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Through-hole soldering to ground planes
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Through-hole soldering to ground planes
PacificState
So I've just built the Random Source NTO - it works fine, but it's annoying me (just a little!) that solder refuses to flow through to the other sides of the pads which connect to ground planes - even with flux and a pretty good (JBC) iron, and application of the iron for many seconds.

I've since soldered these directly, but it's a little fiddly - is there a good way to accomplish this? Thanks!
sduck
Ground planes act as heat sinks, so yes, it can take a bit more temperature and time to get good solders.
slow_riot
I try to get a good connection on both sides of a PTH board (soldering from both if necessary/possible) but at some point it's not worth the risk, too much heat and you risk damaging the pad. Solder through both sides of a PTH means the component is a bit more secure and there is a bit less inductance, but it's not worth losing sleep over.

Not much you can do as the end user, but the way to get around this problem is at PCB design level, with thermal relief pads:

https://lh6.googleusercontent.com/Ym55FWAt0nCG2PqGviYtewAn86k2adOYoEPd znwya0cTB4lAk-LnzAdTTJeomI8lHGCwtojK53RFM8b09Q6l5kmtZBvHJryMsERRptl1F4 1nYrljmeJRGZPqQqk05UHE7XbGBgWv
oldenjon
I have problems with the R*S boards too, it would be nice if the pads were just a bit bigger. Adding a bit of flux to the lead before insertion might help
indigoid
PacificState wrote:
So I've just built the Random Source NTO - it works fine, but it's annoying me (just a little!) that solder refuses to flow through to the other sides of the pads which connect to ground planes - even with flux and a pretty good (JBC) iron, and application of the iron for many seconds.

I've since soldered these directly, but it's a little fiddly - is there a good way to accomplish this? Thanks!


The shape of your soldering iron's tip seems to make a difference here, with the right one you can solder more quickly at a lower temperature. Both of these work well for me for that situation with the ground plane, the 3.2mm wedge especially, but it's annoyingly wide the rest of the time

http://www.goot.jp/en/kotesaki/px-60rt-3-2d/
http://www.goot.jp/en/kotesaki/px-60rt-1-6d/

I'm sure similar tips are available for the iron you're using
NV
You don't need to have the solder travel entirely through the hole to have a solid electrical and mechanical connection, even if it isn't ideal. As others have said, ground planes can act as great heat sinks if the pads don't have some level of thermal relief. I don't know about the R*S PCBs so can't say if thermal relief is an issue or not, but if it isn't quickly forming a joint on both sides of the board then the problems you might run into from applying the iron for excess time will far outweigh any benefits from having extra solder on the joint. A lifted pad is a serious annoyance and some components can also be damaged from excess heat during soldering.
CLee
NV wrote:
You don't need to have the solder travel entirely through the hole to have a solid electrical and mechanical connection, even if it isn't ideal. As others have said, ground planes can act as great heat sinks if the pads don't have some level of thermal relief. I don't know about the R*S PCBs so can't say if thermal relief is an issue or not, but if it isn't quickly forming a joint on both sides of the board then the problems you might run into from applying the iron for excess time will far outweigh any benefits from having extra solder on the joint. A lifted pad is a serious annoyance and some components can also be damaged from excess heat during soldering.


Yes, there's no need to get solder to flow through to the other side of a 2 sided board. I doubt anyone is making 2 sided boards without plated holes. Every pad is like a via, electrically connecting the two sides, so just solder one side, the pad, or hole on a plane, will connect through to the opposite side.
Reese P. Dubin
Component replacement with one leg in a fat ground plane is hell. Clearing the ground hole is so hard!! Yes i have no desoldering iron.

My only (small) gripe with RS is those tiny tiny pads, I dont really like gold either. But god is it al so incredibly nice when its done.
Rex Coil 7
With any PCB's that I designed myself, I always used a two sided "via" as the component hole.

While my head tells me that I don't have to have solder on both sides, the OCD freak that lives rent-free inside my skull mandated it. So after I finished populating the entire board, I'd hit the component side .... cuz reasons. Cuz engineering. Cuz stuff.

