Precise control of coating deposition is critical to the application of conformal coatings to selected areas of printed circuit board assemblies. The coating must be applied in a defined pattern and film thickness to ensure that there is adequate coating present on areas to be coated such as soldered connections and no coating on other areas such as electrical connectors. In many cases,the areas to be coated are immediately adjacent to areas where coating cannot be applied (no-coat areas). Automated coating application techniques are increasingly being utilized to replace the less controllable hand spray and
dipping techniques for conformal coating application. Typical coating applicators include air-atomized spray,film coating and needle dispensing.
In recent years,automated systems have been developed for the application of coatings with the goal of eliminating the masking and de-masking process. These systems typically consist of a coating applicator for large areas,a coating applicator for small areas,a motion and positioning mechanism for the coating applicators and a system controller.
Typically spray valves or film coating applicators are used for coating the large areas on the substrate quickly to minimize the time required for coating application. However,typical large area coating applicators deposit the coating pattern with irregular edges. The coating cannot be applied close to the no-coat areas with these applicators due to the irregular edge of the coating pattern. In order to eliminate masking another applicator is required to coat the smaller areas immediately adjacent to the no-coat areas. Needle dispensing valves are typically used for coating the smaller areas.
These types of applicators have been effective in certain circumstances but do not produce a uniform coating and do not completely eliminate the requirement for masking.
Limitations of dispensing applicators include imprecise flow rate control,difficulty producing short coating line segments,heavy coating deposition at the start and end of a coating segment and susceptibility to uneven or warped substrate surfaces. The coating flow rate from a dispensing valve is set with a manual screw to adjust the stroke of a piston that is connected to a needle. The distance that the needle moves from the seat controls the effective orifice size at the nozzle tip and thus the flow rate of the coating. This manual adjustment is subjective and will necessarily produce different results each time the valve is adjusted.
The needle and seat arrangement of dispensing valves produces discontinuities as the flow starts and stops. This flow behavior coupled with the head motion profile tends to produce heavy spots at the start and end of a coating segment and makes it difficult to create a short coating segment. Programming techniques can somewhat overcome this effect,but the process can be tedious and difficult to repeat.
To apply coatings to very small areas or in straight lines with a dispensing valve,an external dispensing needle is required.
To achieve optimal results,the outlet of the needle must be very close to the substrate,typically within 1 mm. If the substrate
is uneven or slightly warped coating skips may result due to the changing distance between the needle and substrate.
Additionally,the needle has a tendency to contact previously applied coating and pull it along with it causing skips and
smears. The needle is also subject to being damaged if it comes into contact with the substrate.
An automated method for the precise application of conformal coatings has been developed that utilizes the combination of a
dual mode “nozzle-less” ultrasonic spray head,a precision digital dispensing head and a precision X-Y-Z-?-Ø motion control
platform. The ultrasonic spray head uses ultrasonic energy to break the liquid into small drops to form the spray,but the
liquid does not pass through the ultrasonic device. The liquid is applied externally,to a solid surface,vibrating at an
ultrasonic frequency (> 20 kHz). Directed air streams are used to expand or focus the ultrasonically produced spray,
providing two distinct spray patterns: 1) narrow mode with a pattern width of approximately 5 mm at a distance of 25 mm
between the tip of the head and the substrate and 2) wide mode with a pattern width in the range of 3 to 25 mm,proportional
to the distance between the tip of the head and the substrate. The digital dispensing head uses a micro flow solenoid valve
and a streaming nozzle that produces a pattern width of 1 mm from a distance of 5 mm to 15 mm between the nozzle and the
substrate.

In the printed circuit board industry there are generally two main types of circuit boards; there are rigid printed circuit boards and flexible printed circuit boards. There is a tremendous variety of these general types; however the industries that
specialize in one type may have some weakness in understanding some issues related to the other type. Specifically,the flexible circuit industry has come to understand bending,forming and dynamic flexing motion of circuits. The rigid circuit board industry typically will not understand these issues as well. Those who work in the rigid board circuit industry are typically those who fabricate the High Frequency circuit boards. Due to this,there have been several issues with bending,forming and flexing high frequency circuit boards.
All types of circuit boards have the same basic theory for bending,forming and flexing. However the circuit board construction and the materials used,will limit which type of board can feasibly be bent,formed or flexed. Normally woven
glass reinforced circuit boards cannot be bent,formed or flexed reliably. There are many different types of materials used for fabricating high frequency circuit boards and there are several that are non-glass woven reinforced. This paper will address
bending,forming and flexing circuits built with non-glass woven circuit materials.

Oxide alternatives,as well as traditional and reduced oxide chemistries,are coatings or “adhesion promoters” used to enhance the bond between imaged and etched inner layer copper surfaces and the pre-preg resin used to bond the layers together in multi-layer printed circuit boards (PCBs). These chemistries impart varying degrees of roughness to the surface of the copper conductors and as a result electrical performance can be affected. The electrical performance characteristics of two oxide alternatives are examined in this study.

The RoHS legislation in Europe has far reaching consequences,which necessitates a change in lead coating on component leads. Although some suppliers are using a tin finish,there is a tendency for pure tin plating to form whiskers over time which can cause failure of the circuit. To prevent the formation of whiskers different companies have designed different plating schemes and used different materials. Industry has yet to standardize on a lead finish to replace the Sn:Pb solder used in the past.
This paper examines several different lead materials before and after exposure to tin whisker promoting environments to determine the effects of those environments on the soldered connection. In addition to promoting the growth of tin whiskers,these stressful environments also age the solder connections. Based on components used in the telecom industry,solder connections are examined for the presence of tin whiskers,grain structure,intermetallic formation and cracking after being temperature cycled (-40C to 85C) and soaked at 50C and 85% RH.

