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Buried gold line stacked DIE packaging
Release time:
2021-01-25
With the increasing convenience of electronic products, the requirements for products are also becoming smaller and thinner. This means that the existing packaging components are required to be smaller and thinner, while the content of the products themselves continues to increase. How to meet all these requirements under such contradictory conditions? This poses new development challenges for the entire packaging industry.
The miniaturization development in the packaging industry includes directions such as CSP and BGA. This article introduces the methods of package miniaturization from the perspective of stacked DIE.
Packaging Process
Substrate → Mounting Components → Attach DIE → Wire Bonding → Encapsulation → Cutting → Appearance Inspection → Testing → Packaging
Packaging Forms
● Planar Attach DIE Method (Figure 1)
Planar Type
● Vertical Attach DIE Method (Figure 2)
Directly attached between DIE, stair-type
A layer of spacer is placed between DIE
Limitations of the Two Methods
Planar Attach DIE Method:
Multiple DIE are laid out on the same plane, occupying the packaging space to the maximum extent, making it difficult to meet size constraints.
Vertical Attach DIE Method:
The stair-type (1) stacked DIE method reduces space utilization compared to the planar type, but when stacking multiple layers of the same type of DIE, it will also occupy a lot of space. Each additional layer increases the size of the DIE by about 500um, so when the number of DIE reaches 8, it will increase the space by 500×8=4000um. It is also difficult to meet compact size requirements.
In the stair-type (2) method, the size of the stacked DIE must be smaller than that of the lower layer DIE to allow space for wire bonding, which limits its application.
The interlayer method adds a layer of Dummy DIE between two layers of DIE, leaving height for wire bonding, increasing process flow, material costs, and reducing UPH.
New Attach DIE Method
The new attach DIE method combines the advantages of the two vertical methods (buried type) (Figure 3).
This method uses a new type of material called FOW (film on wafer, as shown in Figure 4), which adheres to the bottom of the DIE using film attach technology. The attached DIE can be directly attached to other DIE above it, with no positional requirements, meaning it can directly press onto the loop of the lower DIE. (Multiple identical DIE can completely overlap, greatly reducing the space occupied by stacked DIE.)
The usage conditions, process flow, and effect diagrams are shown in Figures 5-7.
The advantage of this method is that multiple DIE of the same size stacked together occupy the space of one DIE, greatly saving horizontal space. It is a good choice for products with strict size requirements. The reduction in size can also lower product costs.
When stacking multiple layers of DIE, after wire bonding is completed, the next layer of DIE can be directly mounted without adding a spacer layer. This shortens the production process, reduces external factors' impact, and improves UPH.
This method can effectively solve the situation where multiple DIE are included in a PACKAGE while horizontal space is constrained. As the miniaturization of devices accelerates, the application of this method will also become widespread.
This article is from IC packaging design, authored by Yuan Zhenghong, with copyright owned by the original author. If there are any copyright issues with the videos, images, or text used in this article, please inform us immediately, and we will delete the content.
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