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Design/Manufacturing FAQ's

What is LLP?
a)LLP is a "Leadless lead frame package". There are no leads extending beyond the package body. The contact pads are exposed and flush with the bottom of the package.
What are the advantages of LLP?
- Small footprint (yields savings in PCB real estate)
- Thin package (<0.8mm package height)
- Excellent thermal performance (Soldering the exposed thermal paddle to the board provides an excellent path for heat transfer from die to the board)
- Smaller size, form factor, and location of contact pads allows parts to be placed closer to the other components on the board
- Negligible package lead inductance which results in:
- Faster signal response
- Low package induced noise (less cross talk and ground bounce)
- Uses standard surface mount equipment and flow for PCB assembly.
- There are no lead coplanarity issues with this package.
Is National the only company offering this type of CSP package?
a) No. There are s everal major package assemblers offering the LLP type package with the same JEDEC outline drawing. They are shipping millions of packages per month.
Are there any guidelines for using LLP?
a) General guidelines for LLP are included in National’s application notes AN-1187. Based on National’s experience, these recommended guidelines are important for the end user to follow during PCB design, stencil design and SMT assembly steps to ensure a successful SMT process.
Is this package lead-free?
a) No. The current lead finish is 85/15 Tin/Lead.
Is this package compatible with lead free paste?
a) Yes. If the peak reflow temperature exceeds 240 degrees C, the MSL package rating may need to be downgraded.
What is the maximum lead count available or qualified at National today?
a) LLP packages up to 56 leads have been qualified by National. Development for greater lead counts is in progress.
What MSL does this package meet?
a) In general LLP meets JEDEC MSL 1. MSL for specific package size and lead count can be found in the application notes AN-1187
Is this a widely used package in the industry?
a) This is becoming a very popular package and we see a migration from other packages to LLP.
Can I get mechanical samples?
a) Yes. Daisy chain samples are available in stock at our warehouse.
Where can I get a copy of the Applications Notes AN-1187?
a) These notes are available on the National Packaging Web page: http://www.national.com/packaging/llp/

Design FAQ's

What applications use LLP?
a) Portable applications are the natural beneficiaries of this package due to size and performance requirements. However, this package can benefit many other applications where size and performance is critical.

Examples:

Cell Phones

GPS Receivers

Pagers

PDA’s

Personal stereo / CD

Hard disk drives

Hand held portable devices

Toys

Notebooks

What is the difference between LLP, Laminate CSP and Micro SMD?
a)

National Package	Industry Package	I/O Range	Interconnect
CSP	Laminate CSP	16 – 208	Laminate substrate
LLP	Leadframe CSP	3 – 56 (currently)	Copper leadframe
Micro SMD	Wafer Level CSP	4 –28	Solder Ball

What is the UL Rating?
a) UL –94-V0.
Does National have thermal data for different LLP body sizes?
a) Yes. National has performed thermal modeling on all offered LLP packages and has done actual thermal measurements on a selected number of packages. This data is available upon request.
Does National have electrical data for LLP?
a) LLP electrical characteristics have been modeled and data is available.
What is the frequency limit where this package can be used?
a) The LLP package has been modeled electrically at frequencies as high as 10 GHz. Actual maximum frequency is design dependent.
What reliability data is available for this package?
a) National has done extensive reliability testing and the summary of the results is included in application notes AN-1187.

Manufacturing FAQ's

Are there any precautions that need to be taken with the LLP package?
- It is critical to follow National’s guidelines for successful surface mount process
- Like BGA’s and other land grid array packages the solder joints can not be viewed from the top without X-ray
What pick and place equipment can be used for LLP?
a) The standard pick and place equipment that can handle BGAs and QFPs with 0.5mm pitch can handle LLP. The LLP has been picked and placed successfully using Fuji, Panasonic & Quad, Siemens, ESEC, Sanyo, Amistar, and Universal equipment.
How do customers determine if the solder joint is reliable after re-flow?
a) Using X-ray inspection of the solder joint after re-flow is the recommended method.
What is the recommended solder reflow profile?
a) The recommended soldering profile is included in National’s LLP package application notes, AN-1187, and meets IPC-9502.
Can the LLP package be reworked after soldering on the PCB?
a) Yes, commercially available rework equipment can be used to rework LLP .
Is LLP shipped in Tape & Reel?
a) Yes. LLP is shipped in tape and reel using industry standard guidelines (ref. EIA-481-1).
Can this package be hand soldered?
a) No. The contacts are on the bottom of the package and no contacts on the side.
What is the reliability of the package after rework?
a) With proper rework the reliability is the same as a new part
Can this package go through wave solder?
a) No. Due to specific design of LLP with contacts on the bottom wave soldering is not possible.
Is National available to assist in manufacturing?
a) Yes. Please contact the LLP team in the Package Technology Group through your local National Semiconductor sales engineer.
Are voids acceptable in the solder between the PCB land and the thermal pad of the package after surface mount?
a) National has done extensive modeling and studies on the impact of voids and the results are summarized in AN-1187.
What is the standoff for this package after surface mount?
a) Typically about 2 mils
Can a "no" clean solder paste be used?
a) Yes.
Can we use a type 1 or 2 solder paste?
a) No. These are not recommended for fine pitch. Type 3 or 4 is the recommended solder paste for LLP packages.