Week 8 - Electronics Production

Introduction To PCB Production

Electronics manufacturing process involves the steps needed to assemble electronic components and parts through electronic and mechanical assembly and connection to make electronic products that meet the requirements of the design.

The manufacturing process starts when the design files (usually in Gerber format) for fabrication and BOM are sent for assembly. DFM tests are done by the manufacturer so as to identify and resolve any PCB layout issues that could create manufacturing problems during fabrication and assembly. It is also done to optimize cost of the board and eliminate potential design failures. Key areas like PCB pad design, trace width, and component locations are checked for any defects in advance. Other considerations include proper thermal management, mechanical or dimensional constraints and test provisions.

There are various types of PCBs ranging from single sided PCBs to multi-layer or even flexible PCBs.

FR PCB stands for Flame Retardant Printed Circuit Board, and it typically refers to PCBs made using flame-retardant materials. There ar different grades of FR PCBs and they are as follows:

1. FR1 PCB: Material: Paper-phenolic laminate. Cost: Cheaper than FR4. Applications: Suitable for single-layer PCBs and simple circuits. Limitations: Not ideal for high-frequency or complex designs.
2. FR2 PCB: Material: Similar to FR1 but with slightly improved heat resistance and durability. Applications: Used in consumer electronics and other applications where cost is a factor.
3. FR3 PCB: Material: Combines paper with epoxy resin, offering better performance than FR2. Applications: Suitable for applications requiring slightly higher performance and durability than FR2.
4. FR4 PCB: Material: Glass-reinforced epoxy resin laminate. Cost: More expensive than FR1, FR2, and FR3. Properties: Good adhesion to copper foil. Excellent moisture resistance. High heat resistance. Versatile and widely used in various applications. Applications: Suitable for a wide range of applications, including general-purpose PCBs, multilayer PCBs, and high-frequency applications.

The most common material used for FR PCBs is FR-4, which is a flame-retardant epoxy laminate. FR-4 is widely used in the electronics industry due to its excellent electrical and mechanical properties.

The Process

1. The blueprint of the PCB is used to fabricate the PCB. PCBs are made of non-conductive substrates with copper layers. The circuit layout is transferred onto the copper layer using photosensitive dry-film and exposure to UV light.

2. Then chemicals are used to etch the copper layers on to the pcb according to the gerber file, in order to remove the unwanted copper layers leaving just the circuit traces.

3. Inspection is done to ensure that the connections are free from defects such as shorts, opens, etc.

4. Computer controlled drilling , Drilling of Via holes, is done to facilitate the electrical continuity between the different layers. Then the holes are made conductive by depositing a thin layer of copper (electroless copper deposition)on the walls of the holes.

5. Imaging will be conducted for the outer layers of the panel using a positive image. Here, the process follows print-plate-etch method. The first step involves cleaning the panels to prevent contaminants and dust particles from sticking to them. Next, a layer of photoresist is applied to the panel. Right after this, LDIs are used to print the imagee.

6. Copper plating: the holes and surface are electroplated with copper. The panels are loaded into the flight bars by the operator. The panels act as cathodes that electroplate the hole and the surface since the holes already have a thin layer of conductive copper deposited that enables electroplating. It is done with the automated plating lines. The panels are cleaned and activated in multiple baths before they are electroplated. Every set of panels is computer-controlled to ensure that they stay in each bath precisely for a particular duration. Usually, the deposition will be 1-mil thick copper inside the hole barrel

7. Photoresist stripping :Once the panel has been plated the photo-resist becomes undesirable and needs to be stripped from the panel in order to expose the unwanted copper. Here, a single continuous process line is used to dissolve and wash off the resist which covers the unwanted copper. This is the first phase of the strip-etch-strip procedure.

8. Final etching: The unwanted exposed copper is removed using an ammoniacal etchant during this step. In the meantime, the tin secures the required copper. At this point, the conducting areas and connections are properly established.

9. solder mask is given to the whole board It provides insulation resistance to the traces. Distinguishes solderable and non-solderable areas. Provides protection against environmental conditions by covering non- solderable areas with ink.

10. LPI (liquid photo imageable) mask combines solvents with polymers to produce a thin coating that adheres to different circuit board surfaces. A printer images the coated panel. A UV lamp in the machine hardens the ink in the transparent areas. Later, all the unhardened resist is stripped off from the imaged panel.LPI curing (drying) merges the ink with the dielectric. It facilitates the bonding of the solder mask. A final baking step is carried out either in an oven or under infrared heat sources.

11. Green was chosen as the typical solder mask color because it doesn’t strain the eyes. All inspections were done manually before machines could inspect PCBs during the production and assembly process. The top light used by technicians to inspect the boards does not reflect off of a green solder mask, making it safer for their eyes.

