QFN Soldering - How To Replace QFN / How To Rework QFN
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- čas přidán 4. 10. 2020
- See how QFN soldering rework is successfully carried out with this clear and easy to follow soldering tutorial.
Every stage of the removal and refitting of your QFN's is clearly shown with the added bonus of clear photographs after every step of the procedure.
See how you can test your QFN after fitting to prove the Heatpad is soldered to the PCB with a "SECRET" testing method which not a lot of people know about.
Finally to carry out QFN rework properly you really must use a Hot Air Pencil as you need to melt the solder on the underside of the device.
If you found this video of use please like and subscribe and hit the notification bell so as to not miss out on my future releases . Thank you for your time and Good Luck with your projects.
Mr SolderFix
#qfnrework. #replacingqfn - Věda a technologie
Thanks! I'll definitely try this technique.👍
That last bit will be important for me to remember when designing my boards.
Thank you for pointing that out.
In the middle of replacing one in a critical area with much copper plane below. The secret is bottom and top heat of course. Your video is one of the better, if not best, showing QFN with center pad.
Hi , thank you for your comment , much appreciated. I'm glad you enjoyed the video , you are spot on about the bottom heat , but I guess not many hobbyists will have a hot plate at home. If you have , it does make it a bit easier to rework . Thanks again 👍
Great videos, thanks for sharing your knowledge. Very helpful.
Hi . Thank you . I am very happy to share what I have learnt over the years . Im glad your finding it of use . Happy soldering👍
i learn heatpad test point at that video. thanks.
Hi . Glad the video could help you out. Thank you for watching , much appreciated.
thanks for all the efforts. Really a great sharing.
Hi , thanks for watching the video and commenting , very much appreciated 👍
Got it. Excellent. Thank you
Hi . Excellent . Thank you for watching , hope you find it useful 👍
what a great and clear video dear friend, indeed, the best!
Hi , thank you for your comment, it's very kind of you . I'm glad you enjoyed the video , hopefully you get on ok with all of your soldering projects, thanks again 👍
I want to do a shout out to the good Dr. - I really enjoy your videos and even though I have been soldering for years but not a lot of SMD work. Currently I am bing watching your videos. Just replaced my hot air station as my old el cheapo died during a micro switch replacement. :( . Any who... Thanks for such great videos and hope to see more from you. Be nice to see one on choosing the correct tips as per quality wise. I find using a conical tip the solder tends to run up away from the tip. Its probably my heat setting on my iron.
Hi , thank you for watching the videos and supporting my channel , very much appreciated 👍
I think it may be good to add heatpad test points out side QFN IC when designing schematic. So you can verify easily if the heatpad conducts well to either ground or Vcc.
Brilliant channel.
Hi , thank you , your support is really appreciated . I'm glad you enjoy the video's . I will be posting more brand new ones when I get some time 👍
Great video & explanations. QFN has always been a bit of a nightmare for me, and your tips will help !
Thanks for the time you put into this
Hi . Thank you for your nice comment . QFN's seem harder than they really are , so I hope the video helps you .
Very nicely done clip. If you allow I would like to point out the importance of solder amount on the grond pad. If you apply too much you may create open connections on the outside. Industrial rework procedures typically remove the residual solder and apply new solder paste by e.g. printing the component with an apropriate stencil. To answer also a below question: how to do it with a regular iron - basically this is not a good idea. Simply because the solder joint(s) cannot be reached with the tip.
You may refer to the entry level Ersa rework station HR 100 for a controlled heating process or all other rework systems if you need to do it professional.
If you need more advice, do not hesitate to contact us.
Hi . Thank you for your comment . I'm always very careful about the amount I put back on centre pad . Sometimes I use solder paste but I realize most people watching this video wont have paste or a stencil at hand .
I never push down on the body ensuring no shorts will occur , and over the years I've got to know how much solder or paste to place on centre pad .
Lots of these devices the excess runs down the via's or if no via's I just put a little less on .
I guess if people want to check they can buzz out each pin to the points I show in the corners of the device.
