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Warpage Control Method of 3 Layers Embedded Trace Substrate

IP.com Disclosure Number: IPCOM000248388D
Publication Date: 2016-Nov-23
Document File: 5 page(s) / 571K

Publishing Venue

The IP.com Prior Art Database

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Warpage Control Method of 3 Layers Embedded Trace Substrate

Background

Substrate warpage exhibits in various profiles of contortions, it is controllable by material CTE properties, structure designs, and process adjustments. The warpage issue is one of the major challenges for package using the conventional 3-layer embedded trace substrate (ETS), which constituted by 2 prepreg (PPG) layers of same thickness.

This invention is revealing few viable solutions for warpage control by disclosing the fundamental structure variations such as ply layers of PPG, and asymmetrical PPG layer thickness (z-axis). The process is refined corresponding to the improvement on the conventional 3-layer ETS fabrication.

Figure 1A: Prior art - Conventional 3-layer embedded trace substrate

Description

The first embodiment of invention is to increase the ply layers of prepreg (PPG), which focus on the modification on upper layer of PPG, so called prepreg 1. More ply layers for upper PPG while remaining its total thickness comparable to the lower stack of PPG, so called prepreg 2 to form a rigid contraction structure against the thermal or mechanical stress that lead to warpage as illustrated in Figure 2A.

Figure 2A: New invention - Increased ply layers of PPG


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Warpage Control Method of 3 Layers Embedded Trace Substrate

A total of two ply layers of PPG 1 to constitute an entire stack of prepreg 1 is given in the example of Figure 2A, additional ply layers would enhance its rigidity to refrain the warpage.

The second embodiment in Figure 3A is applying the asymmetrical PPG thickness. This invention is combining the concept as presented in the first embodiment; Figure 2A to apply more ply layers for PPG 1, however, the PPG 1 ply layers are different in thickness and thicker for the layer under one another as given in the example showing top layer PPG 1-1 is 30um, while the layer just under it, PPG 1-2 is double in thickness as 60um. This asymmetrical PPG structure is also applied to the entire upper and lower stack of prepreg, which is having the the entirely formed prepreg 1 as 90um thicker than prepreg 2 as 70um respectively. The prepreg thickness ratio is variable and subjected to modify according to the mode of warpage profile.

Figure 3A: New invention - Asymmetrical PPG thickness

The refined process by half curing method to control substrate warpage is disclosed in embodiment 3, which is pertaining to improve the PPG curing process without major modification on the conventional processes. The process steps for 3-layer ETS fabrication is started with the detachable core film preparation represented in Figure 4A which has symmetrical sides for processing. The first patterning of Cu metallization denoted as Cu 1 layer is deposited onto the Cu seed layer through the Cu electroless plating process as shown in Figure 4B. The first PPG layer with defined...