Open Defects in PBGA Assembly Solder Joints

2003 ◽  
Vol 125 (1) ◽  
pp. 157-161 ◽  
Author(s):  
S. H. Fan ◽  
Y. C. Chan ◽  
J. K. L. Lai
Keyword(s):  
Solder Joint ◽  
Mechanism Analysis ◽  
Solder Paste ◽  
Soldering Process ◽  
Insufficient Amount ◽  
Solder Balls ◽  
Defect Mechanism ◽  
Open Defect ◽  
Very High ◽  
Thermal Stability Of

PBGA has the advantage of being compatible with existing surface-mount process. The eutectic solder balls collapse during reflow accommodates the lack of co-planarity, the surface tension between solder ball and associated pad creates a strong self-centering property to compensate for any placement offsets. However, some problems emerged in practice due to its special features. The major challenges for manufacturer are the inspection of solder joint and to perform touch-up. In most cases, the defect of solder joint cannot be found until in-circuit or functional testing is performed. At this stage, it becomes difficult to determine whether the defect is due to a solder joint or the component itself. Hence controlling the open defect is very important in the PBGA assembling process. It was found that three kinds of defective modes are responsible for the open defect; insufficient heating in the solder melting phase, poor thermal stability of PCB and PBGA and insufficient amount of printing solder paste. Based on the defect mechanism analysis, by optimizing the soldering process, very high assembly yield was achieved.

scholarly journals Head-on-Pillow Defect Detection: X-Ray Inspection Limitations

2019 ◽  
Vol 16 (2) ◽  
pp. 91-102
Author(s):  
Lars Bruno ◽  
Benny Gustafson
Keyword(s):  
Solder Joints ◽  
Solder Paste ◽  
Wafer Level ◽  
Reflow Soldering ◽  
X Ray ◽  
Soldering Process ◽  
Irregular Shapes ◽  
Fine Pitch ◽  
Solder Balls ◽  
Ball Grid Array Packages

Abstract Both the number and the variants of ball grid array packages (BGAs) are tending to increase on network printed board assemblies with sizes ranging from a few millimeter die size wafer level packages with low ball count to large multidie system-in-package (SiP) BGAs with 60–70 mm side lengths and thousands of I/Os. One big challenge, especially for large BGAs, SiPs, and for thin fine-pitch BGA assemblies, is the dynamic warpage during the reflow soldering process. This warpage could lead to solder balls losing contact with the solder paste and its flux during parts of the soldering process, and this may result in solder joints with irregular shapes, indicating poor or no coalescence between the added solder and the BGA balls. This defect is called head-on-pillow (HoP) and is a failure type that is difficult to determine. In this study, x-ray inspection was used as a first step to find deliberately induced HoP defects, followed by prying off of the BGAs to verify real HoP defects and the fault detection correlation between the two methods. The result clearly shows that many of the solder joints classified as potential HoP defects in the x-ray analysis have no evidence at all of HoP after pry-off. This illustrates the difficulty of determining where to draw the line between pass and fail for HoP defects when using x-ray inspection.

CONTROLLING AND OPTIMIZATION OF THERMAL PROFILE IN REFLOW SOLDERING

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1949-1955
Author(s):  
JIANWEI SHI ◽  
PENG HE ◽  
XIAOCHUN LV
Keyword(s):  
Solder Joint ◽  
Circuit Board ◽  
Solder Paste ◽  
Thermal Profile ◽  
Reflow Soldering ◽  
Soldering Process ◽  
Joint Reliability ◽  
Controlling Parameter ◽  
Technical Evaluation ◽  
Reliability Of Solder Joints

Heating factor, Q is a quantitative parameter describing a process of reflow soldering. It can be used to evaluate a reflow soldering process and the reliability of solder joints. The value of Q is directly related to the energy absorbed by solder joint during heating and the morphology of Intermetallic Compound formed at the interface between solder and pad. Electronic product manufacturers use heating factor as a technical evaluation parameter to guide the adjustment of reflow soldering process and the optimization of reflow soldering curve, to ensure the best reliability of the circuit board. Solder paste manufacturers use heating factor to represent characteristics of their reflow soldering products, and to customize products according to consumer's requests. Equipment manufacturers for reflow soldering use heating factor as an important controlling parameter to establish automatic system for managing solder joint reliability. A reliable soldering result can be achieved using the automatic reflow management system, to control and optimize thermal profile, which leads to the adjustment of the heating factor.

