Selecting Materials For Back End Test Sockets

Semicon Scott

A Process For Selecting Materials For Back End Test Sockets (Back End Test Part One)

Likely no one segment of plastics for the Semiconductor market has been more profoundly affected by Moore's Law and the constant miniaturization of the chip then Back End Test sockets (BiTs).

Materials are constantly being developed as others are obsoleted due to the need to machine smaller and smaller features to match up with todays IC chips. It essentially creates a rheological teeter-totter. 

On one hand you have the need to machine smaller hole patterns with ever reducing pitch sizes yet on the other hand you need a material that is more dimensionally stable as a completed socket. In rheological terms, these two variables work against each other in the development of viable solutions for the BiTs market.

For example, materials can be made to have enhanced dimensional stability by the addition of fillers such as glass fiber or ceramic however the micro machinability of a hole is reduced as a result.

The table below shows the reduction in the sizer of the node or transistor of the IC chip through the last 20 years, a typical hole size associated with that chip size and the typical required stiffness of the material to achieve dimensional stability during test. It also shows the dominant leading edge materials used.

As shown, the dominant material technology is constantly shifting to meet the changing requirements of the BiTs industry. As one can see... the trajectory is getting to the point of rheological impossibility and is already there for virgin materials. Todays materials require a razors edge innovation to increase dimensional stability while not sacrificing micro machinability. 

What we plan to propose in the opening of this series on Back End Test materials is quantitative methodology to compare materials for Dimensional Stability in use vs Micro Machinability in the manufacture of a test socket. This will allow us to then propose a model to help select the best material for the application.  

    Year         Node Size         Hole Size         Material Stiffness (psi)     Leading Edge Plastic Used
2000 130 nm 0.8 mm 420,000 PEI Ultem & PEEK
2003 90 nm 0.6 mm 500,000 PEI Ultem & PAI Torlon
2006 65 nm 0.4 mm 600,000 PAI Torlon & PI Polymide
2009 45 nm 0.25 mm 980,000 PI Polyimide
2012 28 nm 0.18 mm 1,000,000 PI Polymide & Ceramic Peek
2015 14 nm 0.15 mm 1,200,000 Laminated Mtls & Hi End PI Polyimide
2017 7 nm 0.1 mm 1,400,000   Laminated Materials & Specialty Filled Materials  
2021 5 nm 0.08 mm Next Gen Hello Vendors!

In the next #SemiconScott post, we will define the properties that are critical to micro machinability. In the following post we will define the physical properties that play a critical role in achieving dimensional stability of a completed socket.

Finally we will introduce technologies that we find bring unique value to this market. 

So many factors to consider when selecting the optimum material for your Test Socket or Micro Machined application. Feel free to contact Port Plastics for suggestions on materials, whether static controlled ESd products or non static controlled, we have the largest selection of Semiconductor materials on the globe.


Download As PDF

Process for Materials BET Part One - PDF