PCBA Assembly Process Material Testing

- Mar 18, 2019-

1. Solder alloy testing

In the PCB process, the solder alloy is generally not required to be tested for incoming materials, but in the wave soldering and lead immersion tin processes, The molten solder in the tank continuously melts the metal on the soldered material, causing metal contaminants and changing the solder composition.

This leads to poor soldering. To this end, it is necessary to conduct regular inspections, and the inspection cycle is usually once a month or according to the actual production situation.

It is determined that the detection method includes an atomic adsorption quantitative analysis method and the like.

Flux detection

(1) Shui Rong took the resistivity test. The water extraction resistivity test mainly tests the ionic characteristics of the flux, and the test method is

There are provisions in the standards such as QQ-S-571. The water extraction resistivity of the inactive rosin flux (R) and the medium active rosin flux (RMA) should be not less than 100,000 Ω•cm; and the active flux has a water extraction resistivity of less than 100,000 Ω•cm.

(2) Bronze mirror test. Bronze mirror test is to test flux activity by the effect of flux on the thin copper layer coated on the glass substrate.

of. For example, QQS-571 specifies that for R and RMA fluxes, regardless of the results of their water extraction resistivity tests, it should not have the activity of removing copper on the copper mirror, otherwise it is unacceptable.

pcb assembly

(3) Specific gravity test. The specific gravity test mainly tests the concentration of the flux. In wave soldering and other processes, the specific gravity of the flux is affected by the evaporation of the agent and the amount of SMA welding. Generally, it needs to be traced and adjusted in the process to ensure that the flux maintains the set specific gravity and ensures the smooth progress of the welding process. The specific gravity test is usually carried out by means of timed sampling and measurement by a hydrometer. It can also be carried out continuously and automatically by the online automatic flux specific gravity detection system.

(4) Color test. Color tests show the chemical stability of the solder and the deterioration of the mountain due to exposure, heating and service life. Colorimeter testing is a common method of color testing. When the tester has a wealth of experience, the simplest visual method can be used.

4. Other incoming inspection

(1) Pointing agent detection. Adhesive testing is mainly viscous testing. The bonding strength of SMD adhered to the PCB by the bonding agent should be tested according to the relevant standards to determine whether it can ensure that the bonded components are damaged by vibration and thermal shock during the process. And whether the binder has deteriorated.

(2) Cleaning agent detection. The composition of the solvent changes during the cleaning process, and even becomes flammable or corrosive, and at the same time reduces the cleaning efficiency, so it needs to be tested regularly. The detection of cleaning agents is generally carried out by gas chromatography.

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