Reliability test: main factors and reference standards affecting weldability

Date：2021-07-27 15:35:00Views：2658

Solderability test, English is "solderability". It refers to the qualitative and quantitative evaluation of the weldability of components, PCB boards, pads, solders and fluxes through the principle of wetting balance. It is of great help to the level 1 (IC packaging) and level 2 (electronic components assembled to printed circuit board) processes of modern electronic industry, which need high-quality interconnection technology and high-quality and zero defect welding process.

In fact, the major international standards organizations IEC, IPC, DIN and JIS have recommended various methods for the evaluation of weldability. However, regardless of the repeatability of the test and the ease of interpretation of the results, wetting balance is currently recognized as a weldability test method for qualitative and quantitative analysis.

The main factors affecting weldability are analyzed as follows:

1. The main factor affecting the weldability of steel is its chemical composition. The most influential element is carbon, that is, the amount of carbon in the metal determines its weldability.

2. Weldability refers to the difficulty of obtaining excellent welded joints of metal materials under certain welding processes, including welding methods, welding materials, welding specifications and welding structure forms. A metal is considered to have good welding properties if it can obtain high-quality joints by more common and simple welding processes.

3. Most alloy elements other than carbon in steel are also not conducive to welding, but their influence is generally much smaller than that of carbon. With the increase of carbon content in steel, the hardening tendency increases and the plasticity decreases, which is easy to produce welding cracks. Generally, the sensitivity of metal materials to cracks during welding and the change of mechanical properties of welded joint area are regarded as the main indexes to evaluate the weldability of materials. Therefore, the higher the carbon content, the worse the weldability. The amount of carbon in steel is often regarded as the main symbol to judge the weldability of steel. Low carbon steel and low alloy steel with carbon content less than 0.25% have excellent plasticity and impact toughness, and the plasticity and impact toughness of welded joints after welding are also very good. Preheating and post weld heat treatment are not required during welding. The welding process is ordinary and simple, so it has good weldability. With the increase of carbon content, the tendency of welding crack is greatly increased.

In the process of tin welding, under the action of welding heat, the solder, weldment and copper foil will not melt, and the solder will melt and wet the welding surface, resulting in the diffusion of solder metal, forming a metal attachment layer between the copper foil and weldment, and connecting the copper foil and weldment together to obtain a firm and reliable welding point, The above process is the effect of mutual physical interaction process. Solderability test is generally used to evaluate the weldability of components, printed circuit boards, solders and fluxes qualitatively and quantitatively.

In the assembly and welding process of electronic products, the welding quality directly affects the quality of the whole machine. Therefore, in order to improve the welding quality, in addition to strictly controlling the process parameters, it is also necessary to carry out scientific solderability test on printed circuit boards and electronic components.

Weldability test:

The product is divided into 1) lead and 2) lead-free

·Reference standard:

·Edge dip test: j-std-003 test a (lead tin) / j-std-003 test A1 (lead free)

·Solder float test: j-std-003 test C (lead tin) / j-std test C1 (lead free)

·Wave holder test wave soldering: j-std-003 test D

·Wetting balance: j-std-003 test f (lead tin) / j-std-003 test F1 (lead free)

·Solvency for metallic surface: IPC-TM-650 2.4.14

Weldability test standard:

J-std-002b 2003-2 solderability test of components, lugs and terminals

J-std-003b (2007-3) solderability test of printed circuit board

IPC-TM-650 2.4.14 weldability of metal surface

IPC-TM-650 2.6.8 thermal stress test

GB / T 4677 test methods for printed boards

Iec60068-2-58 / iec60068-2-20 weldability and thermal stress test

GB2423. 28 basic environmental test procedures for electrical and electronic products

GB2423. 32 basic environmental test procedures for electrical and electronic products

Mil-std-202g method 208h weldability test

Mil-std-202g mehtod 210f thermal stress test

Mil-std-883g 2003.7 weldability test