HDD GURU FORUMS

Desoldering NAND memories: Which is better Higher temprature shorter duration, or lower temprature longer duration ?

I have read a lot of articles as to what the optimum temprature for NAND memory chip hot-air desoldering is. But, when it come to practical experience, it is a little confusing. I have desoldered quite a number of memory chips at tempratures, both in the lower and upper ends of the recommended range.

It is easy to desolder at the upper end, at about 365 Degree Centigrade; it takes about a minute to get the memory out. But it is a little worrying as one sees the little components nearby smoking.

At the lower end, at about 230 Degree Centigared, it takes quite a long time, sometimes about four or five minutes; it sometimes make me wonder if te temprature is high enough to ever take the memory out.

Can you forumers share your experience about the optimum temprature that you use, and the time duration that is required to get the memory out, with the best quality of data in mind ?

I haven't unsoldered NANDs but have unsoldered computer GPUs (graphics processor units) which are attached by BGA (ball grid array) connections. To prevent damaging the GPU, one has to pre-heat the circuit board until it is at about 180C, then apply heat to the GPU following a profile that doesn't increase temps at too fast a rate (3C/sec. maximum) until the circuit board temp is around 225-230C., at which point the solder will have liquified and the GPU can normally be lifted. Lead-free solder melts at 217C.

The NAND and circuit board have much lower mass, so it should heat up very quickly. I would suggest following the same IPC profile that is recommended for re-flowing BGA ICs. Keep the heat focused on the circuit board rather then the NAND to minimize stress, and don't go over 240C or it is probably game over for the NAND, if it's anything like most BGA ICs.

Be careful with newest TLC high-cap chips they are very sensitive to temperature.
Hot Air gun doesn't work anymore (as many recommend), because overheating chips and corrupt them forever (uncorrectable bit errors).
BGA rework station for BGA chips, soldering iron and needle-like tool for TSOP chips.

Larry and Sasha have right. Best option is use profile to desolder NAND, especially BGA NAND chips.

Sasha Sheremetov wrote:Be careful with newest TLC high-cap chips they are very sensitive to temperature.
Hot Air gun doesn't work anymore (as many recommend), because overheating chips and corrupt them forever (uncorrectable bit errors).
BGA rework station for BGA chips, soldering iron and needle-like tool for TSOP chips.

Sasha Sheremetov,

I fail to imagine how a soldering Iron can be used (distribute heat to all pins uniformly) to desolder TSOP chips. Please explain this. And, what is needle-like tool ?

Thanks

Matiw wrote:

Sasha Sheremetov wrote:Be careful with newest TLC high-cap chips they are very sensitive to temperature.
Hot Air gun doesn't work anymore (as many recommend), because overheating chips and corrupt them forever (uncorrectable bit errors).
BGA rework station for BGA chips, soldering iron and needle-like tool for TSOP chips.

Sasha Sheremetov,

I fail to imagine how a soldering Iron can be used (distribute heat to all pins uniformly) to desolder TSOP chips. Please explain this. And, what is needle-like tool ?

Thanks

You can do it by adding some more solder. After that you can put the thin tip sideways and go from side to side.. because there is more solder, the solder stays molten longer. If you are gently keeping outwards pressure on the chip by some method, the chip does come loose fairly easily. Takes some practice but does work fine.

(with visible pins), no one using Flux - Lowmelt Solder - Vacuum pen?

There are also tips for the hot air station that break the air out into 2 thin lines each side to blow on the pins only. I don't use them though, a little awkward. quite a few different ways, such as Kerns also.

Thank you Haque. I are more comfortable with your last suggestion, the one with the split-nozzle that directly targets the Pins, and only the pins.

I have made some experiment, on an 8 GB BGA NAND chip, to see if directly heating the chip with a hot-air gun from the top damages the data. with a temperature setting of 230 centigrade, it took about five minutes to get the chip out. The chip was identified and read without any problem; but no further. PC3000 could not identify the ECC the XOR, the Interleaves althoughter.

HaQue wrote:There are also tips for the hot air station that break the air out into 2 thin lines each side to blow on the pins only. I don't use them though, a little awkward. quite a few different ways, such as Kerns also.

I've been getting a lot of jobs that pc3000 can't do
It may be the XOR and ecc is not worked out yet and even could be dynamic cor or something
What does the data look like in a hex editor or in a bitmap

Here are sector 0, sector 2, sector 67798:


