| Electronics > Projects, Designs, and Technical Stuff |
| Vapour phase Soldering |
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| tautech:
--- Quote from: zucca on January 30, 2015, 09:55:57 am ---Sorry to jumping in without having read all those previous pages in details. Looks a cool project, I´m wondering if it would be possible to get a cheap liquid and change the boiling point by changing the (vapor) pressure in the chamber: Surely there is a big elephant I am overlooking... --- End quote --- Yep. SAFETY This WHOLE thread is worthy of reading and this nicely sums up what is required: --- Quote from: gxti on January 30, 2015, 04:42:27 pm ---You'd have to find something chemically inert, because evaporating flammable liquids is a great way to get an explosion. But realistically I think all the added complications of containing a lower (or higher) pressure make it a far worse alternative than just paying for the inert, non-toxic, ambient pressure stuff. --- End quote --- When I wanted to get into SMD, a rework station cost more than a litre of Galden. :palm: |
| IconicPCB:
Jeremy, Apropos the stainless steel balls.. there aretwo types of steel generally speaking .. austenitic and martensitic. The type is dependent on the manufacturing process how these metalurgical properties are developed ( crystaline structure which affects how the magnetic domains are established and formed. This also applies to stainless steel. Some alloys are magnetic others are not. 300 series alloys are not magnetic where as 400 series alloys of stainless steel are. On the question of temperature measurement: addition of aluminium heat sink to the thermocouple would only detract from the quality of temperature measurement and subsequent tightness of the control loop. Temperature of the vapour cloud is unimportant so long as the cloud exists, gets "consumed" and is replenished from the boiling liquid. Essentially the only reasonone would measure the temperature of the space where the cloud is to form is to confirm it has formed. As the fluid is heated the volume of the cloud increases but it's temperature remains constant as all the energy is consumed in evaporating the fluid. So simply use the measurement of temperature to confirm the probe is immersed in the cloud . With a batch oven a tall batch oven the cloud needs to be stratified and the way to do it is to set up energy sinks and sources which would contain the cloud; namely a heater and a cooling jacket which will place a lid on top of the cloud. The cooling jacket will cause vapour to condense and drip back into the fluid reservoir. Vapour pressure will tend to level off any un evenness in the vapour layer by ensuring a continuous interface between the vapour jacket and the cooling jacket. This equilibrium will ensure a uniform blanket of vapour into which the PCB needs to be immersed. The space above the vapour layer will be at increased temperature through natural convection of air and it is this volume above the vapour that is used as preheat and cooling zone. This is my understanding and I shall be making an oven in line with this understanding. I have made some enquiries with a local sheet metal shop and stainless steel hardware suppliers. My expectation is to start spending money during the coming weeks. |
| jeremy:
--- Quote from: IconicPCB on January 30, 2015, 09:37:58 pm ---Jeremy, Apropos the stainless steel balls.. there aretwo types of steel generally speaking .. austenitic and martensitic. The type is dependent on the manufacturing process how these metalurgical properties are developed ( crystaline structure which affects how the magnetic domains are established and formed. This also applies to stainless steel. Some alloys are magnetic others are not. 300 series alloys are not magnetic where as 400 series alloys of stainless steel are. --- End quote --- Yep, I made sure to get 420 stainless and from an amazon supplier so at least I can try to get my money back (all $5 :P ) if they ship me 303 or something. Please keep us updated on your progress. I intend to do something similar when I get the chance, but I've not really dealt with much sheet metal before. |
| mrpackethead:
--- Quote from: IconicPCB on January 30, 2015, 09:37:58 pm ---Jeremy, On the question of temperature measurement: addition of aluminium heat sink to the thermocouple would only detract from the quality of temperature measurement and subsequent tightness of the control loop. --- End quote --- the sensor i was thinking of putting in the aluminum would be on the carrier that was carrying the board. I'd also have fixed sensors in the tank, and they would be set up to have minimal thermal 'interia'. what i was trying to achieve was something that "mimiced" a pcb that will have to heat up ( which takes time ). It might be ( and not sure yet ) useful for helping to determine when the pcb has reached melting temp and also to help establish when it has cooled enough to be able to safely move it. ( and cool it rapidly with air ).. Don't want to be moving it too quickly when its still molten. I'm thinking of of using some linear guides ( http://us.misumi-ec.com/vona2/detail/110301962560/?Inch=0 Misumi stuff is not overly expensive, not as cheap as flea-bay, but it is reliable, and they have a million options and cad drawings. ) for the carrier inside the tank. That will require a reasonablely careful approach to ensure they are all runnign parallel. About to order my "modified" HT230. ( its HT230, thats been reprocessed ). As for loss, i was talking with a guy who's got a commercial machine and he has done over 20,000 boards in theres, and he thinks, they might have used 3/4 of a 5kg bottle. So, provided you don't lose the stuff, you'll need very very little over time. Seems also that it might be good to have a "well" in the middle of the tank, to heat the liquid in, rather than try to heat the entire base of the tank. I'm looking to do something that i can put a 250 x 350 mm sized board / panel in. |
| MK:
i mole of any liquid gives 22.4 litres of gas at normal temperature and pressure, so with a molecular weight of about 80? just a guess here, then 80 gms gives 22.4 litres of vapour. That should help you size how much you need, you also need to consider that the heating element needs to stay immersed in the liquid portion. |
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