Comparison between Ultra Fine Pitch QFP and BGA

2018-12-04 14:54Writer: qyadminReading:
      Through-hole technology (THT) that began flourishing with IC (built-in circuit) in 60s has been steadily replaced by the first era of SMT (surface attach technology) that arrived onto the stage as soon as 80s combined with the quick development of LSI at the later stage of 70s. Peripheral deals have grown to be the main blast of consumer electronics deals with QFP (quad smooth package) for example. 90s has observed fine pitch of QFP, leading table assembly technology to meet plenty of challenges. Regardless of the advent of fine pitch technology (FPT), board-level circuit assembly with pitch less than 0.4mm still features many specialized conditions that should be handled. As an ideal solution, the next era of SMT premiered at the previous stage of 90s, that is, BGA (ball grid array) bundle. Then, chip-scale bundle (CSP) became people's concentrate in 1990s. Particularly when turn chip (FC) technology can be used, PBGA (plastic material ball grid array) begins to be employed in super computer systems and work channels and steadily become practical. The 3rd era of SMT is immediate chip assembly (DCA) that is applied in special areas due to restrictions in conditions of reliability, cost and KGD etc. Modern times has seen the involvement of wafer level packaging (WLP) and advanced FC in the 3rd era of SMT appropriate for the necessity of semiconductor multiple pins and powerful. Therefore, it could be figured IC deals in the 21st century will establish towards styles of high density, fine pitch, high versatility, high reliability and variety. Because of this, it's of much significance to understand the difference between QFP and BGA and their development pattern.

  Plastic material Quad Flat Bundle (PQFP)

  PQFP certainly features competitive advantages in IC packaging market. Nowadays, electronic devices bundle is moving towards deals BGA, CSP and ultra-fine pitch QFP because of the high added value. With pin count number constantly increasing, if pin depend is greater than 200 with pin spacing less than 0.5mm, pin spacing is approximately 0.3mm so far as deals with 300 pins are worried. Small pin spacing is, product reduction will exponentially rise. As pin spacing becomes smaller, bridging soldering will easier happen. If pin spacing is 0.3mm, a good few particles with diameters significantly less than 15μm provides ahead solder balling, which really is a usual reason behind bridging. It's even more significant to regulate solder paste particle size. Once pin spacing becomes smaller, it's necessary to control business lead planarity and spacing tolerance. With regards to QFP, a size (40mm2), pin rely (360) and pitch (0.3mm) have attained a limitation.

  Certainly, QFP is very easy to be examined and reworked that the leads on QFP is seen.


  • Assessment between BGA and QFP

  Typical BGA components are so durable they can be used for assembly even if indeed they accidentally fall onto the ground, which is impossible for PQFP somewhat. The essential benefit of BGA deals is based on its array form and in most cases BGA components can handle providing more I/O within the same device area than QFP components. Whenever I/O count number exceeds 250, the area accounted by BGAs is always smaller than QFPs. Since BGA usually features bigger pitch than QFP, BGA components are easier installed so that relatively high efficiency will be produced. When defects worried about packaging are examined prior to assembly, assembly failing rate can be less than 1ppm. Until now, the biggest problem faced with BGA assembly is based on defect issues associated with deals that probably are based on lacking solder balls, humidity sensitivity, collision during delivery process and extreme warpage during reflow soldering. An enormous deviation comes in conditions of solder ball size, which is two times or 3 x of quantity deviation between solder balls. Double-layer solder balls possibly can be found at the positioning of solder joint and defects related to metallization such as inadequate soldering between solder balls and element pad. Because of technique, BGA assembly permits the cheapest defect rate (ppm).

  The building of BGA deals features shorter leads than QFP with comparative functions and performance, that leads to excellent electric performance of BGA deals. However, the biggest defect of BGA structure is based on its cost. BGA features more expensive than QFP in conditions of laminate panel and resin cost correlated with substrate transporting components. BT resin, ceramic and polyimide resin carrier consists of original components with more expensive while QFP includes plastic-type molding resin and metallic sheet lead framework with low priced. Array carrier features quite large cost because of to fine collection circuits and chemical substance digesting technology. Furthermore, with QFP and BGA deals compared, high-output developing pass away and molding press equipment can be employed with fewer packaging specialized procedures. Once quantity creation is applied, BGA bundle cost will be reduced but it is not easy for it to fall to the extent of QFP.

  So far as BGA bundle cost can be involved, BGA bundle with suitable quantity of I/O pins would be the most common. This sort of bundle consists of all the circuits beside package deal carrier and bears no regulated through openings. Thus, extra cost needs to be kept by BGA bundle. However, the extremely high assembly efficiency of BGA deals can locally compensate for his or her drawback of high cost. From your perspective of financial value, when I/O pins are less than 200, QFP works suitably. When I/O pins exceeds 200, QFP fails and multiple types of BGA deals can be employed, resulting in the wide selection of applications of BGA deals.

  • Inspection and Rework of BGA Packages

  BGA inspection and rework is also a kind of technology that steadily makes maturity. Though it can be inspected, BGA demands high-precision equipment such as X-ray imaging system.

  BGA components conceal their contacts under packages, resulting in more troubles of rework than components with leads at periphery. Leading issues regarding BGA rework include: harm on detachable parts, harm on alternative parts, over heating system of plank and adjacent components, table warpage because of to local heating system and cleaning and production of some parts. Rework must take the next issues under consideration: chip temperature, temperature distribution of components within rework period and panel temperature distribution. If all the required devices need purchasing, BGA rework train station will be expensive for the next reasons:

  a. You can't really modify only 1 brief circuit or open up circuit defect and rework needs to be completed on all assembly defects of BGA.

  b. Rework is more difficultly applied than QFP, calling for added equipment investment.

  c. BGA components after rework can be no more used while QFP components can.

  Therefore, mass creation of BGA deals derives from assembly defect decrease, ensuring high complete rate.

  • Cleaning of BGA Packages

  The protruding drawback of BGA deals is based on their incapability to completely clean off flux remaining in the bottom of array deals. Until now, how big is BGA components with lot of pins is around 45mm2. Therefore, cleaning concern becomes so significant. BGA cleaning requires that flux and solder paste needs to be washed off because they may lead to electric failure or transmission leakage to the bottom in high-power applications.

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