High Current PCB Connections - Page 1
Forum section: electronics / general

author: Revky27
author_rank: Contributor
timestamp: February 21, 2023, 04:53:08 pm
content: Hi All,I am currently designing a power distribution board which can carry up to 100V, 60A per channels with a number of channels available. Due to the high power of the design I will be using bus bars for each channel to keep power dissipation to a minimum.Previously I used single bus bar in the design where the transition from the controlling high-side switch to the bus bar and from bus bar through to the connector was done through the PCB and kept as short as possible. However on this design i have a few parallel channels so I was hoping to have an elegant solution without having to get my high current through the PCB ( apart from potentialy a SMT mosfet)My question is if anyone came across any solutions/recommendations/examples in implementing a direct connection between mosfet/bus-bar/output connector? Ideally looking to minimize any large currents flowing onto the PCB. The bus bar will be custom so there is some flexibility to integrate with existing optionsThanks

author: jpanhalt
author_rank: Super Contributor
timestamp: February 21, 2023, 05:08:16 pm
content: I just used solder from the bus bars (0.025" copper) to link to an intermediate board and then to the MCU/controller (attached). At the power end (12V marine battery), I used a terminal block and screw connections.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 21, 2023, 11:55:15 pm
content: Quote from: jpanhalt on February 21, 2023, 05:08:16 pmThat doesn't look like 60 A to me. More like a fuse.

author: Whales
author_rank: Super Contributor
timestamp: February 22, 2023, 12:04:23 am
content: 60kW * multiple channels is a lot of power. Are you sure a PCB is the right solution here? Assembling it industrial-cabinet style with bolt-on thick cables might be better.eg take everything that currently needs a PCB and turn it into some very small PCBs with bolt-on connections. Assemble and mount everything into an appropriate explosion-proof box.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 22, 2023, 12:04:58 am
content: I used it for years to run a 6V Ford long shaft starter motor (e.g., something appropriate for a tractor) at 12V to launch model sailplanes weighing about 5# or so. The estimated current was about 200A. That short section going to the PCB was well "heat sunk." Of course, that short section was only needed to carry very low continuous current for monitoring and providing gate current of about 5A for a short period. The rest of the bus bar could handle more amps than the mosfets.Did you realize the short section was not carrying anywhere near 60A?.

author: tszaboo
author_rank: Super Contributor
timestamp: February 22, 2023, 01:45:45 pm
content: Harwin has SMT jumpers that can handle 10A according to the specification, but in my experience you can easily push them for higher currents.https://www.harwin.com/products/S1621-46/, so if you have a few in parallel that could work for short distances.60A connectors are also available from Würth called redcube. I considered them for busbar connections, but usually wave soldering the busbar into the board is cheaper.

author: jonpaul
author_rank: Super Contributor
timestamp: February 23, 2023, 03:38:57 am
content: At multi KW power levels neither SMD switches nor PCB are optimal, especially for industrial applications and productions designMany IGBT, FET, BJT GAs, SiC devices at 50..500A are packaged in plastic modules, built-in HS transfer plate, massive connectors, etc.Often the control, driver's and isolation on separate PCB coupled to power switches via TP balanced cable, transformers, FO or optocouplers.This avoids issues of CM noise, SMD components and connectors.The magnetics design and termination is often the most interesting and difficult part.Bon chanceJon

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: February 23, 2023, 03:24:09 pm
content: Würth Elektronik Redcube Terminals are a solution for high-current PCB interfaces.

author: uer166
author_rank: Super Contributor
timestamp: February 23, 2023, 09:19:32 pm
content: Quote from: jonpaul on February 23, 2023, 03:38:57 amQuite the opposite, there is nothing wrong with PCB and SMD if you do it right, I've done a 22kWx2 board that has both small SMD and bigger TH stuff. The Wurth Redcube are perfect, even the SMD terminals work at up to 50A per terminal totally fine.

author: Wolfram
author_rank: Frequent Contributor
timestamp: February 24, 2023, 11:38:09 am
content: The most affordable way to do it with PCBs is to use multiple layers of moderate thickness like 70 um copper, that way you get a solid amount of copper without the cost, difficulty and minimum trace width issues of thicker copper. Component placement is the most critical, to allow the high current connections to be wide and short. I've done a 70 kW, 140 A output interleaved buck converter on a six-layer 70 um PCB with no issues at all. The PCB has been tested up to 250 A while staying within safe thermal limits.

author: Psi
author_rank: Super Contributor
timestamp: February 24, 2023, 11:43:39 am
content: Quote from: Neomys Sapiens on February 23, 2023, 03:24:09 pmyeah, i use their M6 press-fit terminals myself. great product.You can run 60A through a PCB without any issues if you have enough layers and the copper is thick.4 layer 4oz should handle that no prob. might even be able to get away with 2oz

author: nctnico
author_rank: Super Contributor
timestamp: February 26, 2023, 01:18:40 am
content: Quote from: Psi on February 24, 2023, 11:43:39 amWhere it comes to any connector and high current: derate by 40% to 50% to have a decent margin. If you look closer at connector specs, you'll see that the current specification is for a single contact, not a whole bunch of contacts in close proximity. Thermal performance is key.If you can use a 4 layer board, then running 2 traces in parallel over 2 layers (1 on the outside) will be ok for 60A. Using 75um (4oz) copper will help as well if power dissipation is critical. A bigger problem is getting the current into a component though.