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JLCPCB Aluminum PCB manufacturing notes + USB connectors

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thmjpr:
Its hard to find some information on JLC aluminum process. For most cases the specs are the same as their FR4, but, I wasn't sure how it would actually turn out. Here is what I found.

Rules:
The two rules they specifically call out for Alu, in place of the regular rules are
- minimum 1mm drill
- minimum 1.6mm slot

Routing:
- Curved route path for an internal slot I put was almost perfect
- The outer route of the entire PCB was also very clean, just slight bump in where they started or ended the cut.
- Some of the holes had more burrs than others, none are bad but its still a sharp edge. No annoying FR4 fibers that I noticed.

Clearances:
- Appears to be the same as their regular FR4 spec.
- Plated holes, the copper comes right up to the edge of the aluminum, maybe within 1mil of the edge of a hole. There is no electrical connection of course. True plated holes that connect with the aluminum are available from other manufacturers at much higher cost.
- non-plated holes, there is an added gap to the copper
- Board edge to pad: seems not quite as close as a plated hole, but still very usable.



USB connector options:
- Through hole is possible (type B), what I did was heatshrink the "+" lead as thats the only one I care about shorting. Then solder the tops as usual to the PCB pads. Or glue could also be used to fill in the area around the pins with a small needle. Glue can be applied around the USB housing for support as well.





- SMD, multiple options are possible. The one I went with is mid-plane type-C 6 pin. You can solder the sides of the connector to large pads on the PCB, providing good strength. Pads at the edge of the PCB work OK.





I don't know if these are options for serious production, as the gap between the solder connecting Vbus and the aluminum is incredibly small.

Soldering:
- Wasn't quite as bad as expected, any pads I had could be soldered with a T12 iron. The large ones did require a long dwell time.
- Preheater will help a lot if you have one.
- Hot air just didn't work at all, could work with the preheater though

Board spec:
- 1W/mk
- Thickness info: https://www.eevblog.com/forum/manufacture/jlcpcb-now-do-aluminium-pcbs!/

thmjpr:
Aluminum PCB Bending Notes:
- I used a bending tab width of 6mm, spacing of 2mm (the minimum routing out spec for JLC), and PCB thickness of 1.6mm (1.0, 1.2, and 1.6mm are available).
- Distance from the center of the bend to the nearest component was 2mm. This was a bit close, the part is a 1206 resistor so its robust and had no issue, but smaller components or capacitors should be further away as they could crack.
- An angle of 18 degrees was tested without issue, no cracking or delaminating of the copper traces were visible. In the future if I get some spare boards I'll test one to destruction.

The bend was fairly easy, if you needed a stronger PCB for mechanical reasons you could go thicker. Or if you wanted an easier bend for a longer tab size, could go thinner. To me 1.6mm seemed like a good trade off. Although the actual board received measures closer to 1.45mm.

Bending jig:
- Bending jig can be 3D printed in PLA to get consistent bend angle
- Springback can be calculated online, but for aluminum it is very low. I only ended up needing to add 0.5 degrees or so on the over-bend angle.

Initially I was considering how to make a bending jig out of aluminum. But its just not necessary, the softness of the al-core is easy to work with. The jig would also end up fairly complex to machine. 3D printed PLA seems fine for low volume tests.

Cutaway of the jig:


Parts:


Fit:

Infraviolet:
Are aluminium PCBs mainly just about better thermal conducitivity to take heat away from high components (motor drivers, high power LEDs...), or are there other common uses too? I gues with the right tolerances one could use the aluminium PCB service as a way of getting precicion cut 2D aluminium parts for mechanical use?

thmjpr:

--- Quote from: Infraviolet on February 02, 2023, 10:13:34 pm ---Are aluminium PCBs mainly just about better thermal conducitivity to take heat away from high components (motor drivers, high power LEDs...), or are there other common uses too? I gues with the right tolerances one could use the aluminium PCB service as a way of getting precicion cut 2D aluminium parts for mechanical use?

--- End quote ---

That is the main common use, yes. The board I am working on can dissipate 3-5W or so, trying to do the same with FR4 would not be realistic.

Your mechanical use idea is good, if you need something that is roughly 1 to 1.6mm thick, in low volumes. I have seen a few postings of people using them for front panels, guitar pedals, etc.
But that is what I am trying to get at here, there are many more possibilities. With bending, you could form the board into a box shape, triangle pyramid, etc. FR4 will not bend and stay in place, you need flex PCB and some structure to hold it.

JohanH:

--- Quote from: Infraviolet on February 02, 2023, 10:13:34 pm ---Are aluminium PCBs mainly just about better thermal conducitivity to take heat away from high components (motor drivers, high power LEDs...), or are there other common uses too? I gues with the right tolerances one could use the aluminium PCB service as a way of getting precicion cut 2D aluminium parts for mechanical use?

--- End quote ---

I've created front panels for some project cases. White soldermask and black text works nicely. No circuits, but I guess you could theoretically have a PCB integrated in the front panel.

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