
In this technique, a heated nozzle is used to remove plastic directly onto a surface. This process can then be repeated until a certain number of times to create a 3D structure, that we mentioned earlier. In this way, 3D layering can be obtained. The nozzle and the head is moved onto a moving platform and is coordinated with the flow of plastic metal. Like SLA method, the structures created by DFM also require the use of support structures that are water soluble.
The disadvantage of the method is it creates a porous structure due to extrusion of the melted plastic. The structures are not self leveling and contain air bubbles in the structures. This goes in contradiction to the concept of 3D structure.
This demerit of the process can be overcome by using high resolution prints and controlling overlapping parameters.
The finishing obtained by this method is rough and it needs to undergo additional processing to deliver a smooth finish.
The resolution is in the order of 0.005 inch but the structures produces are rigid which allow their usage for mechanical parts.
Printed electronics
This approach of printing is used to achieve printing on various substrates as cheap as vinyl. This technique is designed for fast and low cost printing to achieve small features. The different approaches in this class are:
1. Screen printing : This is well known in solar cell manufacturing industry. Screen with a set pattern is laid on top of the work material and is pressed to it. The resolutions can be as good as 100 micrometer with a throughput (the amount of material) of 50 m2/h. It has a capability to produce thick layers with a wide range of materials having different measure of viscosity.
2. Direct Digital Manufacturing (DDM): This requires ink jetting to be done on a substrate with a low viscosity ink. The ink particles have conducting and self adhesive properties. A throughput of around 100 m2/h with a thickness of around 0.0005 inches can be made.
3. Electroless plating: A metallic film is deposited on the substrate with the help of a chemical (reducing) agent. The process is slower than the electrolytic plating but the resolution achieved is higher and thin lines are obtained.
4. DP (Direct print methods) : A quill is dipped in the depositing material. The material sticks to the tip of the quill. This tip can then be moved over a substrate in 3 axes to produce a 3D print. It can produce a 14 nm line width and 5nm resolution in 3D patterns.
Major challenges and remedies
As the structure is getting smaller and smaller, the electromagnetic interference between the traces and components become a larger problem. This can be minimized with the use of anisotropic materials and spatially variant lattices.
Additionally, this method is still premature due to lack of development of required automation tools. Currently, 3D printing and DP method are used collectively to achieve objectives but a technology named Direct Printing Additive Manufacturing System (DPAM) is being developed to build a common automation tool to the above problem statement.
