Packaging information

[Alistair George]

Hi I am used to using DIL packages, but the new product will be SMD, but am confused with the various package names and also dont know what is easiest to work with eg if I use a Hako station with smd hot air, can anyone recommend what package I should go for for example using the CY8C27x43 in 28 pin, or should I go for the 44-Lead TQFP for future upgraded packages? Any comments appreciated.

Also, designer help does not say anything about packages. Say I want to change package, but still use same device and project details, do I do a 'clone'??
Al.

[werner]

Hi I am used to using DIL packages, but the new product will be SMD,

SOIC is bulky (1.27mm/50 mil pitch) but easy to solder in a
traditional way. SSOP (0.65mm) and TQFP (0.50mm-0.80mm)
are more compact, but at least the sizes < 0.80mm need
special soldering techniques. MLF/QFN (0.50mm) is the most
compact but also the most difficult to solder one.

But let's first have a look at what the future will bring. A quick
count of the packages shown in TRM 2.01 vs. 2.10 yields:

TRM 2.01:

Code: Select all

        8 16 20 24 28 32 44 48 56 100   Total
PDIP    3  -  2  -  3  -  -  -  -  -        8
SOIC    3  2  3  -  3  -  -  -  -  -       11
SSOP    -  -  4  -  4  -  -  2  -  -       10
TQFP    -  -  -  -  -  -  2  -  -  1        3
MLF/QFN -  -  -  1  -  4  -  2  1  -        8


TRM 2.10:

Code: Select all

        8 16 20 24 28 32 44 48 56 68 100        Total
PDIP    3  -  2  -  3  -  -  -  -  -  -           8     (+0%)
SIOC    3  2  3  -  3  -  -  -  -  -  -          11     (+0%)
SSOP    -  -  4  -  6  -  -  2 +4  -  -          12+4   (+20%)
TQFP    -  -  -  -  -  -  2  -  -  -  1           3     (+0%)
MLF/QFN -  -  -  1  -  6  -  3  3 1+1 -          14+1   (+75%)


(+n are the special debugging chips.)

So new things are SSOP and MLF. This makes perfect sense,
considering that these are the most compact dual and quad
packages.

You can solder SSOP and TQFP with a regular soldering iron
by 1) applying flux, 2) soldering the chip down at two opposite
corners, 3) applying lots of solder to "flood" all pins, and 4)
removing the excess solder with (quality) solder wick. It's easy
once you've figured out how to do it, and works quite reliably.

MLF/QFN is harder, also because of the central pad underneath
the chip. So you need to work with solder paste and use hot
air or an oven. The packages Cypress use expose a fairly
large part of the pads, so you can make corrections with a
soldering iron. (Apply flux, then pass the tip in the direction of
the traces. This will redistribute the solder, separating bridges
and soldering unconnected pads.)

A solder paste plus oven solution also has the advantage that
you can use the same approach for all other components,
which is a lot faster and tidier than soldering them individually.
In my limited (still trying to find an oven with decent
temperature control) experience, anything with more than 2
terminals needs inspection and frequently manual correction,
tough.

There's also a thread on those issues over there:
http://www.psocdeveloper.com/forums/viewtopic.php?t=223

- Werner

[Alistair George]

Thank you Werner.