JLCPCB Aluminum PCB manufacturing notes + USB connectors

[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]

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?

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]

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?

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.

[tooki]

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 don’t even think they existed until high power LEDs came along, since they’re really the only power semiconductors where the heat must be dissipated through the back. For everything else you’d just put a heatsink onto the top of the package, but with LEDs that’s obviously impossible. I don’t think I’d use aluminum for serious non-LED applications anyway, since the thin FR-4 layer is still going to add a lot of thermal resistance; a heatsink is going to be better anyway.

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?

I’ve thought about using them for this, too!!