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Old 14th Nov 2018, 4:36 pm   #1
Al (astral highway)
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Default SOIC ICs with no tab/ bar

Hi everyone,

I've received a batch of SOIC IC's (555s) which are supposedly Texas Instruments but I think not!

Anyway, there is no bar or tab on them. The only orientation is the direction of writing, across the longest direction of the IC.

Presumably this means pin 8 is in the left corner above the N in the lettering NE555 if the IC is placed horizontally?

I've only recently been gathering SOIC IC's, (having started workflow practice soldering with SMT resistors and capacitors) and note that most have a white bar marked across one end, across, it seems, pins 1 and 8, where a dink would be on an 8DIL package

Thank you!
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Old 14th Nov 2018, 4:39 pm   #2
barrymagrec
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Default Re: SOIC ICs with no tab/ bar

Sometimes there is an extremely small / feint dot indicating pin 1.
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Old 14th Nov 2018, 4:46 pm   #3
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Default Re: SOIC ICs with no tab/ bar

Hello,
Sometimes one of the longer edges is chamfered, with that edge to the left as you would look down on it then the left hand top pin is pin 1. Sometimes it is just a corner which has a slight chamfer which denotes pin 1. Others I've seen have an almost invisible circle in one corner. Hope that is of some help, if not would it be possible to post a photo?
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Old 14th Nov 2018, 5:04 pm   #4
Al (astral highway)
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Default Re: SOIC ICs with no tab/ bar

Quote:
Originally Posted by Beardyman View Post
Hope that is of some help, if not would it be possible to post a photo?
Thank you, photo tricky as it's hard to focus on such a tiny thing with my smartphone. But this is as good as I can get...
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Old 14th Nov 2018, 5:17 pm   #5
Beardyman
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Default Re: SOIC ICs with no tab/ bar

Not a bad photo! Well done!
Looks like there is a chamfer on the left hand side so the left hand top pin would be pin 1.
We use devices here at work that are in a SOT-223 package and have 6 pins!! Absolute nightmare to place correctly.
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Old 14th Nov 2018, 5:28 pm   #6
Al (astral highway)
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Default Re: SOIC ICs with no tab/ bar

Quote:
Not a bad photo! Well done!...
Looks like there is a chamfer on the left hand side so the left hand top pin would be pin 1.
Thank you! I've actually got a better way of photographing things but it's a faff to get out, so I'm glad this worked!

I'll take a closer look for that elusive chamfer.

I bet six pin devices are fiddly!

Thanks again!
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Old 14th Nov 2018, 8:58 pm   #7
Maarten
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Default Re: SOIC ICs with no tab/ bar

Looks like it was made by ST. I also think top left to be pin 1.
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Old 19th Nov 2018, 10:16 pm   #8
julie_m
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Default Re: SOIC ICs with no tab/ bar

Well, whether by accident or by design, that shot has actually turned out really well. I can see what appears to be the usual index notch ..... one in each end. Not so much use! But there appears to be a definite slope on the left-hand side of the package, so I would say that was the "low-numbered" side. That is to say, pin 1 is top left in your picture.
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Old 19th Nov 2018, 10:35 pm   #9
Argus25
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Default Re: SOIC ICs with no tab/ bar

Al,
There are plenty of new SOIC package chips with nothing at all on the physical case to show pin 1. I have some like this. However, it is identified by the axis of the writing on the body/case top. If the IC is sitting in front of you and you are reading the label normally from left to right, pin 1 is on the lower left.The writing is never upside down. So on the axis of your photo, pin 1 is the upper left pin.
Hugo.
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