Aoyue 701A++ soldering iron thermal capacity issue

[tony359]

Hi there - my first post here!

I have recently purchased an Aoyue 701A++ mainly for the desoldering gun but it's handy to have a soldering iron handy as well.
I am just a tinkerer - no serious work to be performed, hence the Aoyue. I have been playing with the kit and I can say that I am pleased with the desoldering gun but for the life of me my £10 handheld 25W soldering iron massively outperform the 70W Aoyue's. At first I thought the supplied tip was not large enough as I could not melt anything on an actual board! So I purchased some more tips - Ayoue tips - but even the largest one really struggles to solder a small through-hole capacitor on a board. I am using leaded solder and plenty of flux. I have experience in soldering so I feel my technique is ok.

What I noticed on the Ayoue iron is that the tip is hold in place by a collar but you need to slide on the actual heating element a metal tube which - from what I can understand - prevents the tip from being tightened too hard against the heating element itself.
The problem is that it seems that this tube prevents the tip from touching the heating element altogether. The tip is 'loose' around the element and the top part of the tip is not allowed to touch the element itself.

See the attached picture, I have highlighted the small tube which I am talking about - taken from a different manual as Ayoue did not bother to include any instructions for the iron itself!!

I have measured the temperature with a thermocouple and it's consistent with what the display says. However if I try and do some actual work, solder will barely melt with the iron set at 400 degrees celsius (750 F). Solder melts perfectly when the tip is not on a board of course.

I'll try to post some more pictures but I was wondering if you had any suggestions before I turn back to the distributor for help.

Thank for your help!
Tony

[eKretz]

 Welcome to the EEV! There's one thing you could check for sure. Heating element resistance (manual looks like it says the resistance should be between 2.5  and 3.5  . How long does the tip take to come up to solder melting temperature? When you tried to flow solder on an actual board did you apply solder to the tip first to help with heat transfer?

[tony359]

Hi,

Thanks for your reply! I will check the resistance and the timing.

Yes, tip is clean and I apply fresh solder just before touching the solder joint to start the process. The applied solder and part of the solder joint melt for a split second and then all solidifies again. To me, that means the board is drawing all the heat away and the iron cannot cope with the drop in temperature fast enough.

As I am getting old, I tried today on a scrap board with some large components using a Weller station and my trusted £10 iron and I could easily melt big solder points with both irons. In fact, I managed to remove a couple of connectors just using the soldering iron. I will try to do the same on the same board when at home and I'll report back.

[Gyro]

It is a known problem with these sort of irons, very poor contact between the ceramic element and the tip (basically a narrow air gap!). Don't be tempted to try to modify the spacer tube, you'll just crush the end of the element.

The only thing that works is to inprove the thermal contact between the element and the bore of the tip. Some people have tried thermal compounds, others, shims.  I've found that copper foil shim can work quite well - the copper foil screen from decent quality (CT100) satellite coax is nice and thin works quite well.

Apparently genuine Hakko tips are better toleranced... but that depends whether the element diameter is accurate too.

My 48W Weller TCP iron has better thermal regulation than these 70W irons by a mile!

[tony359]

wow, that really sucks. I thought they would be able to make a decent soldering iron for just some DIY... Yes, I did notice a large gap between the tip and the element - and thanks for your advice on NOT touching the spacer, I thought I could give it a go.

I'll find some copper foil but I'll also ask Aoyue. I am not expecting first class performances from that iron but as it is it's just unusable. I could not solder a small capacitor on a board!!!

Thanks for your input.

[tony359]

I have done some further tests.
The diameter of the element is 3.85mm. The tip is 4.1mm.

I could not find any copper so I had to try with some kitchen foil. It seems marginally better. Solder flows after about 20 seconds - better after 30s. I am testing using the same temperature of my £10 iron (measured with a thermocouple) and I can always do a better job with my £10 iron... disappointing.

[tony359]

Update. With some kitchen foil the situation had improved considerably. I ordered some copper foil and also a genuine HAKKO tip which arrived today.
I have just tested the tip 'as is' (no foil) and the iron is totally different. Ok it's a bigger tip than I thought but I did my initial tests with the largest Aoyue tip I could find on big solder joints. With the HAKKO - and no foil - the Aoyue beats the portable 25W iron hands down.

