PCB Libraries Forum : Multi-component Footprint When Small Changed

Multi-component Footprint When Small Changed : We took several months to create...

Thu, 05 Jun 2025 09:17:44 +0000

Author: Tom H
Subject: 3492
Posted: 05 Jun 2025 at 9:17am

We took several months to create the JEDEC library for the MO, TO, MS, DO series.

The JEDEC was one of the first libraries we created.

When you have package dimensions in an FPX file and you add new package dimensions, Footprint Expert will throw a warning that the package dimensions already exist and ask if you want to add a duplicate footprint.

After creating the JEDEC FPX library, we downloaded over a million datasheets and entered all the package dimensions into the JEDEC library and not one manufacturer package dimensions matched JEDEC. Altera was the only manufacturer that had package dimensions that were close to the JEDEC dimensions.

So the question is, why would we continue to support a JEDEC library when no component manufacturer uses those dimensions?

Multi-component Footprint When Small Changed : Hello Tom,Thank you for your replying. ...

Thu, 05 Jun 2025 02:29:17 +0000

Author: Emilien38
Subject: 3492
Posted: 05 Jun 2025 at 2:29am

Hello Tom,

Thank you for your replying.

Tom H wrote:

However, in the SOT23, are the component functions swappable between manufacturers?

Do you need to create a unique footprint for every SOT23 manufacturer?

Yes exactly, component are swappable between manufacturer, so unique footprint shall be created.

Tom H wrote:

Lastly, the ST Microelectronics P/N LD3985 is a BGA, not a SOT23.

LD3985.fm SOT23-5L, isn't it?

Could we asked to add "JEDEC", "JEITA" or others standard as manufacturer in POD ?

Emilien

Multi-component Footprint When Small Changed : Package body dimensions that are...

Wed, 28 May 2025 08:53:27 +0000

Author: Tom H
Subject: 3492
Posted: 28 May 2025 at 8:53am

Package body dimensions that are within a 0.20 mm difference from each other can be combined into a single footprint by taking the average dimensions.

The only problem is a different pin pitch cannot be tolerated.

There's another issue with component manufacturers. With chip components like 0603, there are many vendors and the electronic function can be the same values between manufacturers. You might have an AVX chip resistor but the assembly shop stock is an equivalent value in Vishay. Just because the value is the same, doesn't mean the package dimensions and tolerances are the same.

However, in the SOT23, are the component functions swappable between manufacturers?

Do you need to create a unique footprint for every SOT23 manufacturer?

We would us 'Silicon Expert' as a source to find out all the equivalent vendors and then try to create a master pattern to accommodate all the SOT23 vendors that have identical functions. If the NXP component electronic function is unique and no other vendor has an equivalent function, then you need to single source NXP as your vendor.

However, Silicon Expert has all the vendors with equivalent electronic functions for the same component package.

It's the package tolerances that vary from vendor to vendor. These can be rounded up and down to make them match between vendors.

Lastly, the ST Microelectronics P/N LD3985 is a BGA, not a SOT23.

Multi-component Footprint When Small Changed : Hello, We started building...

Mon, 26 May 2025 04:12:06 +0000

Author: Emilien38
Subject: 3492
Posted: 26 May 2025 at 4:12am

Hello,

We startedbuilding our footprint library without the support of a PCB footprint expert,and we also face several internal constraints:

We designboards with a very long expected lifetime (up to 40 years), which means we needto manage component obsolescence over time.
Forthis reason, it’s easier for us to avoid redesigning the PCB when replacingcomponents, as long as they share the same footprint (e.g., SOT23 replaced bySOT23).
Weuse some components with multi-source MFRs/MPNs, and the EMS is free to choosethe source they prefer.

- OurAltium component library is managed by a small team, so it’s more efficient forus to keep the number of components and footprints to a minimum.

Given theseconstraints, we’re unsure how best to manage footprints for multiple componentssharing the same package.

For example, with SOT23-3 components, generic name, MFR/MPN equivalent, FootPrintName according to pcblibraries

