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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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14th Nov 2018, 4:36 pm | #1 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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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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Al |
14th Nov 2018, 4:39 pm | #2 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,562
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Re: SOIC ICs with no tab/ bar
Sometimes there is an extremely small / feint dot indicating pin 1.
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14th Nov 2018, 4:46 pm | #3 |
Hexode
Join Date: Jan 2018
Location: Portsmouth, Hampshire, UK.
Posts: 430
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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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14th Nov 2018, 5:04 pm | #4 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: SOIC ICs with no tab/ bar
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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Al |
14th Nov 2018, 5:17 pm | #5 |
Hexode
Join Date: Jan 2018
Location: Portsmouth, Hampshire, UK.
Posts: 430
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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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The difference between stupidity and genius is that genius has its limits. (Einstein) |
14th Nov 2018, 5:28 pm | #6 | |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: SOIC ICs with no tab/ bar
Quote:
I'll take a closer look for that elusive chamfer. I bet six pin devices are fiddly! Thanks again!
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Al |
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14th Nov 2018, 8:58 pm | #7 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,203
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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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19th Nov 2018, 10:16 pm | #8 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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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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19th Nov 2018, 10:35 pm | #9 |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
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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. |