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Best Chip Form Factor

S

Stiganator

Platinum Member
What is the best form factor for ICs in your opinion if its being custom made? LQFP, BGA, etc etc

What about if you're doing it in your garage?

Anyone ever tried to do there own PCBs with those kits or done reflow surface mount with a toast oven?


 
If you are talking about what types of ICs to chose if you are doing all the soldering in your garage, then i would stay far away from BGA as they are the hardest. L"QFP" would be probably your best bet in terms of high pin count and being able to solder by hand, still if it has +200 pins you would still want to have some nice soldering equipment.
 
Well I just ordered some samples off of Texas Instruments. They have a great sample set up. I stuck mostly with LQFP ICs or ones very similar to that.
 
I've designed a PCB and done all the soldering to it for my senior project, but we used all through hole devices so it was all pretty simple. I'm not sure what components you are looking at, but for alot of stuff if there is a DIP package and you don't care all that much about size then its the way to go. For example we used a 40 pin DIP microcontroller and its pretty darn big, but it also had a great deal of functionality and im not sure what all you would be needing SMD with hundreds of pins for.
 
SOIC are the perfect size for hand-soldering; if you get much smaller, you're likely to need flux and a decent iron. If you have access to those, you could probably go down to TQFP/LQFP.

The main thing is the lead pitch. The finest I've hand-soldered is 0.4 mm (distance between pins) and it is a pain. I'd keep it above 0.6mm lead pitch unless you like hours of debugging just to find a minuscule solder bridge or poor pin connection.

BGAs require special soldering tools like at least solder paste and a heat gun.

Reflow ovens are a mixed blessing; if you have the paste and tools and a lot of boards to make, they're the way to go. If you're just making one board, I'd just go by hand as you're more likely to end up with a working board assuming you're decent at soldering. There are some tricks you have to watch out for with solder paste and reflow ovens.
 
Originally posted by: Stiganator
What is the best form factor for ICs in your opinion if its being custom made? LQFP, BGA, etc etc
Click to expand...

LGA-775. but i'm biased.

What about if you're doing it in your garage?

Anyone ever tried to do there own PCBs with those kits or done reflow surface mount with a toast oven?
Click to expand...

one option is to use a hot plate for pre-heat (bring the assembly to the
low 200 F's, temperature-wise), then use a fine-tip soldering iron
for localized heating.

toaster oven, IR conveyor belt - have some similarities. unless all
your packages are ceramic, and you're using a low-temp solder,
etc. - requires some process tweaking.

packages with leads on the bottom -
having heard a few co-workers k'vetch about how hard it is to CLEAN
underneath these devices, to clean flux residue for example - on the
other hand, if you're doing work at home you might not care about
flux residue, you just need all the leads/output terminations soldered
right.
 
Oh Geez, I got the chips today (fast shipped considering it was all free). They are small! I was thinking there were going to be northbridge sized, but no they are more micro-SD sized. I'm going to need a new iron.
 
If your doing it at home as a hobbyist try to get dip or pdip chips.
Its going to be the easiest to work with.

If your looking for some powerful microprocessor samples check out microchip.com.
They will send you samples of the 30Fxxx line , these have CAN, USB, PWM, SPI,I2c, etc and run at 40Mhz. If you go to purchase them they are about 10.00 each.
I think the limit they will send is 4.


I really don't recommend doing smd at home until you have the whole thing breadboarded and working. I use the laser printer / photo paper method for making the actual pcb.

A site for hobbyist kits and parts I highly recommend :
http://www.sparkfun.com/commerce/categories.php
 
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