SDG #086 What's the best flux for soldering? A comparison with PCBs from JLCPCB

hi in this video we're going to be taking a look at some different types of looks and how they perform so this video was prompted by the fact that whenever anyone asks what type of flux they should use the default on the internet seems to be to recommend this an Tek NC five five nine flux but I've not really seen any evidence to suggest that this is any better than any other type of flux that you can buy it just seems to be the default answer that people use so what I wanted to look at is how all of these perform for general PCB soldiering so what we're not going to be doing in this video I might follow up in a future video is we're not going to be testing how well these deal with heavily oxidized components because if you're soldiering old components for example in an old TV or something like that and you're doing some repair work something with some organic fluxes might be more appropriate because it's a lot more active but for general PCB assembly where you're going to be soldiering new components you just want to use it to help flow the solder on the board that isn't too critical so you know most of these should be fairly well performing unless there's there's something wrong with the formulation but there's a whole range of price ranges across the the fluxes that we've got on the table obviously the Amtech is the most expensive I think this cost me about eighteen pounds for ten CC and the cheapest was probably this 150 gram tub of flux jelly and that was something like three pound delivered from banggood but I'll put the prices as an overlay on top of all of these so you can have a look at what we're talking about but we've got a various range of brands here so we've got some Kester branded stuff some SIF branded mg chemicals and some top nick gel Weller and then some of the more Chinese brands and these are you know most of these are quite generic you can buy them from a lot of places but some real cheap to really expensive flux so to do the test I've ordered some PCBs from jlc PCB so thank you to jail CP TV for providing these boards for this video but basically what we've got is a series of 24 pin s sop packages on this PCB with an immersion gold finish so we should get a nice flat surface to solder these components onto and then from LCSC I ordered some SOP components so we've got some hadurok microcontrollers these are actually the cheapest components I could find in this package and what we're going to do is we're just going to drag solder each of these components onto the board and each component will be done with a different type of flux and to do the soldiering for this video we're going to be using the KSG RT 12 soldiering station so click on the link up here if you haven't watched the video review that I did of this particular station but this is a really nice unit really low cost excellent performance and the really nice thing is that you can buy a whole wide range of soldering tips for a really low price and the one that we're going to be using for this video is this concave hoof shaped tip and the really nice thing about this is you can hold a nice little ball of solder in the tip and then when you do the drag soldiering it it keeps them solder in here and stops you leaving too much excess solder on the pins so we should get some fairly decent results with the soldering and for cleaning the tip we've got the damp sponge and we've also got this wire wool and little container here from banggood up at a link down below for this this was really low cost but it's also a really nice form factor and just means that you can clean any oxides off the tip to make it nice and shiny so to start off with I wanted to show what happens if you try to drag solder without any additional flux so I've applied some solder to the tip of the soldering iron and then when you drag the solder line across the pins you get no wetting of solder onto the pins or onto the pads so then if you apply some flux over the PCB when you then run the solder going along the pads again what actually happens is the flux causes the solder to wick onto the pads onto the legs and creates a really good solder joint and then once you've cleaned up the PCB you can see we're left with a very nice solder connection so to start off we're going to begin with the flux that comes in the yellow pot from Vanguard so this is three pound 28 for 150 grams and we're going to apply it with a cocktail stick onto the leads of the IC you can see it's a little bit difficult to apply when it's not in the tube and then if we run the soldier along it you can see it immediately turns to a much thinner liquid and gives us a really nice finish on all of our leads we'll have a closer look at the cleaned PCB at the end of the video so then we've got the mechanic solder paste and you can see this seems to have quite a lot of rosin content it's got that deep amber color and again applying this with a cocktail stick because it's not in a tube so again a little bit messy a little bit inconsistent with the amount I'm applying here but once you applied the soldering iron tip to the pins you can see that the flux starts to boil off I just missed off that first pin start to move backwards again but we get good wetting of solder onto all of the pins it flows really nicely and again gives a really nice finish