Ideas? Interfacing with an off-pcb ic

[qa9b]

Hi all,

I'm trying to figure out a small design issue. I have a few ICs that must be mounted to a heatsink (datasheets are below).

I could solder the ICs into my circuit board and then mount them (along with the pcb) to the heatsink. However, having had poor experiences in the past using this method (and also because of the sheer number of ICs that require heatsinking), I think it would be a far better idea to mount all my ICs to a single heatsink and then run leads to a pcb.

Anyway, I'm looking for a good way to solder leads onto the pins of these ICs. Let's assume for now that my soldering skills are perfect. Should I still try to solder wires directly onto the leads of my ICs? An idea I had was to purchase something like this. I could slide the female connector onto a pin, connect a wire, solder and heat shrink it.

Another concern is interference. I am, after all, handling audio signals. Do you think I could get away with un-shielded cable? It's difficult to find single conductor shielded cable for reasonable lengths/prices. The leads would only be a few inches long.

If you have any input/advice, I'd love to hear. Thanks!
qa9b

datasheets:
https://www.electro-tech-online.com/custompdfs/2011/06/LME49830.pdf
**broken link removed**
https://www.electro-tech-online.com/custompdfs/2011/06/91210.pdf

 

[KeepItSimpleStupid]

I don't understand why you would have trouble.

You mount them at the edge of the PCB. The heatsink is drilled/tapped or whatever at the correct spacing. PC board is also fastened.

Add the IC's one at a time and mount. Solder all after flipping.

 

[qa9b]

I understand how this process works, it's simply not feasible in my case. Total count of ICs that require heatsinking at the moment are about 20. Mostly power MOSFETs. Each of which have non-insulated metal tabs that require an insulating thermal pad. I have a single large PCB (for cost reasons) and a single large heatsink (again, cost reasons). This is a 10" x 6" heatsink, and I'd like to be able to spread out all the ICs across it for better heat dissipation. I have no doubt that this would lead to a much cleaner layout and help a ton when it comes time for me to modify/add to the PCB (which is likely to happen frequently). Both the LME49830s and LM3886s also have quite odd pin spacing that prohibits easily inserting them into a .1" pitched PCB.

Either I have a bunch of PCBs with wires running between them, or I have a bunch of wires running from the HS to my PCB.

Thanks for the suggestion though. What I'd really like to know is if anyone has a better idea of how to solder leads to my ICs. It's completely doable with bare wires, but I was wondering about better ways.

 

[crutschow]

Some choices are:

1. Mount the all devices on one circuit board and attach the heat sink to those devices that require it.

2. Use one circuit board and run bare (insulated) wires to the heat sink.

3. Use one circuit board for most of the parts and another circuit board just for the parts on the sink. You could use a ribbon cable and edge connectors to go between boards.

If you have more than one of these to build it might be easier to use connector pins (or a small connector if you can find ones with the right pitch) to connect to the IC pins.

Don't understand your concern about a 0.1 pitched PCB. All PCB design software allows the pitch to be anything you want.

 

[qa9b]

Yeah, either #2 or #3 is what I'm going for. I am only constructing one of these. I'm using a .1" pitch protoboard, so therein lies my dilemma. Once I finalize the design and work out the bugs, getting a custom pcb made would be the next step. However, seeing as it's not horribly crucial to my amplifier's performance, it's out of the picture for now. I did buy a whole bunch of pcb headers and connectors to make the wiring easier.