■ PRECAUTIONS
Precautions on the use of Multilayer Ceramic Capacitors
2. PCB Design
◆Pattern configuration（s Capacitor layout on PCBs）
1-1. The following is examples of good and bad capacitor layouts ; capacitors shall be located to minimize any possible mechanical stresses from board warp or de-
flection.
Items
Not recommended
Recommended
Deflection of board
Technical
consider-
ations
1-2. The amount of mechanical stresses given will vary depending on capacitor layout. Please refer to diagram below.
1-3. When PCB is split, the amount of mechanical stress on the capacitors can vary according to the method used. The following methods are listed in order from
least stressful to most stressful: push-back, slit, V-grooving, and perforation. Thus, please consider the PCB, split methods as well as chip location.
3. Mounting
◆Adjustment of mounting machine
1.When capacitors are mounted on PCB, excessive impact load shall not be imposed on them.
2.Maintenance and inspection of mounting machines shall be conducted periodically.
Precautions ◆Selection of Adhesives
1.When chips are attached on PCBs with adhesives prior to soldering, it may cause capacitor characteristics degradation unless the following factors are appro-
priately checked : size of land patterns, type of adhesive, amount applied, hardening temperature and hardening period. Therefore, please contact us for further
information.
◆Adjustment of mounting machine
1. When the bottom dead center of a pick-up nozzle is too low, excessive force is imposed on capacitors and causes damages. To avoid this, the following points
shall be considerable.
（1）The bottom dead center of the pick-up nozzle shall be adjusted to the surface level of PCB without the board deflection.
（2）The pressure of nozzle shall be adjusted between 1 and 3 N static loads.
（3）To reduce the amount of deflection of the board caused by impact of the pick-up nozzle, supporting pins or back-up pins shall be used on the other side of the
PCB. The following diagrams show some typical examples of good and bad pick-up nozzle placement:
Items
Not recommended
Recommended
Single-sided
mounting
Double-sided
mounting
2. As the alignment pin is worn out, adjustment of the nozzle height can cause chipping or cracking of capacitors because of mechanical impact on the capacitors.
To avoid this, the monitoring of the width between the alignment pins in the stopped position, maintenance, check and replacement of the pin shall be conducted
periodically.
Technical
consider-
ations
◆Selection of Adhesives
Some adhesives may cause IR deterioration. The different shrinkage percentage of between the adhesive and the capacitors may result in stresses on the capaci-
tors and lead to cracking. Moreover, too little or too much adhesive applied to the board may adversely affect components. Therefore, the following precautions
shall be noted in the application of adhesives.
（1）Required adhesive characteristics
a. The adhesive shall be strong enough to hold parts on the board during the mounting & solder process.
b. The adhesive shall have sufficient strength at high temperatures.
c. The adhesive shall have good coating and thickness consistency.
d. The adhesive shall be used during its prescribed shelf life.
e. The adhesive shall harden rapidly.
f . The adhesive shall have corrosion resistance.
g. The adhesive shall have excellent insulation characteristics.
h. The adhesive shall have no emission of toxic gasses and no effect on the human body.
（2）The recommended amount of adhesives is as follows;
［Recommended condition］
Figure
212/316 case sizes as examples
a
b
c
0.3mm min
100 to 120μm
Adhesives shall not contact land
ꢀꢀ
＊This catalog contains the typical specification only due to the limitation of space. When you consider the purchase of our products, please check our specification.
For details of each product (characteristics graph, reliability information, precautions for use, and so on), see our Web site (http://www.ty-top.com/) or CD catalogs.
mlcc_prec_e-01
mlcc_prec-P2
TAIYO YUDEN [ TAIYO YUDEN (U.S.A.), INC ]
