| Electronics > Projects, Designs, and Technical Stuff |
| Vapour phase Soldering |
| << < (27/48) > >> |
| Kjelt:
--- Quote from: jeremy on January 27, 2015, 06:39:41 pm ---Ok, so I've been reading the manual of the weller WAM3000 very carefully, and here is my guess at how it works. --- End quote --- I am with you untill the level the board is lowered to. My gut feeling (nothing more so another guess) tells me that the three sensors are covering the entire heating volume so the lowest sensor is the bottom and the highest sensor is the top, so the middle sensor is the middle and that should be the location of the pcb (my guess). So if the highest sensor reaches the set temperature or above all power should be cut because vapor is then escaping the zone, just my guess to it if I should build it. |
| jeremy:
--- Quote from: Kjelt on January 28, 2015, 08:00:13 am --- --- Quote from: jeremy on January 27, 2015, 06:39:41 pm ---Ok, so I've been reading the manual of the weller WAM3000 very carefully, and here is my guess at how it works. --- End quote --- I am with you untill the level the board is lowered to. My gut feeling (nothing more so another guess) tells me that the three sensors are covering the entire heating volume so the lowest sensor is the bottom and the highest sensor is the top, so the middle sensor is the middle and that should be the location of the pcb (my guess). So if the highest sensor reaches the set temperature or above all power should be cut because vapor is then escaping the zone, just my guess to it if I should build it. --- End quote --- Hrm, I can see your point, but I would worry that the second sensor has a much faster thermal time constant than the PCB itself, and would report being fully heated well before the PCB is. The sensor is mounted in the wall remember, not on the PCB. I think I read somewhere (I can't find it now any more) that asscon uses the third level as the end-of-soldering sensor. And I suppose it isn't possible to lose any fluid or vapour if the gate is properly sealed. But of course, both of these things would be easy to verify with a real system, so it should just be a case of trying them both. Thanks for your input. |
| mrpackethead:
--- Quote from: jeremy on January 28, 2015, 08:09:33 am ---Hrm, I can see your point, but I would worry that the second sensor has a much faster thermal time constant than the PCB itself, and would report being fully heated well before the PCB is. The sensor is mounted in the wall remember, not on the PCB. --- End quote --- And you wondered why i wanted to put a thermal sensor in a block of alluminum. To give it some thermal mass. I'm also pretty convinced that there is minimal need to actually have the shutter system. I'm sure that the vapour height can be controlled pretty well. and that in a reasonably well controlled system the vapour won't escape the tank anyway. The systems with shutters are doing it for a different reason. They are blowing air across them, which is for cooling, and from what i see they are looking to cool the boards quickly for inline systems. for doing low voume batch work, this doe'snt seem to be a requirement. Control here, is critical. |
| jeremy:
--- Quote from: mrpackethead on January 28, 2015, 08:58:26 am --- --- Quote from: jeremy on January 28, 2015, 08:09:33 am ---Hrm, I can see your point, but I would worry that the second sensor has a much faster thermal time constant than the PCB itself, and would report being fully heated well before the PCB is. The sensor is mounted in the wall remember, not on the PCB. --- End quote --- And you wondered why i wanted to put a thermal sensor in a block of alluminum. To give it some thermal mass. I'm also pretty convinced that there is minimal need to actually have the shutter system. I'm sure that the vapour height can be controlled pretty well. and that in a reasonably well controlled system the vapour won't escape the tank anyway. The systems with shutters are doing it for a different reason. They are blowing air across them, which is for cooling, and from what i see they are looking to cool the boards quickly for inline systems. for doing low voume batch work, this doe'snt seem to be a requirement. Control here, is critical. --- End quote --- Actually, I was wondering why because aluminium has far too good thermal conductivity. Fibreglass has a thermal conductivity of something like 0.05 while aluminium has a conductivity of ~200 W/(m.K). So given this large difference (X 4000) you could possibly tune your control loops for the wrong parameters, and you might not be able to find hotspots in the oven because the aluminium will hide that. Why fake the load if you can just have a real one? It is a common thing to mount thermocouples on PCBs. I think the gate on the weller machine is mostly for safety. It isn't an inline system. |
| helius:
Even the inline vapor-phase machines aren't continuous, they are more like a buffered batch system. The reflow profile should control both the heating and cooling steps for uniformity and to save the components. |
| Navigation |
| Message Index |
| Next page |
| Previous page |