Technical Library | 2019-05-23 10:30:22.0
Increasing I/O numbers, device complexity, and product miniaturization requires high precision bonding tools, and sophisticated equipment. Careful consideration should be given to wedge geometry while selecting the tool for a fine pitch wire bonding application. Wire bonding is a process that creates an electrical connection between a die and a substrate or lead typically using gold or aluminum wire. Wedge bonding is a specific type of wire bonding that uses a wedge shaped tool to create the welds. The design of the wedge tool has changed very little over the past decade. The wire is fed at an angle through the back of the wedge. This angle is typically 30 to 60 degrees and is application dependent. Some applications require a higher feed angle due to package clearance issues. Some deep access applications require a 90 degree feed angle. In this configuration, the wire is fed through a hole in the shank of the wedge tool. Wire feed is shown in Figure 1.
Technical Library | 2023-07-25 16:50:02.0
Some of the new handheld communication devices offer real challenges to the paste printing process. Normally, there are very small devices like 01005 chip components as well as 0.3 mm pitch uBGA along with other devices that require higher deposits of solder paste. Surface mount connectors or RF shields with coplanarity issues fall into this category. Aperture sizes for the small devices require a stencil thickness in the 50 to 75 um (2-3 mils) range for effective paste transfer whereas the RF shield and SMT connector would like at least 150 um (6 mils) paste height. Spacing is too small to use normal step stencils. This paper will explore a different type of step stencil for this application; a "Two-Print Stencil Process" step stencil. Here is a brief description of a "Two-Print Stencil Process". A 50 to 75 um (2-3 mils) stencil is used to print solder paste for the 01005, 0.3 mm pitch uBGA and other fine pitch components. While this paste is still wet a second in-line stencil printer is used to print all other components using a second thicker stencil. This second stencil has relief pockets on the contact side of the stencil any paste was printed with the first stencil. Design guidelines for minimum keep-out distances between the relief step, the fine pitch apertures, and the RF Shields apertures as well relief pocket height clearance of the paste printed by the first print stencil will be provided.
Technical Library | 2007-05-31 19:05:55.0
This paper discusses solder paste printing and flux dipping assembly processes for 0.4 and 0.5mm pitch lead-free WLCSPs and the corresponding assembly results and thermal cyclic reliability obtained. Variables evaluated include reflow ambient, paste type, and stencil design. Reliability is also compared to results for the same components assembled under identical conditions using SnPb solder.
Technical Library | 2019-06-03 21:07:34.0
The objective of this White Paper is to provide users of the above products in the electronics industry a clear understanding of the different types of stencil cleaning paper/fabrics that are currently available. Fine pitch applications are more the norm now and so the performance of stencil cleaning rolls is more critical than ever before. This White Paper will give solder paste stencil printing engineers and purchasing professionals an insight into the main products on the market, thereby enabling them to make informed decisions.
Technical Library | 2021-11-16 22:17:27.0
Ultrasonics, coupled with an aqueous detergent process that cleans at below 43ºC, may be best suited for fine-pitch SMT screens and stencils. Aqueous detergents clean more effectively than solvents, with little or no environmental impact. Because of the environmental concerns driving today's technology decisions, the once simple decision of selecting a stencil cleaning process is now clouded with different chemicals, different cleaning machines and various types of solder paste, all with specific environmental, health and safety related issues and regulations.
Technical Library | 2015-12-31 15:19:28.0
Today's consumer electronic product are characterized by miniatuization, portability and light weight with high performance, especially for 3G mobile products. In the future more fine pitch CSPs (0.4mm) component will be required. However, the product reliability has been a big challenge with the fine pitch CSP. Firstly, the fine pitch CSPs are with smaller solder balls of 0.25mm diameter or even smaller. The small solder ball and pad size do weaken the solder connection and the adhesion of the pad and substrate, thus the pad will peel off easily from the PCB substrate. In addition, miniature solder joint reduce the strength during mechanical vibration, thermal shock, fatigue failure, etc. Secondly, applying sufficient solder paste evenly on the small pad of the CSP is difficult because stencil opening is only 0.25mm or less. This issue can be solved using the high end type of stencil such as Electroforming which will increase the cost.