Thank you again , for your nice comment , you make some good points👍
Thanks sir
Hi , thanks again for watching my videos , very much appreciated. Hopefully you are finding them interesting . I just like to show people what I've learnt over the years so hopefully they can fix their soldering issues. Good luck with all your soldering projects and again thank you for your support👍
Great video, I'm just curious, could you not also probe to another ground solder pad to test? When the chip was off, there was another 2 ground pins (one on the left and the other which you pointed out to the top)
Hi . Yes , you could probe the small test point on the corner to another point as long as it is part of the same plane. I just find it easier using one of the pads connected to the centre pad ( i just pointed out a couple I saw quickly ) .My main focus of showing the points at each corner of the device was to show people they are connected to the pad on the bottom of the device as I know from speaking to a lot of people that they didn't know this little fact. Thank you for your question , it's very much appreciated 👍
Pretty cunning!
Hi , thank you for your comment , much appreciated 👍
Any ideas how to get stuck QFN chip off board easier? Just finally managed to get rid of dead DC stepdown converter in a laptop in QFN-20 package, but it was damn hard. Seems it was soldered with some high melting point ROHS solder plus board has thick copper layer beneath the chip. In end it came off only when I literally broke it in half with soldering iron knife tip from top.
Soldering back the new chip with regular 60/40 solder, Amtech NC-559-V2 flux and hot air was not a problem though.
how to test the QFN for continuity to the center pad was the best tip. could you show the side of the Chip so we could see the spot that you tested to?
Hi , thank you for your comment. The photographs at the end of the video actually show these test points , hope that helps , thanks again 👍
Super
Hi . Thank you , glad you enjoyed the video 👍
Hi there. This has been a very helpful video. Have managed to use the tehniques in this to replace some motor driver and LED drive IC's. I just want to know what flux you are using as the ones that I have don't hold the chips as well as the one that you are using.
thanks a lot for great information, I have a question and i hope you answer it, is(AWV7BA) chip can be replaced with one of those chips (AWV5QB) (AWV5BB) (AWV5JA)?
Hi , thank you for your comment , unfortunately I am not really a design engineer who could work out alternative components to use on circuitry , so I'm not able to give you the answer to your question , sorry.
Nice video. Thanks for sharing your knowledge. Ive recently bought a re work station. I'm an auto electrician who is keen to get into SMD soldering a lot more. This will be helpful. It looks easy to do but I reckon it's a long learning curve????
Hi . Thank you for watching . Soldering does take a bit of practice to get right , the smaller parts need good tools and soldering iron and lots of patience . A great help to people is a thin solder , 0.25mm ( from BLT Circuits ) good tweezers , SMFL 200D flux ( my favourite ) , use all these for any fine pitch stuff , and Ultrasolve cleaning fluid , which I love . The solder I use for larger joints is 0.5mm thick ( I don't like anything bigger ).These give me a good base to do any kind of Soldering. Anyway good luck I hope you stick with it and you will get there , thanks again 👍
Thank you kindly for your tips. 👍
Hi . No problem , glad you found them useful . I will be posting more videos soon ( just been a bit busy lately ) so hopefully you'll watch and enjoy them . Thanks again , much appreciated 👍
Very nice job, I'm looking to replace a QFN on an orange lcd flex, but concerned with how long it took to desoldering this one, but maybe the heat pad on flex will be easier, just don't want to burn the flex.
Thanks
Hi . Boards can vary massively in the time it takes to get some components off , due to the amount of layers , the amount of copper on the layers , ground planes etc so my video time is not going to be the same for everyone. So I can't really comment on your flex cable . I have worked on flex with a rework station and it has taken the heat , but again the standard of flex can vary massively. So best of luck and I hope all goes well 👍
@@mrsolderfix3996 Thanks for the fast reply, have to say enjoying your videos, keep it up 👍
Hi . Thank you , I will be posting more videos when I get some time . I still have lots to show . Thanks again for your support 👍
Hi. Very good video thank you. What microscope are you using
I have hot air and a hot plate, can they be used in combination to help with components like this?
Hi . I personally do not own a hot plate . I know some people put them on about 100 degrees just to warm the underside of the board gently to aid component removal but Ive never really needed to do this so I can't really answer your question 100% correctly. Thank you for your comment.
Great Vid, especially the slow temp warming before hitting with enough to melt and make connections .
I about to try a tiny 1285A reg chip which is only a couple of mm's so pretty small. should i use same tech and temps and time? i worry about overheat insides of chip but have a few spare. Never soldered a chip this small but it makes 3.3 and 5v and about 21 pins and central earth so have to dab solder on that too. Should be fun!!
