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Micro-Fiberglass Reinforce Solder Joint at the Interface

IP.com Disclosure Number: IPCOM000033867D
Publication Date: 2004-Dec-30
Document File: 2 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that improves the solder joint strength at the second level interconnects by using micro-fiberglass laid across the pad opening and the SRO.

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Micro-Fiberglass Reinforce Solder Joint at the Interface

Disclosed is a method that improves the solder joint strength at the second level interconnects by using micro-fiberglass laid across the pad opening and the SRO.

Background

Currently, brittle failures effect solder joint strength during dynamic loading. And during temperature cycles, thermal expansion mismatch between the package and the board induces fatigue loading near the joint interface. Current solder joint technology normally fails near the joint interface, or across the IMC layers at the package side (see Figure 1).

To solve these problems, a bigger solder joint geometry is used to improve shock and vibration performance, as well as improve temperature cycles. Heat sinks and an Electro-Magnetic Interference (EMI) can also shield the solder joint from direct mechanical loading.

General Description

The disclosed method uses micro-fiberglass to enhance solder joint reliability. The micro- fiberglass is coated across the pad opening as shown in Figure 2[a]. The micro fiberglass is attached to the substrate using an adhesive that surrounds the pad, but leaves the pad opening region porous for solder joint to form (seeĀ  Figure 2[b]). Prior to ball attach, the flux is printed on the substrate and fills up the porous fiberglass (see Figure 2[c]). Then the solder ball is attached to the substrate using the tackiness of the flux to hold the solder ball in place. After ball attach, the units are reflowed and the molten solder flows into the porous fiberglass either with capillary action or any other means to form a joint with the pad. Due to the high viscosity of the molten solder, the micro-fi...