Accompanied by the rapid development of electronic information technology, printed circuit board assembly (PCBA) assembly process requirements are increasingly high, and the stability and quality of electronic products are mainly at the stability and quality level of PCBA. In the actual operation of the process and its PCBA failure analysis, it is not difficult to find PCBA residue on the PCBA stability degree of influence is very large.
In the residue, inorganic residues will reduce the insulation resistance, and increase the leakage current between the solder joints or wires, in the humid air environment, but also lead to corrosion of the metal surface; organic residues (such as rosin, grease, etc.) will form an insulating film, thus affecting the connectors, switches and relays, and other components between the surface of the electrical contact, but also with the change in the natural conditions of the impact and the time becomes longer and more serious, may be able to This may cause poor contact or even short-circuit failure.
Testing is a very important part of the PCBA (Printed Circuit Board Assembly) manufacturing process. Through testing, it can ensure that the electronic components on the board are installed correctly and work properly. For this reason, PCBA fabricators usually employ several different test fixtures to perform various types of circuit board testing.
PCBA test method 1: 300X microscope
1. Place the observation object on the platform.
2. Adjust the appropriate magnification, and focal length for the test, until you see the clearest picture.
3. Use the 360-degree rotating lens to observe the state of the item.
Scope of application: including empty, cold welding judgment, foreign object identification, tin bead identification, parts damage to view, and parts to eat the height of the tin surface judgment.
PCBA test 2: Red ink test
1. first 336A clean machine flux residue with a little, and then the test object is to be added to the appropriate amount of red ink.
2. after confirming that the red ink has been completely penetrated, put the object to be tested into the oven to bake, and then use pliers to force it to remove;
3. Use a 300X microscope for observation.
Application scope: including the parts bonding surface of the crack as well as empty welding.
PCBA Test 3: Slicing
1. Mix the acrylic powder and hardener according to the ratio of one to one, and then put them into the box. 2.
2. 30 minutes later, after the mixing of the material is cured, remove it, and then grind it to the bad point.
Range of application: Crack, air welding, cold solder, observation of the joint surface of each part foot, etc. are all included.
In addition, there are PCBA testing methods such as Side Microscope, X-RAY, Solder Paste Printing Inspection Machine, ORT, etc.
How to clean the contaminants on PCBA?
1. Manual cleaning: suitable for small batch and single piece production.
Cleaning agent: anhydrous ethanol + isopropyl alcohol.
Cleaning process: put the cleaning agent into the container, and brush with a brush dipped in cleaning agent to brush the PCBA solder joints. printed wiring assembly
2. Ultrasonic cleaning
Cleaning agent + ultrasonic cleaning machine.
Cleaning process: PCBA into the cleaning basket immersed in the cleaning machine boiling tank, in the boiling tank with freon heating immersion 4min, and then transferred to the cleaning machine cooling tank, ultrasonic freon cleaning 4min, lifting the cleaning basket, and finally the cleaning basket placed in the boiling tank freon above the steam area, until the surface of the parts condensation drops, remove the cleaning basket to dry for 15min.
3. Water-based cleaning: the best cleaning effect, the most stable, to meet the high reliability of military electronic products’ ionic contamination requirements.
Cleaning agent: cleaning reagent + deionized water + cleaning equipment: PCBA water cleaning machine PBT-800P.
Cleaning process: PCBA into the cleaning machine on the frame, and run the cleaning program. Full-automatic cleaning mode, the workpiece in the cleaning basket with the cleaning basket moves back and forth, while the spray system high-pressure jet heated cleaning fluid, can make the PCBA all-round get automatic cleaning, rinsing, and drying the whole process. printed wiring assembly