THE TROUBLES WITH ORIENTATION

Most of us overlook the incredible changes our industry has undergone during the past century or that its been almost 50 years since the Radio-Electronics-Television Manufacturers Association changed its name to the Electronic Industries Association (EIA) in 1957.

For more than 20 years, EIA 481 has been evolving along with the electronics industry. Ironically, it is the components that were first tape and reeled (SOT’s) that are causing frustration through out our industry. Some of the highlights of this often misunderstood and misquoted standard are:

EIA 481 – the original – Anybody out there have a copy??? Please let me know.

EIA 481 – 2 (3/1991) 16 MM, 24 MM, 32 MM, 44 MM & 56 MM EMBOSSED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

EIA 481 – 3 (11/1991) 32 MM, 44 MM AND 56 MM EMBOSSED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

EIA 481 –1A (8/1994) 8 MM & 12 MM PUNCHED AND EMBOSED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

EIA 481 – 2A (4/2000) 16 MM, 24 MM, 32 MM, 44 MM & 56 MM EMBOSSED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

EIA 481 – B (8/2001) 8 MM THROUGH 200 MM EMBOSSED CARRIER TAPING AND 8 MM & 12 MM PUNCHED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

EIA 481 – C (10/2003) 8 MM THROUGH 200 MM EMBOSSED CARRIER TAPING AND 8 MM & 12 MM PUNCHED CARRIER TAPING OF SURFACE MOUNT COMPONENTS FOR AUTOMATIC HANDLING

As you can see there have been 2 complete revisions in the past 2 ½ years. That by itself should tell you the industry is changing. And of course with change there is always some confusion.

An issue we have seen since the release of ANSI/EIA 481-C (October 2003) is confusion as to how SOT 23’s should be orientated. Now, orientation of these devices has been a sensitive issue for years, and nobody agrees on which way it should be done. In the following illustrations, all orientations are based on looking at the carrier tape with the round sprocket holes away from you and looking down into the pocket.

According to EIA 481-C both are wrong and the side with 3 leads should be oriented to the left.

We fell head long into this trap with yet another manufacturer of components we tape and reel for. Historically they had us orient the components with the 3 leads and Pin 1 towards the sprocket hole. This worked fine until they shipped parts to a new customer of theirs who was used to seeing them the other way.

For those of you who have too much time and want to start a riot; go to the person who programs the pick and place equipment and tell them that Page 4 of EIA 481 – C section 4-14(g) states "The rules described in this standard shall supercede all prior standards established in EIA-481 and EIA-800 for the following component packages: SOT23, SOT143, SOT89, SOT223, IPD." Then with a straight face ask them when they are going to rewrite the programs. Run quickly.

Don’t get me wrong, none of us walk on water and frankly, EIA has the right idea here and is trying to bring ALL components under the same orientation rules. The real issue is nobody in the industry wants to incur the expense retooling, rewriting and re-documenting something that doesn’t seem broken.

A second dilemma is the 3 leaded SOT 23. Traditionally the side with 1 lead points towards the sprocket holes, but the EIA 481 C shows the side with 1 lead pointing towards 3 O’clock (sprocket holes at 12). To the best of my knowledge, no major manufacturer of carrier tape manufacturers carrier tape for this orientation. The alternate orientation would be to have the side with 1 lead pointing away from the sprocket holes. There is no carrier tape for that either.