top heater uneven heat

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top heater uneven heat

Postby demonspride » Sat Mar 25, 2017 11:10 pm

So I bought a replacement Elstein heater for my top ACHI or LY heater, and i've had 3-4 BGA's mount lopsided, after lots of different testing i finally had the bright idea to turn off the lights, and check if its heating properly! well this was my discovery!
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has anyone had this? is this uneven heating normal? and should i be looking into a replacement? these things are 70$ a piece!
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top heater uneven heat

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Re: top heater uneven heat

Postby code0102stinks » Sun Mar 26, 2017 5:06 am

Seen worse than that with guy's still lifting and installing chips before on here in the past. Makes me wonder if you are preheating the board
hot enough with the bottom heat. What is the topside temp of the board before you come in with top heat on the chip?


And how far above the chip is your top heater?
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Re: top heater uneven heat

Postby demonspride » Sun Mar 26, 2017 4:48 pm

im usually about 3-4 cm above chip. bottom side is set to 195, my profile usually hits 175 bottom heat before topside starts, my last heater was perfect, but maybe it is bottom heat not high enough, weather is starting to change here in Iowa so gonna have to start building new profiles:/
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Re: top heater uneven heat

Postby gkop » Sun Mar 26, 2017 8:03 pm

I have the same issue and additionally, I have notice that my heater starts heat heavy on one side and then evens out with duration. The problem is that during quick ramp up cylces the duration required to even out heat is never achieved. This part is definitely a quality issue as heating wire should heat up from center out, so somewhere in the build the cheap manufacturers have jacked up the wiring. Either they were really shitty and wired it poorly, or my suspicion is that their casting process is more for speed and less for reliability and at some point during the pour the wire was distorted which results in uneven heating. By the end of this, you'll start to realize that I tend to obsess over these types of problems until I figure out there exact cause and how to overcome.

In an attempt to resolve, Im getting ready to order a variety of new heaters and opto-switches...non-elstein; they are just too pricey for my liking and from what Ive been told by nextthemal (a direct Elstein dist) is that they will also experience these issues. they also admitted that the heaters could have internal rattle, but insisted that it would work just as well. Its my belief that it wouldn't. Internal rattle is caused by internal chips of ceramic coming apart and floating around the hollow cavity inside. This mostly likely a result of shipping and handling as ceramic doesn't travel well. If my limited understanding in thermodynamics is correct then distortions, cracks, fissures, etc will in fact affect performance.

My impression from nextthermal is that the primary use of these heaters is in larger scale farm production and factory assemblies. The use they are suggesting the off the shelf models of Elstein heaters are in environments that require a little bit less temperature accuracy. My suspicion is that true BGA ready IR heat plates are more customized by need with much higher quality controls and therefore they are more rare and more expensive; probably more expensive than any independent or small business owner would like to spend.

options to obtain less fragile IR heat plates would be to go for solid core as the higher density and full shroud of the heating wire would reduce opportunities for damage while in transit. This would not prefvent poor QA during manufacturing, so I would certainly suggest Elstein or searching for a high quality chinese manufacturer that you can :shock: trust :shock: ... However, Im starting to look back into top hot air with bottom IR Plates.

What I dont understand yet, and hopefully someone here can clue me in on is... How does the external coating affect performance? I understand that color choices between dark and light can filter between high and low IR, but is there any effect caused by composition. If composition of coating is a factor in IR performance, in relation to bga, then what types of resins/coatings are optimal for creating the best spectrum of IR heat. Additionally, for that matter, what is the optimum spectrum for BGA IR Rework.

One last thought for performance tuning is the use of ir heater with temp wire. However, having internally controlled heat presents an issue with working for bga profiles. I would think a new type of PID would have to be created to monitor and control internal temp and an external temp monitor for that signals the internal temp to start/stop/bump-up/bump-down temp in correlation to the external top of board temp readings.
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Re: top heater uneven heat

Postby code0102stinks » Sun Mar 26, 2017 9:20 pm

demonspride wrote:im usually about 3-4 cm above chip. bottom side is set to 195, my profile usually hits 175 bottom heat before topside starts, my last heater was perfect, but maybe it is bottom heat not high enough, weather is starting to change here in Iowa so gonna have to start building new profiles:/


So, is your bottom heat TC touching one of the bottom plates? Or touching the bottom of your motherboard? Where are you getting 175 bottom heat
when your topside start? From the reading of your bottom PID controller? Or from the PV on the PC410 top controller? The TC for the top controller
should be close to the chip on top of the board. That is what you want to read about 170C before top heat kicks in.
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Re: top heater uneven heat

Postby demonspride » Sun Mar 26, 2017 11:53 pm

my bottom tc is roughly half an inch from the bottom heaters, the 175 is coming from the top tc that touches the board by the BGA being heated, so essentially the bottom heater heats until about 175, this being read by the K-sensor, then the top kicks in to do its job, i've switched out the top elstein for the original chinese branded heater it came with originally, and it seems to actually be heating evenly, had 2 BGA's mount no problem with the same profile... sometimes youre just unlucky with heaters..
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Re: top heater uneven heat

Postby code0102stinks » Mon Mar 27, 2017 12:10 am

demonspride wrote:my bottom tc is roughly half an inch from the bottom heaters, the 175 is coming from the top tc that touches the board by the BGA being heated, so essentially the bottom heater heats until about 175, this being read by the K-sensor, then the top kicks in to do its job, i've switched out the top elstein for the original chinese branded heater it came with originally, and it seems to actually be heating evenly, had 2 BGA's mount no problem with the same profile... sometimes youre just unlucky with heaters..