Microstructure evolution of Au/SnSb-CuNiAg/(Au)Ni during high temperature aging

2019 ◽  
Vol 32 (2) ◽  
pp. 57-64
Author(s):  
Bangyao Han ◽  
Fenglian Sun ◽  
Tianhui Li ◽  
Yang Liu
Keyword(s):  
High Temperature ◽  
Solder Joint ◽  
Content Type ◽  
X Ray ◽  
Soldering Process ◽  
Cu Alloy ◽  
Solder Balls ◽  
High Temperature Aging ◽  
Harsh Conditions ◽  
Temperature Aging

Purpose The purpose of this paper is to investigate the morphology evolution and the composition transformation of Au-Sn intermetallic compounds (IMCs) of the new Au/Sn-5Sb-1Cu-0.1Ni-0.1Ag/(Au)Ni solder joint during the high temperature aging. Design/methodology/approach Sn-5Sb-1Cu-0.1Ni-0.1Ag solder balls (500 µm in diameter), heat sink with structure of 7.4 µm Au layer on 5 µm Ni-plated Cu alloy and Si chip with 5.16 µm plated Au were used to fabricate micro-solder joints. The joints were performed in a furnace at 150°C for 150, 250 and 350 h aging. The samples were polished and deep etched before analyzed by metallographic microscope and scanning electron microscopy, respectively. Energy dispersive x-ray spectroscopy was used to identify the composition of the IMCs. Findings ß-(Au,Ni,Cu)10Sn phase is formed during the soldering process. The IMCs evolution has two periods during the aging. The first is the ξ-(Au,Ni,Cu)5Sn, ξ-(Au,Cu)5Sn and δ-AuSn were formed and grew to form a full-compound joint after about 150 h aging. The second is the conversion of the full-compound joint. The IMCs converted to ξ′ phase when the aging time extends to 250 h, and transformed to ε-(Au,Ni,Cu)Sn2 and η-(Au,Ni,Cu)Sn4 after 350 h aging. The thicker gold layer and thinner solder joint can promote the growth of the IMCs. ß-(Au,Ni,Cu)10Sn emerged in Au/SnSb-CuNiAg/(Au)Ni in this research, which is not usually found. Originality/value The results in this study have a significant meaning for the application of the new Sn-5Sb-1Cu-0.1Ni-0.1Ag in harsh conditions.

APPLICATIONS OF SOLDER PREFORMS TO IMPROVE RELIABILITY

2011 ◽  
Vol 2011 (1) ◽  
pp. 000258-000263 ◽  
Author(s):  
Carol Gowans ◽  
Seth Homer ◽  
Ronald Lasky
Keyword(s):  
Solder Joint ◽  
Process Design ◽  
Solder Paste ◽  
Passive Components ◽  
Process Step ◽  
Soldering Process ◽  
Wave Soldering ◽  
Placement Machine ◽  
Through Hole ◽  
Improve Reliability

As early as the 1990s people were predicting the end of through-hole components, but they are alive and well with the numbers of dual in-line packages (DIPs) and connectors still measured in the 10s of billions per year. Many of these components are assembled by wave soldering, however in mixed technology (SMT and through-hole on the same board) where the through-hole count is low, it is often advantageous to consider selective soldering or the pin-in-paste process (PIP). PIP is a process in which solder paste is printed over or near the PWB through-holes. The through-hole components are then placed and the solder joint is formed during the reflow process. PIP has the advantage of eliminating the wave soldering process step. In many cases it is difficult to print enough solder paste to make an acceptable through-hole solder joint. Solder preforms were developed to meet this need. These solder preforms are typically shaped in the form of 0402, 0603, or 0805 passive components. The preforms are placed on the appropriate printed solder paste deposit by a component placement machine. Preforms come in tape & reel packaging. Today solder preforms are also used in other “solder starved” applications such as radio frequency (RF) shields, connectors, and under QFN thermal pads. In all cases, the extra solder delivered by the preform is vital to the reliability of the assembled product. In this paper, process, design, and assembly methods for solder fortification using preforms will be discussed. Four successful solder fortification examples will be presented along with the associated defect reductions.

Solder Joint Encapsulant Adhesive – LGA High Reliability And Low Cost Assembly Solution

2013 ◽  
Vol 2013 (1) ◽  
pp. 000291-000297 ◽  
Author(s):  
Mary Liu ◽  
Wusheng Yin
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Capillary Flow ◽  
High Reliability ◽  
Low Cost ◽  
Cycling Performance ◽  
Solder Paste ◽  
Assembly Process ◽  
Soldering Process ◽  
Capillary Underfill

More and more Land Grid Array (LGA) components are being used in electronic devices such as smartphones, tablets and computers. In order to enhance LGA mechanical strength and reliability, capillary flow underfill is used to improve reliability. However, due to the small gap, it is difficult for capillary underfill to flow into the LGA at SMT level. Due to cost considerations, there are usually no pre-heating underfill or cleaning flux residue processes at the SMT assembly line. YINCAE solder joint encapsulant SMT 256 has been successfully used with solder paste for LGA assembly. Solder joint encapsulant is used in in-line LGA soldering process with enhanced reliability. It eliminates the underfilling process and provides excellent reworkability. The shear strength of solder joint is stronger than that of underfilled components. The thermal cycling performance using solder joint encapsulant is much better than that using underfill. Bottom IC of POP has been studied for further understanding of LGA assembly process parameters. All details such as assembly process, drop test and thermal cycling test will be discussed in the full paper.

