Electronics > Projects, Designs, and Technical Stuff

1960s pellet parts

(1/3) > >>

Alex Eisenhut:
So I collect plugins for 500 series Tektronix scopes. One of those plugins is a 1GHz sampler called the 1S1.
Last week I discovered that the 1S1 actually uses embedded components in the PCB itself.

This isn't mentioned in the 1S1 manual, but if you look at the input to the sampling bridge (R4 R5 C4 C5) and look up the Tek part numbers, they are odd.

There is a Tek document that does mention these parts.

http://w140.com/tekwiki/images/f/f7/Tek_1s1_field_training_package.pdf

"The  circular  pellet  parts  are  inserted  in  the  board  before  plating.
They  are  bonded  into  the  board  and  then  plated  over.  The  board  is  then
etched  in  the  usual  manner,  leaving  the  location  of  the  parts  practically
invisible  to  the  eye"

Wow. Now I never looked that closely at the PCB to notice that certain parts aren't there, since the failures were always further down the signal chain.

Googling for "pellet parts" doesn't yield much except for pellet stoves and pet food pellets.

What could these parts be? Something like a 0402 part inserted into an unplated hole which is then plugged with conductive filler and plated over? Capacitors to ground I could picture, but how do you embed a series resistor into a trace?

This obviously wasn't beyond 1960s tech, but I've never heard of them used in 1960s Tektronix stuff. The faster plugins like the 1S2 don't mention it either but now I have to find out!

I have an itch to completely strip a 1S1 apart, removing the PCB from the chassis and seeing what my naked eye can't see.

The closest thing I saw was what's called "leadless" capacitors which are just a stack of dielectric with electrodes soldered directly to the board.

RoGeorge:

--- Quote from: Alex Eisenhut on June 20, 2020, 06:49:38 pm ---"The  circular  pellet  parts  are  inserted  in  the  board  before  plating.
They  are  bonded  into  the  board  and  then  plated  over.  The  board  is  then
etched  in  the  usual  manner,  leaving  the  location  of  the  parts  practically
invisible  to  the  eye"

--- End quote ---

Wow indeed!  :o
I'll be very curious, too, to find out more.

Since on the page 210 of 218, in the schematic diagram, the R4 R5 C4 C5 have an asterisk explained as "denotes an integral part of the PCB & can not be replaced", I guess Google won't know much about them.  The best source will be to find an engineer who designed/manufactured that PCB, and ask about more info, and only if there is no NDA about that.

T3sl4co1l:
You can get PCBs with embedded components (mostly R and C chips), and some other things.  Or say, carbon ink screened around vias, for inline terminators.  Don't know quite how specialized or common these processes are (e.g., IBM did it first, because of course they did, good luck to anyone else?).  I know several US fabs that mention it so it's not entirely non-standard, but you'll likely want to be sitting down to read the quote. :)

Next best I think is beam lead SMTs, which aren't supposed to be so much SMT'd, as wire bonded or welded, on hybrids; but can still be soldered if you don't mind the tiny pitch.

Tim

edpalmer42:

--- Quote from: RoGeorge on June 20, 2020, 07:11:41 pm ---
--- Quote from: Alex Eisenhut on June 20, 2020, 06:49:38 pm ---"The  circular  pellet  parts  are  inserted  in  the  board  before  plating.
They  are  bonded  into  the  board  and  then  plated  over.  The  board  is  then
etched  in  the  usual  manner,  leaving  the  location  of  the  parts  practically
invisible  to  the  eye"

--- End quote ---

Wow indeed!  :o
I'll be very curious, too, to find out more.

Since on the page 210 of 218, in the schematic diagram, the R4 R5 C4 C5 have an asterisk explained as "denotes an integral part of the PCB & can not be replaced", I guess Google won't know much about them.  The best source will be to find an engineer who designed/manufactured that PCB, and ask about more info, and only if there is no NDA about that.

--- End quote ---

No worries.  Bob will tell you anything you need to know. 


--- Quote ---The important thing is, have faith in these parts, if there is a
rise time problem or a termination problem, every other avenue should be
explored first, before suspecticig the pellets. If the pellets do become
suspect the current advice is to ship the unit back to Portland, Attn.
Bob Wruble.
--- End quote ---

 ;)

I can't believe they actually gave a guy's name.  Yes, he was a real person.

T3sl4co1l:
Hah, guessing ol' Bob was extremely confident in the performance of his unconventional solution... :-DD

Tim

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod