Premolded QFN packages for

RF & MEMS applications

Andy Longford – PandA Europe

ACP ... for MEMS

2PandA Europe - 2010

• MEMS sensory devices require Air-Cavity packages in

order to contact the media to be sensed ...

• The ACP is usually made up of 3 parts;

– a copper leadframe,

– a molded body (open, and not sealed)

– a lid.

• The ACP QFN type construction enables:

– Excellent thermal management

– Short Interconnects (for microwave applications up to 20-25GHz.)

– Small size “real estate”

– Multi options for lidding

Elements of a QFN package

Cover material **

Lid seal

Sidewall material**

Lid to lead seal

Base material and finish

**Sidewall and lid could be 1 piece … See Type 1

Or Sidewall and base could be one piece (Cavity Package approach)

Background

• “Standard” QFN options

1. Flat base + Cavity Lid = RJR type

2. Cavity base - Flat lid = :

1. Mirror

2. SemPac

3. Quick Pack

4. QLP

3. Cavity base – Cavity Lid = IEP type

Type 1• RJR types

Custom ACP QFN leadframes

Type 2

• Mirror Semiconductor– A Matrix array of (transfer)molded cavity

QFN units

• Sempac– As with Mirror, Transfer molded parts either

singulated or in arrays

• QuikPak– Plasma etched out ‘dummy’ package units

from standard QFN assembly lines

• QLP – A singular QFN package option from early

website ...

– Note QPL blue material

Type 3

• Cavity Base, Cavity Lid –

– Unique leadframe design

• Matrix format with ground i/o

– Unique Cavity Body

• Allows optional fill and seal

– Unique “waffle” lid

• One piece alignment

– Simplifies assembly processes

• Leadframe assy & transport

• Alignment and post assy dicing

RF component Package needs:

• Low height

• Air cavity

• Non-metallic lid

• Ground plane Die pad

• RF type I/O (ground signal ground)

• Short lead lengths

• Cost effective assembly ...

QFN for RF/MEMs Applications

• Low height

• Air cavity

• Lid options

• Leadframe options

• Scalable in sizes

• Gel seal compatible

• Cost effective assembly ...

New QFN Package options ...

• QFN IEP – Inverted Exposed Pad

– Interplex design project for

Improved Thermal management

of Power devices

• Downpad QFN

– New design for high frequency

applications ....

Down Pad QFN

• New Design Issues:

– Flatness of Die pad ?

– Die pad should not

have raised edge

– Molding cannot be

done with flat Plate

(not an RJR style)

– Cost ....?

Flat form base,

Cavity lid and

downpad frame

IEP design ...

• Basic design, 2 leadframe style

• Utilise “Cimptech” Molding

iQLP ...

• “Quantech” Polymer

• Process defined

• LCP type Materials

• Meets MSL3

• Direct Bond to Copper

• AuSi Eutectic compliant (420˚C)

• CTE match to Copper

• High Strength LCP

• Quantech is an expensive LCP

• Specialist Process – costs

• Developed for LDMOS

• QFN .... not ready yet

• Market ?

• Cost ?

• Quantities ?