Pad Crater Project “Definition Stage” Joe Smetana Alcatel-Lucent Asia Meeting 5/18/2011

The issue(s) Pad Cratering defects are a significant challenge with Pb-free PCB materials and/or Pb-free solders, particularly associated with large BGA devices Pad Pull or Ball shear testing has not shown to consistently represent the actual propensity for pad cratering of a material and in some cases can give misleading and/or opposite results from what actually occurs in real assemblies A way is needed to rank order materials that is directly related to actual pad cratering

Project Overview Create a relatively simple test vehicle with a single large BGA assembled in the middle – 6 or 8 layers, thickness.093 Fabricate the bare boards from multiple different materials – Include a significant variety of materials, filled and unfilled – Include materials that have also done “well” in HDPUG Pb-free materials projects – Don’t test materials that have done poorly in HDPUG Pb-free materials projects – Other materials as suggested by members Perform bend to break testing to rank order the materials – Design TV to virtually ensure trace breaks simultaneous with laminate (Electrical break) – Spherical bend testing preferred or 4-point bend? – Will need to include some amount of strain gage measurements – Both Single Bend to Break and Repeated Load to Break On the same boards ALSO perform Cold Ball Pull testing for a correlation to actual pad cratering. – Intel will support this Other Possibilities – AE (Acoustic Emission) Testing – identifies actual onset of pad cratering (Anurag Bansal – Cisco) Challenges – need to understand test equipment/test and evaluation – Charpy Impact testing – Doug Sober taking lead on how to get this done. Bob Nevis (Microtek) will support testing. Suggested by Shengyi Could correlate extent of impact damage to pad cratering propensity Promising idea since may track with fracture toughness/pad cratering – If it does – can readily also test this at higher temperatures (200C) Key question – how to design to QUANTIFY results

What this Project will Provide Rank order of materials to Pad Cratering in mechanical bend testing – At selected strain rate uε/sec (sweet spot) – At single bend to break – At repeated load to break 60-70%? (TBD) lowest single bend to break load Correlation or lack thereof of HPP testing to mechanical bend to break testing – Currently no support for this Correlation of AE to Electrical open? Correlation of AE and/or Electrical open to Charpy Impact test?

Bend to Break Testing Meadville to support Bend to Break testing – Need to better define this – uε/sec is the sweet spot to minimize scatter in the results and lower introduces a different failure mode, exhibits twice the scatter in the results... this is typical of behavior seen in a brittle material.

Simplified Bend to Break Test This will not necessarily catch the first break point, but should correlate to it and should properly rank order the materials.

Key Issues Define the test component – Practical Components A-PBGA mm-35mm-DC-LF-305 PBGA x35mm Perimeter+ BGA, 1mm pitch 689 x 689 mil die size Quote of 1000 for $10, Define the materials to be tested – Compare filled vs. unfilled, FR4 – brominated and HF, Selected High speed materials – Look at “cap” technologies – such as Zeta – Select “good” materials (HDPUG Pb-free Materials 1 and 2) Material suppliers need to supply the materials at no cost – First Draft/Proposed Material List follows Define/Design the Test Board (ALU/Meadville) Define the required sample size – 10? Single Bend to Break – 20? Repeated Bend to Break

Proposed Component

Rough Proposed Stackup

Design Rough Header for event detector attach BGA at 45 degrees to allow for either spherical or 4 point bend Need the following specifics defined: Minimum distance from component to board edges? What type of header or board connector is needed the event detector? Edge contacts? BGA pattern duplicated on bottom side using either VIP or SMD pads for comparison

Considerations for Pad Cratering Test Materials – Filled vs Unfilled Hi Tg Phenolic Resin – Halogen Free – Dicy – Mid Tg – High Speed – Cap Layers Resin Content/Glass style effect on outer layers – 106 vs between L1-2 and N-N-1 Pad Size – Normal vs. enlarged solder mask defined pads, – Enlarged pads at corners – Microvia in Pad vs. No Microvia in pad (including Dogbone Microvia vs Dogbone Through Via), – Conformal Microvia vs Filled Micro via Note - With a single design can only do 1 of the options

Preliminary Material List (part 1) High Tg Filled Phenolic FR4s – Isola 370HR – EMC EM-827 – Panasonic R1755V – Shenzen Pacific (PIC) FL-170 – ITEQ IT-180i – Panasonic R2125 – Grace GA-170LE High Tg Non-filled Phenolic FR4s – Isola 370 Turbo – Shengyi S1170 – TUC TU-722 High Tg Halogen Free FR4s – Grace GA-HF-17 – ITEQ IT-170GRA – EMC EM-370(D) or EMC-370 (one but not both) – Panasonic R1577 (Megtron 2) – Shengyi S1165 – Ventec VT-447 – TUC TU-862HF – Hitachi MCL-HE-679G

Preliminary Material List (part 2) Mid-Tg FR4s – ITEQ IT-158 – EMC EM-825 – Isola This a dicy FR4 -OK in low layer count Pb-free High Speed Materials – Isola FR-408HR – Panasonic Megtron 4 – TUC TU-872L or SLK – EMC EM-828 – MGC FL-700 – Panasonic Megtron 6 – Nelco Mercurywave 9350 Cap Materials (over what material?) – Zeta – Shengyi S1160F – Hitachi KS-6600 – Hitachi CUTE

What this Project WILL NOT DO (as currently planned) It will not provide data that necessarily correlates to pad cratering occurring by thermo-mechanical stresses – such in reflow/cooldown as material properties above Tg will be very different from those at room temperature. If Charpy Impact correlates to pad cratering – can repeat on hot boards comparatively easily (Phase 2 – using same boards built as same time in this project?)

Where are we on this Project? Need to resolve – Board design related issues (slide 10) Meadville – Can we do AE? (Cisco) Impact on test location (Cisco or Meadville) – Can we do Charpy Impact Yes probably – who will do it? How to quantify the result (design input?) – Materials list/sample sizes Current funding for 500 parts only Either we increase the funding to get 1000 parts or decrease either – Samples size per material – Number of materials/options

Project Milestones Define the full extent of the Project - Team Define the test vehicle - Team – Component – Board (layers, thickness, size, etc.) Design the Test Vehicle - ALU Determine materials to test - Team Determine the required sample sizes - Team Material suppliers provide materials at no cost in return for rank ordering (coded) Fabricators to build the test vehicle - TBD Procure components – Sun +? Assemble Test vehicles – Celestica/Flextronics? Bend to break testing- Meadville – Include AE testing? (Cisco?) Hot Pin Pull testing (assuming we include this) Charpy Impact? Data analysis and reporting