LM2903: About SOIC package

Hello Yusuke,

This is a question for the packaging people. I will try to find a resource.

But reading the footnote #1, the "A" dimension is a single number in parenthesis, which means it is a "reference only" (typical), and is not a controlling dimension, like the B and C dimensions.

My guess is that the angle (0-8 deg) is tough to control and is the largest variance. The "C" dimension would be determined by the actual B length, the bend angle and the total package height.

If you are concerned of the farthest width of the package, that would be controlled by the total width spec (0.228 - 0.244) from the center line. The recommended footprint takes these variables into account, and is the recommended pad layout.

Hi Paul,

Thank you for your kind support.
I understand your explanation.

>If you are concerned of the farthest width of the package, that would be controlled by the total width spec (0.228 - 0.244) from the center line.
>The recommended footprint takes these variables into account, and is the recommended pad layout.

Customer wants to know the minimum distance of the pin that contacts the board.

Customer want that information to determine the pad size on the PCB.

This length is a minimum of 3.85mm.

Is my understanding correct?

Best regards,
Yusuke

Hi Tsukui,

as customers' variations of land patterns often end up in improper soldering results, I would strongly recommend to adopt the TI's land pattern examples given in the datasheet.

Kai

Hello Yusuke,

The recommended TI land patterns are derived from the JEDEC standards. These take into account the lead tolerances and assembly variations.

The pad must be wider than the actual footprint of the leads for proper solder fillet formation.

If the pads are too narrow, the fillet will be too small and will be weaker.

If the pad is too wide, solder will be drawn away from the joint, and can get under the body and push it up.

Is there a particular reason they need narrower spacing?

For more information, please see the packaging appnotes, particularly the Handling & Process Recommendations :

General Packaging Information

Hi Kai, Paul,

Thank you for your kind support.
〉Is there a particular reason they need narrower spacing?
This device is being considered for replacement with other devices.
For this reason, it is necessary to compare and consider the PKG size of other companies' devices.

Current pads cover the length of the LM2903.
However, the distance of the part in close contact with the substrate is slightly longer than the recommended pad.

In order to optimize the PAD size,Customers need that information.
Could you tell me the length of the figure below?


Best regards,
Yusuke

Hi Tsukui,

can you say what devices the customer wants to replace?

Kai

Hello Tsukui,

Would the device being replaced come from a Japanese manufacturer? Such as JRC, Renesas or ROHM?

Please realize there is a difference between the Japanese "SOP" package and the JEDEC "SOIC" package. TI follows the JEDEC standard.

The Japanese SOP package is very similar to the SOIC, but the package body is wider and the leads are shorter, resulting in a footprint 0.8mm wider than the JEDEC SOIC standard.

We run into this all the time. What is the *exact* part number they are trying to replace? I'll bet it ends in "M", "F8" or "G2".

Hi Paul, Kai,

Thank you for your support.
The device before replacement is BA10393F-E2.
Is it possible to apply the pattern of BA10393F-E2 to LM2903?
Could you give me your advice?



Best regards,
Yusuke
 

Yusuke

You would need to confirm with your board assembly house but it appears that you would need to lengthen the PAD widths (grow then inwards) to accommodate the narrower SOIC package.

Chuck

Hi Chuck,

Thank you for your response.
Is there no problem with the pattern size on the left side?

Regards,
Yusuke

Yusuke-san

what you are showing is different than what we recommend in our datasheet.  However, it is quite possible that having pads of varying heights is ok but I cannot say that it is ideal.  I still would recommend that you follow up with whoever you use to assemble your boards to make sure that this does not violate any requirements on their side.  I am most concerned with the corner pads that are larger than the interior pads.  There will be excess solder paste on these pads and you need to make sure that does not cause any shorts on your board.

Chuck

Hi Chuck,

Thank you for your strong support.
I understand your explanation.
I will inform the customer of that your information.

Let me ask you a question.

As I first asked in the thread,
I need to tell the customer the distance of the blue line.
>what you are showing is different than what we recommend in our datasheet. 
Could you tell me the ideal recommended distance?

Best regards,
Yusuke

Chuck-san,

Thank you for your kind support.
I understand.
I will report that information to the customer.

Best regards,
Yusuke