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Die and flip-chip processing of die stacks and 3D ICs

Amicra’s high-accuracy NOVA and AFC die- and flip-chip bonders and wafer-ink systems are well suited for today’s die and flip-chip processing including 3D-IC and stack-die, because they cover the full scope of high-volume micro and nano assembly applications, and they are offering optional flip-chip bonding, wafer mapping, and post-bond inspection as well.

The ultra-high-precision AFCPlus die and flip-chip bonding system is one of Amicra’s well received state-of-the-art systems. It is laid out in a modular concept for flexibility and customer accommodation and it realizes a placement accuracy of +0.5µm at 3 Sigma for die and flip-chip attach. At a cycle time of <15 sec, it is well suited for processing micro-optic and micro-mechanic components, with eutectic bonding via diode laser or heating plate. AFCPlus offers auto loading of wafers and substrates, wafer mapping, epoxy stamping and dispensing.

Figure 2: The ultra-high precision AFCPlus bonding system realizes a placement accuracy of +0.5µm at 3 Sigma

and highly demanding devices and their stringent requirements for relentless cost reduction in the back-end packaging processes.

The current company product focus is providing the highest micro-assembly placement accuracy in the 0.5 mm to 2.5 µm range, possible-being best-in-class, as well as offering fully automated wafer inking systems that are coupled with highly flexible customization and fulfilling the latest requirements in vertical 3D stacking and horizontal SoC assembly, points out Dr. Weinhändler. Amicra has acquired a substantial number of important customers in the U.S. and Asia – with the understanding that few are willing to be named in public.

An exception is a leading Taiwanese contract manufacturer, which has recently installed one of Amicra’s Nova Plus systems for a large fan-out application with a panel size of 370 x 470 mm. Back in Europe, a major LD manufacturer has reportedly also selected the NovaPlus die-attach and flip-chip machine for its high-volume HDD assembly.

In another on-going customer project a NOVAPlus is used in a WLP packaging application, which attaches 20-mm diameter Au dies with 5/10µm-pitched CuSn microbumps per flip-chip on 8-inch wafers. The temperature of the (vacuum) thermo-compression is 150 to 225 °C, at a bond force of 1 to 2 kilograms. Parts are pre-fixed at 80 °C by epoxy dispensing (which evaporates during thermo-compression).

The dies are placed at a temperature range of 65 to 95 °C. With our broad product line of semi-automatic and fully automatic wafer ink systems, Amicra is currently setting industry standards at a dot size down to 70µm, as well as the inking of diced or undiced wafers. Amicra’s AIS system enables inking of up to 12-inch (300mm) diameter wafers.

Active alignment is also provided on request, while post-bond inspection is included; UV curing is featured as an option. The NOVAPlus die-attach and flip-chip bonder, introduced in 2010, currently is the industry-leading platform in terms of precision and productivity.

Figure 4 offers a glimpse of its inner workings. The machine was first field-approved as a basic platform in 2007 to combine extremely high accuracy (+2.5µm at 3 Sigma) with high-speed processing at a very low cycle time of <3 sec. Figure 5 shows its dual bond head concept.

Auto-loading is provided for wafers up to 12 inch (300 mm) diameter and up to 450 mm substrate wafers, 370x470 mm fan-out panels or even larger substrates up to 600 x 600 mm.

Figure 3: The die-attach and flip-chip placement system NOVAPlus combines high accuracy of +2.5µm at 3 Sigma with a very low cycle time of <3 seconds

Issue IV 2013 27

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