Page 13 - Chip Scale Review_May June_2021-digital

technologies that require process-related
development and changes, an adjustment
in our new probe design does not
slow down the process. With a simple
software modification, the probe can be
redesigned and manufactured within
a very short period of time, with no
changes to the process. In order to keep
the costs and lead times of MEMS probe
cards down, all, or as much as possible,
of the manufacturing process is set up
in-house.

MEMS RF & high-power IC probing
Nearly all semiconductor devices on
the market today include an RF or higher
speed component along with increased
power domains that require entirely
novel approaches to test. Considering
that the characteristics of the physical
probe are one of the main contributing
factors to an efficient test solution, it
is now more essential than ever to take
a customizable pin approach when
designing a probe card. The probe card
must be capable of high frequency and
higher power requirements, while at the Figure 3: MEMS hybrid probe layout example.
same time, have the capability to handle card design process and optimizing
these stringent test conditions to prevent the stack-up is critical to allow for heat
burning the probes. In addition, it must dissipation so the probes can pass higher
meet electrical and increased parallelism current at elevated temperatures. In
requirements, all of which lead to a order to produce an ideal structure, we
lower cost of probe card ownership. start by experimenting with a variety
Combining the test requirements of materials. Then, by working with
noted above, the need for higher different configurations in the stack-up
speed s, h ig her cu r rent- ca r r y i ng and performing finite element analysis
capability and better signal integrity, (FEA) and electrical simulations,
creates a challenge for a probe card the optimal probe head design can
solution that must accommodate all be modif ied to the electrical and
these requirements and perform to Figure 4: MEMS hybrid probe head array. mechanical requirements over a wide
expectations. A proven MEMSFlex™ range of temperatures [1].
solution for RF/high-power testing Figure 6 illustrates two separate
involves a hybrid probe head concept probe head stack-ups, the guide plate
manufactured with a combination of gap variations, and the heat dissipation
larger diameter probes for high-current comparison. During test, a tremendous
and smaller diameter probes to handle amount of current is going in and out
the non-high-current portions of the IC of localized areas on the chip, typically
(Figure 3). By mixing the larger power in the center of the array (Figure 7).
probes with the smaller ground probes, With traditional buckling beam probe
the card is capable of handling high- technologies, the manufacturer must
current transference and the fine-pitch remove hundreds or even thousands
I/Os, simultaneously. Currently, these of probes to access the burnt probe
MEMS probes can handle up to 40GHz Figure 5: Microscopic image of MEMS hybrid probes. area. Because of this, repair becomes
of frequency with research in progress a significant factor when choosing or
to steadily increase this capability going head, thereby making it possible to building a probe card. The flexible,
forward. Because of the flexibility of probe pads or bumps with varying customizable, and easy to repair
our new probe technology, the probes heights (Figures 4, 5). structure of our new probe makes
will still maintain the same probe force, The MEMS hybrid probe card begins it much easier to develop a working
stroke, and probe length, regardless with a distinctive probe head stack-up. solution that does not require an
of diameter size utilized in the probe This is a significant part of the probe expensive repair budget.

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