The following topics are covered in this newsletter: |
Invitation to the IPC Midwest Lead Free Rework Session
Info on the new BEST SMT Assembly Class
Info on Reworking Underfilled Devices
Space Solar Power as an Alternative Energy Source
See you at IPC Midwest or SMTAI Florida!!!!!
Bob Wettermann BEST Inc.
BEST's SMT electronics assembly course provides SMT technicians, SMT operators, engineers and other personnel new to SMT assembly with the knowledge and understanding of the steps involved in the manufacturing of modern electronic assemblies. This course is meant for those involved in electronics manufacturing who desire a thorough understanding of the assembly of surface mounted electronic assemblies. Practical assembly techniques, hands-on demonstrations, local area plant tours and explanations by a variety of experts in the field as well as classroom lectures are used to emphasize the teaching points. The student will be exposed to 50% lab/plant tour information with the balance being classroom lectures.
The course is designed to teach students through classroom lectures, hands-on experiences both at BEST as well as surrounding commercial businesses. The teaching methods include in-class lecture as well hands-on lab time. The labs allow the opportunity for students to immediately apply the lessons learned during lecture. The latest manufacturing and processing equipment as well as techniques are featured in the class.
Upon completion of the course, students receive a BEST certificate of completion for the completing the following topics:
Bare Board Fabrication
Stencil Design and Fabrication
Call Katy Radcliff at (847) 797-9250 for further details. More info on the boot camp
Underfills protect the active surface of the die of flip chips, BGA ad CSP package types while improving their reliability by distributing stress away from the solder interconnects. This increases the performance of products in meeting drop, shock and bend criteria. Newer underfills are specifically designed to minimize the need to scrap entire boards with high cost devices bonded on them because testing has determined that a device is defective. However, the ability of these devices to be reworked once they have been underfilled, is challenging and time-consuming.
The goal of a typical underfill rework project is to remove the underfilled device replacing it with a good die. The removal of this material can be accomplished either with mechanical grinding or through high temperature vacuum extraction or hand tools depending on the modulus of elasticity of the underfill.
The rework process begins with the even heating of the substrate to a temperature above the softening point of the underfill. The package is mechanically gripped or pried with enough torque to break the fillet's adhesions to the board. The chip undergoing rework is then heated above the solder reflow temperature to melt the solder connections and break down the underfill. The device is then removed from the PCB. Residual solder and underfill are cleaned off the substrate. Cleanup after chip removal removes any underfill residue and excess solder on the substrate. This part of the process must be done with extreme care in order to not damage the pads and adjacent components on the substrate. The site is then cleaned prior to inspection. Once cleanup of the substrate is complete, a new chip can be aligned, reflowed, and underfilled.
Call us today to discuss your rework project at (847) 7979-9250 and ask for Laura Ripoli. To see what the device looks like after rework
For years humanity has dreamed of a clean, inexhaustible energy source. This dream has lead many people to do what, in retrospect, seems obvious, and look upward toward nature's "fusion reactor", the sun. However, while sunlight is clean and inexhaustible, it is also dilute and intermittent. This led Peter Glaser of the Arthur D. Little Company to suggest in 1968 that solar collectors be placed in geostationary orbit. Such collectors are known as solar power satellites (SPS). The solar energy collected by an SPS would be converted into electricity, then into microwaves. The microwaves would be beamed to the Earth's surface, where they would be received and converted back into electricity by a large array of devices known as a rectifying antenna, or rectenna. (Rectification is the process by which alternating electrical current, such as that induced by a microwave beam, is converted to direct current. This direct current can then be converted to the "slower" 50 or 60 cycle alternating current that is used by homes, offices, and factories.) At geostationary orbit (36,000 kilometers or 22,000 miles high), the SPS would have a 24-hour orbital period. It would therefore always hover over the same spot on the equator and can keep its beam fixed on a position at a higher latitude. Since the Earth's axis is tilted, an SPS orbiting over the equator outlawing above or below the Earth's shadow during its daily orbit. Sunlight would not be blocked, except for a period of about an hour each night within a few weeks of the equinoxes.
It is interesting to compare the availability of sunlight in space with that on Earth. A solar panel facing the sun in near-Earth space receives about 1400 watts of sunlight per square meter (130 watts per square foot). (Of course, only a fraction of this is usable due to conversion inefficiencies.) On Earth, the day-night cycle cuts this in half. The oblique angle of the sun's rays with respect to the ground cuts this in half again for a typical spot on the Earth. Solar panels on the ground can be angled upward to circumvent this, but they must then be spread out over more ground to avoid casting shadows on each other. Clouds and atmospheric dust cut the available sunlight in half again. Thus, sunlight is about eight times more abundant in geostationary orbit than it is on the Earth. Although the microwave beam from an SPS would also be dilute, it would be converted to electricity at a greater efficiency than sunlight. However, the largest cost savings in SPS versus terrestrial solar collectors may be the elimination of the need for storage at night .
Spurred on by the oil crises of the 1970's, the US Department of Energy and NASA jointly studied the SPS during that decade. The result of this study was a design for an SPS which consisted of a 5 x 10 kilometer rectangular solar collector and a 1-kilometer-diameter circular transmitting antenna array. The SPS would weigh 30,000 to 50,000 metric tons. The power would be beamed to the Earth in the form of microwaves at a frequency of 2.45 GHz (2450 MHz), which can pass unimpeded through clouds and rain. This frequency has been set aside for industrial, scientific, and medical use, and is the same frequency used in microwave ovens. Equipment to generate the microwaves is therefore inexpensive and readily available. The rectenna array would be an ellipse 10 x 13 kilometers in size. It could be designed to let light through, so that crops, or even solar panels, could be placed underneath it. The amount of power available to consumers from one such SPS is 5 billion watts. (A typical conventional power plant supplies 500 million to 1 billion watts.) Nevertheless, even the peak of the beam is not exactly a death ray. Underneath the rectenna, microwave levels are practically nil.
The reason that the SPS must be so large has to do with the physics of power beaming. The smaller the transmitter array, the larger the angle of divergence of the transmitted beam. A highly divergent beam will spread out over a great deal of land area, and may be too weak to activate the rectenna. In order to obtain a sufficiently concentrated beam, a great deal of power must be collected and fed into a large transmitter array