While I'm not super good at it, I'd try to make those "Hershey Kisses" out of each hit. It became something of a competition with myself with each successive PCB.

Here's one from an entire model range I had for customers that wanted that 1960's unmasked board look. Some people prefer that type of board ... cuz mojo! Who am I to tell them they can't have what they insist sounds better? It's just an overdrive .... sooo .... yea.



I must admit, sometimes boards with vias make certain situations easier (for me) to deal with. When I installed some "off BOM" diode sockets to this Ring Mod board, lack of plated vias made installing the sockets nice and straight more difficult.





On topic, I can imagine what trying to hit the top of a heat sink (ground plane) must be really tough without roasting the board.

seriously, i just don't get it
whoop_john
Slightly off-topic, but great for replacing components. Have you seen these fine reamers?

I bought this set on ebay for less 84 pence UK price. $1 USD. Including shipping. Aliexpress.

They are made specifically for cleaning out holes in PCBs - most have ribbed sides.



I tend to use them by placing the reamer on the hole and heating it with my iron until it pushes through the hole. A few jiggles and it leaves a neat hole for resoldering.
wsy
CLee wrote:


Yes, there's no need to get solder to flow through to the other side of a 2 sided board. I doubt anyone is making 2 sided boards without plated holes. Every pad is like a via, electrically connecting the two sides, so just solder one side, the pad, or hole on a plane, will connect through to the opposite side.


Strong disagree!

Properly made thru-hole PCBs should be plated all the way through and when you solder the top side, between
gravity and capillary forces, the other side SHOULD show a nice solder bead.

When this doesn't happen it almost always was due to a bad plate-thru; there's a zone in the middle of the thru-hole
that didn't get enough copper, or the copper was thin enough that it cracked; then the copper on the other side doesn't
conduct heat and the solder doesn't wick through. The connection looks good on one side but it doesn't work with
thru-connectivity (or is intermittent, depending on the springiness of the thru-hole component lead). I've seen
sectioned boards where this happened and it is does happen and it's real but fairly rare with good PCB process control.

Another possibility is that the thru-holes are contaminated with solder mask, but that's also a manufacturing problem.

For now, solder both sides, use lots of flux. And report the problem back up to your board supplier!

- Bill
Rex Coil 7
wsy wrote:
CLee wrote:


Yes, there's no need to get solder to flow through to the other side of a 2 sided board. I doubt anyone is making 2 sided boards without plated holes. Every pad is like a via, electrically connecting the two sides, so just solder one side, the pad, or hole on a plane, will connect through to the opposite side.


Strong disagree!

Properly made thru-hole PCBs should be plated all the way through and when you solder the top side, between
gravity and capillary forces, the other side SHOULD show a nice solder bead.

When this doesn't happen it almost always was due to a bad plate-thru; there's a zone in the middle of the thru-hole
that didn't get enough copper, or the copper was thin enough that it cracked; then the copper on the other side doesn't
conduct heat and the solder doesn't wick through. The connection looks good on one side but it doesn't work with
thru-connectivity (or is intermittent, depending on the springiness of the thru-hole component lead). I've seen
sectioned boards where this happened and it is does happen and it's real but fairly rare with good PCB process control.

Another possibility is that the thru-holes are contaminated with solder mask, but that's also a manufacturing problem.

For now, solder both sides, use lots of flux. And report the problem back up to your board supplier!

- Bill
I'm right there with you, Bill. If a solder joint on one of my own boards hasn't wicked through, I feel like the joint wasn't properly done. Just this feeling of "NOT RIGHT!" washes over me (whether technically it is ok or not).

I'd add that another reason for inconsistent wick through can be holes that are too small. My own boards I use holes that are larger than most. Soldering from the back of the board, I hit each point with three 1mm feeds of .032 solder .... one ... two ... three. Flows through really nicely more times than not. After I'm totally done with the entire board, I flip it and hit any of the joints on the top side that look a little "starved".

seriously, i just don't get it

No "golden touch", I. That's for sure. But I do try!

smile
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