SOT23 transistor beta testing (hfe) jig

[maxwall]

Is there a available and inexpensive jig or fixture that can be used to test for beta ( hfe ) matching. These are surface mount three leg transistors that are very small to work with unless you have micro robot hands. I was wondering if anyone had the same issue with this transistor package. I'm using this in conjunction with zener bridge limiter pcb build , transistor code numbers are 1G =BC847 NPN , and 3G = BC857 PNP. Any guidance appreciated.

 

[abbey road d enfer]

What is a "zener diode pcb" that requires hfe matching?

 

[mrclunk]

How about using a magnet under a little jig pcb to locate the part on test pads?

 

[maxwall]

Are'nt SOT23 device legs non magnetic ( tin over copper ) since you can apply solder ? second issue would be to wire up a hfe meter from a handheld dvm to the test jig pcb or make a pcb with legs so you can plant it in the DVM sockets for testing.

 

[JohnRoberts]

for automatic test fixtures in production we use spring probes

you probably don't need 100 probes ($12 amazon)

uxcell 100 Pcs Spherical Radius Tip Spring Test Probes Pin​

but you drill holes in bakelite/phenolic/wood and space the probes as needed... the prober tips are sping loaded so you just push down on the device pins to make contact.

JR

 

[Flatpicker]

Strange as it seems, SOT23 and other SMD devices are in fact magnetic, and mrclunk's idea sounds like a great one to try! I've got a discrete SMD op amp design on the drawing board that I've been wanting to build, but my greatest dilemma was how to hold the SOT23 input pairs so they could be measured for matching. Mrclunk may have just solved that dilemma.

 

[maxwall]

What is a "zener diode pcb" that requires hfe matching?

Zener comp limiter pcb , the rest are usual transistors , caps , resistors etc. based on older circuit layout with these newer modern parts.

surprisingly, sob , the Sot23 is magnetic , news to me . just put a magnet to it and it jumped straight away , thanks for the tip MrClunk. I'm a little new to smd stuff , good learning experience. the rest of this should be a challenge since I usually only use a dvm for matching using through hole parts. Maybe their some special tweezers with leads for this purpose. more research.....

Thanks , JR for the spring probe idea , I'll see if I can locate few and give it a try.

 

[Ilya]

This one is useful:
https://www.peakelec.co.uk/acatalog/pca23-peak-component-adapter-sot23.html#SID=27My current problem is how to store the sorted parts after you pulled them from the reel. Any ideas?

 

[Khron]

How about these little connectable Wentai boxes?

https://a.aliexpress.com/_mNMCWj2

 

[Ilya]

These are nice, but too large. Ideally, I'd like to pack each transistor separately. Maybe in pairs. These containers are too big for single part.

 

[Khron]

Reuse the reel, and replace the top with clear sticky tape? Or that's not an option either, because you want to also label each one?

 

[mrclunk]

I've used masking tape in the past. Bonus is you can write on it too.
Not good for long term tho.

 

[Bo Deadly]

This one is useful:
https://www.peakelec.co.uk/acatalog/pca23-peak-component-adapter-sot23.html#SID=27

That socket and sockets like it are made by a company called Sensata and previously by Wells CTI. The part number for that particular SOT-23 socket is 499-P36-20. But apparently these are not sold through the usual component distributors and even if they were, they look quite expensive.

I wonder if a PCB could be made with various footprints with another PCB on top just to position the part and then maybe a third PCB with spring loaded contacts from mill-max just to press the leads down onto the first PCB. Make one set of boards to make a jig for a bunch of parts at once.

 

[Khron]

Are there no SOT23 zif sockets available anywhere? 3 to 6 pins would work just the same, as long as the physical connections are right.

 

[maxwall]

a zif socket would be ideal or a socket much like the ones that are used to program smd eproms where you fold the second half of a spring loaded fixture or lid on a hinge over the legs of the smd device then some pcb traces leading to some test point pins that you can attach a dvm with lead clips for hfe testing. The adapter suggested by Bo Deadly would work, but Ideally would want to source the black spring loaded folding fixture so I could make my own pcb on through hole or smd protoboard to keep the cost even lower. It does'nt need to be expensive and fancy, I prefer to implement my own design to suit my preferences if possible.

Notwithstanding , the way things are headed for DIY , through hole parts are being slowly phased out of production.

 

[Khron]

Looks like there's plenty to choose from:

https://www.aliexpress.com/wholesal...olesale&SortType=price_asc&groupsort=1&page=1
Or, no doubt, even from western distributors, but for 5-10x the price...

 

[maxwall]

Yep , I just did a search and revealed a good source from one you suggested.

Looks like this should be easy fixture to add to bench test devices. I'll pass on the 5-10x price option.