Optimization of PCB SI Coupon Design That Minimizes Discontinuity Through via-in-Pad Plated over (VIPPO) Technique

The importance of signal integrity is emphasized as signal speed increases, and higher frequencies are applied. The Print Circuit Board (PCB) manufacturer uses signal integrity coupons that can replace the in-product circuit to measure and calculate the signal loss. In this study, we tried to minimize the discontinuous path of Delta-L coupon by using the via-in-pad plated over (VIPPO) technique to improve the signal integrity. We compared the VIPPO-applied design that has minimal discontinuity with the conventional Delta-L design. To minimize discontinuity, circuits connected to pads and via holes were removed from the outer layer, and the pads were designed directly above the via holes. First of all, we simulated the optimized design that eliminated discontinuities using signal integrity software, Simbeor. Second, we measured and verified Delta-L by using Introbotix’s Accu-Prober program. In the future, higher measurement frequencies will further increase signal loss because of unnecessary pathways and discrete signals; therefore, minimizing the effects of discontinuity will be an important issue, and using the VIPPO technique will help improve signal integrity.

The resin-flowing model in prepreg lamination of print circuit board

Purpose This paper aims to show a resin-flowing model based on Darcy’s law to display the flowing properties of prepreg during lamination. The conformity between the model and experimental results demonstrates that it can provide a guideline on print circuit board (PCB) lamination. Design/methodology/approach Based on the theoretical derivations of Darcy’s law, this paper made an analysis on the flow of prepreg in the pressing process, according to which a theoretical model, namely, resin-flowing model was further formulated. Findings This paper establishes a resin-flowing model, according to which two experiment-verified conclusions can be drawn: first, the resin-flowing properties of material A and B can be improved when the heating rate is between 1.5 and 2.5 min/°C; second, increased pressure gradient can add the amount of flowing resin, mainly featured by increasing pressure and reducing filled thickness of prepreg. Originality/value This model provides guidance on setting lamination parameters for most kinds of prepregs and decreasing starvation risk for PCB production.