High-volume assembly provides numerous good things about customers: great procedure repeatability, big stocks of parts neatly dry packed and ready to be used, and every thing positioned in adhesive tape-and-reel or matrix trays directly from the factory. Additionally, when you use high-volume assembly, the assemblers know their work and also have the set up sketches memorized, and problems instantly stand out like warning signs. While there nevertheless are locations where issues can (and will) fail, most elements of the process are controllable.
Higher-mix/low-quantity, however, is an additional story. Components are available in from vendors in packaging that is certainly not manufacturer refreshing, components are partly utilized and then sent back to stock, and jobs start and prevent based on changing customer requirements and contradictory due dates as you try to sustain good flooring practices. Seem familiar?
Reducing Moisture Issues
One method to decrease the chance for problems with moisture sensitivity is with the use of Dry Storage Cabinets. There are numerous manufacturers of those cabinets that offer high quality models, and it’s a smart idea to shop around to get a dried out cabinet that best suits the company’s needs. Here, we’re referring to Trenton Technologies, Inc.’s 10 year knowledge of McDry cabinet systems, which may have constantly supplied extremely dependable service. These products are higher-high quality steel cupboards with lockable metal framework window window doors which have closes to them similar to the closes applied to a fridge. Attached to one of the doors is really a battery-run moisture meter along with a dehumidifier unit is attached to the lower back wall. The business has greater than a dozen of these cupboards, and the only upkeep actually required is an annual battery change for that humidity indication. Some places may want to send out the recorder to be calibrated, but at Trenton, we just use its adjusted graph recorder to verify just what the meter reviews.
Coming from a parts standpoint, utilisation of the cupboard is straightforward. Open up the dampness barrier handbag, take away the parts to be used instantly and store the rest within the dried out cabinet. This manages a number of concerns: resealing the moisture buffer handbag (MBB), stressing about moisture indication cards (HICs) and desiccant hand bags, and making certain the operator sealed the MBB right after becoming properly purged without leading to any nicks and achieving an effective seal. How many times perhaps you have taken resealed components out from the carry space, opened up them along with the HIC are convinced that the parts have been exposed to moisture? This generally seems to occur prior to performing an essential job with sensitive parts once the make-out time needed will put you behind routine. An additional less-than-ideal aspect of MBBs long-term components storage would be that the optimum handbag life is a couple of years per IPC/JEDEC J-STD 033C area 5.3.2. Having a cupboard ranked for 5 percent RH or less, the storage time is virtually limitless. (See IPC/JEDEC J-STD 033C desk 7-1.) Generally, Trenton nevertheless helps to keep components within MBBs to make sure part amount marking, and to maintain the Faraday cage properties from the bag and to make sure that operators usually are not touching the various components immediately when removing a batch of components from the cupboard. The main difference is the fact that bags are certainly not sealed, merely folded away over. This will not obstruct the qualities of the cabinet because humidity does not need air movement to propagate.
No Popcorned Parts
Since implementing the cupboards, the organization has already established no known cases of popcorned parts. Before cabinet installation, popcorning was uncommon due to good regular methods. However, it did occur a couple of times. With the actually-increasing complexity of parts which come packaged on tape-and-reel, the organization purchased extra deep dried out cabinet models with feeder shelves within. The packed feeders are maintained there when a line powers lower, if these feeders will likely be utilized the very next day. While most parts possess a three-day floor life and will be utilized before time elapses, Trenton’s exercise is always to put them within the cabinet overnight.
IPC/JEDEC J-STD-033C has information about space heat dehumidification of parts and implies that the trend reverses alone. Level 2 and 3 devices use a reset of 5X the ground exposure, and level 4 and 5 devices should be considered 10X flooring visibility. Please note that the IPC specifications derive from 10 percent RH cupboards, which suggests there may be an extra border of security if utilizing a higher quality cabinet. The Dry Storage Cabinets For Optics from 10 years back were 3 % units; nevertheless, all of its recent purchases are 1 % models.
Sometimes, elements on tape-and-reel can be found in possibly recognized moist or questionable problem. In these cases, per IPC J-STD-033C Table 4-1, Trenton works with a heated bake cabinet at 1 percent RH heated to 40°C to make out adhesive tape-and-reeled components without having to unreel and holder the ingredients so that you can withstand the 125°C make. This method demands days as opposed to hours, so sometimes you could be forced to holder up components should you need them in a big hurry. Considering that oxidation and intermetallic layer growth improve greatly as heat increases, the preference is to avoid high-heat make out whenever it really is practical.
In-Procedure Storage space
One unanticipated but advantageous utilisation of the cabinets is within-procedure storage of double-sided boards. As assemblies boost in intricacy for double-sided SMT assemblies, a lot more devices on the boards are moisture-sensitive. Should you assemble the base side and after that instantly put together the very best, you can find no problems. Nevertheless, if organizing, the weekend, collection malfunction as well as other unforeseen occurrence stops the immediate handling of panels, these parts are actually out on to the floor absorbing dampness just as surely just as if they were sitting on a table inside an opened package. In the event you put together the base side and then put the boards in the dry cabinet, there is no doubt the parts are dried out heading in (they lately arrived of reflow and must certainly have been dried out when this occurs) and are becoming kept dried out till the top side of the table is able to be built. Trips to other facilities have shown that when one side of the board continues to be refined, it is actually considered that the dampness problems on those parts have been removed.
Unfortunately, not everybody knows that the parts remain absorbing moisture at the exact same rate as an unprocessed part, and that they will discover exactly the same (roughly) reflow user profile when handling the best side. (See review IPC/JEDEC J-STD 033C section 5.4.4.)
Based on technology, also consider keeping uncovered panels in a dry cabinet. For high-coating matter, military services and aerospace products, Trenton stores all uncovered boards in dried out cupboards as soon as they arrive from the board home. The cupboards have extremely durable shelving and there has been no negative problems launching all of them with panels. Nevertheless, it is best to talk with the stress ratings for your shelves in accordance with the cupboard producer because piles of uncovered panels turn out to be weighty quickly.
Smaller sized Doorways Are Better
When choosing a cupboard, consider door layout. Trenton has found that except for the cabinets that are employed to keep packed feeders, the models with 6 smaller doors are superior to individuals with two big doorways since there is less atmosphere trade when opening the cupboard, which results in quicker recovery. An additional benefit is it helps for labeling job areas within the cupboard, and specific segments could be secured whilst other segments remain open to the operator. Also consider the way you store your loaded feeders. Because these could get quite weighty, a fixed installed holder within the cupboard instead of the optional grab style drawer may be the better option. In the event the owner extends a lot of weight, it is conceivable that the cupboard could become volatile, possibly tipping. Because of the safety concerns and the price of feeders and parts, it is advisable to err along the side of caution here. Finally, in terms of heated up Dehumidifying Dry Cabinets, Trenton finds that the little device is all that is needed because, if parts are bought correctly, this cabinet only will likely be used for bake-out sparingly.
The business labels shelf locations with specific agreement customers’ names and job component numbers, enabling operators to quickly become familiar with retrieving components through the cabinet and replacing them after the day. A jcdose training regarding the effects of moisture-dependent damage along with a couple of photos will greatly assist toward proper element handling, and getting cupboards locally at each set up line makes the work so much easier. Combining correct training with the correct resources offers much better results and, for Trenton, one of the most basic tools in the world of high-mix/reduced-volume is its dry cupboard storage.