Automated Optical Inspection (AOI) equipment has become an option for electronics manufacturers who are considering how to improve performance on the production line. During the last few years rapid changes have occurred in mounting technology for PCB assemblies. At the same time that equipment has changed in order to be able to build to the new market requirements,new techniques are needed to test/inspect those new products.

The latest types of components launched by the leading component manufacturers have increased the need for process control in rework. These packages are referred to by the generic name Land Grid Array (LGA) or the specific package names Leadless Leadframe Package (LLP) and Micro Lead Frame (MLF). These packages are unique because they contain multiple pad sizes and shapes on the same device. They are also soldered with all terminations on the underside of the package,similar to BGA. These components lend themselves to normal assembly techniques such as screen-printing the PCB,automatic pick and place,then convection reflow. The LLP design has a large center pad that is often soldered to PCB as a ground or power connection. The soldered center pads can also act as a heat spreader to the PCB substrate. This helps keep the part cool and controls expansion of the part to the substrate so that the TCE (Thermal coefficients of expansion) tolerances of the part to the PCB board material are minimized. The rework process for LLPs requires all the pads to be soldered to the same height or the potential for small land connections could be an issue. The solder paste volume used for the center and array pads must be controlled to achieve good,reliable joints.

As imaging requirements continue to move towards finer resolution,accurate layer-to-layer alignment becomes an increasingly important factor that influences product yield. One of the major contributors to yield loss in fine-line products is the dimensional instability of the substrate. Large rigid substrates as well as flexible films often undergo
slight dimensional changes as a result of the different PWB manufacturing process steps. In addition,the changes in the substrate dimensions are often non-isotropic. Manufacturers have been compensating for this problem by measuring the changes in the substrate and plotting new artwork that is matched to the dimensions of the processed substrate. This time-consuming and costly manufacturing practice can be eliminated through the use of the new
Anamorphic X-Y Scaling technology that enables independent magnification compensation in two dimensions for laser projection exposures. In this paper,we present the results of studies conducted on laser projection imaging equipment and specifically review the performance of the X-Y scaling capability.

New vertical continuous plating equipment has been developed while taking into consideration production and environmental requirements. The vertical continuous plating equipment conveys printed circuit boards continuously without using any racks and carries out high quality plating. This paper discloses an outline and features of our
newly developed vertical continuous plating equipment for printed circuit boards,and various data such as surface deposited thickness distribution and throwing power on the through hole and blind via holes (BVH).

Permittivity and dissipation factor (Dk and Df) are effects of polarization of different components of the dielectric substrate material when subjected to an electrical field. Reliable design of PDAs to be used at very low temperature (-5 °C) and very high temperature (60 °C) with different amounts of humidity,require knowledge of range of Dk and
Df within this domain. A database of these important design parameters for PWBs,has been developed for THERMOUNT® RT materials. Effects of variations in the level of moisture (bone dry to completely saturated at various relative humidity levels),testing temperature (-5 °C to 60°C) and testing frequencies (500 MHz to 1.5 GHz) on Dk and Df are reported. A very reliable design of PWB can be accomplished with this database.

Using conventional PWB copper electroplating techniques (DC bath chemistry with air agitation),non-uniform deposition inside blind via features may arise when the vias have diameters less than 6 mils and aspect ratios greater than one. These observations result from two main causes: unfavorable solution hydrodynamics and the presence of air bubbles. Ultrasonic agitation (UA),well known for cleaning purposes,can provide a strong local agitation that "refreshes" the plating solution inside holes together with punching small trapped air bubbles. It has been demonstrated that UA greatly enhances the throwing power inside small blind via features. It must be pointed out that low UA power densities were used (2 to 8 W.gal-1). The frequency was 40 kHz and air was bubbled during plating. Using a conventional DC plating solution at 15 ASF,throwing power was improved on average by 35.9 %
for vias having a diameter of 6 mils and aspect ratio between 1.25 and 1.5. A more drastic 74.6 % throwing power improvement was noted for 4 mils blind vias having an aspect ratio of 1.9 and 2.4. Through ductility measurements,it has been also demonstrated that plated through hole reliability was improved using mild UA.

Among the many advantages of Periodical Pulse Reverse (PPR) technology,improvement in throwing power and plating thickness uniformity are the most obvious. Traditionally,the biggest drawback of the technology is that it plates well in one size hole but poorly in others,when there are several sizes of holes within a board or different
current density areas. Modulated Current Technology Controller (McTc) is a new technology in PPR,which generates modulated complex waves to overcome such drawbacks of the current technologies. High aspect ratio holes of various sizes on a board and irregularly distributed circuitry in pattern plating boards may all achieve more uniform plated thickness and throwing power using this technology.

Copper plating in the printed circuit board industry has traditionally used soluble copper anodes in a vertical configuration. Newer,high speed,horizontal plating lines utilize insoluble anodes which provide better current distribution and throwing power,higher operating current density,fixed and closer anode/cathode spacing,and lower copper cost. This paper presents results of a direct comparison between soluble and insoluble anodes on the plating performance on various types of printed circuit boards. This includes ductility,copper finish,and operating current density versus throwing power. Addition agent consumption at insoluble anodes and copper ion replenishment,as required for insoluble anodes,are discussed.

This paper presents a method both to enhance the yield of embedded resistor processes and to print embedded resistors using drop-on-demand ink-jet device capable of dispensing a precise volume of intrinsically conductive polymers (ICPs) onto plated or screen printed resistors. By controlling the volume of ICPs,and in turn its thickness,
the resistance per square can be controlled and brought to the PWB industry tolerance. This method can be used as complementary to laser trimming method to enhance the overall yield of embedded passives processes.

It is not often understood that when electrical signals travel along a wire or trace --- they reflect. Always! We intuitively understand that when we send audio waves across a room,a field or a canyon,they reflect. We call those “echoes.” Echoes can happen in a great many places,even in small rooms. But we have a harder time understanding that electrical signals reflect also. We call that,well,reflections!