4
\$\begingroup\$

I've just soldered a SOIC-16 am26c32 on to a breakout board.

The datasheet shows the orientation of the chip by means of a semi circle at one end (http://www.ti.com/lit/ds/symlink/am26c32.pdf). However, on the actual device, there is no such semi circle to be found - only the name of the chip.

Am I to assume that pin 1 is the bottom left, when the chip shows the writing the right way up?

\$\endgroup\$
  • 5
    \$\begingroup\$ you don't happen to have a photo of the IC in question? \$\endgroup\$ – Marcus Müller Jul 30 '18 at 16:54
6
\$\begingroup\$

Mechanical Drawing

As Olin said, and as you can see from the mechanical drawing, one side should have a bevel.

Also, in practice, TI prints/etches/lasers a pretty clear bar onto the left hand side (in above drawing), something like:

soic

\$\endgroup\$
  • \$\begingroup\$ I can see the bar. is that where pin 1 is then? \$\endgroup\$ – 19172281 Jul 30 '18 at 17:05
  • \$\begingroup\$ if that bevel is on the same side, yes :) \$\endgroup\$ – Marcus Müller Jul 30 '18 at 17:11
20
\$\begingroup\$

Some SOIC type of packages don't have a dot or semi-circle. The first row is designated by a bevel,

enter image description here

\$\endgroup\$
  • 6
    \$\begingroup\$ +1 for choosing the view that actually shows the important feature clearly. \$\endgroup\$ – The Photon Jul 30 '18 at 17:20
12
\$\begingroup\$

Look more closely in the Mechanical Data section of the datasheet. It shows that the edge is shaved off along the whole row of pins that includes pin 1:

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Most likely the bevel is molded into the package from the tooling rather than being shaved off which implies a post packaging machining operation. \$\endgroup\$ – Michael Karas Jul 30 '18 at 18:41
  • \$\begingroup\$ @Mich: Yes, of course. I was describing the shape, not the process. \$\endgroup\$ – Olin Lathrop Jul 30 '18 at 19:48
  • 2
    \$\begingroup\$ I know you were describing the shape. It's the use of the word "shaved" that expresses a process. You could use the word "beveled" in its place. \$\endgroup\$ – Michael Karas Jul 31 '18 at 9:31
0
\$\begingroup\$

In addition to the features already mentioned, you may also see a white dot on the chip by pin 1. It's more common on DIL packages, but I've seen it on SOIC too.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.