When I took the Aoyue tip off and went removing the foil, I realised that there is a tube in the Aoyue tip which acts as a shim. I had trouble removing it as it was stuck to the element because of the foil underneath. The HAKKO tip BTW seems to have the same play on the element when inserted. Any chance that the tip then expands a little and fits the element better?

Anyway, I now know what to do.

Thank ALL for your inputs on this!

[RoGeorge]

...
I have measured the temperature with a thermocouple and it's consistent with what the display says. However if I try and do some actual work, solder will barely melt with the iron set at 400 degrees celsius (750 F). Solder melts perfectly when the tip is not on a board of course.
...

I have similar disappointments for this kind of soldering tips/handle, too (type 900M).

You should try a solder station that uses T5/T12 model tips. It's not necessary to be a Hakko, $25-$50 clones are working just fine.

For the same electrical power, there is a huge difference in thermal power and temperature control of a T12 versus a 900M. This came from the different technology of the tip: T12 have the heating cartridge embedded in the tip, so they are thermally coupled very tight. Moreover, the temperature sensor in a T12 is right at the tip and is part of the heating coil (they call them monolithic), so it can sense very fast and compensate any temperature loss by pushing more energy into the heating element.

On the contrary, a 900M is very lousy coupled with the temperature sensor. Try heating an unpowered 900M externally, with another soldering iron. The thermocouple from the 900M will feel the temperature variations coming from the tip, but only after a couple of seconds. This huge delay, together with the lousy thermal coupling between the heater and the tip, makes any temperature control useless and the power of the heating element irrelevant: https://rogeorge.wordpress.com/2016/09/23/zero-parts-thermostated-soldering-station/

[tony359]

I see your point - very nice analysis on your link.

Are you aware whether such tips/handles would be compatible with my station? I'm just a DIY'er and to be honest I feel I have already spent enough money on this machine.

[RoGeorge]

I'm glad you liked it, thank you.

A T12 handle can not work directly with a station for 900M. T12 have only 2 wires, not 3 like for the 900M, but there is an open source project for an adapter. You can also find the adapter as a kit or assembled on AliExpress, Ebay and so.

Considering the price for an adapter + handle + cartridge tip(s), it's cheaper to buy a whole T12 station, something like this one: https://www.aliexpress.com/item/EU-Plug-T12-Digital-Soldering-Station-Portable-soldering-iron-BGA-solder-station-220V-50W-5-pcs/32665048370.html

I don't know if this particular seller is good or not, the link is just to show what model I had in mind.

Sometimes it might be handy to have 2 working soldering stations, because you could use them both in the same time as soldering tweezers.

[tony359]

I'll keep that in mind - that design is indeed better than anything else even though $35 for a complete set... Anyway, I have another portable ERSA iron, an SMD station and I am not really a pro so I guess I'll consider a better iron if/when I'm going to use it properly. So far having a temperature controlled station - even though it's not actually controlling the tip in real time as you pointed out - is a great improvement over the non-temperature-controlled irons I've been using all my life! In fact, I purchased the 701++ for the desoldering gun, which works ok once you realise it takes 10 minutes to fully warm up! I decided to add a little extra for the iron just to try and save space on my desk.

In fact the feature I appreciate most of that station is the fume extraction, which works using the same pump used by the desoldering gun. It's a little clumsy as one needs to unplug hoses and push two buttons simultaneously (Really, Aoyue? Would a dedicated button have moved the equipment to another price range???) but it's great.

Too bad the pump seems to exhaust inside the machine, which in turns literally exhaust smoke from any possible gap when soldering - making extraction out of the room a little complicated.

[kikook]

I'm using this 701A++ for more than 3 years without any problems.
Using Hakko filters/springs/tips for a better life and quality.
There is a procedure to calibrate the gun and the Iron temps. It can be useful...

Thierry.

[NYKing]

Hi, I know the OP had been warned not to alter the spacer or nipple covering the bottom part of the heating element but I can confirm it is safe to do so and will drastically improve the iron’s thermal transfer performance. I, too, had thermal resistance issues with my own “Hakko 907” style clone iron which, as mentioned by many others, is due to the air gap between the top/sides of the element and the hollow part of the tip. On my iron, the air gap between the top of element and the deepest hollow part of the tip was a whopping 2mm! I really had no choice but to trim the nipple down. I did this easily by basically grinding down the nipple using my Dremel. I also bought some 0.1mm thick copper foil to make a shim to fill the small gap between the sides of the element and tip.

