Removing surface mount parts without damaging surrounding components.

okay so today I want to try to let's I get a lot of questions from people soldering soldering soldering how do you solder how do you desolder taking parts off and this is the question I get a lot is how do I get parts off of word like this without damaging other parts and specifically we're talking about surface mount parts a lot of times what you'll run into is when you're working on surface mount components are of course boards aren't all surface mount there's still a lot of other through-hole components electrolytic capacitors in a case of a board like this which I have no idea what this was it was a I think I sling something sling it's got a mini din plug a LAN connector power jack there's a switch and couple LEDs on I've got got well over a hundred jump boards from ATM machines routers just all kinds of crap people give me and I scavenged the parts off of them for recycling they like this one has had all the tantalum capacitors removed anything I got take off now as a processor but you know then recycle those for money though all high-value scrap metals off of it basically but this is a perfect board to use for this demonstration what I want to try it well I'm not going to try to I'll get it off but that's what I do we want to take this deep hack off but I want to show you how to get it off without damaging let's say this electrolytic capacitor and we're what we're going to be taking it off with is hot air and the problem you can run into is because this component it's not like a lead a normal League component that only has new leads on this side leads on this side this has the entire back side of it is soldered directly down to the board okay the tap it's just like a normal transistor it like you'd see a normal through-hole transistor but the tab that's on the back of it is soldered directly to a huge pad on the board here and to make matters worse that's attached to a huge ground plane make matters even worse this is a multi-layer board and it has multiple layers of pet ground plane so when you're trying to heat this part up on the top side with hot air it takes a while to because you're heating up this entire board and the whole area around it in all of you all this ground plane area is sucking the heat out is you're you're heating it but it's quickly being dissipated throughout all of this this ground plane area and when and when you're doing that then inevitably you end up possibly damaging stuff like this like actually this one I can see the plastics melted a little bit because when I removed all the tantalum capacitors off of this I did use hot air but I didn't care if I damaged anything because it's it's going to be going into the recycle bin yeah so I heated this up that's slightly melted the plastic there and actually if we look at the switch down here I can just see a little bit of melting on the back of that because there was a tantalum capacitor right there that I pulled off and that heat slightly damaged the plastic of this switch well if this was something I was trying to fix I wouldn't want to do that you know there's plastic plastic there's plastic inside disconnect this connector shield real a plastic plastic on the outside and it's an electrolytic you know an aluminum electrolytic can capacitor which just by its nature can be damaged by heat not not talking about the outside I'm talking about electrically damaging it you know the two most damaging things you can do to an electrolytic capacitor is over volt it you passed its voltage rating and heat it up that's that shortens the life it's just it's almost an exponential curve whether it's just the the lifespan of a capacitor electrolytic capacitor once you've reached a certain point in temperature that its lifespan just plummets so you know what you want to protect that you may want to protect this kind of stuff this stuff if it's unevenly heated you're trying to but you're blasting this area with heat you could you know possibly damage this little tiny BGA or the big main processor this chip over here so you want to try to keep that heat off of those areas so there's a few things you can do for starters use a circuit board pre heater lots of them on the market I'm sure you can get these things made in China the when is a heyco no it's not a piece actually everything I'm using here right now for this demonstration is gonna be heyco I will at some point be getting a it's one of the pieces of equipment I need to upgrade is my all my hot air stuff here I want to switch over to pace equipment but like I say by preheating the board you're already heating up all these ground planes but you're evenly heating the entire board so it's not getting shocked with that that hot air you're using out of your hot air reflow gun that's at the melting point of solder you bring the board up to a warm temperature then you can come in with your hot air and in just a matter of seconds the solder melts you can take the part off and then in the case of like the board heater like this it has a cooling feature so I can hit switches switch it over into cool and then that cools the board back down now you could do this by hand I just happen to have so I'm going to be using you know this system here so this is the hit this is the mount that's meant for this hako hot air pan piece right here but it has a lot of nice features it has the you know the raising and lowering lever you swing it around it also has the built-in vacuum pickup tool which well we'll go ahead and give that a try I wasn't going to use that but I do occasionally from time to time so you can see there is actually I can just bring it out a little bit far there's a little stainless steel tube that goes up into and then inside the the cord that goes to this it's blowing air its supplying electricity and then there's also another line that actually is attached to a vacuum pump in the machine but we'll try to pick it up with that sometimes these work sometimes they don't usually they do now if you get something like this part here a lot of times it can be a little iffy because there's a lot of surface tension for all that solder that's on the back of that but we'll give it a try if it doesn't work then I'll just I'll NAB that little guy with pair of tweezers but none of this is still none of this is going to do anything for and it's a hand piece has a what I'm doing to raise and lower that's this little knob right here but what we main thing we want to do is is protect these other components make it short and sweet eBay it's probably the cheapest place you're gonna find it what you're gonna get for what you want to get is a ceramic mat now this is a the brand name I think is Keo wool kao wo o L made in the USA sold in the USA ships from the USA so for me that's convenient you can get stuff like this from companies that sell surface mounts servicing products the problem is when you buy stuff like this from a lot of those companies a lot of times they're selling you a little like four inch by four inch or a six inch by 6 inch piece for like ten dollars or more where you can get a you know like a 2 foot by a foot piece of this for around the same price maybe a little bit more you know orders of magnitude more I mean good lord you