Generic Name		1		2		3			https://www.pcblibraries.com/
Manufacturer	Manufacturer Part Number	Manufacturer 1	Manufacturer Part Number 1	Manufacturer 2	Manufacturer Part Number 2	Manufacturer 3	Manufacturer Part Number 3	Footprint (internal)	Footprint 1	Footprint 2	Footprint 3
MULTI	BAV199	Nexperia	BAV199-QR	Diodes	BAV199Q-13-F	ON Semi	SBAV199LT1G	SOT95P230X110-3N_I	NEXPERIA_SOT23	SOT23-3P91_290X240X120L52X44	SOT23-3P95_292X237X111L42X43
Vishay	BAW56	Nexperia	BAW56,235	Nexperia	BAW56,215	Vishay	BAW56-HE3-08	SOT95P230X110-3N_I	NEXPERIA_SOT23	SOT23-3P95_290X240X115L40X40 ??
Diodes	BAV70	Diodes	BAV70Q-7-F	Diodes	BAV70Q-13-F	Rohm	BAV70HYFHT116	SOT95P230X110-3N_I	SOT23-3P91_290X240X110L40X44	SOT23-3P95_290X280X130L45X42
Nexperia	BSR14	Nexperia	BSR14,215					SOT95P230X110-3N_I	NEXPERIA_SOT23
Onsemi	BSS138L	ON Semi	BSS138LT3G	ON Semi	BSS138LT1G			SOT95P230X110-3N_I	SOT23-3P95_292X237X111L42X43
Nexperia	BSS84AK	Nexperia	BSS84AK,215	Nexperia	BSS84AKVL			SOT95P230X110-3N_I	SOT23-3P95_290X230X110L30X43
MULTI	BC847B-Q	Nexperia	BC847B-QR	Diodes	BC847BQ-7-F	ON Semi	SBC847BLT1G	SOT95P230X110-3N_I	NEXPERIA_SOT23	SOT23-3P95_292X237X111L42X43
Nexperia	TL431A	Nexperia	TL431AFDT,215	Nexperia	TL431AQDBZR,215	TI	TL431AQDBZRQ1	SOT95P230X110-3N_I	NEXPERIA_TO-236AB	SOT23-3P95_292X237X112L40X40

Table : 1

NEXPERIA_SOT23

= SOT23-3P95_290X230X110L50X45 ??

Pcblibrariesnaming conventions :

For thefirst line of the table 1, there are three multi-source parts. This meansthat these three footprints must be exactly the same. Many companies usemulti-source components to manage the supply chain without issues during theassembly process.

Manufacturer	Footprint pcblibraries
Nexperia	SOT23-3P95_290X230X110L30X43 ?? (NEXPERIA_TO-236AB) SOT23-3P95_290X230X110L50X45 ?? (NEXPERIA_SOT23)
Onsemi	SOT23-3P95_292X237X111L42X43
Diodes	SOT23-3P91_290X240X120L52X44
TI	SOT23-3P95_292X237X112L40X40
Rohm	SOT23-3P95_290X280X130L45X42

Note: On PCBLibraries.com component from Nexperiaseems to have NEXPERIA_SOT23 Casecode insteadof TO-236AB (except TL431A) ? Why Nexperia doesn’t have a generic footprintname like SOT23-3P95_290X230X110L30X43 ?

Question is: All of they footprint are compatible for assembly ? Only one footprint can becreated with the worst case dimension? There is a difference about the pitch with “diodes”footprint with 40µm less.

One differenceis the length and height of the body which have an influence only in the 3Dbody (we used max 3D body with additional margin, so not a big issues)

It shouldbe very interesting for us (and other companies?) to link these footprints andmaybe to add some acceptable tolerance (+/-100µm ? or 5% for some criteria) tocheck the compatibilities in order to generate only one footprint if possible.

Same thinghere : with SOT23-5

							pcblibraries Name
Manufacturer	Manufacturer Part Number	Manufacturer 1	Manufacturer Part Number 1	Manufacturer 2	Manufacturer Part Number 2	Footprint (internal)	Footprint 1
ST	LD3985	ST	LD3985M33R			SOT95P280X145-5N	~~SOT23-5P95_290X280X145L35X42~~ SOT23-5P95_280X295X145L45X40
onsemi	NCP730ASN500T1G	ON Semi	NCV8730ASN500T1G	ON Semi	NCP730ASN500T1G	SOT95P275X140-5N_I	SOT23-5P95_300X275X110L40X37
TI	OPA188AIDBV	TI	OPA188AIDBVT			SOT95P275X140-5N_I	SOT23-5P95_290X280X145L45X40
onsemi	NCV20061	ON Semi	NCV20061SN3T1G			SOT95P275X140-5N_I	SOT23-5P95_300X275X110L40X37

Table : 2

Note: OnPCBLibraries.com, the ST LD3985 seems to have an incorrect case code:"SOT23-5" instead of "SOT23-5L". The listedfootprint SOT23-5P95_290X280X145L35X42 appears to be incorrect — it seemscloser to SOT23-5P95_280X295X145L45X40.

Samequestion here: the footprint provided by ST shows lead dimensions that are 0.2 mm smaller… How should we handle this?

(Sorry for this big post)

Thank you for your help.

Emilien