Easy and Accurate Measurement of Chip Components

Along with the miniaturization of electronic components and higher density of PCB mounting, reflow soldering has become mainstream.

Solder paste, which is a uniform mixture of powdered solder and flux, is applied onto a metal plate with holes punched in it, and spread into a thin layer with a spatula to make a print. Components are then mounted on the circuit board, heated, and soldered.

Normally, heat is applied in two steps. In the first heating step, the circuit board is brought to and maintained at a uniform temperature. In the second heating step, the solder paste melts. The heating temperature and time vary depending on the type of reflow oven and on the components being used.

PCB warpage is caused by temperature changes that occur when power is supplied, or by environmental changes. Analysis is performed to determine whether defects have occurred due to these temperature changes. Warpage caused by temperature fluctuations can be measured from room temperature to 260°C 500°F.

The flatness of capacitor terminals, which can lead to PCB mounting defects and can influence the mounting strength of the PCB, can be measured.

The thickness of the solder layer applied on a PCB can be measured.

The thickness and volume of a resistive film in a wet state can be measured prior to sintering after the film has been printed. The film thickness can be measured while it is wet, so the conditions for the sintering process can be set efficiently.

Chip resistors are small, square fixed resistors consisting of a resistive element formed on the surface of an insulating base, such as ceramic, with electrodes on both ends. They are mainly suited for surface mounting.

The length and depth of films can be measured to ensure that chip resistors remain within specification.
The width and depth of cracks that occur in trimmed areas can also be measured.

The layers of a chip resistor are formed by screen printing. Since several hundreds of resistive elements are formed on a ceramic base, even minute variations in the printing conditions directly cause variations in the resistance.
If the resistance varies among chip resistors, their electrical characteristics will not satisfy their rating. This leads to the need to perform laser trimming to adjust the resistance. Laser trimming involves measuring resistive elements one by one, and cutting them to ensure the specified resistance and to minimize variations.

• Resistive elements are printed by aiming for a slightly lower resistance than the target resistance.
• Trimming a resistive element makes its current path narrower, which increases resistance.
• Trimming stops when the target resistance is achieved to minimize fluctuation among chips.

The pattern width and thickness of a dielectric in a wet state can be measured.

The basic structure of a capacitor consists of a dielectric between two electrode plates.

• Dielectric material such as barium titanate (BaTiO³), a ceramic dielectric, is applied to a carrier film.
• The material is dried to create a thin sheet.
• Paste of electrode material containing metals such as palladium, silver, or nickel, is printed on the sheet.
• The sheets are stacked in 10 to 1000 layers, pressed and cut into chips.
• The final steps in creating multilayer ceramic chip capacitors are sintering and plating external terminals with silver. The chips shrink by around 10% during the sintering of the ceramic, which is important to take into account when determining their dimensions.

Connecting multiple capacitors in parallel is equivalent to increasing the area of the electrode, so you can increase the electrostatic capacitance by increasing the number of capacitors.
Using multiple capacitors will take up a large volume on the circuit board, so this method is not appropriate when there is a need to save space.

To avoid this, multilayer ceramic chip capacitors achieve both miniaturization and large capacity by having multi-layered structures of ceramic dielectrics and internal electrodes stacked alternately.