In any surface mount assembly process, achieving a high first pass yield (FPY) is a key factor for production operation efficiency and final product quality. Two elements that contribute to high qualification rates are particularly relevant to solder pastes: the performance window of solder pastes and the stability of vertices. Much of this information can be obtained from solder paste suppliers, because functional performance, or usability standard programs, are an integral part of the product development process.
A solder paste manufacturer must understand the applicability of each formula to meet many different performance standards: telecommunications, automotive, contract manufacturing, computers, computer peripherals, aviation and commercial applications. However, it is important to know exactly how the special formula behaves in a particular process. For this reason, the standard program, whether implemented by the solder paste supplier or the applicator, is a necessary factor to achieve high productivity. Many manufacturers, original equipment manufacturers (OEMs) and those who provide contract assembly services rely on solder paste suppliers to conduct process specific standard programming research.
In addition, those manufacturers that focus on high-quality production should conduct their own standard program research. Field testing using equipment that is actually used to assemble the final product will produce the most accurate prediction of production level results. Whether performed by users or suppliers, their programs should produce measurable results comparing one formula with another. Even if the manufacturer only relies on the supplier for standard procedures, it should understand the procedure steps so that the results can be properly evaluated. In design test standards, a typical strategy is to develop a "worst-case scenario" for most elements of design and process conditions.
This framework provides a target method against which data can be compared and contrasted. The following standard procedures are used to provide a comparison of the amount of functional characteristics of the wash free solder paste, including the determination methods of printability, spread and collapse characteristics, solderability, and the efficiency of solder beads/balls. The manufacturer can use all or part of the programs to develop internal standard setting programs or evaluate the standard program data of solder paste suppliers. A comprehensive standard program should consist of a set of tests to measure the usability of solder paste from printing to testing.
Since 52% - 72% of surface mount defects can be attributed to printing defect 1, this program should pay special attention to printing. Recommended tests, listed by process, Yes: printability of fine pitch printability squeegee compatibility spread of printed graphics slump model of printed graphics tack force/tack life/capability reflow soldering wetting temperature profile sensitivity solder bead/balling residue level Other probe testability Dense spacing printability of viscous ion chromatography is rarely required to be less than 0.5mm in the current market. Based on the typical market demand, printability test should focus on the spacing of 20-mil (0.508mm). The printing speed varies from 15mm/s to 70mm/s, and the density spacing is mostly 25mm/s. Using the "worst case" strategy, 70mm/s is selected for this standard program printing test. Metal scraper is the mainstream of industry, with two angles of 45 ° and 60 ° commonly used. The 45 ° angle tends to guide the solder paste to roll and print better than the 60 ° angle, but it may require more pressure to clean the template with some data. The 60 ° metal scraper is selected because the complaint of solder paste "sticking" to the scraper is more serious when using a steeper scraper angle. In order to quantify the small difference of printability in the similar data formula, a flat inert substrate is selected on the typical HASL (hotair level soldering) light plate. This PCB shape will not affect the printability of solder paste.
Other elements of the process are also limited: a metal scraper with an angle of 60 °, a scraper speed of 70mm/s, a template to be wiped after every twelve times of printing, a template to be chemically etched with a thickness of 6-mil, an internal design (Figure 1), an aluminum substrate with a length of 1 "x2", and a spacing of 0.5mm measured by sampling from 100 parts during operation. The measurement system program is designed together with the test program design and a series of macro commands in the spreadsheet used for data analysis and display. The program runs 10 grids (rows) on each printed pad, and measures its height every 0.5mil along the grid. The sensor used has a height resolution of 0.03 mil and a width resolution of 0.5 mil. All 64 pads for each printing are measured, resulting in 28160 height measurements for each printing, and a total of 140800 height measurements for each test. The height data can be reduced to manageable information through the following three steps: 1. The measurement system outputs the partition area per square mil, the pad width and the average pad height of each partition of the pad. Multiply the partition area by the partition spacing (6mil) to obtain an approximate accurate volume, cubic mil. 2. The data is then input into the spreadsheet, where a series of macro commands are started to calculate the pad volume (drawing parallel and vertical pad data), the average height of the pad (on the solder paste platform), and the average width of the pad. 3. Because many materials and data only come from step 2, the result is a subjective assessment of printability using data from objective sources. A fractional system in which the standard deviation is divided by the average value and used to round off the calculation of variables (Figure 2). The "collapse" is calculated and defined as the absolute difference between the average width and 10 mils (the width of the sample opening). The printing width smaller or larger than the opening width shall be treated equally. Give a score to those lacking change. In addition to the characteristics of scraper angle, the shape of scraper can also affect the performance of solder paste at a specific angle.
Basically, the duller the scraper is, the greater the pressure will be required to completely scrape the top surface of the template. A simple microscopic examination of the edges of various metal scrapers will reveal great differences. The visual difference between the shape of the coated metal scraper and the electroforming scraper is equivalent to the scraper pressure required for a pair and a half of scraping. The efficiency of solder paste is affected because the smaller the scraper pressure, the less often the template is wiped. The formula compatibility of some "hollow scraper" options provided by printer manufacturers is also critical for solder paste formulators. The closely spaced printing test can be used to characterize the process window for a given recipe.
Hongqiao Technology Co., Ltd. is a high-tech enterprise specializing in the research, development and production of cutting fluid, electronic hardware cleaner, surface treatment agent, welding materials: solder paste, tin rod, tin wire, BGA solder ball, SMT tin, electronic flux and thinner, electronic welding equipment and accessories, electroplating anode plate (rod), semi tin ball and other products.
Hongqiao Technology Co., Ltd. is a high-tech enterprise specializing in the research, development and production of cutting fluid, electronic hardware cleaner, surface treatment agent, welding materials: solder paste, tin rod, tin wire, BGA solder ball, SMT tin, electronic flux and thinner, electronic welding equipment and accessories, electroplating anode plate (rod), semi tin ball and other products. Hongqiao Technology Co., Ltd. is a high-tech enterprise specializing in the research, development and production of cutting fluid, electronic hardware cleaner, surface treatment agent, welding materials: solder paste, tin rod, tin wire, BGA solder ball, SMT tin, electronic flux and thinner, electronic welding equipment and accessories, electroplating anode plate (rod), semi tin ball and other products. Hongqiao Technology Co., Ltd. is a high-tech enterprise specializing in the research, development and production of cutting fluid, electronic hardware cleaner, surface treatment agent, welding materials: solder paste, tin rod, tin wire, BGA solder ball, SMT tin, electronic flux and thinner, electronic welding equipment and accessories, electroplating anode plate (rod), semi tin ball and other products. Hongqiao Technology Co., Ltd. is a high-tech enterprise specializing in the research, development and production of cutting fluid, electronic hardware cleaner, surface treatment agent, welding materials: solder paste, tin rod, tin wire, BGA solder ball, SMT tin, electronic flux and thinner, electronic welding equipment and accessories, electroplating anode plate (rod), semi tin ball and other products.