The Application of FIB Voltage-Contrast Technique Combining with TEM on Subtle Defect Analysis: Via Delamination After TC

1997 ◽  
Author(s):  
X. Yang ◽  
X. Song
Keyword(s):  
Cross Section ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
New Product ◽  
Defect Analysis ◽  
Transmission Electron ◽  
Contrast Technique ◽  
Defect Mechanism ◽  
Open Defect ◽  
Voltage Contrast

Abstract Novel Focused Ion Beam (FIB) voltage-contrast technique combined with TEM has been used in this study to identify a certain subtle defect mechanism that caused reliability stress failures of a new product. The suspected defect was first isolated to a unique via along the row through electrical testing and layout analysis. Static voltage contrast of FIB cross-section was used to confirm the suspected open defect at the via. Precision Transmission Electron Microscope (TEM) was then used to reveal the detail of the defect. Based on the result, proper process changes were implemented. The failure mode was successfully eliminated and the reliability of the product was greatly improved.

scholarly journals Study on the Reliability of Sn–Bi Composite Solder Pastes with Thermosetting Epoxy under Thermal Cycling and Humidity Treatment

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 733
Author(s):  
Lu Liu ◽  
Songbai Xue ◽  
Ruiyang Ni ◽  
Peng Zhang ◽  
Jie Wu
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Composite Solder ◽  
Solder Joints ◽  
Solder Paste ◽  
Epoxy System ◽  
Mechanical Reinforcement ◽  
Microstructure Observation ◽  
Temperature And Humidity ◽  
Thermosetting Epoxy

In this study, a Sn–Bi composite solder paste with thermosetting epoxy (TSEP Sn–Bi) was prepared by mixing Sn–Bi solder powder, flux, and epoxy system. The melting characteristics of the Sn–Bi solder alloy and the curing reaction of the epoxy system were measured by differential scanning calorimeter (DSC). A reflow profile was optimized based on the Sn–Bi reflow profile, and the Organic Solderability Preservative (OSP) Cu pad mounted 0603 chip resistor was chosen to reflow soldering and to prepare samples of the corresponding joint. The high temperature and humidity reliability of the solder joints at 85 °C/85% RH (Relative Humidity) for 1000 h and the thermal cycle reliability of the solder joints from −40 °C to 125 °C for 1000 cycles were investigated. Compared to the Sn–Bi solder joint, the TSEP Sn–Bi solder joints had increased reliability. The microstructure observation shows that the epoxy resin curing process did not affect the transformation of the microstructure. The shear force of the TSEP Sn–Bi solder joints after 1000 cycles of thermal cycling test was 1.23–1.35 times higher than the Sn–Bi solder joint and after 1000 h of temperature and humidity tests was 1.14–1.27 times higher than the Sn–Bi solder joint. The fracture analysis indicated that the cured cover layer could still have a mechanical reinforcement to the TSEP Sn–Bi solder joints after these reliability tests.

The Benefits of Flux-Coated Solder Preforms in a QFN Assembly Process

2015 ◽  
Vol 2015 (1) ◽  
pp. 000827-000832
Author(s):  
Brandon Judd ◽  
Maria Durham
Keyword(s):  
Mechanical Properties ◽  
Form Factor ◽  
Solder Joint ◽  
Circuit Board ◽  
Electrical Performance ◽  
Solder Paste ◽  
Assembly Process ◽  
Circuit Board Assembly ◽  
Difficult Challenge ◽  
Small Form Factor

The use of bottom terminated components (BTCs) such as quad-flat no-leads (QFNs) has become commonplace in the circuit board assembly world. This package offers several benefits including its small form factor, its excellent thermal and electrical performance, easy PCB trace routing, and reduced lead inductance. These components are generally attached to PWBs PCBs via solder paste. The design of these components with the large thermal pad, along with the tendency of solder paste to outgas during reflow from the volatiles in the flux, creates a difficult challenge in terms of voiding control within the solder joint. Voiding can have a serious effect on the performance of these components, including the mechanical properties of the joint as well as spot overheating. Solder preforms with a flux coating can be added to the solder paste to help reduce voiding. This study will focus on the benefits of utilizing solder preforms with modern flux coatings in conjunction with solder paste to help reduce voiding under QFNs, as well as the design and process parameters which provide optimal results.

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