It is currently Sat Dec 16, 2017 4:14 am

Desoldering : "A Workshop Conundrum"

 
Posts: 5844
Joined: Sat Jul 23, 2011 8:19 pm

Desoldering : "A Workshop Conundrum"

Post by crustytv » Sun May 08, 2016 3:43 pm

This is something we all face in our hobby, the age old dilemma "de-soldering". The method, the product/s and of course the costs. Maybe others don't find it a problem maybe some do, I thought I would just cover my corner of this personal "workshop conundrum".

Over the years I've approached this in a number of ways and mostly settled on the solder braid option. Then I obtained a vintage de-solder station by Charles Austen, it was from the late 60's, although OK the iron finally packed up and the bladder in the pump failed.

sol1.jpg

I then modified it to have a solder bulb sucker and made my own bladder out of a old water bottle, it worked but was never ideal, the pump is always on and the constant "bupp!.....bupp!.......bupp!.....bupp!" drives me nuts.

sol2.jpg

I've used various solder suckers over the years too, all are not equal though. A lot of the cheaper ones fall apart fairly quickly but eventually I was given a quality one by a local ex TV engineer, a Philips model and this was much better.

sol3.jpg

On its own the solder sucker does not fully give a tidy job, its good for getting the bulk of the crud out but in addition I use solder braid to clean up properly. Now again I'm sure many of you have found, not all solder wick is equal either. I've bought the cheap stuff and the medium priced stuff, almost always I get really peeved trying to get the damn stuff to act like wick. In the end I've found you have to settle for the good stuff which without fail is consistently good and that's Chem-Wik by Chemtronics. However I get through a lot of PCB work ( 4 BRC PSU modules recently) and I get through it fairly quickly, there's little point buy the tiny reels so order 30 meter reels and at £1 a meter as I say, not cheap.

sol4.jpg

I've looked at the Duratool de-solder station which you could get until recently for £75, its now up to £85. I've read mixed reviews about this model and a lot of reported problems. Personally I'm not enamoured with a gun type so decided against this despite the fairly modest price tag. http://www.totalsuppliesuk.co.uk/durato ... -132-p.asp

sol5.jpg

Stepping back for a second and looking at soldering irons/stations. Over the years I used various soldering irons and stations, eventually settling on Weller. I've never looked back since, not only are they are reliable but perfectly weighted and generate consistent superb heat. With the interchangeable bits for temperature I've never had a problem with heavy duty or light soldering requirements.

So a Weller de-soldering station for me would be my preferred choice but they prices..... Ouch! Then as explained above a few reels of Chem-Wik and its pretty much paid for itself, so this week I took the plunge and got myself a Weller DS900PD. What's great is you not only get de-soldering gun but also another iron. There is a foot controlled pump so unlike my old Charles Austen the pump is not running all the time.

ds900-1.jpg

ds900-2.jpg

ds900-3.jpg

ds900-4.jpg


Hopefully some food for thought, if like me you've been spending a small fortune on other options and in particular Chem-Wick braid, it might be worth considering the de-soldering station option. I'm sure others will have different experiences and may disagree with much I write, this will at least stimulate an area worth exploration.

 
Posts: 1218
Joined: Thu Jul 28, 2011 10:28 pm
Location: Sunderland

Re: Desoldering : "A Workshop Conundrum"

Post by Red_to_Black » Sun May 08, 2016 4:12 pm

I found a desoldering pump such as the Weller type (though very good) was overkill outside of a production environment.

In a day to day repair workshop we mainly just used the spring loaded manual sucker for large (Lopts etc.) components and just two sizes of wick, large course braid and the very fine 3mm stuff.
The larger size for cleaning up after the solder sucker and for general use (normal lead through components) and a much finer type for SM components etc.

I try not to use the sucker on small lead through components such as normal resistors and capacitors, and definitely not on fine print/SMDs

The trick to not wasting wick is to leave about six inches of used (solder laden end) on to use as a "handle" this prevents burnt fingers and stops you contaminating the un-used wick with grease from your fingers.
A bottle of re-work flux is also valuable to activate any portion of wick which doesn't seem to work, which you sometimes find even with good quality braid.

