Technical Library | 2007-12-13 17:03:02.0
Printer-hosted processes for solder ball placement are now widely used for package technologies ranging from BGAs using ball diameters above 750μm to the latest WL-CSPs demanding 250μm diameter. This broadening spectrum of applications brings more choices in terms of stencil design rules and production methodologies.
Technical Library | 2017-10-05 17:13:04.0
Intermetallic compounds (IMC) in solder bonds are commonly considered critical for the reliability of interconnections. The microstructure and thermal aging characteristics of solder bonds of crystalline silicon solar cells are investigated, whereby two solders, Sn60Pb40 and a lead-free, low melting point alternative Sn41Bi57Ag2 are considered.
Technical Library | 2015-11-19 18:15:07.0
The move to lead free (Pb-free) electronics by the commercial industry has resulted in an increasing number of ball grid array components (BGAs) which are only available with Pb-free solder balls. The reliability of these devices is not well established when assembled using a standard tin-lead (SnPb) solder paste and reflow profile, known as a backward compatible process. Previous studies in processing mixed alloy solder joints have demonstrated the importance of using a reflow temperature high enough to achieve complete mixing of the SnPb solder paste with the Pb-free solder ball. Research has indicated that complete mixing can occur below the melting point of the Pb-free alloy and is dependent on a number of factors including solder ball composition, solder ball to solder paste ratio, and peak reflow times and temperatures. Increasing the lead content in the system enables full mixing of the solder joint with a reduced peak reflow temperature, however, previous research is conflicting regarding the effect that lead percentage has on solder joint reliability in this mixed alloy solder joint.
Technical Library | 2019-01-02 21:51:49.0
Failed solder joints remain a constant source of printed circuit board failure. Soldering is the bonding of metallic surfaces via an intermetallic compound (IMC). The interaction between thermal energy delivery, flux chemistry, and solder chemistry creates the solder bond or joint. Today, reliability relies on visual inspection; operator experience and skill, control of influencers e.g. tip geometry, tip temperature, and collection and analysis of process data. Each factor involved with the formation of the solder joint is an element of risk and can affect either throughput or repeatability. Mitigating this risk in hand soldering requires the identification of these factors and a means to address them.
Technical Library | 2013-03-14 17:19:28.0
Commercial-off-the-shelf ball/column grid array packaging (COTS BGA/CGA) technologies in high reliability versions are now being considered for use in a number of National Aeronautics and Space Administration (NASA) electronic systems. Understanding the process and quality assurance (QA) indicators for reliability are important for low-risk insertion of these advanced electronic packages. This talk briefly discusses an overview of packaging trends for area array packages from wire bond to flip-chip ball grid array (FCBGA) as well as column grid array (CGA). It then presents test data including manufacturing and assembly board-level reliability for FCBGA packages with 1704 I/Os and 1-mm pitch, fine pitch BGA (FPBGA) with 432 I/Os and 0.4-mm pitch, and PBGA with 676 I/Os and 1.0-mm pitch packages. First published in the 2012 IPC APEX EXPO technical conference proceedings.
Technical Library | 2015-08-13 15:52:40.0
Pad cratering has become more prevalent with the switch to lead free solders and lead free compatible laminates. This mainly is due to the use of higher reflow temperature, stiffer Pb-free solder alloys, and the more brittle Pb-free compatible laminates. However, pad cratering is difficult to detect by monitoring electric resistance since pad cratering initiates before an electrical failure occurs. Several methods have been developed to evaluate laminate materials' resistance to pad cratering. Pad-solder level tests include ball shear, ball pull and pin pull. The detailed methods for ball shear, ball pull, and pin pull testing are documented in an industry standard IPC-9708. Bansal, et al. proposed to use acoustic emission (AE) sensors to detect pad cratering during four-point bend test. Currently there is an industry-working group working on test guidelines for acoustic emission measurement during mechanical testing.
Technical Library | 2016-01-12 11:03:35.0
With the pitch size of interconnect getting finer and finer, the bonding strength between flexible and rigid (e.g. PCB, ceramic) substrates becomes a serious issue because it is not strong enough to meet the customer’s requirement. Capillary underfill has been used to enhance the bonding strength between flexible and rigid substrates, but the enhancement is very limited, particularly for high temperature application. The bonding strength of underfilled flexible/rigid interconnect is dramatically decreased after being used at 180◦C, and the interconnects are weakened by the internal stress caused by the expansion of underfill at high temperatures. In order to resolve reliability issues of the interconnect between flexible/rigid substrates, solder joint encapsulant was implemented into the thermal compression bonding process, which was used to manufacture the interconnect between flexible/rigid substrates. Compared to the traditional process, the strength of the interconnect was doubled and the reliability was significantly improved in high temperature application.
Technical Library | 2009-11-05 11:17:32.0
Head-in-pillow (HiP), also known as ball-and-socket, is a solder joint defect where the solder paste deposit wets the pad, but does not fully wet the ball. This results in a solder joint with enough of a connection to have electrical integrity, but lacking sufficient mechanical strength. Due to the lack of solder joint strength, these components may fail with very little mechanical or thermal stress. This potentially costly defect is not usually detected in functional testing, and only shows up as a failure in the field after the assembly has been exposed to some physical or thermal stress.
Technical Library | 2023-01-10 20:08:36.0
Nickel corrosion in ENIG and ENEPIG is occasionally reported; when encountered at assembly it manifests as soldering failures in ENIG and wire bond lifts in ENEPIG. Although not common, it can be highly disruptive, resulting in missed deliver schedules, supply chain disruption, failure analysis investigations, and liability - all very costly.
Technical Library | 2013-03-21 21:24:49.0
This paper explores the behaviour of a copper test vehicle with multiple reflowed solder joints, which has direct relevance to ball grid arrays (BGA) and high density interconnect structures. The paper explores the relative stress conditions on the distributed joints and the sensitivity to ball joint shape... First published in the 2012 IPC APEX EXPO technical conference proceedings
