Technical Library | 2008-03-18 12:36:31.0
This paper examines the construction of a notebook mainboard with more than 2000 components and no wave soldering required. The board contains standard SMD, chipset BGAs, connectors, through hole components and odd forms placed using full automation and soldered after two reflow cycles under critical process parameters. However, state of the art technology does not help if the process parameters are not set carefully. Can all complex BGAs, THTs and even screws be soldered on a single stencil? What will help us overcome bridging, insufficient solder and thombstoning issues? This paper will demonstrate the placement of all odd shape components using pin-in-paste stencil design and full completion of the motherboard after two reflow cycles.
Technical Library | 2020-07-15 18:29:34.0
In the early 2000s the first fine-pitch ball grid array devices became popular with designers looking to pack as much horsepower into as small a space as possible. "Smaller is better" became the rule and with that the mechanical drilling world became severely impacted by available drill bit sizes, aspect ratios, and plating methodologies. First of all, the diameter of the drill needed to be in the 0.006" or smaller range due to the reduction of pad size and spacing pitch. Secondly, the aspect ratio (depth to diameter) became limited by drill flute length, positional accuracy, rigidity of the tools (to prevent breakage), and the throwing power of acid copper plating systems. And lastly, the plating needed to close up the hole as much as possible, which led to problems with voiding, incomplete fill, and gas/solution entrapment.
Technical Library | 2019-09-24 15:41:53.0
This paper focuses on three different coating material groups which were formulated to operate under high thermal stress and are applied at printed circuit board manufacturing level. While used for principally different applications, these coatings have in common that they can be key to a successful thermal management concept especially in e-mobility and lighting applications. The coatings consist of: Specialty (green transparent) liquid photoimageable solder masks (LPiSM) compatible with long-term thermal storage/stress in excess of 150°C. Combined with the appropriate high-temperature base material, and along with a suitable copper pre-treatment, these solder resists are capable of fulfilling higher thermal demands. In this context, long-term storage tests as well as temperature cycling tests were conducted. Moreover, the effect of various Cu pre-treatment methods on the adhesion of the solder masks was examined following 150, 175 and 200°C ageing processes. For this purpose, test panels were conditioned for 2000 hours at the respective temperatures and were submitted to a cross-cut test every 500 h. Within this test set-up, it was found that a multi-level chemical pre-treatment gives significantly better adhesion results, in particular at 175°C and 200°C, compared with a pre-treatment by brush or pumice brush. Also, breakdown voltage as well as tracking resistance were investigated. For an application in LED technology, the light reflectivity and white colour stability of the printed circuit board are of major importance, especially when high-power LEDs are used which can generate larger amounts of heat. For this reason, a very high coverage power and an intense white colour with high reflectivity values are essential for white solder masks. These "ultra-white" and largely non-yellowing LPiSM need to be able to withstand specific thermal loads, especially in combination with high-power LED lighting applications. The topic of thermal performance of coatings for electronics will also be discussed in view of printed heatsink paste (HSP) and thermal interface paste (TIP) coatings which are used for a growing number of applications. They are processed at the printed circuit board manufacturing level for thermal-coupling and heat-spreading purposes in various thermal management-sensitive fields, especially in the automotive and LED lighting industries. Besides giving an overview of the principle functionality, it will be discussed what makes these ceramic-filled epoxy- or silicone-based materials special compared to using "thermal greases" and "thermal pads" for heat dissipation purposes.
Technical Library | 2019-12-13 00:39:29.0
Salt spray corrosion chamber can test the ability of material and its protective layer to resist salt mist corrosion, or compare the process quality of similar protective layers, at the same time; this equipment is suitable for parts, electronic components, protective layer of metal material and other industrial products. Salt spray test is divided into neutral and acid test. What is the difference between neutral and acid in salt spray test? First, the temperature applied in the test method is different: Neutral test: a. Laboratory:35°C ±1°C, b. Saturated air drums:47°C ±1°C Acid test: a. Laboratory:50°C ±1°C, b. Saturated air drums:63°C ±1°C Second, the production material is different,neutral test chamber adoptes the traditional PVC plates, acid test chamber asopts PP sheet,which is more high temperature resistance and suits strong acid test. Third. Different test methods satisfied Neutral salt spray chamber according to GB/T 2423.17-2008, GB/T 2423.18-2000, salt spray test method and GB/T 10125-1997, GB/T 10587-2006, GB10593.2-1990, GB/T 1765-1979, GB/T 1771-2007, GB/T 12967.388, GB/T 1705.8-2008, etc. In addition to the test methods specified in the national standard, acid salt spray chamber also needs to expand the standard setting such as IEC,MIL,DIN,ASTM,IS,CNS. Last, Comparison of neutral test solutions China: NaCI distilled water solution NaCI mass concentration (50 ±5) g ≤ l pH value 6.5 ≤ 7.2 United States: distilled water solution NaCI mass concentration 5% ±1% pH value 6.5 ≤ 7.2 Germany: NaCI distilled water solution NaCI mass concentration (50 ±5) g ≤ l pH value 6.5 ≤ 7.2 Japan: NaCI distilled water solution NaCI mass concentration 5% ±1% pH pH value 6.5 ~ 7.2 France: NaCI distilled water solution NaCI mass concentration 5% pH 6.5 ≤ 7.2 https://climatechambers.com/articles&latestnews/difference-between-neutral-and-acid-salt-spray-corrosion-test.html