Of course this just my opinion and experience, each to their own and all that. :cca

 
Posts: 377
Joined: Sat Jun 15, 2013 10:59 am
Location: Near Glasgow

Re: Desoldering : "A Workshop Conundrum"

Post by Niall » Sun May 08, 2016 5:48 pm

I've always used the spring loaded solder suckers, never tried braid. When I started working on Clansman 351s which have multipin modules which can only be removed by thoroughly desoldering all the pins, I found that the size of the pcb pads meant that the solder hardened as soon as I lifted the iron off to get the sucker in. The service manual for this equipment says that the use of a vacuum desoldering system is mandatory.

I looked at the various suction systems but couldn't justify the cost. Many Chinese ebay vendors sell what is basically a soldering iron with a hollow shaft and tip with a solder sucker built in to the handle, for under a tenner. I thought this was worth a try, and in fact it is very effective. It certainly did the job on the 351s.
A big advantage is that there is no plunger in the tip as in the conventional solder sucker so you can get a module pin or component lead right inside the tip and fire the device which effectively cleans out the hole around it.

 
Posts: 368
Joined: Sun Aug 19, 2012 11:16 pm
Location: Salisbury

Re: Desoldering : "A Workshop Conundrum"

Post by TVJON74 » Sun May 08, 2016 5:54 pm

I agree with Red to black. A desolder pump for larger items and braid for the smaller items, with a bit of extra flux if needed works a treat. Also a good iron with a clean tip is a must. I also find applying some new solder before trying to unsolder can sometimes help. I have a pair of hot tweezers for SMD R's & C's & T's and a proper hot air SMD removal tool with a vacuum lift for SMT IC's.

 
Posts: 184
Joined: Sat Nov 22, 2014 9:43 pm

Re: Desoldering : "A Workshop Conundrum"

Post by Rebel Rafter » Sun May 08, 2016 6:09 pm

Hi from RR. This talk about desoldering is interesting and I'm not surprised to hear that the Weller gear seems to be the best. I like the old 140 watt Weller soldering guns which are no longer made. I've never found the 100 watt newer models any good. I've got an old 140 watter complete with it's original case. I've never had any proper soldering gear like solder stations as I've never been shown how to properly use one and the only decent ones were always way too dear for me, and with what little stuff I do I could never justify the cost. They're ok for busy workshops. What I'd like to know is what is best for desoldering components from double sided print with through hole plating? I know you have to get all the leads or pins totally loose first or else the PTH gets pulled out which can ruin an expensive or rare obsolete board and desoldering from PTH is something I've always struggled with as the basic Antex X25 and XS 25 watt irons are just not up to the job. This is especially true when trying to remove things like a transductor from an old GEC board with double sided print. RR.

 
Posts: 1218
Joined: Thu Jul 28, 2011 10:28 pm
Location: Sunderland

Re: Desoldering : "A Workshop Conundrum"

Post by Red_to_Black » Sun May 08, 2016 6:20 pm

Hi Niall,
I am sure there are situations where this type of tool is almost essential, I never found that the case in a busy general TV/VCR workshop though.

I worked with an engineer whom had one, and I had a play with it, I was quicker with braid, I found it a bit cumbersome tbh, maybe if I was reworking boards production line style day in and day out I might have found it better/quicker/cheaper.

Personal preference has a lot to do with it, and how you were trained probably has a large bearing on it too, outside of where it is probably almost essential to use this type of tool.
I should imagine if you were working on say computer type boards and the like where some chips are soldered in plated through hole type assemblies it may also be almost essential, but even here I found I ended up flooding about half the joints with fresh solder and using wick.( for rebel rafter :bba )

I never used it on Pb free solder though, only the 60/40 stuff, this lead free solder may be better suited to this type of iron ? I have no idea.

It might be a "nice to have" rather than essential on the mostly single sided boards that were seeing in our day to day stuff, I still found braid quicker and easier as outlined in my earlier post, bearing in mind these things (hollow pumped irons) were a fairly expensive upfront outlay at the time.

I am neither for nor against these as I said, I just found it easier with braid.
Also bear in mind in a normal TV/VCR workshop back in the day we weren't un-soldering a massive amount of components relatively speaking, most day to day repairs we mostly knew what was wrong before we even took the back off the set most of the time (he says laughing), of course there was the odd pig of a fault, but most stuff generally speaking had stock faults, 10 to 15 "normal repairs" in a day was the norm rather than the exception, of course we had stuff that took far longer to diagnose and repair, but even here you could mostly pin it down to one section or other and bulk component changes willy nilly were mostly frowned upon, except where complete repair/mod kits needed to be fitted.