next up is the pros kit this is a much lighter color it doesn't look like it's really got any rosin in this and applying this with a cocktail stick yet again again a little bit messy but the thing that I found with this particular flux paste is that it tends to spit quite a lot so if you look as I run the soldiering iron along the pins you can see we're getting a little bit of flux spitting all over the board and it's coating the IC again it doesn't give too much of a bad finish but it's a little bit messy to apply and then we've got the Weller which again looks very similar to some of the others so a fair amount of rosin in there so you can see here that it's a little bit thinner than some of the other pace that we've used so far but it spreads quite nicely on the pins and when we run the soldering iron across the pins it seems to cause the solder to flow quite nicely onto the pads and onto the pins so this is the first liquid flux that we're going to use and you can see that this is applied with a little brush that's attached to the lid so a really nice application method and it spreads very nicely into all of the joints and I'm not sure if it was just my soldering technique here but it flowed really well for the first sort of 10 pins or so and then started to tail off in its effectiveness so I'm not sure whether that's the flux that boiled off or whether and you know I just didn't a solder those pins very well but I seem to get the same results on the other side of this IC and then we've got another liquid flux this is top nikhyl p1 and it's slightly more environmentally friendly than the other liquid flux same application method and I did actually have the same problem with the last few pins again so I didn't notice this with any of the paste fluxes but those last few pins didn't really want to flow quite as well a little bit of rework with a little bit more flux and it behaved itself but it just needed that little bit of extra work in comparison next up we've got the SIF branded flux which is supplied in a syringe and being dispensed with my solder paste dispenser it's got a really unique smell quite a lemony smell quite pleasant I've applied a little bit too much to the pins here but you can see it gives a really really good result so absolutely excellent flow of solder into the pins and onto the pads so next up we got the mg chemicals no clean flux paste and this was a little bit lumpy and quite viscous it didn't want to come out the nozzle on the syringe very well had to turn the pressure writer but it did seem to flow quite well it seems to have a fair amount of rosin in there certainly no problems with its actual capabilities as a flux then we've got the best branded flux which is a very very thick flux it really didn't want to come out the tip of the nozzle and even though it was applied quite heavily onto the pins it immediately caused a solder bridge between pin 1 and 2 and then reflow in the entire joint caused further solder bridges so I had to reapply the flux again and rework it a couple of times just to get an acceptable result so this wasn't a great flux then we've got the real life branded BGA flux paste and this is supposed to be quite a strong activity flux very very thick in terms of its viscosity and I had no real problems with this particular flux I think the only thing that I observed is unlike a lot of the other fluxes this one didn't boil or anything didn't spit anywhere and it just sort of sat there and melted into the area but it gave a good result in the end just a little bridge at the end there then we got the green real life flux which is the halogen-free flux and it flows much nicer out the tip of the syringe so really nice flowing and didn't really give any negative results really I did have to run the soldier 9 along the pins a few times but I think that was user error rather anything else but you can see that gives a really really nice joint next up is the top nick zell gel flux from Turner pasty and this was really thick had to cut the tip of the nozzle off to get anything out also a little bit clumpy so you saw there it came out quite heavy at the end but this was really good this is probably the best folks that I tried so far gave really really good results then we've got the KSS flux paste this was again another thick paste which needed the tip to be cut off the nozzle in order to get it out the syringe and this one also flowed really quite nicely no trouble at all really with this flux next up is the genuine Amtech flux the NC 559 and I'll surprised how free-flowing this was out the tip of the syringe it's supposed to be quite a tacky flux but it was very low viscosity but as you can see it gives really really good results next up is the fake antique flux from Vanguard and this is a little bit more tacky actually it's kind of general behavior is much nicer certainly no real trouble in terms of its behavior it seems to work quite well possibly not quite as well as the genuine stuff but you can see here it gives a really good result and then finally we've got the castor flux which is high in rosin and you can see it's got a really deep amber color it flows really really nicely out the tip of the syringe and this gave outstanding results I was surprised how good this was actually it possibly was the best out a lot in terms of how well it caused the solder to flow all right so before we