How do I solder an HTSSOP package by hand? - Page 1
Forum section: electronics / projects

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 20, 2016, 09:18:45 pm
content: So I'm sitting here with a couple of TI TPA3001D1PWP devices in 24 pin HTSSOP package (class D amps) and all I've got is a Weller TCP, a Hakko 936 clone, a roll of teeny multicore solder and a flux pen floating round. If it was a TSSOP, no problems but this has a heatsink bonding pad on the bottom of it hence the H.The board has not been designed or produced yet so this is a hypothetical question. It will be bog standard single sided home etched FR4.So the question: how do I solder this to the board?Options I can see:a) Use solder paste and buy a rework hot air gun.b) Use the tube of arctic silver I have floating around to provide thermal contact.C) Leave it and pray.Any other options I can use? Any help appreciated!

author: Skimask
author_rank: Super Contributor
timestamp: February 20, 2016, 09:26:37 pm
content: Punch some small holes thru the board in the middle of the pad and flow some solder down thru there.In the past, I've used solder paste on the pad and hit it with hot air from the backside thru the extra via holes, then followed that up with solder. Not optimal by any stretch, but it's worked for me.

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 20, 2016, 09:33:14 pm
content: Will have a bash at using holes - thanks - good idea. I've ordered another two as I'm almost certainly going to kill one

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 20, 2016, 09:37:11 pm
content: http://www.ebay.com/itm/1-X-30W-Class-D-Audio-Amplifier-Board-TPA3110-/351287449342?hash=item51ca5d16fe:g:uEUAAOSwa39UuLxr

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 20, 2016, 09:44:45 pm
content: Yeah that's roughly where I started. Now I'm building a single board unit with a switch mode on board.I like doing things the hard way. This is replacing a rather inefficient analogue class A I built 22 years ago that blew up a couple of weeks ago thanks to the heatsink goop degrading. One active module per speaker and separate pre-amp which is being upgraded with bluetooth.

author: nali
author_rank: Frequent Contributor
timestamp: February 20, 2016, 09:51:02 pm
content: Considering that you are only intending to use a single sided board, are you sure you have enough heatsinking even if you do manage to make a connection to the thermal pad?

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 20, 2016, 10:03:24 pm
content: I ran the numbers on the through plane thermal conductivity and the peak wattage and it should be absolutely fine. The IC doesn't kick out a lot of heat (the joys of class D!). The rear of the board will be bonded to a 1/4" thick chunk of aluminium as well.

author: amyk
author_rank: Super Contributor
timestamp: February 20, 2016, 10:09:42 pm
content: Hot air gun... you'll find it much easier than doing each pin individually and will soon use it for everything SMD.

author: Rerouter
author_rank: Super Contributor
timestamp: February 20, 2016, 10:12:50 pm
content: A second vote for hot air gun, just keep your air flow lower or you will blow away he chip.

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 20, 2016, 10:35:05 pm
content: Thanks for tips all. I've tried to solder one on a PCB blank and it's a PITA even with holes. I did it but it's messy.Hot air gun purchase order raised with the finance department (wife)

author: Howardlong
author_rank: Super Contributor
timestamp: February 21, 2016, 12:23:35 am
content: Yes, definitely hot air gun. These are the same as QFNs which genrally have power pads.If I'm fabbing the board myself without plated vias, then I drill an oversized via hole in the board where the pad is so I can reasonably reflow it and ensure there's a proper ground connection through the hole. For "proper" boards, then use several vias for both thermal and conductivty/low inductance reasons.For my own fabbed boards, I usually solder the pad first separately from the other pins. This allows you to check the pad's connected as usually (although not always) the pad's connected to another pin so you can check continuity. If it's not directly connected to another pin, for example it's the only ground connection, you can measure for ESD diodes. That last technique you can use to check BGA fan outs too.As I think you're not far from me, feel free to come over if you need some help. In the end you need just the right amount of bravado and a couple of spare chips and boards just in case. After that, you'll wonder what all the fuss was about.

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 21, 2016, 09:56:34 am
content: Thanks for all the tips. You're right about the bravado - £5 a pop when you get it wrongOrdered an Aoyue 950A+ and similarly valued toys for the wife and will approach this one in a week. Now to knock up a proper board for this...

author: nali
author_rank: Frequent Contributor
timestamp: February 21, 2016, 11:27:50 am
content: Quote from: MrSlack on February 21, 2016, 09:56:34 amYou might want to look into a preheater. I only do odds 'n' sods in SMT and I bought this Tenma hot air heater for £36 +VAT from CPChttp://cpc.farnell.com/tenma/21-10135-uk/pre-heater-540w-350c-uk/dp/SD01742which works fine albeit a bit on the small side. It definitely makes soldering/desoldering easier!

author: Gyro
author_rank: Super Contributor
timestamp: February 21, 2016, 12:52:39 pm
content: That looks really good value, one for the shopping list!QuoteOr "demolition and welding" as the product overview describes it.

author: MrSlack
author_rank: Frequent Contributor
timestamp: February 21, 2016, 01:19:12 pm
content: That's less than I spent on pizza last night (friends over). How depressing!Added to shopping list - thank you

author: tggzzz
author_rank: Super Contributor
timestamp: February 21, 2016, 04:57:27 pm
content: I do my SMD devices with solder paste, a saucepan and a little sand. So far I have 100% success rate, but I haven't tried pads under the package - but I don't see why it wouldn't work.FFI:https://entertaininghacks.wordpress.com/2015/03/25/assembling-pcbs-with-surface-mount-components/

author: dadler
author_rank: Unknown
timestamp: February 21, 2016, 08:26:51 pm
content: Quote from: tggzzz on February 21, 2016, 04:57:27 pmNice blog post. How do you handle components on the bottom side of the PCB? Hand solder?

author: tggzzz
author_rank: Super Contributor
timestamp: February 21, 2016, 08:37:01 pm
content: Quote from: dadler on February 21, 2016, 08:26:51 pmThanks.I've never tried to do boards with components on both sides of the boards. At the local Hackspace people have done that in the homebrew reflow toaster. If I needed to at home, I would try using steel spacers in the board's mounting holes to suspend the board above the sand.Obviously I would do a few experiments to watch the temperature profile of the boards before trying with components. Fortunately small PCBs are very cheap nowadays.If you do any experiments at home, let us know your results, please.