Praveen, For the evaluation and selection of an AOI system there are a few key points that I suggest you focus on. 1. Solder Joint Inspection - Most AOI suppliers claim solder joint inspection capability but this is really one of the differentiating points. You need to decide how badly you want good solder joint inspection capability. Truly capable systems are more complex mechanically as well as in their programming thus requiring a higher level of expertise, as well as investment in time, for program development and optimization. For low volume-high mix and prototyping environments, it often takes more time to develop robust solder joint inspection that it takes to build and ship the product! Solder joint inspection will increase the false call rate of any system. Finally, it is important to remember that video based AOI systems can only operate in a line of sight fashion. Packages like SOJ's, PLCC's, and BGA's will not support solder joint inspection. There are x-ray "combi" machines available as well but you have to weigh the cost and throughput implications of a combi. If you make the required commitment in capital expenditure and engineering support, solder joint inspection can yield very good results and help to take your process to the next level. If you don't provide the appropriate level of commitment in support resources, then the investment in solder joint inspection capability will be a waste and cause frustration and confusion on the line until you ultimately turn off that portion of the inspection. Look for systems that use convergent software technology where the s/w keeps track of false calls and the conditions surrounding them as a means to automatically and statistically refine inspection algorithms as a means to reduce false calls. 2. Production Environment - As eluded to above, it is my opinion that the state of the AOI industry today does not provide a single machine that "does it all". If you are running in a high mix/low volume/high change environment then machine speed/throughput is less important than ease in program development. In this environment if you can't get a program cranked out and reasonably optimized in 2 hours or less you will spend all of your time programming and very little time running the machine in production. Look for off-line programming capabilities as a means to help free the machine up a bit more, but you still always need machine time for initial image capture and final debug. 3. Vector Based versus Pattern Recognition - Vector based machines will find the edges of packages and leads, determine centroids, compare this to CAD data, and except/reject based on numerical tolerance settings. This allows for the building of numerically based part data files, like with pick-n-place machines. Vector based machines can provide you with very accurate x-y offset data to validate and tweak in your p-n-p equipment. This keeps the AOI machine from "learning" a bad placement or condition as the "golden" model. There is also at least an order of magnitude greater complexity, difficulty, and time investment in the programming and optimization of vector based machines, but vector based machines generally offer greater flexibility over the long run for odd packages, special measurement applications, and fine pitch lead measurement. The vector machines I am familiar with (MVT and VI) are generally faster than the pattern rec. class of machines although some companies like CR Technology are steadily developing faster and faster machines, thus closing the gap. Pattern Recognition, or correlation based vision processing compares a bit map from the camera field of view FOV for the current board to a saved "golden" image for the same FOV. The user defines the degree of bit map correlation required to achieve the pass threshold. Bit map correlation algorithms are used to break up the FOV into smaller chunks, allowing for the detection and identification of a small defect like a skewed 0402 although comparing FOV images that may be larger (~1" x 1"). The advantages to pattern recognition is that it is generally easier to program, using wizard style teach functions combined with cad data, and easier to understand. Great for a proto or high mix shop, or an environment where you don't have the luxury of throwing a high level tech(s) or engineer(s) at the process. The disadvantage is that often acceptable manufacturing variation, such as a different color tantalum cap off of the approved vendor list, will result in a reject. It then requires you to teach this as an alternate acceptable image. Depending on who is allowed to teach alternates, you can get in the situation where pretty soon you have dozens of alternates for many FOV's which can start to affect the speed of inspection and inadvertently create opportunities for false passes. 4. SPC - It amazes me how many AOI systems out there provide inadequate supporting SPC packages. Without a system that provides good real time SPC feedback up the line, the AOI machine is only a failure screen that helps you increase your ICT yields but does not reduce rework (assuming you are repairing AOI detected defects in advance of ICT). Look for systems that allow for web based live SPC reporting so you don't have to invest in a separate data server and set of applications/licenses requiring dedicated data terminals. Web based output allows you to leverage your existing plant PC infrastructure in the factory and at the desks of those who need this data. All you need is an Ethernet card in the machine which writes data to a network target, and a standard browser to run the AOI manufacturer's Java scripts for displaying the live data from that target. If you want to integrate the AOI data real time and automatically into your plant's existing quality tracking system, evaluate the data output structures and communications interfaces that the machine supports. 5. Company Stability/Structure - There is something like 20 players in this market today. Considering the current electronics industry market condition, and the natural tendency for consolidation in this type of business, I think we'll see many of these 20 disappear over the next couple of years either through lack of funding, lack of market share, or acquisition by larger companies. Work to understand the AOI company's financial health (private, public, venture capital funded, cash??, etc.), short and long term business strategy (IPO, acquire or be acquired), historical and current growth rate compared to competitors, and if they posses any differentiating technology that has inherent value over their competitors (this point often makes a small company ripe for acquisition which can be good over the long haul). The quantum leap in PC processor speeds, cheap RAM, and quality high resolution color CCD cameras available today is the primary reason for this explosion in AOI products, i.e. we can finally afford them due to affordable components! This levels the playing field so to speak from the hardware standpoint, making the software side of the product the key differentiating feature. Look for companies that recognize this and possess evolved machine algorithms, program development tools, and SPC packages. They should have a large software development resource with many experienced software engineers and developers. They should be able to demonstrate active software improvement projects and have a "roadmap" of additional features and enhancements they are working on. If they cant, and are focused on hardware and speed improvements only, beware! There's more to think about but I feel these are the biggies. Good luck, Glenn Woodhouse MCMS Advanced Technology Development (208) 898-2753 > -----Original Message----- > From: Automatic digest processor [SMTP:[log in to unmask]] > Sent: Thursday, August 30, 2001 11:00 PM > To: Recipients of TechNet digests > Subject: TechNet Digest - 30 Aug 2001 (#2001-510) > > There are 4 messages totalling 370 lines in this issue. > ------------------------------ > > Date: Fri, 31 Aug 2001 00:18:31 +0000 > From: praveen kumar manjeshwar <[log in to unmask]> > Subject: AOI equipment > > Hi everyone, > I just wanted to know where would it be preferable to postion an AOI > equipment on a production line. I have known of people who prefer to use > it > before reflow and some who have suggested after reflow. > What would the implications be if this equipment is placed prior to and > after reflow? > Also, if one had to evaluate an AOI equipment (not solder paste measuring > equipments), then what factors would one have to consider to gage the > capability of this equipment? > Thanks > Praveen > > --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------