Fail to make own STM32 board

sragen · ‎2011-08-22

Posted on August 23, 2011 at 05:28

Dear all,

Sorry, I am a newbie on STM32 microcontroller.

Yesterday I have made my own STM32F103RBT6 board. I use L1117-3.3 as my 3,3 volt regulator. The external components are Crystalls, capacitors for crystall, supply capacitors, reset circuit (using R and C), and resistor pull down for boot 0 and boot 1 pin.

When I apply 5 volt voltage to the regulator, firstly its is OK it only draws current about 4mA. But several second after that the current increase over 200mA. and then I check the VDD and VSS has been short Circuit. And the chip has been damaged.

Thus I remove the chip and measure the VDD-VSS voltage, and it is 3.3volt. I've recheck my PCB, and I can't found any mistakes.

I've already burn 5 chips last night, and I don not know whats wrong with the circuit.

If the there any suggestions for my problem will be very appreciated.

Thank for advance.

Best Regard,

Eko Henfri.

#make-own-stm32-board

sragen · ‎2011-09-05

Posted on September 06, 2011 at 01:17

Thanks Becker for the response,

The chip current is increasing gradually, but it will goes to short circuit in just several seconds (vdd to vss resistance almost under 10 ohm). The strage part is if I heating up the chip using iron solder to the chip, the resistance from vdd and vss will increase again (more then 1K ohm). but after I put the supply, the resistance will drop again.

I've tried to give the supply from an adjustable regulated power supply that limit the current flow, but it did not help.

Any clue?

Best regards,

Eko Henfri.

sragen · ‎2011-09-09

Posted on September 10, 2011 at 00:08

Thanks for the responses guys.

Now I got my board working. The problem is the solder paste. Maybe it sound ridiculous, but it was happened. After I removed the solder paste using alcohol and then heating up the chip using solder blower, the chip is working now. I Tested all I/O pin using LED with each bit in the port is set as open drain. I made a simple running led program that circulating on each LED that I put in all pins. Something interesting about my board is some bits are working in abnormal condition. The LED is dimming even though I did not activate it yet according to the program that I made. But finally I can fixed it by applying hot air gun to the chip for several second on the corresponding bit.

Thanks for all suggestions and help.

Best Regards,

eko henfri.

infoinfo989 · ‎2011-09-09

Posted on September 10, 2011 at 01:21

Conductive flux by the sound of it. Congratulations on working it out. Have fun with your new board!

raptorhal2 · ‎2011-09-09

Posted on September 10, 2011 at 01:44

Well I'll be darned ! Good work in finding the problem.

Solder paste will absorb enough moisture to conduct. The resistance is not close to zero, but it is low enough to mess up your circuit. Being in a high humidity climate saved you from ESD problems, but got you where there was solder paste. For the boards you have already made, you probably still have some residue. Use a flux cleaner and a toothbrush to remove all residue.

Then use low residue liquid flux on all future boards, followed by a flux cleaner and toothbrush.

Cheers, Hal

gregstm · ‎2011-09-09

Posted on September 10, 2011 at 04:00

Here's an alternative to solder paste (which you have shown can cause problems):

I hand solder my 48 pin devices using 0.3mm solder wire - you will need a high quality soldering iron with a small tip (not too small, I use a small chisel tip to conduct more heat). If I need solder wire smaller than 0.3mm I squeeze the wire with flat pliers to make it skinnier. These days I use a zoom microscope to solder and check whether the joint is ok.

sragen · ‎2011-09-14

Posted on September 14, 2011 at 11:11

Thanks Guys for all helps and suggestions.

I will use better solder paste and better solder wire for my future board.

As for now, I start to try programming my board.

So, I think it is the time to end this thread.

Best Regards,

eko henfri.

flyer31 · ‎2012-01-18

Posted on January 18, 2012 at 13:25

I am frightened, the VCAP-1 and VCAP-2 pins can lead to such problems. VCAP-1 unfortunately is placed in direct neighbourhood to VDD - if there is any leakage path, this should destroy the chip immediately.

Other chip suppliers as Microchip also place the VCAP pin in direct neighbourhood with VDD bin, and we nevery had any problems with this, also on ''rudimentarily'' soldered sample boards, but maybe their VCAP pin is somehow better protected.

Diego B. · ‎2018-12-26

I've been fighting against the same problem for about two months. After power up the micro it worked fine for 10-20sec and then the current got increased to 200mA with no programer or anything else connected.

After reading this topic I realised that I had been using a new solder paste from Amazon. (now I suspect it was plumber solder paste though). Anyway, after using another flux the problem has been sorted and the micro seems to work fine now.

Thanks for sharing your experience.

Diego B.