1) Storage of solder paste
Solder paste is a relatively sensitive soldering material. Pollution, oxidation, and moisture absorption will cause different degrees of deterioration. Therefore, solder paste is generally required to be sealed and stored at low temperature and low humidity. In the sealed state, the bottle mouth is still required to be placed upright to prevent the flux from leaking out and affecting its activity.
(1) Control the use cycle of solder paste according to production needs, and the inventory storage time should not exceed 3 months.
(2) Solder paste should be stored separately according to different types, batch numbers, and different manufacturers.
(3) The storage conditions of the solder paste require a temperature of 4 to 8 rpm and a relative humidity of less than 50%. Do not put the solder paste in the freezer to freeze, the special solder paste depends on the manufacturer’s information.
(4) The use of solder paste should follow the first-in-first-out principle and should be recorded.
(5) The stored temperature and humidity should be checked and recorded every week.
About the characteristics of BGA package
2) Precautions for the use of solder paste
(1) Take out the solder paste from the refrigerator, paste the “use label”, and fill in the “reheating start time and signature”. The solder paste must be fully warmed up before it can be used. The warming time is specified as 6~12 hours, and the “opening time” and “use effective time” should be filled in the “use label”. If it is used before the temperature is fully restored, the solder paste will condense the moisture in the air, causing problems such as collapse and tin explosion.
(2) The solder paste should be fully stirred in the tank before use. There are two ways of stirring: one is machine stirring, and the time is generally 3 ~ 4 min; the other is manual stirring, which requires stirring in the same direction to avoid There are bubbles in the solder paste, and the stirring time is 2 ~ 3 min o
(3) When removing the solder paste from the bottle, pay attention to adding as little as possible to the template. After adding, be sure to screw the lid to prevent the solder paste from being exposed to the air and causing the flux to volatilize. The validity period of the solder paste after opening the lid is 24h .
(4) Solder paste works best in a (23 ± 2) long, 40% -50% RH environment, and no cold or hot air blows directly against it. The temperature exceeds 26.6 Y, which will affect the performance of the solder paste}
(5) In principle, the solder paste that has been opened should be used up as soon as possible. If this is not possible, the remaining solder paste on the template can be filled into an empty can at the end of the working day and reserved for next use. Used solder paste cannot be mixed with unused solder paste in the same bottle, because the fresh solder paste may be contaminated by the used solder paste and deteriorate.
(6) Before using the solder paste that has been opened, you must first confirm whether it is within the validity period of use.
(7) If the solder paste is not used up on the same day, if it is no longer produced on the second day, it must be returned to the refrigerator for storage and indicated on the label.
(8) Try to finish reflow soldering within 4 hours after printing.
(9) No-clean solder paste can not be scrubbed with alcohol after repairing the board.