Notice
3. Board Design
Relationship with amount of strain to the board thickness, length, width, etc.]
3PL
When designing the board, keep in mind that
the amount of strain which occurs will increase
ꢀ depending on the sizeand material of the board.
Relationshipbetweenloadandstrain
ε=
2Ewh2
ε：Strain on center of board (μst)
L：Distance between supporting points (mm)
P
Y
w
h
E
Y
P
：Board width (mm)
：Board thickness (mm)
：Elastic modulus of board (N/m2=Pa)
：Deflection (mm)
h
：Load (N)
w
L
When the load is constant, the following relationship can be established.
· As the distance between the supporting points (L) increases,the amount of strain also increases.
→Reduce the distance between the supporting points.
· As the elastic modulus (E) decreases, the amount of strain increases.
→Increase the elastic modulus.
2.Item to be confirmed for Flow sordering
·
As the board width (w) decreases, the amount of strain increases.
→Increase the width of the board.
As the board thickness (h) decreases, the amount of strain increases.
ꢀ If you want to temporarily attach the capacitor
ꢀ to the board using an adhesive agent before
ꢀ soldering the capacitor, first be sure that the
ꢀ conditions are appropriate for affixing the
·
→Increase the thickness of the board.
Since the board thickness is squared, the effect on the amount of strain becomes even greater.
ꢀ capacitor. If the dimensions of the land, the type of adhesive,the amount of coating, the contact surface area,
ꢀ the curing temperature, or other conditions are inappropriate, the characteristics of the capacitor may deteriorate.
1. Selection of Adhesive
1-1. Depending on the type of adhesive, there may be a decrease in insulation resistance. In addition, there is a chance
that the capacitor might crack from contractile stress due to the difference in the contraction rate of the capacitor
and the adhesive.
1-2. If there is not enough adhesive, the contact surface area is too small, or the curing temperature or curing time
are inadequate, the adhesive strength will be insufficient and the capacitor may loosen or become disconnected
during transportation or soldering. If there is too much adhesive, for example if it overflows onto the land, the result
could be soldering defects, loss of electrical connection, insufficient curing, or slippage after the capacitor is mounted.
Furthermore, if the curing temperature is too high or the curing time is too long, not only will the adhesive strength
be reduced, but solderability may also suffer due to the effects of oxidation on the terminations (outer electrodes)
of the capacitor and the land surface on the board.
ꢀ(1) Selection of Adhesive
ꢀEpoxy resins are a typical class of adhesive. To select the proper adhesive, consider the following points.
ꢀ1) There must be enough adhesive strength to prevent the component from loosening or slipping during the
ꢀꢀꢀꢀmounting process.
ꢀ2) The adhesive strength must not decrease when exposed to moisture during soldering.
ꢀ 3) The adhesive must have good coatability and shape retention properties.
ꢀ 4) The adhesive must have a long pot life.
ꢀ5) The curing time must be short.
ꢀ 6) The adhesive must not be corrosive to the exterior of the capacitor or the board.
ꢀ 7) The adhesive must have good insulation properties.
ꢀ 8) The adhesive must not emit toxic gases or otherwise be harmful to health.
ꢀ 9) The adhesive must be free of halogenated compounds.
ꢀ(2) Use the following illustration as a guide to the amount of adhesive to apply.
ꢀꢀChipꢀDimension (L/W)ꢀCode:18/21/31
Adhesive
Land
Resist
Resist
Cross Sectional View
Side View
JEMCGC-05049F
25
MURATA [ muRata ]
