Moisture Sensitivity Level

The Moisture Sensitivity Level (MSL, dt » Feuchtigkeitsempfindlichkeitsschwellwert " ) refers to the moisture sensitivity of semiconductor devices in the packaging, storage and installation.

Background

Moulded SMD components are not hermetically sealed so that moisture can diffuse out of the room air into the plastic. If such moisture-laden components now soldered by reflow soldering on printed circuit boards, it may cause " popcorn effect " for so-called. The trapped moisture evaporates abruptly on heating ( soldering temperatures up to 200 ° C). Since the evaporated liquid takes up more space, this can result in rupture of the components. The manufacturer of SMD components are now using the MSL under which conditions the components must be stored and how they need to be processed afterwards.

Standardization

The MSL can be set according to different procedures. Most commonly, the standard J -STD -020 (English Moisture / Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mounted Devices ) of the American organization JEDEC is used.

In determining the MSL components are first dried completely. They are then defined with moisture laden and then subjected to one or more of reflow soldering. By electrical measurement or other examination methods ( eg ultrasound) is checked to see if the components have survived the soldering process without damage.

Within the periods specified, the component is then processed without being damaged during the soldering process.

Handling guidelines

A The supplier delivers, for example, welded a microcontroller and packed on. This is checked for tightness and the LEVEL Note is controlled. When LEVEL information label is noted, is with what level the item after opening the dry pack to treat and when the date of sale was.

B. If an item is delivered, for example, with 504 pieces, but the production needs only 252 pieces, the time after opening the packaging is just to document (eg: sampling on 13 May 2009 10:15 ). As mentioned above, for example, to consume LEVEL 3 within 168 hours after opening. For this purpose, the date of collection / extraction time is written down or noted on the article.

C. There is also the possibility of vacuum-packing the products according to the exact swap pieces back into a package. For as soon as the item is back wrapped airtight, the LEVEL time stops again. The remaining time elapses only when the opened packages ( Outsourced materials in the production of the engine in the rear storage, etc. ).

D For a return transfer of surplus material of the article can be vacuumed again, but the time is not equal to the delivery condition, but only with the rest of stock ( eg 72 hours). That is on the Dry Pack packaging is to record the actual time remaining still.

E. The only way to extend the time is re- baking the product, according to the supplier package ( for example 192 hours at 40 ° C or 24 hours at 125 ° C). If the item is after baking vacuumed equal, is then returned to baseline levels ( in the example: Level 3) and reached the 168 hours are back policy for the next opening of the package.