Need help to buy the right pre-heater - Page 1
Forum section: electronics / beginners

author: YouCanDoIt
author_rank: Regular Contributor
timestamp: March 18, 2024, 10:17:34 pm
content: Hello to all,I always used the soldering iron and hot air and I always thought it was enough. However, for stuff that requires hot air I always had to play with very high temperatures. I never had problems (I must also say that the number of such kind of jobs has been very limited), but there's always a first time. Someusersmade me aware of the risks and how damages can be catastrophic. They suggested me a preheater.I imagine that with a pre-heater some risks could increase because now we have the whole board at 200C° (recommended value is unclear, I seeeach userrecommending a different value), not just the target area.I just saw avideoof one of such cheap chinese preheaters and I have been impressed on how make soldering easy (it doesn't even use a soldering iron).Prices go from $15 until a couple of hundred dollars.Do you feel to recommend some specifics I should ensure this thing has? Additional needed stuff to make it ready to work?Right now, it come in my mind the following considerations (which could be perfectly wrong):I saw how easily the pcb move when touched (hope there is some version with anti-slip mechanism)Buying one with a large plate to me seems a waste of money. The linked one is only 5x5cm and this is more than any required working area. I suppose the same is for the ones supporting higher temp (lethal for boards)There are infrared versions. What are the advantages?Does a preheater breaks ESD safety provided by an ESD workstation?I can't see well in the video, but if the target component get so easily soldered to the board without even a soldering iron, what about all the other components of the board? Is this safe? I don't even want to think to how many micro fractures could be generated when the welding solder of each component is near the molten state. Such soldering techniques are completely new to me, I must miss something obvious!I have no idea on how could be right budget for this, I should first know what the different models can and cannot do.How I always doneI describe here in details how I have always done, so you can tell me if I do something wrong and the changes I should do once I include a preheater in my equipment.I've always used regular welding solder combined with no-clean flux (this one in every operation as it makes everything easier).DesolderingI always use desoldering braid (with the iron tip above the braid) whether it is a small component like a fuse or an IC controller (only difference is when there are multiple pins I incline the iron to cover a larger area). For small components (2 pins or a bit more) this is usually enough (at worst I just need a quick "iron tip touch" "small pressure" combo to detach).For more complicated components like IC controllers with many pins I'm forced to complete the job through the hot air (again, same temp): I put a sewing needle below the chip and I keep it gently pressed with a finger while heating. When I feel the sewing needle moving I know it's time and I continue to heat until detach completely. The heating phase is like this: I heat each side for, may be, a couple of seconds or more, then I go to the next side. I alternate this with a circular movement on all the sides.I never ruined the pads in this way (which would be a disaster), however I can imagine how chances of this happening can increase with lower temperatures. I never protected the components near the working area, mainly because they never reach a melting point (I use small nozles with limited air flow). I should, right? What you recommend as a protection layer?SolderingI omit the small components for obvious reasons. I completely clean all the pads and apply new solder from scratch. With the iron inclined I perform multiple passes to remove the excess solder until I see it is enough for a good "pin to pad" connection, but not enough to join pins. Then I put the chip above and start heating using the same technique mentioned above with the difference that this time I keep for all of the time tweezers or similar gently pressed above the chip in order to make sure it full adhere to the board on all sides. This is very uncomfortable because even a small movement can cause misalignment, so I think that for the future I should use some sort of those calibration weights used to calibrate precision scales (). It's a bad idea? Could it break ESD safety?I attempted to decrease temp. but I had the same experience describedhere. However, by looking at such topic seems that they all end up with such temp. It seems that fast heating is needed to avoid damages and by using the most lower temperature. It is not an easy combination. if you try to optimize one side you risk to increase risks on the other side and vice versa.Related itemsI have discovered for the first time the existence of the soldering paste in that video and I'm very impressed. Should I look for particular specs?Although I think the flux and welding solder are the cheaper ones in the market (no brand), I never had any problem, but I'm wondering if their alternatives of very high quality can make difference. Any recommendation?Something else I should buy?I would like to replace flux and welding solder with the soldering paste, but I feel that, depending on the kind of task, they are all needed. Problem is that now I am confused on how exactly I should modify my habits when such new stuff enter in the game.Thanks to all in advance