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Forum Index : Microcontroller and PC projects : Killed microprosessor
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plover Guru  Joined: 18/04/2013 Location: AustraliaPosts: 302 |
Slip of concentration cost me a small micro in a gas analyser instrument. Because of poor contacts in USB connector I decided to hard wire a usb cable in place. From old times I always remember that many 14 pin ICs have positive on pin 14, well on this chip this is ground and and pin 1 is positive. I reversed polarity and good bye micro, RIP, and I am sorry. I have a rework station https://www.ebay.com.au/i/272041599002?chn=ps&dispItem=1&var=570854548880 858D desoldering rework station need soic 14 (and 28) pin nozzles Need a nozzle for this size SOIC PIC16(L)F1454/5/9 14-Lead Plastic Small Outline (SL) - Narrow, 3.90 mm Body (SOIC) E1=3.9 mm E=6.00 mm over legs D=8.65 mm length Is there anybody who has found a suitable nozzle to remove this IC? Any hints where to go looking as so far I have not had any success. Any other way to remove the chip without upsetting the tracks?   |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
RIP indeed! I also destroyed an early MicroBridge (PIC1454) for the same reason! That will teach me to look at the pinout first! No need for a nozzle . . . For removing the chip I would use a sharp (modelling) knife and cut the pins at the chip body. This will result in the black plastic part falling away, and all the pins sticking up from each track. Then simply use an iron to remove the pins (not much heat need here), and then use solder wick and liquid flux over each pad to remove any excess solder. This will leave a nice set of clean pads ready to resolver you replacement chip. I have used this technique successfully whenever I need to replace a SMD chip. Hope this helps you out . . . WW For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
Here is a pic with USB lines annotated. Should just add that I am reasonably sure I have identified the chip as the 1455 but no guarantee as it is very hard to read after removing a dab of paint hiding details.  |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9081 |
It's nice to know I am not the only one to let the magic smoke escape.....    Smoke makes things work. When the smoke gets out, it stops! |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
WhiteWizzard Thanks for posting, nice to know I am not the first, my pride have taken a real beating. Some months ago I had identified correctly but last night when I had to do the change, plug just not working properly. The little man on my shoulder was baging away on my head but I ignored that I should have gone to bed and rechecked in the morning. Well look forward and try and look at the situation as a challenge. As I understand you are cutting vertically? Not worried about horizontal force at the top of the "stumps" lifting the track? Enough glu force on the small tracks to cause slight bend? (It is FR4 board I think) So far I hgave not tried proper liquid flux and solder wick has been rather a disaster for me over the years, Seems both proper and fake wick has been disapointing. Perhaps getting some liquid flux and dipping the solder wick might help. |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
Grogster I did not even see the smoke, win 7 just said "remove the usb device it is not working" I knew I was in trouble then. Thanks for sharing though.  I may run into the situation being unable to get a replacement chip(s) in which case I will seriously consider replacing with a chip from micromite stable and write a program in BASIC. What is the smallest chip that is running MMbasic, I have been sitting on the sideline following the Maximite, and only progressed to the MaxiMite Colour kit from the local Jaycar shop. Small amount of tinkering with getting Linux to talk to the box. My thinking is that I will have to go for a 28 pin device would that be fair assumption? |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
That's my usual approach, a smear of Rosin paste on the solder-wick. Makes it really thirsty. I refer to it as Turbo Charged Solderwick. Phil. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9081 |
The smallest chip in terms of pin-count is the 28-pin one, yes. If you mean the smallest physically, then that is still the 28-pin, in the QFN package, but these are a pain to hand-solder. You can get the 28-pin chip in SSOP, SOIC and DIL. SSOP is a good choice if you need it to be physically small, but still easy enough to hand-solder. Smoke makes things work. When the smoke gets out, it stops! |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3167 |
WW's method of cutting the IC's pins with a sharp knife works well but don't let the tip of the knife touch the PCB. The first time I used that technique I also cut the copper tracks under the IC. Geoff Geoff Graham - http://geoffg.net |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
