Ironwood Electronics SS-BGA User Manual

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GHz BGA Socket User Manual

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GHZ BGA SOCKET USER MANUAL

Table of Contents

Selecting a BGA socket 3
Socket Mechanics 3
PCB Requirements 4
Backing Plate 5
BGA Socket Assembly 5
MLF (QFN) Socket Assembly: 6
Torque Driver 7
Vacuum Pen 7

Elastomer Cleaning Procedure 8
Surface Mount (SM) Adaptor 10
Thru Hole (TH) Adaptor 13
GHZ socket Mechanical Specifications 14
Elastomer Specification 14
Heat Sink Specifications 15

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Figure 1: GHz BGA Socket

Figure 2: SEM
Picture of Elastomer

Selecting a BGA socket

The IC package drawing is required to select the correct GHz socket. Go to www.ironwoodelectronics.com.

Select the “Products” link, then under the “Browse” menu, select the “GHz BGA & MLF socket” link. For

1.27mm, 1mm, 0.8mm and 0.75mm pitch BGA devices, select the “SG-BGA-6xxx” link. For 0.65mm, and

0.5mm pitch BGA device, select the “SG-BGA-7xxx” link. In the table, select the part number that corresponds

to your IC size (length mm x width mm), array size (rows x columns) and pitch (mm). Note: More than one
part number may match your criteria. A frame on the top of the page will show the socket price and links to
PDF and JPEG files.
The JPEG file is a picture of socket. The PDF file will have three pages. The first page shows the socket cross
sectional views and the material details. The second page shows the recommended PCB layout (Note: BGA
pads are not symmetrical to the mounting holes). The third page shows the compatible BGA specification.
Check the following four parameters.

1. IC co-planarity – the value should match or be less.

2. Maximum total height of IC should match or be less.

3. Maximum solder ball diameter of IC should match or be less.

4. Maximum and minimum solder ball height should fall within the range.

If any of the above parameters do not match, go back to the table and select a different part number that
matched the initial criteria and repeat the four parameter checks. If a part number cannot be found to match IC
parameters, please call Ironwood Tech Support @1-800-404-0204.

Socket Mechanics

GHz BGA sockets provide 6.5 to 10 GHz bandwidth in a small, cost
effective ZIF socket for prototype and test applications. The GHz
BGA socket is a simple mechanical socket based on elastomer
connector technology. The GHz socket is a solder-less socket that
can be mounted onto a PCB using screws and nuts. PCBs will require
mounting and alignment holes
at proper locations (see page 2
of the drawings for
recommended PCB layout
information). The typical
GHz socket is 5mm larger
than the maximum IC size. If

there are pre-existing holes in
the PCB, a GHz socket can be custom designed to accommodate those
holes (please call Ironwood Tech Support @1-800-404-0204).

Figure 1 shows a typical GHz BGA socket. The Z-axis conductive
elastomer used in the socket, as a contactor between the IC package and
the circuit board, is a low resistance (<0.01) connector. Figure 2 shows an SEM picture of the elastomer. The
elastomer consists of a fine pitch matrix (0.1mm x 0.1mm) of gold plated wires (40 micron diameter), which are
embedded at a 63-degree angle in a soft insulating sheet of silicone rubber. Another elastomer used for high-

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Figure 3: Elastomer cross-sectional side view

density application consists of an ultra fine pitch matrix (0.05mm x 0.05mm) of gold plated wires (20 micron
diameter), which are also embedded at a 63-degree angle in a soft insulating sheet of silicone rubber. The
insulation resistance between connections with 500V DC is 1000 M. The elastomer is ideal for high-current
(50mA per filament) applications where a thin, high-density anisotropic connector is required. The gold-plated
brass filaments protrude several microns from the top and bottom surfaces of the silicone sheet. The operating
temperature range for the elastomer is -35 to 100 C.

Solder balls from the IC package come in contact with the top end of elastomer wire. The bottom end of the
elastomer wire contacts the circuit board pad and thereby makes an electrical path for the signal. The number of
wire filaments making contact depends on the solder ball and circuit board pad diameters. Figure 3 shows the
cross-sectional side view of the elastomer with the BGA IC. The GHz socket can be summarized as a
mechanism in which a downward force applied to an IC compresses its solder balls onto an elastomer, which in
turn compresses on the circuit board, thereby making electrical connection.

PCB Requirements

General

• Where IC body size is < 30.5mm: GHz socket requires 4 mounting holes.

• Where IC body size is > 30.5mm: GHz socket requires 8 mounting holes.

• Two alignment holes are employed in all sockets. (See drawing for location details).

• BGA pattern is not symmetrical with mounting holes due to angled wires in elastomer (see drawing for

layout details).

• Please refer to page 2 of the socket drawing for all PCB recommendations.

Thickness

1.6mm minimum. This will change as per customer's application, environment and usage.

Finish

SnPb plating or Immersion Au or Immersion Ag. Other plating may be used but testing may be required.
Ideally pad surface that is flush or higher than the solder mask is recommended.
Note: Our internal tests were successful with 0.001”-0.002” thick solder mask above the pad surface on 0.5mm
to 1.27mm pitch elastomer sockets.

Cleanliness

Isopropyl Alcohol or similar should be used to clean the board surface prior to attaching socket.

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Figure 4: Example Insulation Plate

Backing Plate

For an IC body size of 19mm and above, the GHz socket requires a backing plate to prevent the deflection of
the target circuit board due to the high downward forces. If the backside of target PCB contains capacitors and
resistors, a custom insulation plate with cavities milled for those capacitors and resistors can be designed. The
insulation plate sandwiches between the backing plate and the target PCB. Figure 4 shows an example
insulation plate.

BGA Socket Assembly

Refer to figure 5 for graphical illustrations.

1. Install the socket base assembly on the target PCB with the base mounting hardware (provided).

Because of the asymmetrical location of the tooling holes, the socket can be assembled onto the target
PCB with only one orientation (rotation).

2. Place BGA package (solder ball side down) into the socket. NOTE: BGA orientation on target PCB is

critical. If IC frame (optional) supplied, place it over the BGA package.

3. Place the compression plate on top of the BGA package.

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