lord knows how many chunks and this is just a piece that I've actually it looks like it's about time I need to reorder some of them get kind of short I only got two chunks left here I think this was a when I got it it was a 24 by 48 inch pieces what I normally get but what you want to get is the thin stuff you don't want because you can get this stuff you a thin CH which is what this is quarter half-inch oh I think they even have it in thicker you know thicknesses but huge for lining kilns heat-treat furnaces and stuff like that it's resistant to something like 2200 or 2300 degrees Fahrenheit well above the temperature we need for for melting solder so this is the perfect thing to use as a heat shield so if you wanted to let's say if you were working on something and you only needed to protect this part here you could just tape a piece you know with a piece of Kapton tape which is again this poly aramid Kapton tape is it also high heat resistant but you could tape a piece down on top of that or that little small BGA or the same thing over here with the big one you can just make a mat to tape down over top of it because that's the one advantage of this ceramic material is it's why they use on things like the Space Shuttle ceramic does not conduct this kind of material here is not a good heat conductor so unlike copper which if you lay a soldering iron here the heat just instantly spreads out all over the place this stuff is a horrible conductor of thermal energy so you know you could theoretically lay a pad of this you know sheet of this on your hand come in with a torch and you won't feel any heat on the back because it's just a very poor you know conductor of heat but we can take advantage of that to protect that so let's see if we sometimes you can do stuff like this you don't need any tape sometimes I can get things like this positioned just fine if there's enough ah look at that it actually worked is it gonna stay yeah it looks like it will so yeah this is just a lot of times it'll spring out yeah a lot of times what I do is I just play a piece of tape over top there a piece of tape to hold it in place but yeah it looks like the edge of it just call on the edge of that I see there so I don't even need any tape so we'll turn on the board heater it doesn't take very long just matter of seconds for the board heater to heat up the temperature and it'll heat the board up we're gonna have make sure I have clearance here yeah and I see actually just shorten it a little bit trim a little bit off now when you're cutting this stuff you don't need anything but scissors but just be aware that you don't want to be using something like your White's sewing scissors or anything like that your kids or whatever you but you don't want to go using good high quality scissors that you're going to want to be using for other stuff it is ceramic remember it's very kind of like gritty I'm not a ceramics manufacturer so really have no clue but I just know that it is kind of gritty and crunchy it is a matte it's flexible as you can see but it will doll your says scissors so you don't want to go you you're using good scissors to cut this stuff these are kind of like you know what I call my mom's bench scissors here they're Fiskars but uh yeah I knew I would never be cutting good stuff with those so I'll bring my arm over trying to reach around the camera here which is always a pain enough hooha that down more light over here let me swing the camera off to the side I need to get my and another nice thing about a jig like this it has this positioning so I can move the circuit board of back and forth with knobs I want to get this positioned so right about there looks good okay so now I'll turn on the board preheater you're gonna hear you know jet turbine engine spinning up here it doesn't take that long to heat up like you know come in here and just put my thumb on this BGA here and I can feel it's getting warm already now that is temperature controlled the air that's coming out of that there is a thermocouple in the air streams you know this thing is continuously turning the heater on and off too and yet the board is already pretty much more and yet if the piece just made it figures I should have taped it down maybe I can get a reposition here again and it'll stay doesn't need to stay there very long so now I'm going to turn on the hot air handpiece and it takes it a few seconds to heat up and what I'm looking for now if I'm looking for the melt for the solder okay I see the solder is melted turn on the vacuum pick up oh nope dropped it so now my positioning is wrong so it's out turn the vacuum pump off and swing that out of the way and if I was yo if this was a board that I was actually servicing I'd flip the machine over to the cool position now so that's turned the heating element off but still blows air onto the board and then it cools the board down because you don't want to cook these mew you don't even into elevated temperature it's not this isn't putting out new solder melt heat temperatures but it's still hot air so you want to bring it bring the board temperature back down but yeah that's that's all you need if you're trying to remove parts you don't want to go melting surrounding parts that's basically what this video is get yourself some of this ceramic mat you do not have to buy this stuff from the manufacturers when we turn it pre here alternative fan off you don't have to buy this stuff from the manufacturers that make stuff specifically for doing surface mount work there's little tiny pieces that are really expensive like I say you can buy a whole roll of this stuff and make dozens or even a hundred or more the blasted things you cut out pieces for the same price you buy a little square of it from those companies so if you check eBay like I said you're you will find at least in the USA the kao wo o lko wool I think there's another manufacturer there's another company another another brand name that they sell on eBay at least here in the United States if you're overseas again check your own eBay you can check amazon online like I say companies that sell surface mount products or servicing products sell small pieces but your best bet is to get it from a distributor that's you has a huge role of this stuff that they're cutting off you know big chunks of it to sell they're not selling you the tiny pieces and most of those companies a lot of them what they're selling products for is for furnaces furnaces and kilns and really high temperature places so you know if you can't find it looking for where you're at try and find a company that sells products to four furnaces and kilns they're going to have this type of stuff because this is what they use inside of kilns and furnaces is the ceramic mats so it likes it just big thing make sure it's thin that way you can get like over here you know you can put it in between components it's very like I say it's very flexible it's thin goes round stuff so it's very easy to shape but that's it that's all you need so I hope that helped somebody out from melting parts on their board

Channel: MikesRadioRepair

Views: 6,593

Rating: 4.7894735 out of 5

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Id: wj50mbeSIlg

Length: 15min 38sec (938 seconds)

Published: Sat Apr 07 2018