Package Mounting Methods
3. Selection of adhesive
Adhesives can be broadly classified as UV-hardening acryl polyester materials and heat-hardening epoxy materials, and
there are various combined UV-/heat-hardening types. It is necessary to select the adhesive according to production
performance, such as the application method, viscosity, hardening temperature/time, pot life, etc., but generally, the
following points should be considered:
1) Quick hardening at as low a temperature as possible
2) No adverse effects on electronic components already mounted on the reverse side
3) High viscosity with superior heat resistance after hardening for the soldering process
4) Long pot life and easily stored
5) No stringiness during printing and little sagging after printing
6) Since some will remain even after soldering, no corrosiveness
4. Selection of cleaning agents
After soldering, washing off of flux is recommended. If flux remains, halogen ions in the flux may cause corrosion of
metal.
Due to environmental problems such as global warming due to the destruction of the ozone layer, the use of flon 113, 1-1-
1 trichloroethane, etc. is restricted, and there are shifts to the following cleaning agents:
1) Alcohol-based cleaning agents
Ethanol, methanol, isopropyl alcohol (IPA), high-grade alcohol-based cleaning agents
2) HCFC substitute flon-based agents
AK-225AES (Asahi Glass) etc. Since the use of HCFC substitutes will become prohibited in the future, sufficient
consideration must be given.
3) No cleaning through the use of non-halogen flux
When using no-wash flux, since it contains virtually no halogens which may cause corrosion, there is virtually no risk
of residue causing fatal flaws in devices. However, residue may cause leakage between pins, resulting in device
operation malfunction or damage.
In addition, since there are also products which contain much non-ionic halogenated materials, caution is necessary. Be
sure to perform evaluation of the reliability characteristics of each mounting method, and verify whether or not
washing can be performed.
M12