When reassembling the iron, be very careful NOT to over tighten the tip enclosure. Over tightening it will put a lot of pressure on the heating element since it is now fully touching/mated to the inside of the tip. Just a few turns of the nut by hand until it is snug but not tight will be sufficient.

I was amazed at the performance improvement of my iron after these mods were done. I now have no trouble desoldering large heatsinks and large solder joints. My friend, who has a genuine Hakko FX888D, tested out my iron and was shocked that my iron actually performed just as well as his $100 Hakko (I scored my Yihua 852D+ combo unit years ago for a measly $5 at the local flea market...it was labelled as broken but I later discovered it only had a loose sensor wire in the iron’s handle which was easily fixed  ). The only issue my friend noticed was that my iron handle got a lot warmer than his Hakko handle. I should wrap some silicone tape to the upper handle but I don’t mind the extra warmth.

I decided to check the difference between the measured tip temperature (I borrowed my friend’s Hakko FG100) and the temperature shown on the unit’s LED display and was pleased to see that it had narrowed down to only 5 or so degrees C. Previously, it was off by more than 20 degrees C! These mods were definitely worth the time and effort. Hope this was helpful.

[MadTux]

Aoyue soldering irons are more like toys compared to real tools like JBC or Weller, because of poor heat transfer and low thermal capacity of the tip. But way better than the crap you get in hardware store, with knob that controls ON time of triac switch, regardless of tip temperature.

The small Aoyue soldering irons are great for SMD stuff however, I duct taped together 2 cheap A 937D as improvised soldering tweezers for SMD resistors.

[NYKing]

I think Aoyue and other so-called knock-off Hakko brands are really not that bad considering their cost to performance ratio, especially if you make a few simple mods to them as I have. Some might need safety mods as well depending on the craftmanship or lack thereof. Even my friend who has a genuine Hakko FX888D prefers my cheapie Yihua’s big digital readout and simple control knobs to the difficult-to-operate button controls of the Hakko.

For a cheapskate hobbyist like me, spending over $100 for a name brand iron just does not make sense when you can buy a clone for more than 70% off and still squeeze out 90% of the name brand performance. Of course, you have to be a tinkerer or someone who likes to improve their gear. These “fakkos” are admittedly not exceptional in their stock form but again, once modded, they are fantastic for the money. Some may make a point about higher durability or reliability of the name brand vs the clones but I have been using my second-hand, modded iron every weekend for over 2 years now and it is still going strong. I am still using the same tip and heating element btw.

[RoGeorge]

...the air gap between the top of element and the deepest hollow part of the tip was a whopping 2mm! I really had no choice but to trim the nipple [of the heating element] down. I did this easily by basically grinding down the nipple using my Dremel. I also bought some 0.1mm thick copper foil to make a shim to fill the small gap between the sides of the element and tip.
...
I was amazed at the performance improvement
...
Hope this was helpful.

Yep, very helpful, thank you!

Wanted to try something similar in order to reduce the air gap between tip and heating element, but never took the time to experiment.  Back then, my intention was to cover the heating element in a few turns of kitchen Aluminium foil, leaving some extra width of the foil at the tip side so it can act as a filler all around the heating element when assembled.  I am curious if kitchen Al foil can perform reasonable well in comparison with the Cu foil.

Did you tried Al film at first and it was not good enough, or did you started with the Cu foil from the beginning?

[Gyro]

I would stay with copper.

The element temperature cycles to very high temperatures - If you remove the tip (not recommended) it visibly flashes on and off. I've found that even copper foil oxidises and crumbles over time and needs to be replaced when the tip is removed.

I don't think Aluminium foil would survive.


EDIT: If you check some earlier replies it seems that some people have used Aluminium foil, I'm not sure how well it worked longer term though.

[NYKing]

Gyro is right, definitely use pure copper foil if you can. Some people had reported issues with aluminum like it sticking to the heating element and not conducting heat as well as copper. My copper shims surprisingly never needed replacement so far (it’s probably been a year or so). Granted, I hardly ever change tips (I have several cheapie standalone modded irons with different tips) and that may have prevented the shim from wearing out. Besides, it is very easy to make extra shims. I lift my tips slightly every so often to check the shim and the oxidation on it is not that bad and most importantly, the tip performance have not degraded, at least not noticeably by me.