New graphite tool for micro-coil spring provide compliant interconnects between IC packages and PCB

08-08-2017 | TopLine | Subs & Systems

TopLine has announced a new Graphite Tool (patent pending) for precision positioning of 0.4mm diameter micro-coil springs onto BGA1738 organic substrates as an alternative to conventional solder balls. Micro-coil springs, originally introduced by NASA, provide compliant interconnects between IC packages and the PCB. The footprint of 1738 packages is 42.5mm x 42.5mm with a pad pitch of 1mm. After attaching micro-coil springs, the reworked package provides more compliancy than BGA solder balls to absorb stress caused by CTE mismatch, and to increase solder joint reliability under harsh operating conditions.

The tool securely locks organic or ceramic LGA substrates in place while the springs are attached to the substrate. The procedure is simple: an operator places the LGA inside of the tool. Next, a layer of solder paste is printed on the LGA pads using a 125um thick stainless-steel stencil. Afterwards, the springs are dropped in place using the company’s patented Flip-Pack cassette. After depositing the springs into the graphite, the operator removes the cassette. The next step is to place the graphite into a vapour-phase reflow oven to form solder fillets that permanently secures the spring to the IC substrate. After cool-down, the CGA is gently removed using an engineered extraction tool.

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