With a very sharp knife, I cut one pin at a time cutting at 45 degrees along where the pins meet the body. This way, only the 'point' of the knife may come into contact with the PCB; but I do try to cut with the knife 'in the air' (i.e. above the PCB). And by using a very sharp knife, then minimal 'pressure' is required to cut the pins resulting in the tracks (even very fine ones) remaining in one piece, and not lifting from the PCB itself. I would advise against using a 'slicing' action to cut the pins as this will probably result in cut tracks too. Seems like your bigger issue is how to 'replace' with a suitable 'working' part. Do let us know how you get on . . . For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 8604 |
I don't understand the question. I assume you have one of the small circular nozzles? Just set the temperature to around 350 and play the heat round and round the chip following the line of the pins. There is plenty of thermal capacity to get all the solder liquid at the same time and once it is push the chip off the pads and remove it with tweezers. Use desoldering braid to clean up the pads and replace the chip with new. I've used this technique to move 144-pin chips from one PCB to another without damaging the chip or the PCB so a 28-pin is trivial. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
How big is the entire board? Thee photo looks like there may not be a lot out of frame. Just wondering if an entire reconstruction is an option. New board etc. Phil. |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
WhiteWizzard / Geoffg Thanks very good points I have a clear picture now and will try to cut at less than 45 deg to horizontal so that cutting into the chip itself. Might also get some retired commercial boards and experiment first. matherp Your way I have tried some time ago on faulty commercial boards from routers, it worked but the chip did not survive, most likely because of too big a heat gun at the time. I am not keen on this method as it allows big and fast moving heat gradient towards the chip centre. I expect this will cause micro cracking between plastic and the metal pins thus breaking the hermetic seal allowing moisture ingress. I am old school from late last century and warned about this in the days of through hole chips. The chip at the moment works in over 90% humidity, estimated from the fact moisture/dew can be wiped off the usb plug, which corrodes over 3 months period, roughly Here is an example of what I am looking for: http://www.madelltech.com/nozzles-tips.html You can imagine how quick this would work with a little bit of experience. The air "knife cutting" is two parallel streams of hot air very precisely aimed on the legs/pads thus minimising size temp gradient. Problem finding the correct one and I am not quite convinced what style of "SOIC" I have either. On dense boards you avoid too much effect on nearby components. Phil23 Reconstruction/reverse engineering would be simple but take some time. I am considering this because of humidity problem with existing construction but time is short. The board itself is about twice what I have not shown, 3 small LEDs a few extra resistors a capacitor and trimmer (don't know what that is for) from engineering point simple construction. I think it uses just one analog input. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9081 |
You could always use my favourite - ChipQuik low-melting-point solder for rework. This is not exactly cheap stuff, but you only use a tiny amount each time. This allows you to very cleanly and easily remove a chip, and at low temperature - I usually use about 300'C. Running this carefully(so as not to use too much!) around all the pins, and then keeping them hot like matherp was saying he does, and the chip is very easy to remove, as this stuff stays liquid MUCH longer then standard solder does. An option for you to consider anyway. Many people are put off this stuff cos it is expensive, but it works. Smoke makes things work. When the smoke gets out, it stops! |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
If a chip is fried, then cutting it out causes the least amount of potential heat damage to the PCB. Howeve, if you need to 'save' the chip that is being removed then the Grogster/matherp method is the perfect solution. If I am needing to 'save' the chip then it is likely that the board is damaged (otherwise why remove the chip in the first place?). On these occasions I personally use a low cost heat gun (i.e. a gas soldering iron with a 'heat vent' attachment) and melt the solder knowing that I do not need to preserve the PCB (as it would already be damaged in some way). The exception to this is when I have realised I have soldered a chip in the incorrect orientation  then I need to preserve both ideally. I am yet to try Grogster's method so perhaps I should order some of that 'expensive magic' . . . For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
When replacing a dip I just use small, precision sidecutters. Keep the flat side up against the DIP plastic and clip each pin separately and cleanly without twisting the pin. It's dead easy then to remove each pin from the board by using the soldering iron while pulling the clipped off pin gently with tweezers or such. Greg |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
