6

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?

19172281
  • 685
  • 1
  • 9
  • 24

4 Answers4

22

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

Ale..chenski
  • 38,845
  • 3
  • 38
  • 103
12

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

Olin Lathrop
  • 310,974
  • 36
  • 428
  • 915
  • Most likely the bevel is molded into the package from the tooling rather than being shaved off which implies a post packaging machining operation. – Michael Karas Jul 30 '18 at 18:41
  • @Mich: Yes, of course. I was describing the shape, not the process. – Olin Lathrop Jul 30 '18 at 19:48
  • 3
    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. – Michael Karas Jul 31 '18 at 09:31
7

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

Marcus Müller
  • 88,280
  • 5
  • 131
  • 237
0

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.

Graham
  • 6,020
  • 13
  • 20
  • Sure, but the problem with these TI chips in particular is that there's no such marker. Turns out that the big bar drawn across the top means the same thing, but I'm a tiny bit astonished that they'd invent a new convention like that and not talk about it. I've been trying to figure out a TI TL9002 dual op-amp, and in the datasheet it shows a dot, but there's a bar/bevel in reality! – SusanW Aug 04 '19 at 16:03