12. A base copper surface of the board is susceptible to oxidation without a protective coating. Therefore, surface finish application is essential to protect it from oxidation. Additionally, it prepares the surface for soldering components onto the board during assembly and extends the shelf-life of the board

13. Silkscreen : In this process, inkjet projectors are used to image the legends directly from the board’s digital data. The ink is silkscreened (spread) on the surface of the panel using a jet printer. The panels are then baked to cure the ink. It designates different kinds of text such as part number, name, code, logos, etc.

14. Electrical test : During this step, electrical probes are used to check each unpopulated board for shorts, opens, resistances, capacitances, and other fundamental electrical properties. E-test checks the electrical conductivity of the circuit board based on the netlist file. A netlist consists of the information on conductivity interconnection patterns of a PCB.

15. Profiling and v-scoring Circuit boards are profiled and cut out of the production panel in the final PCB manufacturing stage. The method employed either uses a router or a v-groove. The v-groove cuts diagonal channels on both sides of the board, while the router leaves little tabs along the borders. The boards can simply pop out of the panel in any case.

Tapered bits

1. 0.010” (~0.25 mm) End Mill
   • Very fine tool for high-precision traces.
   • Best for dense PCBs with small SMD components.
   • Slow cutting speed required to prevent breakage.
2. 1/64” (~0.4 mm) End Mill
   • Common for standard trace isolation.
   • Works well for most general PCB milling.
   • Balanced between precision and durability.
3. 1/32” (~0.8 mm) End Mill
   • Used for larger isolation or cutting PCB outlines.
   • Good for wider traces and pads.
4. V-Bits
   • Ideal for engraving and isolation routing with variable depth.
   • Good for fine detail work but can remove more copper at deeper cuts.
   • For a V-bit, the width of the trace is proportional to the depth of cut based on the bit’s angle.
5. Tapered Bits
   • Used for engraving or detailed milling where a stronger bit is needed.
   • Provides sharper isolation cuts while maintaining durability.

Basic Conversions

1 mil = 0.001 inches = 0.0254 mm

1 inch = 1000 mils = 25.4 mm

(materials, bits, system of measurement)

workflow for Rolland

Roland Modela MDX 20

The Roland MDX-20 is a compact, 3 axis (X,Y and Z) desktop milling machine designed for hobbyists, students, and small-scale production.

Setting up the machine

1. Press power button to turn ON the machine. The machine’s axis will move to the location shown in the figure below when you press the Power button.

   

   

2. Next step is to load the copper clad board on the machine’s bed. Apply double side tape on the bottom of the copper clad board and paste it on the machine’s bed.

   

   

3. Open Mods and select PCB from MDX mill.

   

   

Before beginning the milling process, make sure that certain tools are available with the machine, as these will be needed during the PCB milling.

• A vacuum cleaner is needed to remove chips during the milling process.

  

• A scraper is required to detach the finished PCB from the machine after milling.

• A 1.5mm Allen key is needed to change the tool.

  

Milling Traces

1. For milling Traces, we have 3 types of tools available in the lab.

   1. 0.4mm Flat Endmill
   2. 0.2mm 60° V Bit
   3. 0.1mm 20° V Bit

   

2. For inserting the bit, select the position to Change bit option on the mods. Then the machine moves to a position so that we can easily change the tool.

   

   

3. Insert the tool maximum inside and tighten the grub screw.

   

4. The PCB is not positioned at the machine’s (0,0) point, so we need to input the coordinates where the PCB is located. This will be the starting point for the work.

   

5. To set the Z offset, press the Down button to lower the Z-axis until the gap between marked parts 1 and 2 is roughly double the thickness of a PCB board. Next, unclamp the tool, gently touch it to the PCB board’s surface, and then secure the two Allen bolts.

   

   

6. I loaded the PNG file into the mods.

   

7. As we used the 0.2mm 60° V bit, we used the V bit calculator with these parameters and clicked the send calculated settings and the values are loaded in the mill raster 2D section. Click calculate there to generate toolpath.

   

   

8. After verifying the tool path the G codes are sent to the machine using send file option on the WebSocket Python serial.

   

   

Milling Outline

1. For milling outline, we have 0.8mm endmill available in our lab.

   

2. We loaded the tool on to the machine just like the previous tool. Moved the machine to the same origin and loaded the outline PNG on to the mods software.

   

3. 0.8mm tool was used for cutting outline and selected mill outline in the mods and calculated to generate the tool path.

   

   

4. Used the send file option to send the G codes to the machine. After machining we used the scraper to take the board from the machine’s table.

   

   

Final output

From this test it was clear that the minimum spacing between the traces should be at least 17mils and the traces widths should be a minimum of 10 mills.