Sector 0

0: A8 F0 FE FF FF FB F4 F7 - F7 ED 4F 8E 2E F4 9C EF ¿..  ....φOÄ..£.
10: C0 77 FA FF FA 85 FA 8F - FA E6 F4 00 FE 2F FE 2C .w· ·à·Å·µ.../.,
20: FE 4C FE FF FF FC FF 3F - EF DF FE F0 FF 40 E0 DC .L.  ⁿ ?.... @α.
30: B9 D4 FA 8C FA 8D FF 00 - FF BF F5 DB FF 3F EF FF ..·î·ì . ... ?. 
40: 89 47 4C 9E C6 EE 47 7F - 00 FF FE FF FF 3F EE C7 ëGL..εG.. .  ?ε.
50: 89 5F 4D 9C C5 D4 47 76 - C4 DC F7 FF 25 DE 80 A5 ë_M£..Gv... %.ÇÑ
60: 89 47 4C 9E C6 D6 47 7F - 00 FF FF FF F5 0B EE C7 ëGL...G..   ..ε.
70: 89 5F 4E 9E C6 D4 47 7F - C4 DC D7 FF C9 DE 80 A5 ë_N...G.... ..ÇÑ
80: 7F EF EE 7E 7A 8F EF FF - 03 EE FF FF 00 00 00 00 ..ε~zÅ. .ε  ....
90: FF CF FF 1F FA 8F FF FF - 91 EF FF FF 00 00 00 00  . .·Å  æ.  ....
A0: FF EF EF FF FF FF CA FF - 03 EA FF FF 9F 2F FF 9F  ..   . .Ω  ƒ/ ƒ
B0: FF 8F FF FF D3 DF FF FF - FF FF FA 8A 00 00 00 00  Å  ..    ·è....
C0: 00 00 00 00 00 00 00 00 - FF FF FA 8B 00 00 00 00 ........  ·ï....
D0: FA 85 00 00 00 00 00 00 - FF FF FA 88 FF FF FA 89 ·à......  ·ê  ·ë
E0: 00 00 00 AC B4 A6 B2 BA - BB B6 FF FF FF FF 7F 85 ...¼.ª....    .à
F0: A8 FE 38 E7 D7 5B 32 A8 - 9D BC 1C 0C F2 00 00 00 ¿.8τ.[2¿¥.......
100: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
110: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
120: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
130: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
140: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
150: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
160: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
170: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
180: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
190: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1A0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1B0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1C0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1D0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1E0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
1F0: 00 00 00 00 00 00 00 00 - 00 .........






Sector 2

400: FE 03 00 00 7F 7F 2B 08 - B0 A0 2B C8 C5 5B 67 AF ......+..á+..[g»
410: 23 C7 D8 94 35 B4 17 7C - 6B AB A7 43 71 68 C4 C8 #..ö5..|k½ºCqh..
420: E0 82 53 BA 3F CB 70 71 - 71 CD 4E 6E 46 FE F1 55 αéS.?.pqq.NnF.±U
430: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
440: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
450: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
460: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
470: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
480: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
490: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4A0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4B0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4C0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4D0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4E0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
4F0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
500: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
510: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
520: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
530: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
540: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
550: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
560: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
570: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
580: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
590: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5A0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5B0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5C0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5D0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5E0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 
5F0: FF FF FF FF FF FF FF FF - FF FF FF FF FF FF FF FF                 