Hi , I've done many small IC's only 2 to 3mm in size using usual smd temps that I state on a few of my videos ( 350 -370 degrees ). All have worked ok afterwards so you should be fine . Good luck with your projects 👍
@@mrsolderfix3996 My concern is that as its so small and light, a puddle of flux under - will it float and not drop onto solder or should i gently press down as i bring up heat to melt using air? or will squash the solder sideways into others and short it?
Hi , when I use a heat gun to place very small devices i.e a QFN approx 3mm I hold the component in the roughly correct position while heating for a short while . I have the air down very low and what you notice is after a short while you can normally let go of the device and the flux that's there will keep it in position until it eventually starts flowing and then it normally floats by itself into the correct position . I never generally push down onto the component if I can help it as you may cause shorting underneath . You will soon learn when they are correctly done as the floating effect is a very good sign . Hope that helps , good luck 👍
@@mrsolderfix3996 Yes many thanks. I just wasnt sure if the floating in this case would be just from the flux or from the solder melt but i guess it forms a soup together so floating = solder melt and then you are good to go. i have a few spares but i dont want to stress the board area so prefer to get this right first go. Cheap Chinese 5pcs, so will they even work? haha
I can also touch the sides with a very fine tip to be sure of each pin melted and then check for shorts. So damn small but amazing how these things work and after putting 200c on them!!
Hi , I hope you get on ok , take care 👍
Great video & explanations . What type or brand name hot air youre using ? It's Quick 861DW ? :)
Hi . Yes I use a quick station 861DA . The DA varies slightly from the DW in that a couple of the nozzles are slightly angled ( which I prefer ) . It's a great rework station , highly recommend . Thank you for watching , much appreciated 👍
@@mrsolderfix3996 Yes. DA version have higher power and air flow max 200L/m . I have one too , but nozzle hard find than other model . Hard to find 45 degree angle when using under microscope !
Two questions: what liquid flux do you use? I’m struggling to replace a QFN16 that has components all around it. Virtually no room to maneuver or place a stencil for solder paste application. Freehand results in too much solder paste. Any suggestions?
What model microscope your use Sir?
LOL! That looks very much like a Funcube Dongle Pro Plus... I designed that board!
What firmware did you program the new PIC with?
If anyone's wondering the reason why there's a lot of space around this chip, it's because originally I laid it out for a 44 pin version of the same device, but due to board dimension constraints I couldn't route enough GPIOs down to the other end of the board despite it being 6 layer. The solution was to use an I2C GPIO expander at that end of the board, which meant I could use the 28 pin PIC instead
FWIW there's no practical need to have that PIC's thermal pad soldered for either electrical or thermal reasons. It's what the die is mounted on, but it serves no electrical function. But it's good practice to do solder it anyway.
The same isn't true for one of the other QFNs on that side over board, which only exposes its ground connection on the thermal pad, not on any of the pins, so it's essential.
I'm always afraid to over-heat components when I use my hot air station. Apparently ICs like these can take a lot of heat but how high heat can they take and for how long? Are there components that are extra heat sensitive?
Hi , thank you for your comment , much appreciated. I generally use a hot air station at about 370 degrees centigrade , but I have used it hotter , upto 450 degrees and the parts removed were perfectly useable . IC's generally take 370 no problem but there are some that can't .Some parts i.e plastic bodied connectors will melt at a low temperature but others can withstand high heat , it depends on the materials used in the component . Every device will have a datasheet online ( try Farnell or RS Components websites and just type in the search box your component then once up go to datasheet ) this will hopefully help you. 👍
@@mrsolderfix3996 thank you so much, this is great info.
Hi , no problem , hope you get on ok with your projects 👍
Sir, may I ask you where the 1 pin is on the right side of the dot , or the bottom side of the the dot
Hi. With the writing the correct way up on this component , pin 1 is directly to the left of the dot. Hope this helps , thank you.
Thanks you sir for help me ,, thanks you very much to answer me question
Your answer are very helfull thanks you
I subscribe your channel now
No problem . Hope this helped you out.
Biggest problems I'm having while learning is my flux always blows away instantly and I never have any left also the board making a bunch of creaking and cracking noises like separating layers makes me nervous as hell... Seems like my board's always get hot before my components do.. also really have no clue when to use leaded or unleaded solder I'm assuming that leaded always best for removing stubborn components?
I've tried to desolder my old board with qfn chip but i won't come off, any advice? I used 300+ degree celcius with mild airflow for a minute with flux but it still stick to the pcb.
