8. Electronics Production¶

Our task for this week was to;
1. Characterize the design rules for FabLab Kamakura’s in-house PCB production process:
document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
2. Document the workflow for sending a PCB to a boardhouse

3D modeling machine at FabLab Kamakura (We used SRM-20 this time):

Model	monoFab SRM-20	Sainsmart Genmitsu 3018 pro ver
Workpiece area	232 x 156mm	290 x 180 x 40mm
Software Resolution	0.01 mm/step (RML-1), 0.001mm/step (NC code)
Power Consumption	50W	60W
Acoustic Noise Level	45-65dB

For the material we used Copper-clad laminated substrate (cut substrate) / 紙フェノール（FR-1）の銅板 with thickness = 35um.
For endmill; we used 1/64 size bit SE 2FL for milling PCB traces.
For edge cutting and holes we used 1/32 size bit SE 2FL.

SRM-20 SRM-20

1. Milling PCB using test data¶

For test data, we used Neil’s png files linetest.traces and linetrace.interior.

alt text

Creating G-Code file using modsproject ¶

Mods is a modular cross platform tool intended for use with commonly found machinery in fab labs. It is based on independent but interrelated modules and can be used in various tasks, including CAD, CAM, machine control, automation, UI development, input device integration, and responsiveness to physical models.

Visit the mods site.
Start by right clicking anywhere on screen > Program > Open Program > Roland > Mill 2D PCB
A node program appears.
First, we read data (png or svg). This time, we read png.
Then we set PCB defaults to adjust the milling tool settings. After setting the parameters (this time we use the default), select Mill traces or Mill outliine.
→ Speed: 4 mm/s
→ Plunge rate: On Roland SRM-20, there was no option to adjust this
→ Depth of cut (traces): 0.004 inch (max: 0.004 inch)
→ Depth of cut (outline): 0.024 inch (max: 0.072 inch)
We move onto Roland SRM-20 milling machine and Change XYZ to 0.
We also select Save file = ON.
Then we go to Mill Rastor 2D, and select Calculate to generate Toolpath.
A linetest.traces.png.rml file is generated and automatically downloaded. Examine the toolpath. If it’s not displayed automatically, press View. Identify potential errors or issues in the machining process before the actual fabrication.

We also create the toolpath for linetrace.interior (we also used default values).

These are the generated toolpaths:
alt text

Once the toolpaths are completed, we can go onto Milling the PCB. Export the files using USB drive.

Here are some definitions of words that appear in mods: Plunge Rate: Depth of cut: Maximum Depth of cut: Offset number: Offset stepover:

Milling¶

Machine Preparation¶

At Fablab Kamakura, there is a dedicated PC for the SRM-20.

Connect the PC to the SRM-200. Turn on lamp and machine.
Open VPanel software.
Fix the sheet securely to the bed using adhesive, to get a level surface.
Set the bit to machine, not totally tightly as we need to set Z origin first.
Set Z origin by adjusting the bit to just above the surface, lightly supporting the screw with your finger, and unscrewing so the bit drops to surface. Then fix the Z origin.
Set XY origin using the arrow buttons on Vpanel (Remember, we do this only for traces, we DO NOT need to change XY origin when cutting).
We can also adjust feed rate on the VPanel software here.
When ready, we cut. Set Z to more than 0 to lift bit, select Cut, delete all, and open the trace file to cut, and select output.
After cutting, remove the bit, use the brush to remove cutting remains, and use the solution and spatula for removing board.
We do the same for interior cut. Replace the bit to 1/32 inch , and set Z origin (remember we must not change the XY origin).

Results¶

We use the test data to understand 1. how thin we can make the lines, and 2. the pathways surrounding the lines before they start peeling off.
alt text

Results:

Test	Tools and Parameters	Result and Action
1st Test	Tsuchiya san’s bit (3 years old)	Cut was uneven due to slanted surface, so we set a new sheet with better adhesives
2nd Test	Tsuchiya san’s bit (3 years old)	Tried again Clean cut with very little peeling off
3rd Test	Kat’s bit (2 years old, quite used)	Surprisingly clean, but some remaining pieces inside the 0
4th test	Shoko’s brand new bit	Very clean down to the details

2. Sending PCB to Boardhouse¶

Create a Gerber file¶

Choose the Boardhouse¶

This site provides a good comparison.

Major Chinese boardhouses:

Major Japanese boardhouses:

Submit the gerber file¶

Create an account, and upload the file.

You can optionally set these parameters:

Parameter	Description
Dimensions	Automatically set. The larget the size the more expeensive
Base material	Default is usually FR-4
Unit	Minimum is usually 5
Thickness	Default is usually 1.6mm. Extra cost for adjustments.
PCB color	Can change from default of green, but may influence cost/lead time
Finish	Can select non-lead options but will be slightly more expensive. ENIG uses gold to prevent oxidization but will be expensive
PCB Mark	Order # will usually be printed on the board, but you can delete it

*You can make gerber file form plot menu in KiCAD.

*At the very least, if you specify the size, you can get a quote even before the Gerber files are created.

Get a quote¶

• Unicraft

I set parameters as below:

Customer prepares Gerber data (Gerber data creation is not requested)
Rigid board FR-4 (general printed circuit board) [Standard]
Board size: 33.50 x 46.00 mm
Single-sided, single layer
Number of pieces ordered: 3
Board thickness: 1.6 mm [Standard]
Copper foil thickness: 35 μm [Standard]
Minimum pattern spacing: 0.125 mm [Standard]
Minimum hole diameter: 0.25 mm [Standard]
Silk printing: Yes [Standard]
Resist color: Green [Standard]
Board shape: Rectangular [Standard]
Internal cutout: No [Standard]
Oval hole: No [Standard]
V-cut: No [Standard]
Land surface treatment: HASL [Standard]
UL mark: No [Standard]
Continuity test: Yes [Standard]
Lead time: Normal delivery date [Standard]
Component mounting service not used Result:
Estimated price: 14,370 yen (excluding tax)
Price including tax: 15,807 yen

• P板.com