Sector 67798

211AC00: 94 F6 B9 90 95 8B 2E B1 - 61 6D 67 F9 FA BE 7A 69 ö÷.Éòï..amg.·.zi
211AC10: BE 93 09 46 90 6E 8B D1 - 53 D6 7A 65 02 09 F5 46 .ô.FÉnï.S.ze...F
211AC20: 90 91 8B D1 53 8B 79 6C - 9A 0B FF F2 AB 65 78 8B Éæï.SïylÜ. .½exï
211AC30: BE 93 69 67 6E 92 9A 91 - 74 07 F5 8B 9E 43 65 6E .ôignÆÜæt..ï.Cen
211AC40: 8B 9A 8D 9A 9B F4 54 8D - 9E 6E 8C 8F 9E 8D 9A 91 ïÜìÜ¢.Tì.nîÅ.ìÜæ
211AC50: 8B 09 F7 92 6D 48 65 96 - 67 97 8B 03 F1 0E F9 92 ï..ÆmHeûgùï.±..Æ
211AC60: 6D B3 9A 66 8B FC 2C 69 - FA 92 6D 54 6F 8F FC CB m.Üfïⁿ,i·ÆmToÅⁿ.
211AC70: F9 F8 92 92 57 69 9B 74 - 68 03 F6 FB 08 BD 9E 91 .°ÆÆWi¢th.÷....æ
211AC80: 9B 54 79 70 9A FD 04 00 - FF 09 54 8F 8F BB BD 54 ¢Typܲ.. .TÅÅ..T
211AC90: E5 78 8B F6 70 70 BB BD - AB 9A 78 74 33 08 55 8C σxï÷pp..½Üxt3.Uî
211ACA0: 65 8D 4E 61 92 9A F9 F7 - 44 BD AB 65 87 74 31 30 eìNaÆÜ..D.½eçt10
211ACB0: 09 44 9E 74 9E B9 96 65 - 93 64 F9 F4 BC C3 BC A0 .D.t..ûeôd.....á
211ACC0: CE 44 B0 43 7B C9 7D 0C - 44 61 74 61 AF 96 70 65 .D.C{.}.Data»ûpe
211ACD0: 6C 96 6F 75 07 2F 52 42 - B9 6F 8D 92 39 D1 54 41 lûou./RB.oìÆ9.TA
211ACE0: AC B9 96 93 65 F3 B9 90 - 6E 8B 2E BC 68 61 8D 8C ¼.ûôe..Énï..haìî
211ACF0: 9A 74 F8 0F BB 45 B9 BE - AA B3 54 5F 43 B7 41 AD Üt°..E..¬.T_C.A¡
211AD00: AC 45 AB F5 46 6F 91 74 - 6E BC 6F 93 90 72 07 F8 ¼E½.Foætn.oôÉr.°
211AD10: 63 6C 42 93 9E 63 6B 09 - 46 6F 6E 75 D1 B1 61 92 clBô.ck.Fonu..aÆ
211AD20: 65 06 05 41 8D 79 9E 93 - F6 B9 6F 6E 8B D1 D3 69 e..Aìy.ô÷.onï..i
211AD30: 85 65 FD 09 0A B9 90 91 - 74 2E 53 8B 86 6C 9A F4 àe²...Éæt.SïålÜ.
211AD40: 00 F2 54 65 87 8F BE 93 - 69 98 91 92 65 91 8B F8 ..TeçÅ.ôiÿæÆeæï°
211AD50: 50 74 61 AD 96 67 97 74 - B5 75 8C 8B 96 99 69 65 Pta¡ûgùt.uîïûÖie
211AD60: 9B F4 54 8D 61 91 8C 8F - 61 8D 9A 6E 74 F6 10 BB ¢.TìaæîÅaìÜnt÷..
211AD70: 9E 74 9E AF 6B 70 9A 93 - 96 6E 65 4E 9E 6D 65 06 .t.»kpÜôûneN.me.
211AD80: 0F AB 41 AC B9 69 6C 65 - 08 92 92 B7 9A 69 98 68 .½A¼.ile.ÆÆ.Üiÿh
211AD90: 8B FC F1 F1 F9 6D 6D B3 - 65 99 74 FC 1C 71 05 92 ïⁿ±±.mm.eÖtⁿ.q.Æ
211ADA0: 92 54 90 8F 03 CB 06 07 - 6D 92 57 96 9B 74 68 FC ÆTÉÅ....mÆWû¢thⁿ
211ADB0: C0 2F F7 BD 61 6E 64 AB - 86 70 65 02 04 80 00 F6 ./..and½åpe..Ç.÷
211ADC0: 54 70 70 44 42 54 65 87 - 8B F5 8F 8F BB BD 54 65 TppDBTeçï.ÅÅ..Te
211ADD0: 87 74 CE CE F7 AA 73 9A - 8D 6E 61 6D 65 06 F7 BB çt...¬sÜìname...
211ADE0: 42 54 9A 78 8B 31 32 F6 - BB 9E 8B 61 46 96 65 6C BTÜxï12÷..ïaFûel
211ADF0: 64 06 F7 89 43 72 9A 84 - CE CB 7D F3 44 9E 74 d..ëCrÜä..}.D.t

HaQue wrote:I've been getting a lot of jobs that pc3000 can't do
It may be the XOR and ecc is not worked out yet and even could be dynamic cor or something
What does the data look like in a hex editor or in a bitmap

Hi,
well, sector 0 if you invert it (paste into winhex, then choose Edit--Modify Data --then invert bits)

you get:


and some of the SK controllers are a real pain

Hi Haque,

If I read the result correctly, I think that the result of the inversion (SKYMED) indicate that there is a high probablity for the existance of Inversion, and the absence of XOR. I do not what else is visible for the trained eye like yours.

Your further input is highly appreciated.

HaQue wrote:Hi,
well, sector 0 if you invert it (paste into winhex, then choose Edit--Modify Data --then invert bits)

you get:

matiw.jpg

and some of the SK controllers are a real pain

looking at Flash dumps by alone sectors isn't easy. Often there is inversion and XOR, or the SA will be not XOR and rest will, or SA will have different ECC... and an combination you can think of.

But in this case, looks like no XOR, as in the sector 67798 you can see 2 English words "parent" and "Band".

Is it SK6211, SK 6221 or SK6226? Sometimes these have weird structures for SA

It is SK6213.

HaQue wrote:looking at Flash dumps by alone sectors isn't easy. Often there is inversion and XOR, or the SA will be not XOR and rest will, or SA will have different ECC... and an combination you can think of.

But in this case, looks like no XOR, as in the sector 67798 you can see 2 English words "parent" and "Band".

Is it SK6211, SK 6221 or SK6226? Sometimes these have weird structures for SA

since the chips are much smaller i dont think as much heat is required for removal of them

There is a few considerations: BGA, LGA, TSOP, need to resolder or not, type of NAND etc. all should be weighed up and best method used with each.

I haven't used infrared, anyone care to comment on how these shape up?

I have used hot air, quartz ir and ceramic dark ir and i will have to say that i definitely prefer IR plus its way newer technology

If you were looking at any machines, let me know which

xboxhaxorz wrote:I have used hot air, quartz ir and ceramic dark ir and i will have to say that i definitely prefer IR plus its way newer technology

If you were looking at any machines, let me know which

What IR machine do you use or recommend?

It depends on budget of course, but if you can this is made in USA http://thebgareworkmachine.com

Otherwise the ACHI IR PRO SC is affordable and popular however there is quite a few complaints on the quality being as its made in China