Thanks before
Hi . I don't know what rework station you have but myself I have Quick rework station . I use that on about 350 - 370 degrees and I have the air on about 125. I find upping the air sometimes does the trick . Also like you plenty of flux . I also protect surrounding area with foil tape but maybe you don't need to , I don't know your layout. Hope that helps , good luck , let me know if you get it off ok 👍
@@mrsolderfix3996 I use yihua 858 hot air station and tried from 200-350 even 400 degree 😂 at first I thought because I used cheap knockoff flux that's why it doesn't work.
Now I change my flux but it still stick there lol.
If more air flow used, doesn't it blew the flux away from the chip? 😂 sorry I'm totally new at this
Hi . The flux I use will stay in position really well . I always get this type of component off fairly easily . I just circle around the edge of the component then after a short while I concentrate on heating the middle up ( where the pad is underneath . This will eventually work for you I'm sure . Just takes patience. Good luck 👍
@@mrsolderfix3996 Thank you man, I will try that :)
Hi . Good luck . You will get there , just stick with it 👍 circle the outside joints for approx 20 - 30 seconds this helps to preheat the area of the device , then concentrate on the middle.
Hi, I'm curious, did you just use hot air soldering only? Without hotplate under the PCBs?
Thanks before,,
Hi . For this video I used a hot air rework station only . You don't normally need a hot plate for changing QFN's , they come off pretty easy. Hope that helps , thank you 👍
@@mrsolderfix3996 Thanks for sharing Mr SolderFix. This is truly the state of the art! Can I ask a further question? How many layers of board do you usually work with? I have to replace a small qfn op amp chip on a ten layers board with heavy density of copper. Does the method still work without using hot plate? Thanks again!
Hi . If the board your changing the QFN on is for example 10 layers I would always try without the hot plate first . You soon get to know if it's coming off as per normal . I normally use about 360-380 degrees centigrade or in that area , but if your struggling you could use a hot plate as well set to about 80 to 100 degrees centigrade . This should make it easier and shouldn't damage any other parts . Good luck 👍
@@mrsolderfix3996 got it! thanks for the reply! Much appreciated!
Hi , no problem . Good luck I'm sure you'll change it ok 👍
I can't seem to avoid getting some solder bridges. And the space between the IC and the surrounding components is too narrow for even my conical tip.
Hi . To get rid of solder bridges you must use flux , this is a must and will always help achieve your aim . If you can't get to the joints easily I sometimes remove nearby components , fix the IC properly then refit the removed parts . I also shape my solder tips by filing or bending to get what I need . Thank you , good luck👍
Which camera do u use
Hi . Thank you for your question. I just use my phone camera to film my video's. It's a Google pixel phone and I screw an add on macro lens over the camera lens . Thanks again 👍
@@mrsolderfix3996 thanks sir
Hi . No problem , hope that helped .
Hot to do qfn without hot air? How to do with nornal soldering iron?
Hi . Sorry I don't fully understand your question so I can't really answer this at the moment.
@@mrsolderfix3996 I think he means 'how to do...'
Hi . Your probably right . If so you really need a hot air station for doing these devices as you have to desolder the thermal pad underneath , and you can't do this with a soldering iron.
I've done this by placing a 1.6mm plated hole in the centre of the QFN pad. This allows you to get an iron in to solder the bottom pad. Also extending the pads around the side by 1mm helps soldering. I wouldn't do this if you're planning on having the board properly assembled by manufacturing house though.
What is temperature and air settings
At about 50 seconds in, the stated settings are rework at 360 and hot air at 90 (I assume ºC). The hot air setting seems a bit low to me especially as there's the large ground connection in the middle.
@techrah I do say temperature 360 degrees Celsius , it's the air speed of 90 , I do say that . Maybe you misunderstood how I said it ? Hope that clears this up . Thank you for your comment 👍
@techrah thank you for your comment. I clearly say temperature 360 degrees Celsius , air speed 90 . Maybe you misunderstood this . Hope that clears this up . Thanks again 👍
@@mrsolderfix3996 thanks for the clarification
@@techrah hi , no problem . Certain situations depending on ground plains on the boards I will go up in temperature quite a bit , 425 degrees Celsius for example . The boards and devices do tend to cope really well with this . Aluminium foil tape is what I use to protect surrounding parts , amazing stuff . Don't make the mistake of using Kapton for this purpose, just not as heat tolerant. Thanks again for your time 👍
😁👆