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Multi stepped SR structure to interrupt UF resin bleed

IP.com Disclosure Number: IPCOM000248201D
Publication Date: 2016-Nov-09
Document File: 4 page(s) / 470K

Publishing Venue

The IP.com Prior Art Database

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Page 01 of 4

Multi stepped SR structure to interrupt UF resin bleed

Background

A semiconductor die or package is commonly mounted to a substrate. In the case of a flip chip or PoP, the semiconductor die having bumps on the active surface is attached on the substrate. The gap between the die and substrate can be filled with an underfill material for structural support and environmental isolation. Excess underfill material typically overflows or bleeds out beyond the die area. The excess underfill material may unintentionally cover other portions such as contact pads for top ball in PoP. Solder resist (SR) dam is formed around die attach area to hold back or constrains underfill overflow. However, SR dam alone is often insufficient to control the overflow. In addition, due to demand for smaller package, the shorten distance between die and top ball pads and improved structure is necessary.

To solve the problem, multi-stepped SR structure having SR dam and SR trench is disclosed. The SR dam and trench are formed proximal to the die attach area. The multi-stepped structure constrains flow of an underfill material.

Description

Fig. 1 ~ 4 shows a process of manufacturing a multi-stepped substrate, especially having 2 step SR layer. Fig. 1 shows first solder resist (SR) lamination phase. A substrate has top surface, wherein conductive pads are formed and the first SR layer is laminated over the top surface of the substrate.


Page 02 of 4

Multi stepped SR structure to interrupt UF resin bleed

Fig. 2 shows patterning phase for first SR opening area. The first dry film mask layer (DF mask) is laminated on the first SR, at which is needed to opening. The first DF mask is patterned to form trench and first opening for top ball pad. The SR that is not covered by the DF mask is exposed to ultraviolet light (UV). The portion of SR exposed by the UV has been ridged.

Fig. 3 shows forming second SR layer phase. The second SR is laminated on the first SR to form SR Dam. The second DF mask is laminated on the second SR. The DF mask is patterned to form SR dam. The SR that is not covered by the DF mask is exposed to UV.

Fig. 4 shows SR stripping phase. Un-exposed portion of SR is stripped. The SR can be removed by etching, application of a solvent, grinding, or a combination thereof. The trench and top ball pads are exposed and the dam is formed. Thermal curing can be additionally applied to the substrate to cure SR layers.


Page 03 of 4

Multi stepped SR structure to interrupt UF resin bleed

Fig. 5...