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Surface Mount Technology (Surface Mount Technology) is an
electronic mount technology that uses professional automatic assembly
equipment, such as solder paste printing machine, placement machine, reflow
welding, etc. weld surface assembly elements (types include resistors,
capacitors, inductors, etc.) to the surface of the circuit board. The computer,
mobile phone, printer, MP4, digital image, high-tech control system with strong
function are all produced by SMT equipment, which is the core technology of
modern electronic manufacturing.
Most electronic products require working and storage under
dry conditions. According to statistics, more than 1/4 the world‘s industrial
rejected products every year are related to moisture damage. For the electronic
industry, the harm of humidity has become one of the main factors of product
quality control.
In semiconductor industry, moisture can penetrate through
IC plastic package and invade IC interior from the gap such as pin, resulting
in IC moisture absorption phenomenon. in SMT heating processs, the moisture
entering the inside of the IC is heated and expanded to form water vapor, and
the resulting pressure causes the ic resin package to crack, and the metal
inside the device is oxidized, which leads to the product failure.
Furthermore, when the components is in the welding process
on PCB boards, it will also lead to virtual welding due to the release of water
vapor pressure. according to the J-STD-033 standard, SMT components after
exposure to high humidity air environment must be placed in an electronic
drying cabinet below 10% RH humidity for 10 times the time of exposure to
restore the “workshop life” of the components to avoid scrapping and ensure
safety.
Dampness caused serious problems to the quality control and
reliability of products in electronic industry which must be dried according to
IPC-M190 standards.
The chip will be indicated its specific wet sensitive level when it leaves the
factory. Another important criterion in the IPC standard is to specify the
humidity required to store a chip at its corresponding level.
For chip moisture-proof storage, there are two
standards:10% RH below and 5% RH below dry cabinet, which is the common used
series in mainstream chips. “Unsealed MSD, may recover the workshop life
consumed by this MSD at a time of 5 or 10 times of the specified humidity
storage (e.g .10 RH or less) when the exposure time does not exceed 72 hours .”
Exposure time is the time when the MSD is placed in a high humidity environment
after unsealing.
Humidity has become one of the main factors of product
quality control in SMT industry. SMT products storage environment humidity is
below 40%, some also require lower humidity. The storage of humidity sensitive
materials has been a headache for all EMS manufacturers. After absorbing
moisture of electronic components and circuit boards, it is easy to produce
virtual welding, which leads to the increase of rejected products. Although it
can be improved after baking and dehumidification, the performance of the
components is decreased after baking, which directly affects the quality of the
products.
EJER Dry Cabinets can settle all above humidity related
problems, welcome to inquiries!
