Strange WiFi problem on iPhone 3G after 3.0 update

Hi SimpleServe,

I did it and it worked!

Some hints from my side for those still thinking about doing the same:

A normal oven has a hysteresis. So I first monitored the behaviour of my oven (a circulating air oven) by measuring the temperature with a NiCr-Ni type K thermoelement. In my case this was +/- 10°C! When setting to 196°C the temperature was between 186 and 206. This was in my opinion too much. So I regulated the temperature by hand: when it drops to 194°C I turned the knob of the oven to max which started heating. As soon as the temperature reached 197°C I turned the temperature knob to minimum which stopped heating. By doing so I could easily maintain the temperature between 193 and 199°C (to support a rather stable temperature I put some iron stuff - a heavy pan and baking sheets - into the oven to increase the mass).
After putting the pcb into the oven, it tooks about 30s to reach the temperature of 196° again. From that moment the pcb baked 7'. After this I opened the door of the oven and let it cool down to nearly room temperature (took a bit more than 30').

After reassembling and switching on everything was like after the phone was switched off except date and time which had to be set again AND: WiFi worked again! :-))

Will see, how long the WiFi will work ...

hi, I tested the heat gun.... with no success, I will try the oven again, at higher temp... will see ;o)

Awesome, I'm glad you got your wifi back! And thanks for the detailed information. I posted a link in the YouTube video to your post. It's good information that will benefit anyone thinking of trying this.

ndj noumea, will this be the second time in the oven for that particular PCB or are you trying it out on one of your others?

Hi Simple Serve,
This is the same card, I put the oven at 225 during 30 minutes, then "baked" the card at a little more than 200°C for 7/8 minutes, then wait 1 hour with the oven "off" and re-installed the card in the iphone. the grey wifi had disappear and was replaced by "unactive", I active it and found my wifi network, but impossible to join it. I reset the network datas and switch it on.... but again "grey wifi"
One good news, it seems to work, one bad news we need to continue on same way. I will try next time at 225°C and will keep you advised. Anyway thanks for this "possible" way, we were waiting for a long and this is not Apple who helped us (sorry for my english, I am just a little French living in the South Pacific

Your English is great. 225C will be the highest temperature I've seen so far. According to this article http://www.rayprasad.com/home/rp1/page70/smt_-_lead-free_reflow_profile_development_part1.html the peak temperature should be no more than 230-245C, but only for 30 to 60 seconds. So if I baked that high I would shorten the time way down from 7 minutes.

The article also says rapid cooling times are preferred for higher fatigue resistance (solder fatigue is probably the root of our wifi problems). I think you need to leave PCB on the rack during cool down so you don't move the solder when it's molten. But maybe it would be an advantage to blow a light fan into the oven to hasten cooling. However, I don't have expertise in the subject.

Definitely, 225 is too warm, iphone is stuck on Apple logo and when I try to restore via DFU I have an error 1600.
But with the previous optimist result I will try on another card and will keep you advised.
Cross our fingers we are close to victory on this f...... wifi.

Which means using an accurate thermometer and enforcing baking temperature consistency as paraglider was talking about is key. (at least in terms of an amateur hack fix, the professionals who reflow in factories would probably be distraught if they found out what we're doing, LOL).

It would certainly be nice to have a recipe that offered a reasonable rate of success. In addition, it would be nice to implement an improvement on fatigue resistance through rapid cooling (but without moving the board after bake). Maybe a fan directed into the oven during the rack cool. However, there is supposed to be an optimal cooling profile, just wish I knew what that was and how to make it happen WITHOUT moving the board after bake so the solder doesn't run.

Thanks for the feedback, ndj noumea

In professional reflow ovens there are cooling zones (the systems I know use fans) to achieve a certain cooling gradient. The pcb are moved all the time though the movement of course is smooth.
As soon as the solder solidifies after soldering - which means only a few degree less temperature - vibrations are not that critical anymore.
To optimize the temperature profile the used solder should be known and perhaps the presence of critical components. In my case the foil on the top side (according to Simple Serve's video) after baking was a bit bumpy (could be reattached easily by pressing to the pcb again). So I assume during manufacturing process it has been applied after soldering.

Any opinions on using a regular vs an airflow oven? And most modern ovens have a cooldown system using a built in fan.. maybe it's better to leave the oven door closed with this kind of ovens.

paraglider, did you notice any browning of the stickers (I believe there is an orange #5 sticker with an arrow and an oval shaped copper colored sticker) on the board in addition to the effect it had on your emi shield?

Also, did you bake emi shield facing down or facing up? Mine worked face down, but I'm thinking the board was originally placed emi shield side face up. (although the shield may not have been attached during reflow as you suggest)

Azlec, test your oven first. Place the thermometer where you're going to place the PCB (on the baking sheet and everything). I used an el cheapo oven but the temp remained consistent throughout the baking time. paraglider had to adjust the knobs during the process to keep his temp stable.

I have been watching the thread for months and months and suspect I have the same problem that most of us have with WIFI. The freezer worked a few times but eventually stopped working or only gave me a few sec of WIFI after the deep freeze. I was ready to try the oven this week end. Today, after the 4.0.2 update, it worked! I should say that I have had my WIFI turned off for the past month because I got tired of it trying to join networks that it could not join due to the WIFI problem so there is a question whether this is a fix or a coincidence but my WIFI not been connected and working longer at this point than it has for at least the past 5 months.

4 hours and still working. 4.0.2 might be a fix, at least for me.

"unable to join" is back after 6 hours of WIFI. Looks like into the oven she goes.