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FFPs Frequently Faced Problems

During Printed Circuit Board (PCB) Assembly manufacturing, exposure to high humidity/moisture can lead tomicroscopic corrosion on the surface of the circuits. his causes adhesion failures, surface defects and decreasedperformance of the Circuit Board.

General Recommendations

!elati"e #umidity in PCB Assembly Clean !ooms should be maintained at $%&'& !# at $%*C (+%*).

Solutions

The Background

or $% years, the information re"olution has been built on the sandsilicon based chip. -ach year, by cramming more circuits on a memory

or microprocessor chip, engineers ha"e made computing technologycheaper, more plentiful and more adaptable to ne uses. maller hasalays been better, yet ne"er good enough. 0ith the chip becoming thesi1e of a thumbtac2, the si1e of printed circuit boards, or PCBs, is alsogetting smaller.

The Process

he circuit board in it3s simplest form is a piece of insulating material, such as epoxy or phenolic resins, on hichchips (integrated circuits) and other electronic components are mounted and interconnected to form a circuit. 4ostmodern circuit boards use patterns of copper foil to interconnect the components. he foil layers may be on one orboth sides of the board and, in more ad"anced designs, in se"eral layers ithin the board. Photosensiti"e polymercompounds called photo'resistors are applied to the surface to selecti"ely mas2 circuit lines for the etching process.

he hygroscopic nature of these compounds can cause the adsorbed moisture to ma2e cuts in the bridging ofmicroscopic circuit lines, resulting in circuit failures. he relati"e humidity of air in the photolithography clean roomshere etching is done is therefore maintained at controlled le"els. or best results clean rooms are generallymaintained at $%& to & !elati"e #umidity at $%*C.

4oisture control is also absolutely essential hen 5uart1 crystals are incorporated ith the printed circuit boards.he 5uart1 crystal boards, after assembly, are put through an aging process during hich time the humidity le"elmust be carefully controlled to pre"ent the crystal from absorbing ater "apour.

The Problem

-xposure to high humidity can lead to corrosion on the surface of the circuits. his is 2non as microscopiccorrosion. -"en minute layers of corrosion can increase electrical resistance and decrease capacitance, affecting

performance. -xcessi"e moisture, therefore, causes adhesion failures, surface defects and decreasedperformance. 6n fact, the smaller and denser the microcircuit, the larger the problem in performance.

The Solution

Desiccant Dehumidifiers pro"ide the ideal lo humidity en"ironment in the manufacture, assembly and storage ofthese precision, high 5uality electronic Printed Circuit Boards, since they are capable of maintaining !# as lo as7& or e"en loer at a constant le"el, regardless of ambient conditions.

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