If you are getting 175C on top of the board, then you are getting plenty hot enough from your bottom heat. Your bottom heat TC should not be just hanging out trying
to measure hot air. TC bead needs to be actually touching either one of the bottom plates or the bottom of the pcb. TC's don't make a stable measurement of the air
between the plates and the pcb.
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Re: top heater uneven heat

Postby demonspride » Mon Mar 27, 2017 1:11 am

the bottom heaters shouldnt need the tc directly on them, they are close enough to get a good reading, i've always heard you should never have the tc touching the elements, either way, it wont make a difference, as the board is reaching the temperature it needs without damaging anything, and its not over heating, so why would this make any difference to my topside element having glowing uneven heat??? you also shouldnt have your tc touch the pcb because its too far from the source. info like this kills PCB...
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Re: top heater uneven heat

Postby code0102stinks » Mon Mar 27, 2017 4:15 am

demonspride wrote:the bottom heaters shouldnt need the tc directly on them, they are close enough to get a good reading, i've always heard you should never have the tc touching the elements, either way, it wont make a difference, as the board is reaching the temperature it needs without damaging anything, and its not over heating, so why would this make any difference to my topside element having glowing uneven heat??? you also shouldnt have your tc touch the pcb because its too far from the source. info like this kills PCB...


Since you are getting 175C topside of the board, bottom heat didn't have anything to do with your uneven heat at the chip. It is obviously the new element. I asked about
the bottom heat originally because many people don't preheat hot enough and try to do too much of the work with top heater. You are using enough bottom heat, so that
is not an issue. When you mentioned that you just hang the TC out there measuring the hot air above the lower IR plate I was just trying to offer good advice. That hasn't
worked well for many people over the years at all. When your machine was sold, it was designed with the TC touching one of the lower plates. 90% of those machines are
that way.
http://img.weiku.com/a/001/673/Sale_Sco ... _104_2.jpg

The only machines you are going to find that measure the hot air above the board will have the TC in a device like this machine has to trap and slow vent off a hot air
sample coming up from the plate. It protects the TC from the normal drafts in a room that will effect the reading.
http://img.weiku.com/a/001/673/Welcome_ ... _559_6.jpg

Why do you think having TC touch the bottom of the board is going to hurt the pcb? Many very experienced BGA guys do that and it controls the temp better. IR plates
put off infrared that heats the pcb more that it will heat a shiny metal TC bead. More accurate. You top heat is far above the BGA chip and it's controlling TC is placed
on top of the board by the BGA. Does it fry the pcb or chip because it is so far from the source of heat? Nope. Here is a pic of Deusjevoo's of his modded bottom TC that
touches the bottom of the PCB. He has good control if the temp.
http://s652.photobucket.com/user/Deusje ... q.jpg.html

Just trying to help. Couple things you said we just disagree on. I have been skeptical of those green plates. Supposedly are elstein, but safer to buy directly from elstein.
I have looked at the Elstein products on their site many times and never saw the green plates there before.
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Re: top heater uneven heat

Postby gkop » Mon Mar 27, 2017 4:22 am

demonspride wrote:the bottom heaters shouldnt need the tc directly on them, they are close enough to get a good reading, i've always heard you should never have the tc touching the elements, either way, it wont make a difference, as the board is reaching the temperature it needs without damaging anything, and its not over heating, so why would this make any difference to my topside element having glowing uneven heat??? you also shouldnt have your tc touch the pcb because its too far from the source. info like this kills PCB...


my understanding is the same with tc probes. Ive been lead to believe that it is ideal to have probes as close as possible to the bottom of the board without actually touching. Whether or not this is in fact what should be done is unknown to me. However, I can say from experience that, for me, the top of board tends to reach my desired heat faster when the bottom probe is near but not touching.

In short, you can try adding more distance between you top IR and BGA target to even out top IR and compensate for quality issues. However, to make the added distance work you will need to prevent heat dissappation by trapping heat between your air gap. (I added this brief statement for those that dont want the long version. see next paragraph for more details on increasing distance of air gap)

one thing I have been experimenting with to compensate for uneven top heat and faster + more consistent ramps is top IR shrouding. Sounds fancy, but this is nothing more than folded tin foil in the shape of a square which i wrap around the top heater. Adding this shroud allows me to distance the top IR farther away from chip. The farther away you are from your target, the more dispersed the IR waveform gets. This helps to offset minor issues with IR heat uniformity. The downside to this is that the further away you get the easier it becomes for heat loss, which is why the shroud becomes necessary. I have successfully reballed ps4 apu with distances 1.5" - 2" away from bga target. currently results are around 50/50 for not having to adjust height, so Im trying to figure out what variables are causing inconsistencies (other than my shroud being flimsy tin foil that I half ass stuck on before hitting start).
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