 
Posts: 917
Joined: Sat May 26, 2012 5:41 pm

Re: Desoldering : "A Workshop Conundrum"

Post by Valvebloke » Sun May 08, 2016 6:28 pm

I can't add a lot to this very thorough discussion. But I did buy one of the Duratool pumped stations that Chris mentioned a little while back, when they were still £75, and I do find it useful. It's especially effective on pcb's where I reckon I can get a lead loose enough to pull out in much less time (so with much less risk of overcooking the track or the component) than with any of the other approaches. I quite often need to poke plugs of solid solder out of the tube which runs through the tip. And replacing the waste solder reservoir vessel without displacing the soft filter isn't nearly as easy as it could be. But with those proviso's I find it much better than the spring-loaded jobs, which are inevitably one-shot (so I often had to heat and cool the joint several times) and which I found were also not recoil-less, to the point where I could snap off delicate tags if I was unlucky.

VB

 
Posts: 377
Joined: Sat Jun 15, 2013 10:59 am
Location: Near Glasgow

Re: Desoldering : "A Workshop Conundrum"

Post by Niall » Sun May 08, 2016 9:30 pm

I agree, for normal use the standard methods are fine, and outside of 351s I have only powered up the suction iron very occasionally for a particularly difficult joint. It does seem to be a viable alternative to the much more expensive systems for occasional use.

The 351 is a bit of a special case, hence the requirement in the manual that a vac system be used to remove modules. It's not just plated through, some parts of the board have a conventional PCB with an additional flexible PCB overlaid on it, connected by brass rivets through the component holes. These have a considerable heatsinking effect. Also each module has a screening can soldered to the earth track at intervals all round it.

 
Posts: 2513
Joined: Sun Jun 10, 2012 7:23 pm
Location: Basildon

Re: Desoldering : "A Workshop Conundrum"

Post by crackle » Mon May 09, 2016 6:25 am

I use a what I consider a normal solder sucker, that is a tube and spring loaded piston. However there are different qualities of these and it is worth getting a named make.
I have never used de-solder braid, never needed to and it is very expensive. All my recent repairs on the clock module of an ITT radio alarm clock were carried out with the solder sucker.
I think the positioning and quality of the tip are the important things for a solder sucker, and maybe a slightly higher iron temperature.
Mike

 
Posts: 2665
Joined: Sun Sep 01, 2013 6:19 pm
Location: Behind the sofa

Re: Desoldering : "A Workshop Conundrum"

Post by Cathovisor » Mon May 09, 2016 8:38 am

Although not strictly necessary on the sort of stuff we encounter, the Weller DS units were essential where you encountered multi-layer boards; ask anyone who ever had to remove an SBX1601A* from a circuit board! The unit we had latterly at work rather more usefully dispensed with the foot pedal (all my units have these - all three of them!) and moved the pump control to the barrel of the iron itself. One of my former colleagues said it discriminated against left-handed people (such as him) though, due to the position of the switch. I then discovered that you could reposition the barrel relative to the bit so it suited a left-handed operator!

At home though, and at work I use Chemtronics braid, having found it to be the most effective of the bunch and I now buy it by the tin, so useful do I find it. I used older spring-loaded hand pumps and they risked fracturing the more brittle valve holder tags and to be honest, in my experience they were never particularly good.

* Serial Digital Interface chip for SD video - specifically, the encoder.

 
Posts: 6972
Joined: Sun Aug 14, 2011 11:02 am
Location: Co. Limerick

Re: Desoldering : "A Workshop Conundrum"

Post by Michael Watterson » Mon May 09, 2016 12:19 pm

Desoldering gear depends on the target equipment.
  • Pre 1935 gear and wrapped joints.
  • 1930s to 1950s stuff with tag strips
  • 1950s PCBs hand soldered
  • Wavesoldered PCBs with no Plated through holes or rivets
  • Plated through hole PCBs. [Braid is is safest!]
  • SMT without BGA. Use a sharp knife to cut leads off of the SMT ICs! Then use braid.
  • BGA. Needs hotplate and heat gun.

I'd differentiate between one off repairs and production line "rework", which is what most of the vacuum pump stations were for.

Lead free needs special flux.

A good solder sucker is needed for wrapped joints, tags, old single sided PCBs.

