Land Pattern Naming Conventions

[Denisl]

We have (after very much whining and hand wringing) decided to adopt the PCB Standards LandPattern Naming Convention.
I have a copy of the MSWord document and an "older" copy of the PCBStandards Libraries.

I am a bit confused about the various SOP* packages.

In the document there sems to be a pattern established of:
SOPT Body Width X Lead Span - Pin Qty.
When I browse the library it appears that the naming pattern is actually:
SOPT Lead Span X Body Width - Pin Qty

Also - are the units in the Decal names always in mm?

-Denis

[Tom]

Denis,

When creating standards, we always try to strive for the best solution to every aspect of the electronics industry. Many things are taken into consideration including the users recommendations. If anyone has a better mousetrap we evaluate it, vote on it and then incorporate it if the vote passes. The original naming convention had SSOP, SSO, QSOP, PSSOP, PSOP, TSOP, SOP, VSO, MO and several others. It was a mess.

The naming convention for SO's, SOP's and TSOP's was changed a year ago when we were faced with the dilemma that no one could possibly look at a component datasheet and remember the land pattern (decal) name. So we set out to find the ultimate naming convention for this family so that any engineer or PCB designer could look at three items on a component manufacturers datasheet and automatically know the land pattern (decal) name. The Pin Pitch, the Lead Span and the Component Height.

The SO package is the only Inch Based (50 mil pitch device) gullwing package that is still available on the market. Over the next 2 years, component manufacturers will stop production on this part due to three factors.
1. It's GND & VCC pins are on opposite corners of the part and it's not good practice for "High Speed" design. Quote from Lee Ritchey.
2. The size of the package is too large. A 0.5mm pitch package with the same pin count is less than 1/2 the size.
3. All the standard groups (including JEDEC) have agreed that all new packages will use millimeter based dimensioning and lead spacing.

The only other 50 mil pitch devices are used in Japan called the SOP's which are listed in the IPC-SM-782 Section 9.3. I have never seen any of these devices used in the USA.

All the other SOP & TSOP packages are metric based devices with millimeter dimensions and pin pitches. The SOP has a body height greater than 1.6mm and the TSOP packages have a height less than 1.6mm.

The land pattern naming convention is a very simple one. (And yes, all package names use millimeters because the English measurement system will not obsolete from the electronics industry over the next 5 - 8 years)

SOP50X620-40N = Small Outline Package 0.05mm lead pitch X 6.20mm lead span - 40 pins Nominal material condition.

Small Outline IC, Gull Wing (Pitch 1.27mm) - SO + Pin Qty + Size Descriptor L, W, X, M
Small Outline Packages, Thin (Height is < 1.60mm) 0.30mm Pitch - SOPT30X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 0.40mm Pitch - SOPT40X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 0.50mm Pitch - SOPT50X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 0.55mm Pitch - SOPT55X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 0.65mm Pitch - SOPT65X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 0.80mm Pitch - SOPT80X Lead Span (Nominal) - Pin Qty
Small Outline Packages, Thin (Height is < 1.60mm) 1.27mm Pitch - SOPT127X Lead Span (Nominal) - Pin Qty
Small Outline Packages, 0.50mm Pitch - SOP50X Lead Span (Nominal) - Pin Qty
Small Outline Packages, 0.635mm Pitch - SOP63X Lead Span (Nominal) - Pin Qty
Small Outline Packages, 0.65mm Pitch - SOP65X Lead Span (Nominal) - Pin Qty
Small Outline Packages, 0.80mm Pitch - SOP80X Lead Span (Nominal) - Pin Qty
Small Outline Packages, 1.27mm Pitch - SOP127X Lead Span (Nominal) - Pin Qty
Small Outline Packages, IPC-SM-782 Section 9.3 Type I – VI (Pitch 1.27mm) - SOP + Pin Qty

[Denisl]

Thank you, Tom. That clarifies things.
I was a little unclear on the body width as well. Now that I see it is actually the total lead span and not the package body it makes much more sense to me.

Ever grateful;

[Tom]

Denis,

We studied all different naming conventions but when it came right down to it, the package size (body length or width) was not part of the "Soldering Process". In order to avoid naming convention overlap, we needed to narrow down the features that were actually being soldered to the board.

The Quad Flat Package family uses a naming convention with the body length X body width (Which we adopted by IPC - didn't want to reinvent the wheel). But, there are many QFP's with the same exact body dimensions, pin count and pin pitch BUT different Lead Spans. So we had to invent a suffix A, B, C, etc.

Example: The 100 pin 0.65mm pitch QFP has a 14mm X 20mm body, but the lead span has 5 different variations. So we had to incorporate a new suffix.
QFP14X20-100 (14X20 = 14mm body width X 20mm body length)
QFP14X20-100A
QFP14X20-100B
QFP14X20-100C
QFP14X20-100D

If I had my wish we would change the QFP naming convention to adopt the Lead Span instead of the Body Width (because we don't solder the body to the board). This would create a naming convention that would not have any crossover names, but we can't change the QFP naming convention now because it's too late. Thousands of engineers and designers are using the current system and we're at the point of no return. See chart below.

[Denisl]

Again, many thanks.

Since we are just embarking on this, I suppose we can make the change that you were not able to and adopt the lead span rather than body for our QFP's.

[Tom]

I would use the naming convention just as it is. We are in the middle of making the current naming convention a World Standard. Every schematic symbol in the world will point to the current naming convention. Every assembly shop will know the current naming convention. We are building massive search engines with every component manufacturers part number pointing to the current naming convention.

This is why we are at the point of no return. Any changes now will send a ripple through the entire environment. It's too late to change anything now. The integration process has begun.

[KCDesign]

In the PCB Standards naming convention, I see that the connectors are all separated out by manufacturer but what do you do about those connectors from the various suppliers that can all use the same footprint. My EE's want to be able to use multiple vendors for the connectors and not get stuck with a schematic symbol that they have to change each time they decide to use a different vendors connector.

I am trying to get everyone here to buy into using the Pcbstandards naming convention but I am running into resistance mainly because of the connector issue plus the fact that the EE's have to actually think when make their schematic symbols.

[Skip Yutkus]

KCDesign,

What we do here is use our internal part number for the schematic symbol - the Source Control Drawing lists multiple sources for the part - you could name your decal with the internal part number also.

Skip

[Tom]

KCDesign,

I understand what your situation is. Most connector manufacturers make a typical DB9 connector. So, here's what we're doing to help that situation. First we had to decide which connector manufacturer would work with us and would also have a great majority of the standard connectors. So we picked MOLEX.

If you find the MOLEX connector you want, but purchasing it from another vendor, rename the decal to that manufacturers part number and copy it to a different library. This will create some duplication, but hopefully you have an 80Gig hard drive.