Post by: repairman52 on September 02, 2009, 10:44:00 PM
[/color]Reliable solder joints
High quality, low defect soldering requires identifying and repeating the optimum reflow process: every solder joint on every board needs to be treated in exactly the same way. How the heat is applied does not matter as long as it is in a controlled manner. Heating and cooling ramp rates must be compatible with both solder paste and the assembly, and the time of exposure to high temperatures must be defined and maintained. Suppliers of solder paste will recommend different process conditions for their products to obtain optimum performance, particularly with low residue pastes.
The aim is to raise the temperature of the board and component terminations sufficiently far above the reflow temperature of the solder paste for the right length of time to create reliable solder joints. The process has to be hot enough to enable the solder to wet the board and components yet
cool enough not to damage the items being soldered and have
a controlled cooling phase to ensure the joints are sound.
If the reflow temperature of a paste is not achieved, the paste will not become a liquid; if the paste is not at reflow temperature for a sufficient time, full wetting will not take place.
We also need to ensure that both component and board reach the reflow temperature at almost the same time in order to get satisfactory joints.
The temperature profile
As an assembly moves through a soldering system, it is exposed to a controlled rise and fall in temperature. A plot of temperature against time is called a temperature profile.
Double-sided reflow
The key issues with double-sided reflow are that:
The first side is reflowed twice, which ages the joints. That is, the joints are moving towards the point where they may start dewetting
Components on the underside during the second reflow operation are supported only by the surface tension of the solder and are vulnerable to any form of mechanical disturbance, especially where parts are heavy in relation to their pad size/solder volume
During the second reflow, the previously wetted joints are being reflowed without the benefit of any protective flux. Oxidation reduces the surface tension of the solder, and hence reduces the uplift on the components
Microsoft recommends that its ICs and PCBs be reflowed or reworked to a maximum of 3 three times.
If after reflowing 3 times, the problem is not resloved then reballing is the only solution.
Read and reread all of this and then since you people like the internet some much look up how to rework BGA's maybe then you will get the picture. MS is reballing most of the boards not reflowing. It takes expensive machines to do this work with X-ray monitors to aligne the CPU's and GPU's to the board. So do your self a favor and leave the heat gun where it belongs in the tool box collecting dust. SEND IT IN FOR A REAL REPAIR! BY A SHOP THAT HAS THE RIGHT EQUIPMENT!
Post by: repairman52 on September 03, 2009, 12:06:00 AM
Post by: gepal on September 03, 2009, 12:32:00 AM
Cheers to gears.
Post by: MadMaxGR on September 03, 2009, 02:46:00 AM
Post by: repairman52 on September 03, 2009, 11:41:00 AM
QUOTE(MadMaxGR @ Sep 3 2009, 04:46 AM) 
Such posts from people who are new in the forum are taken with a bit of salt. Don't try to compromise the work of many people from here. The methods that are proposed here, are for sure not permanent, but either BGA reflow is 100% permanent either. The only difference is that the reflow methods cost peanuts compared to BGA rework stations and personally, xboxs that I fixed with a method similar to Llama's tutorial and upgrating their cooling functionality, still work!!!, some are even 1+ year old fix and the users play daily!. The point is... don't come in this forum just to tell us "quit telling people that putting heat to the board will fix it" and name as like "so called repair experts". Please next time stop being critical and respect the help that very experienced people provide thru this forum and especially for FREE OF CHARGE! That means, if you believe it will work, do it at your own risk! Nobody pushed you to do anything!
Excuse me for sounding like I know it all. Maybe it will help maybe it won't ,Yet read some data about BGA's.
If MS had placed underfill under the chips it mite have had a chance. I underfill all the boards I rework. I have had no more RROD's. Link to read:http://ap.pennnet.com/display_article/129179/36/ARTCL/none/none/1/BGA-underfills/ and read link for test results:http://ap.pennnet.com/Articles/Article_Display.cfm?Section=Articles&Subsection=Display&ARTICLE_ID=220942. One other tidbit of info for you Reflow
In order to achieve complete reflow of all BGA interconnections, the proper thermal profile must be developed. The profile for rework should be similar to any profile used in the assembly process. It should adhere to the requirements of the solder paste during the initial preheat, soak, and reflow portions of the profile. It is important to ensure that the center of the BGA component reaches the liquid temperature of the alloy used, and is above this temperature for the required length of time. This will ensure the complete reflow of all the BGA interconnections So any way stick to adding fans keep your unit clean and stand it up it helps disapate heat though the sides of the unit. And to what I said before MS screwed up and made junk in the begining all the 203 watt units are junk and will fail sooner or later.Don,t Buy one if you do have one use it untill it breaks then throw it away.get it out of cycle. MS is still send them back out. The sooner we get these out of their hands the better. Q: How many times does an Xbox 360 unit have to be sent in and repaired before they will replace it with a completely new unit?
That's not how it works. You send in a broken box, you get back a working box (hopefully). So there is a rotating stock of the original units that get repaired and returned to service. Plus, they keep finding these cashes of launch units here and there and using them too. Didn't you hear during the holidays that bundles were found with units made in 06? Those were pulled back from the retail channel last spring when the new heatsink was done, and had the new heatsink placed on them and then put into the shipping flow like any other box.
Back to the rotating inventory of launch units. You risk getting one of those back until the last one is out of the system. I imagine the next big outrage will be when some of the folks who waited till Falcon to buy a console for reliability reasons, and has to send it in for service, gets a Xenon back! Even when all of the Xenons are gone, you will likely get a newer gen repaired one back rather than new. Unless the fail rate gets so low there are none available. I'm holding my breath... Well I am sorry if I pissed in your coffee. Go do some follow up what has been posted . And no I am not a know it all I learn every day on these units.
Post by: MadMaxGR on September 03, 2009, 12:06:00 PM