Thermal Reliefs for D²Pak? - Page 1
Forum section: electronics / general

author: Falcon69
author_rank: Super Contributor
timestamp: December 19, 2014, 06:10:37 pm
content: Okay, I just got some boards in. I was hoping my voltage regulator would reflow okay, but upon inspection, it didn't so well.So, I need to put in some thermal reliefs. How is it done? I mean, anyone have a picture of how they did it?? I don't want to sacrifice the ability to use the surrounding copper to help dissipate the heat. So, I don't want to make them too Big.Pictures would help greatly.Thank You,Jason

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 19, 2014, 06:23:57 pm
content: As in paste reflow?Is the whole board achieving the required temperature and dwell time?I haven't heard anything about relief changing reflow. I should think, if anything, that would make it worse: the board can't transfer heat to the component as well!I've seen many D2PAKs reflowed properly with various size pads and fills. It's more about process than layout.Tim

author: Falcon69
author_rank: Super Contributor
timestamp: December 19, 2014, 06:32:45 pm
content: Okay, I will hook up my data logger again and try it. So, I could have a 5 inch² board, with a single D²PAK on it, no thermals, lots of vias to bottom side ground plain, and it will still reflow fine? Seems like a lot of copper to heat up.But, i will check the data logger on the toaster and see if anything needs to be changed. I have a feeling that, maybe, I just had that chip sitting on top of one of the grills.

author: ivan747
author_rank: Super Contributor
timestamp: December 19, 2014, 06:45:40 pm
content: Is it absolutely necesary to have a D2PAK? Will a TO220 work?Otherwise, you can consider D2PAK heatsinks.

author: Falcon69
author_rank: Super Contributor
timestamp: December 19, 2014, 06:51:54 pm
content: Cooling is not a problem, NOW!I had a big heat problem with another chip I was using, but Tim helped me with that.The problem I have now is the reflow process to get the chip to the board.But, now that I think about it, Tim may be right. I noticed that the big capacitors next to the voltage regulator was also not reflowed as they should have been, so maybe the heat profile of the reflow process is off.I need to make more time to allow the board to heat up, correct? And not the solderpaste? Meaning, keep the top of the profile for the reflow (as looking at a data logger graph) the same, but the time it takes to reach that temperature, make it longer by a couple seconds?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 19, 2014, 07:46:36 pm
content: I don't know the particulars of doing great reflow, but just going from physics, you need heat transfer, and you need a precise temperature quickly. So you need lots of ventilation to transfer heat and keep it uniform, you need just enough temperature from the heater to get it there without turning the edges crispy, and you need just enough time for everything to melt. So, if you're good on the first two, the last one is something to adjust. Or more preheat temp or time, so it takes less to ride the final peak, or...Tim

author: Falcon69
author_rank: Super Contributor
timestamp: December 19, 2014, 07:47:56 pm
content: okay, i will adjust the preheat time and see how that works. thanks Tim