This might sound agricultural, but from the bush... While I haven't cut IC pins with a sharp knife, I have removed a couple of 16 pin DIL chips easily by first cutting the legs with a very fine Dremel cutting wheel, then just de-soldering the remaining legs. Phil. |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
I have had a look at a couple of videos regarding the ChipQuick. Interesting will keep it in mind for experiment a little later as this time I will probably just cut or snip followed by cleanup. Have to figure out why I seem to have a problem with solderwick assisted by flux. Perhaps it was my home made flux, a rosin mixture where I may have used the wrong solvent. So long ago that I have forgotten what solvent but I believe it must have been Isopropyl. One way of finding out repeat a batch and see. I am waiting on the manufacturer of the gas analyser to see if they will accept my request for new chips. |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
My request for a replacement pre-programmed PIC16F1455 is pending. While waiting I have taken the unit apart again and tracing out the details. Physically it is very simple, the value in the instrument is in the program it is running not in the harware. I also gut out my Mup ver2 and looked at how I can make this run. Turns out I was clever enough to get a couple of bigmik's USB-serial boards, I almost over looked them they are so small. I have missed out on a socket I think so in spare moment I will have to dig in my parts for suitable one ....... erh I just looked in the box with parts that came with a couple of orders and what do I see, two six pin sockets. So I may be in business over the weekend. During rainy periods today I happened to look at the Mup ver3 and realised this uses the PIC16F1455, that looked familiar and the penny dropped that this is the same chip as the my Gas analyser uses. Followed some leads and links http://www.thebackshed.com/forum/forum_posts.asp?TID=8903&PN=1&TPN=1 I think this took me in various directions about PIC programming. Not sure if I have got it right yet but my understanding is that the USB host computer/terminal can be used to flash via ICSP connection if suitable file is to hand. What I don't understand at the moment, is it possible to read the program installed in the PIC16F1455, when you have only USB access. How can one read/download the program (in hex format?) for inspection with a hex editor? |
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| plover Guru Joined: 18/04/2013 Location: AustraliaPosts: 302 |
I have added the socket to BigMik's USB-serial board and also assembled his Mup-Test board ready to go. As I use linux and plugged in the the USB-serial board, then checked the lsusb in a terminal I do not see a new device. That is a problem, I don't think linux is picking it up. The board uses the FT231XS This is a bit unusual. Anyone any suggestion? Connecting the board to the Mup-ver2 I get the red and green light showing. That is the only testing I done so far. Next step I am going to power up a laptop with Win 7 and see what happens. Well I connected to a Win 7, looked in device manager, no sign of a new device, no response at all, connecting and rescanning for new devices, no activity. (Tested to Mup-TTL boards as I had two) Perhaps my cable, will see if I can manage an ohms check, have a USB breakout box making this reasonably easy if I can hit the right pin on the Mup-TTL. I should have power because the Muv-ver2 powered up the LEDs. Just looking at the Micro USB connector it has 5 pins? Looks like I need to go back to the schematic and look just in case and to figure which ones ar D+/D- Deep scrounge in the cable department turned up a couple more cables. Tested 3 and they all worked, looks like I have a brummy cable. copy from dmesg [ 0.000000] usb 7-1: new full-speed USB device number 48 using uhci_hcd [ 0.000000] usb 7-1: New USB device found, idVendor=0403, idProduct=6015 [ 0.000000] usb 7-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [ 0.000000] usb 7-1: Product: FT231X USB UART [ 0.000000] usb 7-1: Manufacturer: FTDI [ 0.000000] usb 7-1: SerialNumber: DA01IIIT [ 0.000000] usb 7-1: Detected FT-X [ 0.000000] usb 7-1: FTDI USB Serial Device converter now attached to ttyUSB0 [gert@kde64byTexstar ~]$ lsusb Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 007 Device 049: ID 0403:6015 Future Technology Devices International, Ltd Bridge(I2C/SPI/UART/FIFO) Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 006 Device 002: ID 192f:0416 Avago Technologies, Pte. ADNS-5700 Optical Mouse Controller (3-button) Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 002: ID 046d:0a29 Logitech, Inc. H600 [Wireless Headset] Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub [gert@kde64byTexstar ~]$ Ok, next step check out the Mup-Test board |
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