High-quantity set up provides several good things about users: good procedure repeatability, large stocks of parts neatly dry loaded and ready for use, and every thing placed in tape-and-reel or matrix trays right from the factory. In addition, when you use high-volume assembly, the assemblers know their jobs and have the assembly sketches memorized, and problems instantly stick out like warning signs. While there nevertheless are locations where things can (and will) fail, most aspects of the process are controllable.
High-mix/reduced-quantity, alternatively, is another tale. Components come in from suppliers in packaging which is not manufacturer refreshing, components are partly used then returned to carry, and jobs begin and prevent based upon changing customer specifications and conflicting due dates when you attempt to maintain good flooring practices. Sound acquainted?
Reducing Dampness Problems
One method to lessen the chance of problems with dampness level of sensitivity is through the use of Dry Storage Cabinets. There are numerous manufacturers of those cabinets that offer quality models, and it’s a good idea to check around for a dried out cabinet that most closely fits the company’s requirements. Right here, we’re speaking about Trenton Technologies, Inc.’s 10 calendar year knowledge of McDry cabinet systems, which have constantly provided very dependable service. These products are high-high quality steel cabinets with lockable steel framework window windowpane doors which have closes on them like the closes applied to a refrigerator. Installed on one of the doors is really a battery power-run moisture gauge and a dehumidifier unit is attached to the back wall. The business has greater than a dozens of those cupboards, and also the only upkeep actually needed is definitely an yearly battery power alter for that humidity indicator. Some places might want to send out the recorder out to be calibrated, but at Trenton, we just use its adjusted chart recorder to ensure just what the meter reports.
Coming from a parts perspective, utilisation of the cupboard is straightforward. Open up the dampness barrier handbag, remove the parts to be used immediately and store the relaxation inside the dried out cabinet. This takes care of several concerns: resealing the dampness buffer handbag (MBB), worrying about moisture indication cards (HICs) and desiccant bags, and ensuring that the owner sealed the MBB right after being properly purged without causing any nicks and attaining a proper seal off. How many times have you ever taken resealed components out from the stock space, opened up them and had the HIC are convinced that the various components have come across moisture? This seems to happen prior to carrying out a significant work with sensitive parts if the make-out time needed will put you right behind routine. An additional less-than-perfect part of MBBs long term components storage space would be that the maximum handbag life is two years for each IPC/JEDEC J-STD 033C section 5.3.2. With a cupboard ranked for 5 % RH or much less, the storage time is virtually limitless. (See IPC/JEDEC J-STD 033C desk 7-1.) Generally, Trenton nevertheless keeps parts inside MBBs to make certain component amount marking, as well as keep the Faraday cage properties in the handbag and to make certain that operators are not coming in contact with the various components immediately when removing a set of components from your cupboard. The difference is that the hand bags are not sealed, simply folded away over. This will not obstruct the properties in the cabinet because moisture does not need atmosphere movement to propagate.
No Popcorned Parts
Because implementing the cupboards, the company has already established no known cases of popcorned components. Before cupboard installation, popcorning was rare as a result of good standard methods. However, it did happen several times. With all the ever-increasing intricacy of parts that can come packed on adhesive tape-and-reel, the business purchased extra deep dry cupboard models with feeder shelves inside. The packed feeders are kept there whenever a collection powers lower, if those feeders will likely be used the very next day. Some parts possess a three-time flooring life and will also be utilized before time elapses, Trenton’s practice would be to position them inside the cabinet immediately.
IPC/JEDEC J-STD-033C has information on space heat dehumidification of components and implies that the trend reverses itself. Degree 2 and 3 gadgets have a reset of 5X a floor exposure, and degree 4 and 5 gadgets should be thought about 10X floor exposure. Please be aware the IPC specifications derive from 10 percent RH cabinets, which suggests there might be an added margin of safety if employing a better quality cabinet. The Dry Storage Cabinets For Optics from 10 in the past were 3 percent models; nevertheless, most of its recent buys are 1 percent units.
Occasionally, elements on adhesive tape-and-reel can be found in either recognized wet or sketchy condition. In these cases, per IPC J-STD-033C Table 4-1, Trenton utilizes a heated make cabinet at 1 percent RH heated to 40°C to make out tape-and-reeled components while not having to unreel and tray the constituents in order to withstand the 125°C bake. This process demands times rather than hours, so in some cases you may be compelled to tray up components if you need them in a hurry. Given that oxidation and intermetallic layer growth increase significantly as temperature increases, the preference would be to steer clear of higher-heat bake out anytime it is actually practical.
One unanticipated but beneficial utilization of the cabinets is at-process storage of dual-sided panels. As assemblies rise in intricacy for double-sided SMT assemblies, increasingly more gadgets around the panels are dampness-delicate. Should you assemble the base side then instantly put together the top, there are no issues. However, if scheduling, the weekend break, collection malfunction as well as other unexpected occurrence stops the immediate processing of panels, these components are now out on the floor absorbing dampness just like certainly just as if they were located on a table inside an opened bundle. In the event you put together the base part and after that position the boards within the dried out cupboard, you can be assured that the parts are dry going in (they lately became available of reflow and must definitely happen to be dry when this occurs) and therefore are being kept dried out till the top part of the board is ready to be constructed. Trips to other services have revealed that once one part of the table has been refined, it is believed that the dampness problems on these components have already been removed.
Unfortunately, not every person knows that the parts are still absorbing moisture in the same rate being an unprocessed component, and that they will see exactly the same (approximately) reflow profile when handling the best side. (See evaluation IPC/JEDEC J-STD 033C area 5.4.4.)
Depending on technologies, also consider storing uncovered boards within a dry cupboard. For high-layer count, military and aerospace products, Trenton shops all uncovered panels in dry cupboards every time they show up from the board house. The cupboards have exceptionally sturdy shelving and there were no unfavorable problems launching all of them with panels. However, it is best to talk with the stress ratings for your shelves depending on the cupboard manufacturer simply because piles of uncovered boards become weighty quickly.
Smaller sized Doorways Are Better
When selecting a cupboard, think about door layout. Trenton found that with the exception of the cupboards that are employed to keep loaded feeders, the units with six smaller sized doorways are better than those that have two large doors because there is less atmosphere trade when opening the cupboard, which leads to faster recovery. Yet another advantage is that it helps for marking work locations in the cabinet, and certain sectors can be locked while other sectors remain ready to accept the owner. Also think about the way you shop your loaded feeders. As these can get very weighty, a stationary mounted holder in the cupboard rather than the optional take out design cabinet could be the better choice. When the owner extends too much weight, it is actually conceivable the cupboard could turn out to be unstable, potentially tipping. Given the safety issues and the cost of feeders and parts, it is recommended to err on the side of extreme care here. Lastly, when it comes to heated up Desiccant Dry Cabinets, Trenton found which a small device is all that is required because, if components are being bought properly, this cupboard only will be utilized for bake-out moderately.
The company labels rack areas with specific agreement customers’ names and work component figures, allowing operators to quickly become accustomed to retrieving components through the cupboard and replacing them at the end of your day. A jcdose training about the results of moisture-based damage along with a couple of photos will significantly help toward proper element dealing with, and having cabinets locally at every set up collection helps make the job so much simpler. Mixing correct training using the right resources offers much better results and, for Trenton, one of the most basic tools on earth of high-blend/reduced-volume is its dry cabinet storage.