Hole test

• Hole

  A hole in a printed circuit board (PCB) that serves various purposes, such as mounting components, securing the board, or providing electrical connections. Holes can be plated (PTH) for electrical conductivity or non-plated (NPTH) for mechanical mounting.

• Screw

  A hole designed to accommodate a screw or bolt to secure the PCB to an enclosure, heat sink, or mechanical structure. These are typically non-plated (NPTH) and larger than component holes to fit standard screws.

• Rivet

  A metal insert placed into a hole to reinforce mechanical strength and/or improve electrical conductivity. Rivets are often used in through-hole connections when plating is not possible or to strengthen mounting points.

• Via

  A small plated hole that electrically connects different layers of a PCB. Vias come in different types:

  • Through-hole vias: Connect all PCB layers.
  • Blind vias: Connect outer layers to inner layers but do not pass through the entire PCB.
  • Buried vias: Connect only inner layers and are invisible from the outer layers.

  And output of our hole test.

Testing with screws

Testing with rivets For 0.6mm rivet, 0.85 mm hole is required. For 1mm rivet, 1.45 mm hole diameter is required.

Analyze results from using the 3 tools on Rolland

(0.4 and 0.8 mm bits, V-Tool 0.2 mm 60 deg, V-Tool 0.1mm 20deg)

Test Pattern Design and Purpose

The test pattern visible in the images consists of graduated trace width indicators marked at .001, .010, and .020 inches. I design this pattern specifically to evaluate the minimum trace width and spacing achievable with each milling tool. The copper traces appear as thin lines on the FR-1 substrate, with the numerical markings indicating the corresponding width in inches. This standardized test pattern allows me to systematically characterize the capabilities of our in-house PCB production process.

Tools Evaluated

I test four distinct milling tools during this evaluation process:

1. 0.4mm flat end mill (1/64”)
2. 0.8mm flat end mill (1/32”) (used to cut the outline)
3. V-Tool with 0.2mm tip width and 60-degree angle
4. V-Tool with 0.1mm tip width and 20-degree angle

Each tool presents unique characteristics that affect trace quality, minimum achievable width, and overall milling precision.

These one below is the photo of the 3 sample line test that we have done with different tools

Below one is 1/64 bit and the result that we optained .

V-Tool Parameters

0.2mm 60 degree v-tool .

For the 0.1mm 20-degree V-Tool:

Output .

Vtool with 0.1 and 20 deg

RESULTS

Tool	Minimum Trace Width	Minimum Clearance	Observations
1/64” Flat End Mill	All test widths	.015 inch	Wider isolation channels with clean, straight edges. Material removal is more substantial compared to V-bits.
V-bit 0.2mm	All test widths	.010 inch	Moderate isolation channel width. Good balance between precision and durability.
V-bit 0.1mm	All test widths	.005 inch	Finest isolation channels with minimal copper removal. Excellent for high-density designs.

PCB Engraving using XTools F1 Ultra

Laser engraving is an alternative method for fabricating printed circuit boards (PCBs) that eliminates the need for chemical etching or mechanical milling. Instead of physically cutting away material with a milling bit, a laser selectively removes the copper layer from a substrate, isolating traces and pads while leaving the rest of the copper intact. This technique offers a fast and precise way to create PCB prototypes, especially for single-layer designs.

The process begins with designing the PCB layout in software like KiCad or Eagle, ensuring that traces are optimized for laser engraving. Once the design is ready, it is exported in a format suitable for the laser engraving software. The laser then burns away the unwanted copper, leaving only the conductive traces required for the circuit. After engraving, the board is cleaned to remove any residual oxidation or burn marks. If necessary, additional steps such as hole drilling, component soldering, and protective coatings are applied to complete the PCB.

XTools F1 Ultra

Using the XTool F1 Ultra for PCB Engraving

For this assignment, I used the XTool F1 Ultra to fabricate a PCB. The XTool F1 Ultra is a dual-laser engraving machine that can precisely remove copper from a PCB substrate. It features adjustable power, speed, and focus settings, making it suitable for detailed PCB work. Unlike traditional milling, laser engraving does not require physical contact with the material, reducing tool wear and eliminating the need for complex fixturing.

The key advantages of using the XTool F1 Ultra for PCB fabrication include:

• High Speed – The laser can quickly remove copper, reducing fabrication time.
• No Tool Wear – Unlike milling, there are no cutting tools to replace.
• Fine Detail Capability – The laser can engrave intricate trace patterns, depending on power and speed settings.

However, laser engraving also presents some challenges:

• Overburning Risk – Excessive power can damage the board or create inconsistent traces.
• Limited Depth Control – Unlike milling, which cuts through layers, lasers remove material by vaporization, requiring precise tuning.
• Manual Optimization – Power, speed, and pass count must be carefully adjusted to achieve clean results.

