Semiconductor products are just about found in everything nowadays, in white goods, cars, TV’s, lighting, computers, medical equipment etc. Semconductor demand has been growing over the last decade with the supply not able to react to the high demand. One of the factors is that the automotive industry is shifting to electric cars and this is fuelling a large demand for the semiconductor chips. The manufacturing process is complex and today a small 5mm x 5mm semiconductor chip may contain billions of transistors. The manufacturing process due to its complexity requires that all semiconductor chips are tested prior to shipping to the customers, this in itself is a crucial stage of the process which enhances the repeatability and reliability of the parts produced. The testing of semiconductor chips is done at various stages namely at wafer stage and at the stage prior to shipping. Some semiconductor chips are tested as much as 20 times prior to dispatch to customer.
Testing is done on automated testing equipment (ATE). Spring loaded probes (also know as pogo pins) are an integral part of this testing system, where the probes offer the perfect interface to contact each and every semiconductor contact lead/point. The reliability of these pogos is achieved with specially selected materials and coatings together with springs which are designed to withstand repeated insertions of more than 2million. Pogo pins are mounted on specific high accurate machined jigs called test sockets which are capable to receive and guide the semiconductor chips to the correct contact point.
Designers of test sockets must correlate several challenges to find a working design.
Tolerances on the semiconductor test package,
• Test temperature where same package maybe tested at very high temperatures of +150 Deg C and a low -50Deg C.
• Contact resistance of the spring probe and the expected currents to be tested.
• The socket material to be used, which needs to be insulative but dissipates ESD charges which might be created due to the ATE movement inside the chanber.
• The signal path must also be shielded to minimise the effect of electromagnetic interference.
• After all these challenges the socket must operate successfully in a high volume production environment, reliably handling thousands of devices per day.
The design is therefore filled with repeatability features where each semiconductor unit is tested with the same test compression to produce the same resistance value along the pogo pin electrical path.
An extra challenge is the decrease in the size of the semiconductor units and the decrease in pitch between each contact landing. This miniaturization is leading to smaller pogo pins and tighter sockets requiring very precise machining.
At Xtroprecision we are at the forefront of these challenges. We are able to design and provide high quality test sockets which house a variety of high end spring contacts which are used to test semiconductors for several industries. Xtroprecision has delivered sockets for quad flat, no leads (QFN), quad flat pack (QFP), small outline integrated circuit (SOIC), ball grid array (BGA), land grid array (LGA) and more. Xtroprecision sockets have been used in technically differentiated electronic components, subsystems, microwave and RF products that connect, protect and control critical applications in the commercial aviation, defense, space, medical, rail, semiconductor test, wireless telecommunications and industrial markets. Xtroprecision test sockets are optimized to provide superior quality and reliability to a variety of stringent semiconductor test applications