You need flux too, though adding EXTRA solder that has generous flux content can help hugely on old tags and PCBs

It was standard practice from earliest times and on PCBs to cut off the part and make remainder legs have hooks or use a sleeve to attach new part rather than remove wires from tag (can be difficult due to other wires) or PCB (foil may crack or lift).

 
Posts: 2665
Joined: Sun Sep 01, 2013 6:19 pm
Location: Behind the sofa

Re: Desoldering : "A Workshop Conundrum"

Post by Cathovisor » Mon May 09, 2016 12:51 pm

Michael Watterson wrote:SMT without BGA. Use a sharp knife to cut leads off of the SMT ICs! Then use braid.

I've found that that can cause a lot of damage; the knife can cut through tracks passing under the body of the IC when the legs break away, or lever the pads off the PCB. Just use appropriately-sized braid.

The PPAD (PowerPad) devices are particularly awkward, although a hot gas pen deals with refitting them.

 
Posts: 2853
Joined: Wed Jul 27, 2011 7:13 pm
Location: Croydon

Re: Desoldering : "A Workshop Conundrum"

Post by sideband » Mon May 09, 2016 2:10 pm

I got spoilt at Philips. We used proper desoldering stations with a vacuum sucker. Position the sucker over a 200 pin IC and fit the appropriate nozzle for the chip. Press the 'desolder' button. Hot air blows over the chip and heats the solder and 5 seconds later the whole chip lifts away cleanly which sticks to the end of the sucker. If anyone remembers the A10 colour chassis with the infamous 'painter' chip we used it all the time when we reworked the panels.

We also used and infra red gadget when doing BGA's. They took longer but removing and replacing a large device could be done in 15 minutes. That was 10 years ago so no doubt BGA rework has been improved.

At home I don't have the luxury and thankfully rarely encounter SMD in private work but I use desolder braid (Chem-wick) and an electric de-solder pump. I find de-solder braid particularly useful for cleaning up valveholder pins.

 
Posts: 5844
Joined: Sat Jul 23, 2011 8:19 pm

Re: Desoldering : "A Workshop Conundrum"

Post by crustytv » Mon May 09, 2016 2:56 pm

Out of interest for the DS900, does anyone know where you can get replacement filters for the iron chamber? Or know of the part code?

 
Posts: 763
Joined: Sun Aug 07, 2011 5:17 pm
Location: Edinburgh

Re: Desoldering : "A Workshop Conundrum"

Post by Alistair D » Mon May 09, 2016 3:25 pm

I was told a long time ago that cotton wool was a perfectly adequate substitute. There should also be a wad of wool in the chamber below the pressure gauge.

Al

 
Posts: 6972
Joined: Sun Aug 14, 2011 11:02 am
Location: Co. Limerick

Re: Desoldering : "A Workshop Conundrum"

Post by Michael Watterson » Mon May 09, 2016 4:02 pm

Cathovisor wrote:
Michael Watterson wrote:SMT without BGA. Use a sharp knife to cut leads off of the SMT ICs! Then use braid.

I've found that that can cause a lot of damage; the knife can cut through tracks passing under the body of the IC when the legs break away, or lever the pads off the PCB. Just use appropriately-sized braid.

The PPAD (PowerPad) devices are particularly awkward, although a hot gas pen deals with refitting them.


The sharp knife shouldn't be ANYWHERE near the tracks, you cut at body. In 30 years I've never damaged the tracks. It's only for 0.05" and smaller pitch ICs, not power devices.

 
Posts: 5844
Joined: Sat Jul 23, 2011 8:19 pm

Re: Desoldering : "A Workshop Conundrum"

Post by crustytv » Mon May 09, 2016 4:22 pm

Alistair D wrote:I was told a long time ago that cotton wool was a perfectly adequate substitute. There should also be a wad of wool in the chamber below the pressure gauge.

Al

Thanks Al, I replaced it with some cotton wool. :thumb When I removed the old from the iron chamber it looked like glass-fibre loft insulation had been used. The base unit has what looks like correct pads and they look new.

 
Posts: 2665
Joined: Sun Sep 01, 2013 6:19 pm
Location: Behind the sofa

Re: Desoldering : "A Workshop Conundrum"

Post by Cathovisor » Mon May 09, 2016 4:26 pm

Michael Watterson wrote:
Cathovisor wrote:
Michael Watterson wrote:SMT without BGA. Use a sharp knife to cut leads off of the SMT ICs! Then use braid.

