An Optical Inspection System for the Solder Balls of BGA using Support Vector Machine Classification
In this paper, the Support Vector Machine (SVM) is utilized to classify the defective solder ball of ball grid array (BGA) so as to promote the accuracy and efficiency of the optical inspection. The terms of inspections include the ball displacement, the ball over scale, the ball undersize, the ball absence, and ball bridging. There are two step of the SVM processing: the training step and the real testing step. The SVM is more efficiency because of the calculation in testing step is no relation to the number of the input vector. As this point, SVM is fit to build up the high dimension input recognize system such as BGA inspection. From the real testing results, the Support Vector Machine is proved to properly identify and classify the shape defects. The two dimensional BGA optical inspecting system is implemented by Visual Basic as the developing tool incorporated with the Halcon's function which is the database of the image processing on Windows operation system. For the development of the processing procedure of the automatic optical inspecting system with the designed lighting system, the precise geometrical information of the solder ball is evaluated by the sub-pixel method to identify the shape of solder ball and its location under the BGA board is offset and rotated at any angle.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.
English Code-Mixing and Code-Switching in Thai Songs
This study aims to investigate the attitudes of Thai people toward English code-mixing and code-switching in Thai songs and to find out if English code-mixing and code-switching in Thai songs could be an effective pedagogical instrument for learning the English language. The researcher selected a target population of 50 Thai participants (25 adolescent and 25 middle aged participants) and, by using a questionnaire, surveyed their attitudes towards the mixing and switching of English vocabulary in Thai songs. In addition to the questionnaire, two from the 50 participants were interviewed. One was an adolescent who has a very good knowledge of English and the other was a middle aged participant with almost no knowledge of English. The findings show that a majority of the middle aged participants disagree on the positive attitudes and reasons of people who listen to Thai songs which mix and switch the English language while a majority of the adolescent participants believe that some people who listen to Thai songs which mix and switch the English language are knowledgeable as well as show good taste and have a high social status. On the other hand, both the adolescent and middle aged group agree that some Thai songs which mix and switch the English language sound annoying and are inconsistent in conveying the meaning of the lyrics. Both groups also agree that Thai songs which mix and switch the English language may help listeners to enhance their knowledge of the English language. When interviewed individually, the participant who is very good in the English language tended to emphasize only the English competency of the listeners; while the participant who does not have any knowledge of the English language tended to emphasize the listeners‟ liking of the lyrics, the meaning and the melody of the songs. However, the use, as a pedagogical instrument, of Thai songs which mix and switch the English language could open up an additional choice for language learners in English vocabulary learning. Such songs would be acceptable as an effective pedagogical instrument for learning the English language if the English words in the songs also show correct English syntax.