Repairing TVS array on Cypress Miniprog3

[dferyance]

So my Cypress Miniprog3 just died the other day. I was able to diagnose it to the point where one of the diodes in a TVS diode array has failed. Cypress support was kind enough to let me know the part number and I have a replacement on the way but I could use some tips for swapping the part.

The part is a pretty small SOT-353. At first I was thinking of use hot air but I have some concerns. It is a pretty densely populated double-sided SMT board. My understanding is they tend to use epoxy to stick parts on one side of the board. Is there a chance that they don't and I could risk parts falling off when I heat it up? If they do use epoxy, does that prevent me from removing the part? From looking at the board, I guess that the part I care about is on the back but I don't know what was back or front when they manufactured it.

An alternative I thought about is to clip the pin for the single faulty diode and stack the new part on top with some small wires to connect it to the pads. I don't like this as I would like a nice clean repaired board but it might work in a pinch. I might be able to clip all pins, clean up the pads and do it all with an iron but there isn't much room and I could still slip the iron.

Any ideas? Am I risking damaging the entire board by using hot-air?

[tszaboo]

Sorry. Had to do.

[dferyance]

This thread is worthless without pics!

I am not sure how based off of my question. Double-sided SMT boards are quite common I am sure everyone has seen one.

But no problem, I googled a miniprog3 and this looks the same as my board.



TVS2 on the top image is the culprit.

[tszaboo]

Thank you. You should be able to solder that component with hot air, without too much issue, If you have some practice.  If you fear that you might blow off or damage the components close to it, cover them with tin foil (from the kitchen). Even it is glued down with epoxy, when the solder is melt, you should be able to take down the part with a regular tweezers.
Before you solder back the other TVS diodes, try the board, because if it is still doesn't work, something else must be broken (also?).

[dferyance]

Many thanks for the advice. I think I am good with hot air but I have not used it anything that I actually care about yet. More of salvaging old components from junk boards where it was fine to mess something up. Yes, I expect I should be able to test it out without the chip in place. I doubt that anything else is broken but you never know.

[tggzzz]

When using hot air, consider the possibility that your inexpertise might make you so slow that the heat has tiem to travel through the board and melt the solder on the other side.

An alternative, since you are sure you don't want to re-use the TVS, is to cut the leads, remove the body, and then use standard soldering techniques to desolder the remains of each lead one at a time.

Your choice!

[tszaboo]

And one more thing: There is a BGA package on that side of the board, so I'm certain it is not epoxy glued down. It is probably the primary side.

[miguelvp]

If you are curious about their PRoC BLE dev kits for $49 you can get this, which includes a Miniprog3
http://www.cypress.com/?rid=102638

They also have one with a mouse dev kit for the same price

Not sure if they are available yet since it says to contact the sales dept. I'll eventually get one but have been busy.

[dferyance]

Well I am back up and running. I got the new part on and everything seems to be working fine. I was worried about parts falling off the bottom but that didn't happen. The hardest part was getting the old part off. I ended up using tweezers and a SMT tip on an iron. I wasn't able to clip the leads as I couldn't get my angle cutter in there -- it was just too small of a part. I cleaned up the pads added some solder paste and used hot air to solder the new part on.

Thanks everyone for the help. NANDBlog, I can see now how the pictures helped. I will be sure to keep that in mind in the future.

[tggzzz]

Thanks for reporting on your success, and good luck in the future.

[ninz]

So my Cypress Miniprog3 just died the other day. I was able to diagnose it to the point where one of the diodes in a TVS diode array has failed. Cypress support was kind enough to let me know the part number and I have a replacement on the way but I could use some tips for swapping the part.

Hi, could you tell what was the part number, please?

[jonfick]

I continue to appreciate eevblog!  This forum post was helpful. 

Earlier this week my MiniProg3 started to fail.  I could turn on it's 5/3.3/2.5/1.8V power, but the data part of the communications wouldn't seem to connect.  I removed TVS2 first, and found that it immediately started to work.

• Hot air removal is no big deal.
• It runs without the TVS, but without the TVS the MiniPRog3 is more vulnerable to transients or misconnection.
• The TVS appeared to have at least one good zener and it measured a unidirectional 5-6V.
• Although I can't find the particular part marking it appears that the part is in a 5-TSSOP, SC-70-5, SOT-353 package.  The Littelfuse SP0504BAJTG *may* work but I haven't tried it yet.  It's unidirectional, 5.5V working, and 8.5V breakdown.  What I haven't attempted to debug is if the pinout is correct.  It's Digikey F3159CT-ND.
• The hardest part is to get the outer plastic shell apart without damaging it!

[denneyaa]

I just wanted to stop in and say thank you for information. We just had this happen and the parts are on order.