SMTA International Conference Proceedings


PCB PAD SITE DRESS METHODS ON BGA AND SOCKET PAD ARRAYS

Authors: James Wade and Raiyo Aspandiar; Don Naugler and Terry Leahy
Company: Intel Corporation; V. J. Technologies
Date Published: 10/24/2010   Conference: SMTA International


Abstract: This study compares manual and semi-automated Printed Circuit Board (PCB) Pad Site Dress Methods. Each method is analyzed to understand which method can prevent board damage to the PCB pads such as pad lift, pad cratering and solder mask web damage on various Ball Grid Array (BGA) package types. One socket and two BGA land array patterns where used as well as two PCB suppliers and three socket suppliers when the study was conducted. The site redress experiments were conducted in 3 phases.

Phase 1 benchmarked the most current solder stations used in the industry for BGA PCB pad site redress. Phase 2 was done to understand if heating the PCB BGA component location during PCB pad site dress will reduce the thermal/mechanical stress to the PCB lands during the site dress process. Phase 3 compare braided copper wire with solder iron type, vacuum scavenging, and flat rigid copper coupons. Electrical test, x-ray, and Die & Pull (DnP) data was used to quantify the capability of the different site redress methods. All the same Critical To Function (CTF) parameters were used in these experiments and will be described in this paper as well.

The rework reflow CTF parameters used for removal and placement of the BGA and socket can have an impact on weakening the PCB pads during the rework process. The PCB pad site dress method can induce the most significant damage when not done properly due to the inexperience of the operator performing the task and how well they are trained on the method they use.

The results from the three different studies for PCB Pad Site Dress Methods on BGA and Socket Pad Arrays will provide insight on which techniques performed best for either of the two component sites from a time 0 first pass yield assessment (FPA). The FPA will be based on e-test for opens and x-ray for solder joint bridging. Failure analysis (FA) via cross sections will highlight any findings such as component solder joint mis-alignment and PCB pad crater. Die and pull was used to identify the same defects as well.

Key words: BGA repair, PCB pad site dress, Solder scavenging, board damage, pad cratering



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