When using adhesives before soldering the capacitors to the printed wiring board, confirm the application
conditions or consult component manufacturers. Capacitor performance may deteriorate if land pattern size,
type or amount of adhesive, curing temperature, curing time, etc. is unsuitable.
Certain types of adhesive may deteriorate the insulation resistance. Differences in coefficients of thermal expansion (CTE) between the adhesive and capacitors may cause cracks in the capacitors.
If adhesive amount, curing temperature and/or curing time are insufficient, capacitors may be misaligned or fall off during handling or soldering. When adhesive amount is excessive, adhesive that overflows to the land area may cause poor soldering, conductivity, curing and/or alignment. If curing temperature and/or time is excessive, capacitor termination and board land surfaces might oxidize so much that adhesion strength and solderability of capacitors may deteriorate.
Selection of suitable adhesive
- Consider the following requirements when selecting adhesives.
- 1) Sufficient adhesion strength is needed so that components will not fall or become misaligned in the process of mounting.
- 2) Adhesion strength shall not deteriorate when subjected to the high heat of soldering
- 3) Good deispensability and thixotropy
- 4) Long shelf life
- 5) Rapid curing
- 6) Non-corrosive
- 7) Sufficient nonconductivity
- 8) Non-toxic
- 9) Non-halogen compound
The following drawings show optimum amount and shape for adhesive application.
Symbol Example of
a Minimum 0.2mm b 70μｍ to 100μm c No contact with land pattern
Dispensed adhesive After mounting capacitor