Reballing Skyworks SKY77541 problem - GSM-Forum

wz3k · 03-10-2013, 15:59

Today I have an iPhone 4 with "Searching" and "No Service" problem. I bought it cheap. Checked the antenna path all seems to work fine, replace the antenna, clean the metal contacts still no success. I even changed the main board into another housing still no success.

I found the instruction below in this forum. First try, I reheat the two ICs with 285 C, for slightly over one minute each. Success!! but it lasted only like 5 minutes. In this 5 minutes, it found signal, 3G and 2G, can make calls and everything. But then it went back to "Searching" and "No Service"
iphone4_No_servicebmp.jpg

So, I decided I want to reball the SKY77541. Then I hit this problem.. I was using 180C to preheat, then 300C, airflow setting 4, to unsolder the IC. Probably while I was lifting it, the small capacitors and resistors got pushed away.. I managed to resolder the IC back but now some of the small components are gone: C37_RF, C42_RF, C114_RF, C60_RF, R_35_RF, C63_RF, L9_RF, C165_RF,L5_RF.
draw_0310_1.jpg

My questions:
1. What can I do now? Can I just jump some of the components?
2. Was I using the right temperature and airflow setting? Too much? Too little?
3. How to ensure in the future I don't mess with the components around an IC while unsoldering with hot air gun?

I'm a newbie technician trying to learn. Please give me some pointers.. Thank you..

cal_guy · 03-11-2013, 04:41

Is it still turning on????

Important parts you should either replace or jumper them:
R_35_RF, L9_RF

wz3k · 03-11-2013, 09:16

Thanks for the reply. I have not tried to turn it on yet. Will do later and update.

ribsoft · 03-11-2013, 23:10

iff u reballing the SKY77541 dont use more than 240c, u burn insides of ic.

wz3k · 03-12-2013, 04:00

thanks. perhaps I have indeed burn the ic inside.. now the iPhone can still be on, but it is stuck at Connect to iTunes logo. Will try to replace it with another IC from another broken motherboard..

what about desoldering temperature? Can 240c desolder the IC from motherboard?

Quote:

Originally Posted by ribsoft

iff u reballing the SKY77541 dont use more than 240c, u burn insides of ic.

03-10-2013, 15:59	#1 (permalink)
wz3k Junior Member Join Date: Feb 2013 Posts: 19 Member: 1891566 Status: Offline Thanks Meter: 1	Reballing Skyworks SKY77541 problem Today I have an iPhone 4 with "Searching" and "No Service" problem. I bought it cheap. Checked the antenna path all seems to work fine, replace the antenna, clean the metal contacts still no success. I even changed the main board into another housing still no success. I found the instruction below in this forum. First try, I reheat the two ICs with 285 C, for slightly over one minute each. Success!! but it lasted only like 5 minutes. In this 5 minutes, it found signal, 3G and 2G, can make calls and everything. But then it went back to "Searching" and "No Service" iphone4_No_servicebmp.jpg So, I decided I want to reball the SKY77541. Then I hit this problem.. I was using 180C to preheat, then 300C, airflow setting 4, to unsolder the IC. Probably while I was lifting it, the small capacitors and resistors got pushed away.. I managed to resolder the IC back but now some of the small components are gone: C37_RF, C42_RF, C114_RF, C60_RF, R_35_RF, C63_RF, L9_RF, C165_RF,L5_RF. draw_0310_1.jpg My questions: 1. What can I do now? Can I just jump some of the components? 2. Was I using the right temperature and airflow setting? Too much? Too little? 3. How to ensure in the future I don't mess with the components around an IC while unsoldering with hot air gun? I'm a newbie technician trying to learn. Please give me some pointers.. Thank you..

03-11-2013, 04:41	#2 (permalink)
cal_guy No Life Poster Join Date: Oct 2010 Location: Toronto, Canada Posts: 948 Member: 1430995 Status: Offline Sonork: 100.1613203 Thanks Meter: 312	Is it still turning on???? Important parts you should either replace or jumper them: R_35_RF, L9_RF

03-11-2013, 09:16	#3 (permalink)
wz3k Junior Member Join Date: Feb 2013 Posts: 19 Member: 1891566 Status: Offline Thanks Meter: 1	Thanks for the reply. I have not tried to turn it on yet. Will do later and update.

03-11-2013, 23:10	#4 (permalink)
ribsoft Junior Member Join Date: Jan 2012 Location: The Netherlands Age: 49 Posts: 14 Member: 1716821 Status: Offline Thanks Meter: 4	iff u reballing the SKY77541 dont use more than 240c, u burn insides of ic.