Technical Library | 2015-08-25 13:51:27.0
The stencil printing process is one of the most critical processes in the electronic production. Due to the requirement: "faster and smaller" it is necessary to place components with different paste volume close together without regard to solder paste printing. In our days it is no longer possible to control the solder paste volume only by adjustment of the aperture dimensions. The requirements of solder paste volumes for specific components are realized by different thicknesses of metal sheets in one stencil with so called step stencils. The step-down stencil is required when it is desirable to print fine-pitch devices using a thinner stencil foil, but print other devices using a thicker stencil foil. The paper presents the innovative technology of step-up and step-down stencils in a laser cutting and laser welding process. The step-up/step-down stencil is a special development for the adjustment of solder paste quantity, fulfilling the needs of placement and soldering. This includes the laser cutting and laser welding process as well as the resulting stencil characteristics and the potential of the printing process.
Technical Library | 2015-12-02 18:32:50.0
(Thermal Compression with Non-Conductive Paste Underfill) Method.The companies writing this paper have jointly developed Copper (Cu) Pillar micro-bump and TCNCP(Thermal Compression with Non-Conductive Paste) technology over the last two+ years. The Cu Pillar micro-bump and TCNCP is one of the platform technologies, which is essentially required for 2.5D/3D chip stacking as well as cost effective SFF (small form factor) package enablement.Although the baseline packaging process methodology for a normal pad pitch (i.e. inline 50μm) within smaller chip size (i.e. 100 mm2) has been established and are in use for HVM production, there are several challenges to be addressed for further development for commercialization of finer bump pitch with larger die (i.e. ≤50μm tri-tier bond pad with the die larger than 400mm2).This paper will address the key challenges of each field, such as the Cu trace design on a substrate for robust micro-joint reliability, TCNCP technology, and substrate technology (i.e. structure, surface finish). Technical recommendations based on the lessons learned from a series of process experimentation will be provided, as well. Finally, this technology has been used for the successful launching of the company FPGA products with SFF packaging technology.
Technical Library | 2015-08-06 19:17:53.0
Fine pitch/fine feature solder paste printing in PCB assembly has become increasingly difficult as board geometries have become ever more compact. The printing process itself, traditionally the source of 70% of all assembly defects, finds its process window narrowing. The technology of metal blade squeegees, with the aid of new materials, understanding, and settings such as blade angle, has kept pace with all but the smallest applications, e.g., 200μ - .50 AR and 150μ - .375 AR, which have been pushing blade printing technology to its limits. Enclosed media print head technology has existed, and has been under increasing development, as an alternative to metal squeegee blade printing. Until recently, the performance of enclosed print heads had been comparable to the very best metal squeegees, but advances in enclosed print media technology have now made it a superior alternative to squeegee blades in virtually all applications.
Technical Library | 2023-07-25 16:42:54.0
Printing solder paste for very small components like .3mm pitch CSP's and 01005 Chip Components is a challenge for the printing process when other larger components like RF shields, SMT Connectors, and large chip or resistor components are also present on the PCB. The smaller components require a stencil thickness typically of 3 mils (75u) to keep the Area Ratio greater than .55 for good paste transfer efficiency. The larger components require either more solder paste height or volume, thus a stencil thickness in the range of 4 to 5 mils (100 to 125u). This paper will explore two stencil solutions to solve this dilemma. The first is a "Two Print Stencil" option where the small component apertures are printed with a thin stencil and the larger components with a thicker stencil with relief pockets for the first print. Successful prints with Keep-Outs as small as 15 mils (400u) will be demonstrated. The second solution is a stencil technology that will provide good paste transfer efficiency for Area Ratio's below .5. In this case a thicker stencil can be utilized to print all components. Paste transfer results for several different stencil types including Laser-Cut Fine Grain stainless steel, Laser-Cut stainless steel with and w/o PTFE Teflon coating, AMTX E-FAB with and w/o PTFE coating for Area Ratios ranging from .4 up to .69.
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