I've found that that can cause a lot of damage; the knife can cut through tracks passing under the body of the IC when the legs break away, or lever the pads off the PCB. Just use appropriately-sized braid.

The PPAD (PowerPad) devices are particularly awkward, although a hot gas pen deals with refitting them.


The sharp knife shouldn't be ANYWHERE near the tracks, you cut at body. In 30 years I've never damaged the tracks. It's only for 0.05" and smaller pitch ICs, not power devices.

Strangely enough Michael, I know that. And when the knife blade severs the leg(s) and falls through...? To me that's butchery, plain and simple.

 
Posts: 6972
Joined: Sun Aug 14, 2011 11:02 am
Location: Co. Limerick

Re: Desoldering : "A Workshop Conundrum"

Post by Michael Watterson » Mon May 09, 2016 7:24 pm

Cathovisor wrote:And when the knife blade severs the leg(s) and falls through...? To me that's butchery, plain and simple.

Not if knife is at correct angle.
However cheap heat guns with adjustable flow, temp and set of nozzles probably makes the cutting method redundant.
Unlike capacitors, transistors etc there is no concept of testing or reusing SMD 14 pin to 68 pin ICs. The only reason to remove them was to replace them.

A production line re-work or even 1980s to 1990s professional repair shop has different outlook to hobbyist in terms of parts.

My first encounter with SMT was with alumina substrate 1" x 2" hybrid thick film circuits in the early 1970s. I was on work experience. The resistors were screen printed and fired, then trimmed with abrasive jet (laser trimming was later). Then modules screen printed with solder paste. The parts were then glue on using foot peddle controlled syringe glue dispenser and vacuum tweezers. Ceramic capacitor multilayer chip, transistors, IC. Then oven reflow of paste once the glue was cured. Any electrolytic caps were tantalum soldered by hand, but usually avoided and on external host PCB. The pins clipped on down each side.

There was no concept of re-work due to the parts being glued. Then the parts were either covered with coating (fluidised bed dip like HV caps?) or epoxy potted in plastic trays. It was almost another 12 years before I was working in a place that introduced SMT on epoxy PCBs. Then no had assembly except prototypes, all automated placement and wave solder (no paste).

 
Posts: 763
Joined: Sun Aug 07, 2011 5:17 pm
Location: Edinburgh

Re: Desoldering : "A Workshop Conundrum"

Post by Alistair D » Wed May 11, 2016 9:51 am

The user instructions are pretty pathetic but I've attached a copy anyway.

Going back to the cotton wool thing. The reason there are 2 filters is that the first is for removing the solids from the airflow. The second is for removing flux vapours etc. The fact that the first is is for larger objects means that the wool can be packed less densely and thus avoid restricting the airflow too much.

Al

Edit: Forgot that PDF is not allowed. I will email them to you.

 
Posts: 5844
Joined: Sat Jul 23, 2011 8:19 pm

Re: Desoldering : "A Workshop Conundrum"

Post by crustytv » Wed May 11, 2016 10:28 am

Thanks Al,

that's a useful little document in as much as it filled in a few gaps, there's pretty much zilch out there that I've found. At least I now know there are two other de-solder tiplets's giving various temperatures. I've looked on-line and have not found any sources yet. For a cleaning needle I have my Bergeon clock broaches so can carefully clean the desoldering nozzle with those. Yesterday I was working on a Thorn Line timebase module and it made the job a whole lot quicker. Then the were a few boards I had for component recovery, again so much quicker and easier

 
Posts: 763
Joined: Sun Aug 07, 2011 5:17 pm
Location: Edinburgh

Re: Desoldering : "A Workshop Conundrum"

Post by Alistair D » Wed May 11, 2016 10:44 am

I am almost certain these are the ones you are looking for.

http://www.weidinger.eu/en/shop/solderi ... _ds-series

Al

 
Posts: 6972
Joined: Sun Aug 14, 2011 11:02 am
Location: Co. Limerick

Re: Desoldering : "A Workshop Conundrum"

Post by Michael Watterson » Wed May 11, 2016 11:42 am

I use sewing needle for tiny holes and cocktail sticks for bigger ones (PTH, the fluxed braid is fine on single sided).


Return to Test Equipment



Who is online

Users browsing this forum: No registered users and 3 guests