The XTools F1 Ultra with its Safety Pro Filter System. The Filter system consists of 5 layers of filtration for safety.

Dual Laser: Diode Laser and Fiber Laser

The Fiber Laser is used to cut/engrave the metal part of the Copper Clad plate. The Diode Laser is used to cut the paper part of the Clad sheet.

Preparing and Sending a PCB Design to the XTool F1 Ultra

You can download the Xtools Software from the given link: https://www.xtool.com/pages/software

1. Connect the Xtools F1 Ultra

1. Home Window

1. Trace Image

1. Engrave Parameters

1. Parameters

1. Cut Parameters

Parameters Window

After setting both the parameters in engraving and cutting. We have to do the operations one by one not simultaneously, because engraving and cutting wouldn’t work properly.

After sending the start button you need to press the start button on the display system connected to the XTools F1 Laser Engraver. The results were really fine. The trace clearance were engraved to the smallest resolution but the trace width couldn’t be done properly because they got burned.

workflow for Trotec - Akash

We attempted to create a test PCB using a Trotec laser cutter, but the results were unsatisfactory due to issues with the laser. Despite experimenting with multiple power settings and speeds, we were unable to achieve a clean and precise engraving. The engraving that came closest to success involved using 40 passes, as shown below:

However, even in this case, the material was not being properly removed. Instead of achieving a smooth and clean surface, string-like residues were left behind, clinging to the engraved areas. This leftover material not only affected the precision of the PCB traces but also made post-processing more difficult.

From my observations, one possible solution to this issue could be running an additional pass in a different orientation. By increasing the overlap between passes, we might be able to achieve better material removal and cleaner engravings. However, the laser cutter we are using does not provide an option to adjust pass orientation, which limits our ability to experiment with this approach.

To explore alternative solutions, we also tried engraving on a different type of copper-clad sheet with a thinner copper layer. Unfortunately, this approach yielded even worse results:

The thinner copper layer did not seem to improve engraving quality, and in fact, it led to even more inconsistent results. The traces were uneven, and the copper was not being properly removed, which made it unusable for PCB fabrication.

Adding to these challenges, we also encountered issues with the laser itself. At times, the laser beam would not emit properly, resulting in incomplete or weak engravings. We attempted to troubleshoot this by cleaning the lens, as dust or debris could interfere with the laser’s performance. However, even after cleaning, the issues persisted, suggesting that there might be an underlying hardware or calibration problem with the laser cutter.

workflow for X-Tools F1 Ultra - Ashish

Flexible circuits - Noel

This week we also tested PCB design rules for vinyl cutters for applications in flexible circuits. We used the same PNG file as milling for our purpose on the Roland GX-24 GS-24 vinyl cutter.

We use copper vinyl tape for our purposes.

Performing the Test Cut

A force of 100 gF and speed of 1 cm/sec was able to make a good test cut.

Conducting the Line Test

We conducted a lot of testing to find the perfect parameters for cutting.

Force (gF)	Speed (cm/s)	Result	Observations
100	1	Fail	The vinyl cutter tore off the traces from the copper sheet. Reducing speed might work.
100	0.5	Fail	Same as before. Need to reduce speed further.
100	0.25	Fail	Same as before, reducing speed alone is not working. Will need to reduce force as well
50	0.25	Fail	Pen did not penetrate far enough to make the required cuts of the traces
70	0.25	Success	This time the traces cut perfectly.

Other Observations

We tried fine adjusting the pen force based on feedback from instructors, but we found that a fine adjustment of 0 works the best.

Also we found that due to the lack of accuracy, sometimes the vinyl cutter would cut the numbering of the line test on top of the traces, so to avoid this issue we cropped out the numbers, which solved the issue.

Transferring the Cuts

We were not able to properly transfer them to surfaces like we normally do since the backing on the copper roll is not sticky enough.

To solve this issue, our instructor advised us to try first sticking a sheet of copper onto the transfer tape itself and feed it into the vinyl cutter.

With this additional step, we were able to properly peel out the non-required elements, leaving only the required traces that can then be transferred to another surface.

Results for the Vinyl Cutter

In conclusion, The setting that worked the best for our vinyl cutter are

Parameters: 100 gF force, 0.25 cm/sec speed, and 0 fine adjustment in pen force

Material: Copper Vinyl sheet pasted on Transfer tape

Tracing Spacing: 0.17 mils

Tracing Width: 0.001 mils

submit a PCB design to a board house – Tom / Ancy

Here’s an interesting idea:

USB-PCB-Business-Card.

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Last update: April 17, 2025