Packageless Test and SMT assembly

Summary on µPOST1

Removes many aspects of die to board assembly Die can be assembled directly onto copper based circuit boards

Allows die to be fully tested at the wafer level with minimal cost

Known good die program with board level build savings possible

Save wafer real-estate For example 400 connections 2.5x2.5mm with 100µm spacing

Enable for increased connections within existing die geometry

Save on prototype/bring-up costs A device can be mounted onto a bring up board, within one day

Further overall savings are possible Overall component height down to 0.2mm.

Devices can be attached to yielded SMT boards

1. Micro-Precision-Optimised-Shaped-Termination , µPOST is pronounced Micro POST

µPOST formationuses a standard thermo-sonic bonding tool

1) Starts as normal, with ball

formed on end of wire

2) Ball is attached &

ultrasonically extruded into

the capillary to form the

characteristic µPOST shape

3) Wire breaks as capillary

rises, ready for new ball

formation, whilst performing

100% connection pull test

Save Wafer Real Estate

The patented µPOST technology allows die to

be designed with asymmetric sub 150µm area

array pads.

A typical die with 400 external connections….

3.5x3.5mm with peripheral wire bond pads

4.5x4.5mm with 200µm full array solder bump

2.5x2.5mm with 100µm full array µPOST

Save Test NRE

The µPOST technology allows die to be FULLY TESTED at the wafer level, using a simple pressure contact onto a multilayer board.

Transmission line effects minimised to enable operational speed testing while containing costs

Remove probe cards costs for 400 I/O die are around…….

$20k and not suitable for hi-speed, analogue or hi-power.

Pyramid and flex probe cards cost even more

Outperform BGA with µPOST

Solder balls have a low height and a large radius

Typically 100µm (h) x 100µm (w) on a 250µm pitch

µPOST have superior height to radius

For example 100µm (h) x 65µm (w) on a 100µm pitch

Provides improved tolerance to mismatched Coeff. Thermal Expansion

Improved mechanical and electrical characteristics with less cost

The Euler-Bernoulli Beam Equation states Displacement equals (Force x L3 )/3(E x r4)

Radius( r )Height

( L )

For a given displacement:

A contact Half Height will receive 8 x Force

A contact double Radius will receive 16 x Force

Displacement

Force

FEA Results

The gold column stretches, in response to the strain, diffusing shear stress away from the attachment area

Provide for a more reliable connection than lead free solder or tin

Important in devices subject to mechanical shock during use (i.e cell phones)

Displacement 23.5 µm

Stress 131N/mm2

Save Assembly Costs

µPOSTed die can be assembled directly onto copper

based circuit boards.

Simple, low cost, reliable connections

Can be made using standard Ultrasonic or Thermosonic

Can use conductive or non-conductive adhesive

Can use a hot air gun

Typical 400 I/O die would require FBGA technology

Design charges ~$10k

Lead Time 6 to 8 weeks

Assembly Charges ~$1/unit @ 1M/month

Comparing BGA and µPOST Assembly

1. Mount on frame

2. Dice Wafer

3. Pick off frame

4. Die Attach

5. Wire bond

6. Transfer mold

7. Part mark

8. Ball Attach

9. Singulate

10. Test

Wafers In

11. Bake & Pack

12. Screen Print

13. Pick & Place

14. Reflow Solder

15. Final Test

Wafers In

Boards Out

1. Bond µPOSTs

2. Test

3. Mount on Frame

4. Dice Wafer

5. Pick off Frame

6. Tin coat Board

7. Apply glue

8. Hot Place Die

9. Final Test

Boards Out

Save on Prototype costs

As soon as Wafers are available, a device can

be µPOSTed and mounted onto a bring up

board, easily within one day.

Mounted using standard equipment

Heated pick & place or pick & place and bake

Typical Engineering lot for standard assembly….

$2k adder to standard assembly charge

Min lot size ~ 50 units

Lead time 3 days plus freight times

Further savings

Overall component height down to 0.2mm.

Mobile and handheld growth with high pin-count, high functionality devices can

benefit

Pre-underfill can be applied at wafer level.

Superior to imbedded chip on board, significantly less handling

Rapid attach to circuit board with support via pre-underfill

Devices can be attached to yielded SMT boards using localised heating.

After passive and SMD reflow the µPOST devices can be attached

Possible development of test head and heated pick and place

Allows for complete system test before device is committed to be attached

No need for subsequent liquid encapsulation (‘glob top’)

Speeding the assembly line and reducing operational costs

Less raw materials, Pb free process.

Less gold than BGA, no die attach material, no expensive laminate, no plastic

encapsulation, no solder balls.

Conclusion

Save wafer real-estate

Save test NRE

Save assembly costs

Save on prototype/bring-up costs

Further overall savings are possible with minimal

development

Contact Jim Palmer at jim.palmer@semidice.co.uk

for further information

The COB technology provides an attractive alternative to packaging, saving on cost and time to market. We are keen on the µPOST technology for these obvious benefits as well as providing improved RF performance. We are looking forward to see the wide adoption of the technology by board assemblers”. Ebrahim Busherhri, Lime Micro, http://www.limemicro.com/

“Micropost interconnect technology has the potential to both shave time off the critical package design/NPI schedule, and offer a rapid route to the benefits of minimum size packaging.” Mike Warren, Frontier Silicon, http://www.frontier-silicon.com/

What the customers say …