Hi,
I am designing a circuit where i will be using an 84 pin through hole PLCC package, with the pins in two concentric squares. I do not have strict timing and current requirements for the project so PCB routing is not very critical.
Can someone please give me some tips and how to best route the PLCC package as this is my first experience in using such a large package.
Best Regards
Joseph A. Zammit Malta
PLCC in a socket then? It's easy, the pins are 0.1" apart, so the inner traces just go between the outer ones. You can even do it single- sided if you're daft enough. the only difficulty is in working out the correspondence between the PLCC pins and the socket pins. Best done by buzzing it with a meter.
1) Be sure to place the power supply bypass capacitors (usually .1uF) close (next to the package) to the power and ground pins on the socket. If its a digital IC it will need these. 2) Analize the circuit or ask the designer to identify any noise seneitive inputs on the IC and route those signals away from the rest of the pack. Be especially weary of clock inputs and edge sensitive inputs (SPI clock, interrupts, counters, etc)
Thats about all I can think if.
Tip #1 - Patience Tip #2 - Beer. Lots of it!
Seriously, you have the answers from above. Lay power and grounds first, then bypass caps. The socket pins are spaced so you can run the inner track pins in- between the outer track pins. It is important to keep track of pin numbering. Verify as you go.
PLCC's are not my favorite either....
I'd just skip the socket and put the part down directly. PLCC is much easier to deal with directly than in a socket. That's especially true if you're going to etch the board yourself -- you can't solder any of the pins to the top layer with a PLCC socket.
-- Ben Jackson AD7GD http://www.ben.com/
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