draw any conclusions here's a quick look at each of the ICS in terms there each of the different flux types after the PCB has been cleaned up you can see there's quite a big difference in the appearance between each of the solder joints for each flux type despite the same solder being used across the board so some of them are quite dull and some of them are extremely shiny in terms of the overall solder joint they'd all be classed as acceptable in terms of IPC standard so absolutely no problems with the actual soldiering they're just quite a big difference in the appearance and how easy the flux was to work with so I thought that was really quite an interesting test overall and all of them were able to do the job so we all got really good solder joints on all of the ICS it's just a couple of them required a little bit of extra rework for me there were four that were behaving extremely well firstly the banker tub of flux is probably the best value for money out of the lot on here you get absolutely tons of it and it behaved really well I guess the only thing really about these pastes are supplied in terms is applying them is a little bit messy and inconsistent so you do have to tend to use some kind of tool to get it out of here and spread it onto your component you can use a flux brush a bit like you would do with plumbing and you probably could dispense it into some syringes but that's the only downside to these types of fluxes here but this one from Bankard was very good value for money and worked really well also the antec flux was very good it was quite thin in its viscosity but gave really good results it's just the only downside is it's the most expensive flux on the table here the castor flux was also very good so the results from this were really good and also it dispensed really well in the video you know it gave a really nice bead of flux across all of the pins absolutely outstanding flowing the main problem with this is because it's got such a high rosin content you can tell by the color of it it's really difficult to remove from the PCB and from the IC so this was the most stubborn it ended up with some hard deposits on the pins which is fine if you've cleaned off the majority of it but just a little bit difficult to remove then the syph branded flux was probably my favorite out of the lot so this is a relatively cheap I think it comes in between these two and the banggood flux it's got a really interesting smell but it's certainly not offensive it flows really nicely out of a 22-gauge dispensing tip and also it gave really good results so I was quite impressed with this one this probably the the type that I'm going to use moving forward then a little note on the liquid fluxes you'll notice I had a little bit of trouble with these that's possibly my error but what I suspect what's happening is as you're running the soldering iron along the pins you actual conducting quite a lot of heat to the other pins just by virtue of pressed against the PCB and the IC and I think probably what happened as we got towards the end is the temperature had risen high enough that the flux had burnt off and obviously because it's not a gel it doesn't sit in place so it probably run off and then the last bit of folks have burnt often and that's when we started to get solder bridges so these have their place and there are various different types of these fluxes that are designed for soldering different metals so these are certainly very useful and they can be really useful for reactivating solder paste and that kind of thing so they do have their place and they do work just not really for this type of soldiering the pros kit was particularly poor in terms of the fact that it was really messy was spitting everywhere and it gave an okay result but it was spitting everywhere now you know you get it all over your fingers and everything so a little bit messy there the real life fluxes the orange one wasn't great but the green one flowed almost as well as the syph and you know much lower cost surprisingly the banger drip off of the unter tech flux was also very good certainly if you bought this you'd have no problem and it's one of the cheaper ones so I certainly recommend this one if you're looking for a low-cost flux and then the two that I have used quite a bit in the past actually gave me a little bit of trouble in terms of the application not in terms of the soldiering but I don't know if these this is because they're a couple of months old now but they were slightly lumpy in the way that they came out the dispensing needle so no problem in terms of how they actually did the job but dispensing them onto the pins of the IC was a little bit inconsistent and possibly gave slightly inconsistent results so those are just my thoughts he can draw your own conclusions from the video but hopefully you found this video useful I'll put a link to all of these in the description down below if you've got any comments or disagree or want me to do any further tests then don't forget to leave a comment down below it's always really useful to hear your thoughts really until next time thanks for watching you

Channel: SDG Electronics

Views: 424,039

Keywords: soldering, flux, bga, rework, hot air, microscope, amtech, mechanic, termopasty, gel, electronics, smd, smt, tht, ipc

Id: iKDAmY9Rdag

Length: 15min 31sec (931 seconds)

Published: Wed Jun 26 2019