The whisker concern has been greatly affecting lead free RoHS conversion confidence in the lead frame packages,particularly for high end product conversion. Although plenty of related study in E4 and iNEMI have directed standard whisker testing conditions and measurement methods,the practical whisker performance data in service life is still very small due to numerous extra factors involved from surface mounting and waving soldering.
Most of the literature on Tin (Sn) whiskers study are test results based at the component level in storage or reflow preconditioning to simulate backward and forward conversion in service life. However,for practical Sn-whisker issues,it is
necessary to consider the entire structure,i.e.,the component characteristics,solder joint,PCB and process effect. In this study,matt Sn plated packages with Cu and Alloy 42 based in PLCC,PDIP,LQFP and TSOP were subject to lead free
surface mounting and wave soldering on PCBs with OSP surface finish,followed by TCT (-55 to 85?) 1000 cycle,THT (60?/90%RH) 3000hrs and ambient condition 3000hrs to investigate whisker growth propensity. Whisker growth on the PCB after reflow simulation and separate from the component level was examined to understand whether the whisker risk will be reduced or raised because of factors such as the matt Sn structure,lead frame base,reflow profile and solder paste wetting behavior. Furthermore,SnPb and SnBi plated 4 types of the same package types as above were used as controls for whisker growth comparison. Additionally,corrosion phenomenon due to higher temperature THT testing to correlate to whisker growth after the surface mounting condition will be explored with FIB analysis as well.

Transitioning to offshore sourcing has become a seductive argument for cost reduction. Most managers agree that the impact has been beneficial to the consumer and the trading conglomerates. This paper addresses public perceptions,structural issues,geopolitical and demographic factors that fuel the offshore sourcing argument. It addresses design,marketing,sourcing,and
logistics,local and cultural idiosyncrasies of offshore sourcing that assures a successful venture.

Copyright,like all other forms of intellectual property,is based on negative rights. A copyright registrant may exclude others from reproducing a given copyrighted work,composing a derivative work,performing the work publicly,distributing the work (including sale,lease,or rental of the work),or displaying the work. Works that may be protected by copyright include literary works; musical works and accompanying words; audiovisual works,including motion pictures; sculptural works; pictorial,graphic and architectural works; sound recordings; and,pantomimes and audiovisual works.
The power of copyright is especially effective in preventing the rote copying of a work. A work is a fixed,complete form of authorship. To be complete,a work must have all of its component parts. A computer program which does not run and has no utility is a good example of an incomplete project that is not a work. Direct copying is the easiest form of copyright infringement activity to prevent. However,the test in copyright is one of substantial similarity. Whether a copied work is substantially similar to the copyrighted work is a question of fact to be decided by a jury.

The challenge manufactures face when competing in the world marketplace is to offer a product that will meet all performance and functionality expectations without increasing product size or cost. Increased electronic functionality can be
achieved through the development of more complex silicon integration but that route generally requires a great deal of capital resources and an excessive amount of time. Multiple-die package concepts are often proving superior to the system-on-chip alternative because it minimizes risk and has the potential for economically integrating several different but complementary functions. The information presented in this paper will review several existing package-on-package configurations and introduce a new substrate fabrication process developed to improve IC package density and circuit routing efficiency. In
addition,the basic package assembly methodology will be described and examples of high density stacked memory and mixed function variations shown. In keeping with IPC presentation guidelines it should be noted that a portion of the technical information presented focuses on unique fabrication processes developed for the substrate and are a licensed technology covered by several US and foreign patents.

In this paper,factors that influence the ability for a flex circuit,especially a multilayer flex circuit,to survive the lead-free soldering and other thermal processes during the circuit fabrication processes will be discussed. Results and discussion will be given to demonstrate that the main factors that determine the robustness of a multilayer flex circuit to survive lead-free soldering include: (a) the intrinsic thermal stability of the flex circuit materials used to build the circuit; (b) the multilayer construction of the circuit and related processes making it; and (c) the design of the circuit patterns.

We present the electrical characterization of our Liquid Crystal Polymer (LCP) at microwave and millimeter frequencies and the applications of LCP to circuit components. We use several methodologies to determine the electrical characteristics of LCP for microwave and millimeter wave frequencies. Cavity resonators [1],micro strip T-resonators [2],and micro strip ring resonators [1,3] are measured in order to characterize both the dielectric constant and loss tangent up to 40GHz. The measured dielectric constant is shown to be steady near 3.0,and the loss tangent stays below 0.002,which is better than
advanced polyimide materials. Furthermore,micro strip lines are designed and fabricated on both LCP substrate and other conventional materials in order to compare loss characteristics. The measured insertion of micro strip lines on a LCP
substrate (25µm) and a polyimide substrate (25µm) is 0.11dB/mm and 0.18dB/mm,respectively. These results show that LCP has excellent and stable dielectric properties at high frequencies and the data suggests that this material can be used for applications extending through millimeter wave frequencies. LCP’s inherent properties such as multi-layer capabilities,excellent electrical properties,flexibility,and near hermetic nature suit it to a wide range of applications such as passive devices,packages,and RF cables. Finally,we demonstrate the development of a ban pass filter on LCP flex to achieve an
insertion loss less than 1 dB at 6 GHz in the pass band. The microwave characteristics of LCP have provided the feasibility of this material for low cost and high performance substrates for microwave and millimeter wave applications.