Technical Library | 2009-04-23 08:14:37.0
No SMT equipment can place accurately and run efficiently without quality nozzles and feeders. These two factors are the core of the pick and place process. If the machine is either unable to pick parts consistently or hold on to the components during the transport from feeder to PCB, defects will result.
Technical Library | 2020-06-02 15:16:51.0
A commercial systems manufacturer working on a major defense program contacted the Helpline for urgent assistance with an issue of failed parts during reliability testing. They were attempting to incorporate commercial off-the-shelf (COTS) computer-related hardware into a battlefield system and were experiencing reliability issues. It was noted that the parts were labeled by the vendor as "compliant to military (or MIL) standards" but not clearly identified as tin-lead or lead-free. ACI Technologies has supported a number of customers with lead-free issues and we assisted the customer in developing a short term and long-term solution to their problem.
Technical Library | 2019-06-21 10:39:15.0
Recently, an ACI Technologies (ACI) customer called to discuss failures that they had observed with some through-hole capacitor parts. The components were experiencing failures following vibration and accelerated stress testing. Upon receipt of the samples, ACI performed three levels of inspection and Energy Dispersive Spectroscopy (EDS) testing to investigate the root cause of the failures. These analyses enabled ACI to verify the elements comprising the solder joints and make the following recommendations in order to prevent future occurrences. The first inspection was to investigate the capacitor leads using optical microscopy, and no anomalies were found that could indicate bad parts from the vendor or improper handling prior to assembly. However, vertical fill in the barrel of the plated through-holes was too close to the IPC-A-610 minimum specification of 75% to determine a pass/fail condition, and therefore required further investigation.
Technical Library | 2019-06-20 07:45:19.0
One of the two basic risks of employing the commercially accepted, Restriction of Hazardous Substances (RoHS) compliant, lead-free (Pb-free) electronics is the threat to the electronics reliability from the growth of tin whiskers. The other basic risk deals with Pb-free solder joint reliability.
Technical Library | 2019-05-24 09:22:59.0
There is a smaller process window and a much narrower margin of error when creating and using lead-free reflow profiles for surface mount parts on printed circuit boards (PCBs). Solder balls, dewetting, tombstones, voids, and head-on-pillow problems will occur much more frequently because lead-free alloys behave differently than eutectic pastes. Problems are compounded due to the extra heat necessary for some lead-free pastes to reach their melting points.
Technical Library | 2019-06-24 15:54:17.0
Defense systems and its manufacturers are often blamed for not embracing new and innovative technologies to manufacture products compared to its commercial counterparts. Commercial product manufacturers are known to think “outside the box” in coming up with new products which are cheaper, have fewer parts, and easier to manufacture using automation. Automation leads to consistent quality products which are reliable and reproducible. Implementing some of these producibility design practices into defense systems will greatly reduce the cost and insertion time for new products.
Technical Library | 2019-06-17 15:09:43.0
Very often pick and place machines are programmed using CAD data. This data increases the accuracy, precision, and repeatability of its component placement objectives. CAD data makes fine pitch and small component assemblies repeatable, but cannot adjust to a particular board unless it is exactly the same size and shape of the original board used for programming. The process by which printed circuit boards (PCBs) are made only allows some minor changes inboard size and shape, but these small differences are enough for parts to be misplaced. For this reason we use fiducial marks to increase the chances of precise component alignment.
Technical Library | 2019-05-23 10:42:00.0
Why identify flux residues? The primary purpose of flux is to reduce species of metal oxides from solderable surfaces, and to act as a mechanism for lifting and removing debris. If the assembly is not properly cleaned after manufacturing, flux may continue to reduce metals and may eventually corrode the assembly. When the assembly is powered, the metal ions may precipitate along electromagnetic field lines and form dendritic shorts. In addition, the presence of residue can alter the insulation properties of a board, affect the adhesion of the conformal coating, or interfere with the moving parts of the assembly. In radio frequency (RF) applications, flux may change the RF properties on the surface of the printed circuit board (PCB) such as the dielectric strength, surface resistance, and Q-resonance.
Technical Library | 2019-07-11 11:07:08.0
Affordability is not exactly the primary word which comes to mind when discussing the use of design of experiments (DOE) principles, but is generally accepted as a necessary part of the engineering activities required in the development of a product or process. However, a number of studies have indicated that the cost savings derived from a well deliberated experimental design can be substantial in the initial stages where the conditions or parameters of a process are determined. Some studies have shown a greater than 50% cost savings compared to the more conventional means of trial and error approaches to process development. At ACI Technologies (ACI), we have found the use of DOE techniques fundamental in eliminating extraneous costs otherwise spent on unnecessary testing.
Technical Library | 2020-03-09 10:50:17.0
A customer called the Helpline seeking advice for cleaning no-clean fluxes prior to applying a conformal coating. The customer's assemblies were manufactured with a no-clean rosin based solder paste (ROL0) and were cleaned with an isopropyl alcohol (IPA) wash. After cleaning, a white residue was sometimes found in areas with high paste concentrations and was interfering with the adhesion of the conformal coating (Figure 1). For conformal coatings to adhere properly, the printed circuit board (PCB) surface must be clean of fluxes and other residues. In addition, ionic contamination left by flux residues can lead to corrosion and dendrite growth, two common causes of electronic opens and shorts. Other residues can lead to unwanted impedance and physical interference with moving parts.
