Fail to make own STM32 board

[sragen]

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

[infoinfo989]

Posted on August 23, 2011 at 06:15

Sorry to hear you're letting the magic smoke out - that's no fun. Perhaps if you attach your schematic people can review it for you.

[sragen]

Posted on August 23, 2011 at 07:09

Here it is my Schematic.

Any suggestion will be very helpful.

Best Regards,

eko henfri.

________________

Attachments :

STM32F103RBT6_Schematic.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I1FE&d=%2Fa%2F0X0000000bkB%2FxvKD24gTECeuL4ujRTvwc4Hw6U_FzfOZHBTrRpkVZv4&asPdf=false

[Tesla DeLorean]

Posted on August 23, 2011 at 15:41

Any suggestion will be very helpful.

Add some pin numbers.

[raptorhal2]

Posted on August 23, 2011 at 15:47

Before you follow my last suggestion, try these first if you have not done so:

- Look for solder bridges between chip leads and between PCB traces with a 10x magnifier

- Ensure that chip pin 1 matches PCB pin 1

- Disconnect the RS-232 cable in case you have ground, TX and RX mixed up, and in case you have a ground loop between the serial device and the PCB.

If the above isn't helpful, post your PCB layout for review.

Cheers, Hal

[sragen]

Posted on August 23, 2011 at 18:05

Firstly, I would like to thanks for the responses.

I've already check the soldering result using magnifierlens, and I canassurethat there is no short circuit between adjacent pin. And the orientation of the Chip is correct. (pin numberone is in the bottom left corner of the chip)

I did not connect the board to the ISP or serial connector yet. I've just give the supply to the circuit, thus several second after that the chip is short circuit (VDD and VSS is 0 ohm resistance).

The strange part is after I heated the chip using blower solder, the resistance of the VDD and VSS incerease again and not short circuit, but after I re-connect the supply, it will short circuit again.

I've replaced the chip with the new one until 5 times, but there is no sign of success. Every time I tested the board, the same situation has beenoccurred.

I justcuriousthat, is the chip has been damaged when I soldered it?

I use a normal iron solder and a cheap solder paste (LOFTET), not using soldering flux, so the soldering process is a little bit hard.

When i solder the chip, I've connect the solder tip to the chip about 1-2 second each, and the wait for another 3 second before re-solder the chip to put or remove the remaining solder wire of the chip. But I feel the chip never get too hot to touch when I soldered it.

Is there anybody know about how many second the chip will survive again solder iron?

For information, I use 30 Watt solder iron and 0.6mm solder wire.

I put the PCB and schematic of my board in the attachment.

I don't know where the problem is. Is it come from my circuit or from the soldering process or any other else.

Any help and suggestion will beappreciated.

Thank for advance.

Best Regards,

Eko Henfri.

________________

Attachments :

STM32F103RBT6_PCB_and_Schematic.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I1F9&d=%2Fa%2F0X0000000bk7%2FvS6luzwVWMLzBQIPHEqTxxOBr7KTxHm6NDTbKBm.qww&asPdf=false

[raptorhal2]

Posted on August 23, 2011 at 20:48

I don't see anything wrong with the PCB layout (but I am not infallible). To check, use an ohmeter on a PCB with everything but the processor mounted and look for grounds and 3.3V paths where they shouldn't be.

Do you have a dry insulating layer between the 8 MHz oscillator can and the board traces ?

You have probably done it right, but make sure the 32 KHz oscillator is not resting on any leads.

Check that you don't have a solder bridge where a trace passes through the center of the resister pads in the lower left corner.

Your soldering technique may be the problem, but getting all 5 boards wrong is a big coincidence. To eliminate soldering as the problem, use a 15 watt iron. If you can, get a temperature controlled iron. Simple pencil tipped irons can get quite hot after a while. But the biggest help will be to use low residue liquid flux. Wet down all the leads on one side, put a drop of solder on the iron, then slide the iron tip over the ends of all 16 leads. With the right amount of solder and the right motion you should be able to get all 16 leads soldered with very little heating of the chip and no solder bridges. Use more flux and a dry iron to pick up any bridges.

Make sure the chip has no moisture inside before soldering. It should be fresh out of a package that contains silica gel, or heat it under a small incandecsant light bulb for a while.

That is all I can think of. Good luck.

Cheers, Hal

[sragen]

Posted on August 24, 2011 at 00:03

Thanks Hal for the response.

Before I put the second chip, I already measure the 3.3 volt voltage for all VDDs  and VSSs and all are fine. There is also no short circuit under the resistor that has the line beneath it.

As information to make this module I use a PTH PCB with masking material. And to ensure there is no short circuit under 8Mhz X-tall, I put a small paper (ex-SMD resistor reel) beneath it.   

If the problem has been caused by my soldering process, then I just wonder that this chip is very fragile from over heat during soldering. Since I've soldered many SMD ICs (such as FTDI chips and AVR chips) with more radical process (longer contacting time between solder's tip and chip's pin) and with no problem. 

I realize that STM32 chip has smaller physical size, so maybe I need to give more caution when soldering it. Tomorrow I will try to solder STMF103C8T6 that only has 48 pins on another board with same external components. I will try to be more careful to solder it with more proper solder flux. 

I just want to ensure that there is no mistake within my schematic and PCB before try the new STM32 chip.

If there any other suggestion, it will be very helpful.

Best regards,

Eko Henfri.

[jfong]

Posted on August 24, 2011 at 12:12

Hi!

    Maybe you can consider to limit your power supply current to a safer value, say 30mA, so the chip won't be burn-out and you get the chance to find out the problem.

Best Regards,

JFong

[sragen]

Posted on August 24, 2011 at 12:31

Today I made the board using STM32F103C8T6 (48pin). I was very carefully solder the chip so the chip never got too hot when soldered (different with the previous board that uses STM32F103RBT6 chip).

 

After I soldered the components thus I try the board and the result is as follows: 

 - Firstly The board only draws current about 2mA.

 - After several seconds (about 10 seconds) the chip's current is fluctuated about 3 times within about one second thus the chip's current suddenly increased. 

 - Because I use power supply with current limit about 20mA, thus the chip did not got burned yet, but I think if I did not give the current limit, the chip will be burned.

- After I remove the supply about 10 seconds and then I reconnect the power supply, the same conditions above occur.

Until now I did not know what the problem is since I use same schematic with the commercial board that I've bought.

Is there any special treatment for starting up new STM32 chip for the first time (blank chip) ? 

Any suggestion will be very helpful.

Best Regards,

Eko Henfri.

[drzile86]

Posted on August 24, 2011 at 13:52

Hi, 

I have looked at your schematic, everything is OK, except you don't need pull up resistor on the NRST pin, STM32F1xx MCU has it embedded. Look at the AN2586. Maybe this will solve your problem.

Regards,

Dragan