The 0201 - A tiny tale - Components

Electronic News, Feb 11, 2002 by David Shyu

Let's look at the tiniest little passive components--0201 chips.

Just as 0402 chip passive components are quickly supplanting the dominant 0603s, so 0201s are positioning themselves to take the next evolutionary step.

Tombstones and solder bridging are the main defects as they were for earlier generations of passive body sizes. However paste, stencil, placement and oven changes are needed that are significantly different from those in earlier transitions.

Meanwhile, other competing technologies, including integrated passives, are now being implemented and could stem the growth rate of 0201s.

All in all, 0201s will grow in popularity with time. Although 0201 may never achieve the full potential that 0402s have, it will be the dominant passive device for small form factor products by 2010.

Passives are used throughout electronic systems to provide the functions of resistance, capacitance and inductance. There are more than 10 passives used for every active component in a typical system. The Nokia 3285 CDMA phone has 581 passives for 18 actives, a ratio of 32:1. Passives account for 90 percent of components, 40 percent of board area and 30 percent of solder joints in typical systems. The majority of passives are still discrete ceramic based and of standard outline. The 0201s, the smallest passive body size, are now being used in high volumes, for example, in RF modules.

In 1977 atypical passive component measured 3.2mm x 1.6mm (1206) in surface area Ten years later in 1987,0805 passives had become the most common with a size of 2.0mm x 1.25mm. The end of the millennium saw the 0603 passive measuring 1.6mm x 0.80mm claiming the largest usage; and 0402 passives, at 1.0mm x 0.50mm, will become the most popular size this year. The 0201 passives, which are the smallest passives in production to date, have dimensions of only 0.60mm x 0.30mm. They are already used in RIP modules, hearing aids and PC cards. Compared to 0402s, 0201s are five times smaller in area and also five times lighter, which makes them attractive for small portable systems.

Currently, 0201 passives are being produced at a rate of 6.8 billion per year and represent only 0.6 percent of total passive production. They currently serve niche markets and have a significant cost premium over 0402s and 0603s. Prices for 0201s are currently three to four times higher than 0402s, depending on volume. Designers are therefore using 0201s only if they have serious board-space limitations. Clearly, the advantage of 0201s is in area reduction.

Applications that use large area boards may not see a benefit from smaller discrete passives for quite some time. But even in nonportable applications, 0201 passives may be beneficial. Their smaller size allows decoupling capacitors to be placed close to active I/O, thereby increasing performance. Use of 0201s will eventually grow strongly and serve more than 30 percent of the total passive market within the next 10 to 15 years, primarily in portable devices.

The 0201s need placement equipment with higher accuracy, and the capital equipment replacement cycle is a factor in 0201 adoption. For example, 0402 passives have been available for more than six years but have only recently begun moving beyond mobile phones. Perhaps one of the main differences in the introduction of 0402s vs. 0201s is that 0402s did not require processes that were much different from the previous generation 0603s. Handling, placement, and cost premiums will likely not allow 0201s to reach the penetration levels that 0402s have achieved in a similar time frame. The 0603/0402 passives do not mix well with 0201 passives because stencil thickness and reflow oven profiles may be different.

In theory, a 0201 should cost less to produce than a 0402 because many more can be processed from the same panel. However, yield and start-up process costs enable and oblige the passive supplier to charge a premium in the early years.

As the production of 0201s ramps up and yields improve, the price gap will be reduced and the adoption of the smaller and lighter passives will certainly become more mainstream. It is expected that the price of 0201 capacitors will drop to 1 cent by late 2002, as capacity is increased.

Aside from pricing issues, there have also been problems associated with the assembly process of 0201 passives onto PCBs. Issues connected with mass reflow assembly have been observed, leading to tombstones, solder beads and solder bridging. Flux type, pad design, stencil design, spacing between components, orientation of components and solder paste reflow atmosphere are all important factors that may impact the assembly yield.

What are major causes of defects?

Tombstones occur when a component is misaligned in such a way that it stands on one of its sides. This typically happens when one side is being pulled harder than the other, which can be caused by one of the following: when one side of the component reaches a liquid state before the other, thereby creating a surface tension where the molten solder pulls the component vertically; heterogeneous flux wetting speed (the time it takes the solder to wet); usage of attachment pads or component termination that have poor solderability; excessive heating speed or inadequate flux activation time.