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Method for Migrating Via Stub Resonance in Printed Circuit Boards (PCB)

IP.com Disclosure Number: IPCOM000245672D
Publication Date: 2016-Mar-28
Document File: 7 page(s) / 256K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is method for migrating via stub resonance in printed circuit boards (PCB).

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 01 of 7

Method for Migrating Via Stub Resonance in Printed Circuit Boards (

Disclosed is method for migrating via stub resonance in printed circuit boards (PCB). Via stub resonance in PCB has been a serious problem for good signal integrity. To resolve this via stub resonance, there have been several methods suggested. However, these methods are expensive methods. Hence, it would be beneficial if a low-cost method is developed to migrate via stub resonance. In this article, a cost-effective method is suggested to resolve via stub resonance issues effectively using impedance matching concept.

    In today's high-speed PCB in servers, signals that have via transitions have poor signal integrity. The reason for the poor signal quality is via stub, which results in huge resonance in insertion loss. For thick boards with via stub length greater than 60 mils, the resonance from via stub is another major factor affecting signal quality. To resolve via stub resonance, backdrilling of via stub has been used [1]-[3] as shown in Figure 1, which is a conventional method in the industry. However, this backdrilling method is very expensive and also affects manufacturing yield. Also, other methods were proposed to mitigate via stub resonance [4]-[5].

    To overcome this kind of issue, this invention proposes a method that is cost-effective
(i.e., low cost) compared with the backdrilling method. At the same time, this method removes a huge resonance caused by via stub completely. The main advantage of this invention is cost-effective as well as resolves via stub resonance issue in PCB effectively.

To demonstrate effectiveness of this invention, 3-D models were generated. Figure 2 shows 3-D model for via stub resonance using Hugh Frequency Structure Simulator (HFSS), which is 3-D electromagnetic solver. This model was made to show resonance due to via stub.

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Page 02 of 7

    Figure 3 shows resonance due to via stub in Figure 2. As shown, there is a huge resonance dip which ranges from 4 GHz to 11.4 GHz, which is detrimental for high-speed signaling in systems. In fact, this huge resonance deteriorates system performance. In this...