ITAR_Compliantsmta-logoipc-logoiso-logo

Your BEST choice
In Solder Rework/Repair, Solder Training and Tools

BGA Inspection

Visual BGA inspection on all of the BGA joints is not possible as one cannot “see” each of the solder joints through direct visual observation. Visual BGA inspection consists of the BGA rework technician using a microscope or pure visual sinpection in order to see the outer row (and sometimes even the start of the second row) into the center of the device. Here the technician is looking for uniform ball collapse along the outer row taking specific note of the corner balls to make sure they are collapsed (for collapsing balls). Otherwise other inspection tools and techniques will be required in order to determine from a quality assurance perspective if the BGA has been properly reflowed as part of the BGA inspection process.

However, there are two techniques, which if used in combination with one another, can greatly reduce the amount of defects which "pass" and are note noted during the BGA inspection process. With the use of transmissive x-ray, very few defect types pre and post BGA rework, cannot be “seen” by BGA inspection methods. Endoscopic inspection is another good tool for determining if the proper reflow and cleaning post rework has occurred.

Transmissive, real-time x-ray using a tilt function can be used to document several potential defects during BGA inspection. Solder bridges are the most common defect which can be detected by this technique. Gross voids can be seen at greater power and magnification levels. In addition the concentricity, pitch, circularity and solder ball diameter can also be measured as part of the BGA inspection process. With the proper equipment which either tilts the sample or the detector even head in pillow defects can be noted. However, BGA inspection via x-ray has limited ability to detect opens.

A strong supplemental tool to x-ray, an endoscopic inspection tool, allows hidden solder joints or joints that are in close proximity to other nearby parts to be inspected and characterized as part of the outgoing BGA inspection process. The ability to "see" whether the reflow process delivers a defective or a target joint condition can be accomplished with this BGA inspection tool. One of the major benefits of using an endoscope is its ability to "see" underneath the ball grid array and the surface of the individual solder balls. Clues to the quality of joints including its texture, uniformity, smoothness, color and brightness and surface characteristics can be documented with this BGA inspection tool. A poor solder joint with micro cracks on its surface could be "seen" with the endoscopic inspection tool while not showing up on x-ray. Endoscopes can also memorialize these BGA inspection conditions by taking a movie or shooting a picture.

Yields for reworked BGAs have been established at greater than 95% using a paste printing process. Part of this high rework yield is by using the proper BGA inspection process to qualify the process and to perform outgoing quality assurance. Supplemental SIR testing has shown that reworked components can have the same surface insulation resistance. When using the StencilQuik™ rework process SIR testing has shown an increase in surface resistance value by a factor of ten. Testing has shown that properly reworked BGAs joints exhibit the same resistance to thermal fatigue as product that has gone through initial assembly.

Not only are the correct BGA inspection tools required, but a proper interpretation of the inspection criteria and standards is required by a trained and experienced inspector. BEST can be your BGA inspection resource. We rework and inspect hundreds of different BGAs of many different types of boards using industry or customer-developed inspection criteria. You can count on BEST who has this experience and the latest tools to be your BGA inspection partner.

"Course: BGA REWORK - The Process of Inspection"

BGA Reflow Profile - Part Reflow

 "Course: BGA Rework-A Primer-Reflow"

After part placement, the applied solder must be reflowed to attach the BGA to the PCB pads. Preheating the entire PCB to between 70°C and 125°C is critical to minimizing PCB distortion during the heat cycle. The thermal profile already developed should have the following basic characteristics:

  • Peak joint temperature to minimize Pb dissolution
  • Minimum joining temperature high enough to ensure good wettability
  • All joints to be in the solder manufacturer's specified reflow range
  • Ensure dwell time above reflow as per the solder paste manufacturer's specifications

In addition care must be taken to ensure that adjacent components are not damaged during the reflow process. This care must be extended to components with low melting points such as connectors or standoffs or adjacent moisture-sensitive devices. Care should also be taken to not overheat any internal thermal grease if the BGA is capped.

After successfully attaching the BGA to the PCB, and allowing the board to be cooled down, the perimeter row of solder joints should be visually examined. The solder joint between the ball and the PCB pad should be similar in size and shape to the ball/part joint. If a water-soluble paste is used, the reworked area needs to be cleaned. Cleaning parameters should those be used in the original assembly process.

Card warping and bowing should be minimized by the BGA rework process. This can be a serious problem in the case of very thin PCBs. The bowing can be exacerbated by the proximity of other components such as pin-in-hole connectors that may anchor the PCB, thereby enhancing the localized bowing under the BGA. If the PCB is bowed or warped they might not be able to properly fit into the final assembly or opens may be formed.

SOLDERING TIPS

soldering-img

Newsletter

WHAT'S NEW?

ARTICLE: A Look Into PCB Rework and Repair

ARTICLE: IPC-A-620 Gets a Facelift

 

 

LATEST NEWS

WHAT PEOPLE ARE SAYING ABOUT US

  • You Guys Freaking Rock with turnaround time.
    Thank you all SOOOOO much!!

    You Guys Freaking Rock with turnaround time.
    Thank you all SOOOOO much!!

    Welch Allyn

  • BEST is excellent in meeting delivery dates and are very good with clear communication of... View More..

    BEST is excellent in meeting delivery dates and are very good with clear communication of shipments, quantities, issues, etc. Their quality and technical assistance has been superb.

    RW Technologies

  • BEST has solid high quality service every time, and at the right price. They are very dependable. I... View More..

    BEST has solid high quality service every time, and at the right price. They are very dependable. I am able to start a project in less then 24 hours with no hassles. The teams always work to meet the demands placed on them by the customer, and are very honest about what they can do and when they can do it. They offer great value to the customer; they are willing to go the extra mile to make the customer happy.

    Motorola

  • Best has always come through when we needed them. We started using them for board repairs, now they... View More..

    Best has always come through when we needed them. We started using them for board repairs, now they assemble all of our boards. BEST is always responsive to our needs. On many occasions, we needed boards repaired immediately. They have always come through for us.

    Lovejoy Controls Corporation

  • Your company name exemplifies exactly what you are, the BEST!!!

    Your company name exemplifies exactly what you are, the BEST!!!

    Alpha Circuits

  • You guys are really soldering geeks. Keep inventing those cool products.

    You guys are really soldering geeks. Keep inventing those cool products.

    Analog Devices

  • …always are very friendly and try to accommodate my short lead times

    …always are very friendly and try to accommodate my short lead times

    Qualcomm

  • There was not doubt that Francisco know the material, how to present it, and how to make the class... View More..

    There was not doubt that Francisco know the material, how to present it, and how to make the class participants feel at ease..all of my guys came to me and how me how much they had learned.

    Alabama Power

  • Just wanted to let you know what a fantastic job/effort James put in too insure our guys were... View More..

    Just wanted to let you know what a fantastic job/effort James put in too insure our guys were thoroughly training and qualified. Everyone involved was very impressed with his knowledge, flexibility, and work ethic. We really appreciate the fact that he went above and beyond.

    EMAC

  • Man, you guys are unbelievably fast!

    Man, you guys are unbelievably fast!

    Blur Development Product

  • I just wanted to shout a big thank you for your and BEST's efforts for making a flawless stencil... View More..

    I just wanted to shout a big thank you for your and BEST's efforts for making a flawless stencil and a quick delivery! You were a huge help. We greatly appreciate it!

    Evaporative Coating

ABOUT BEST

action-imgView BEST in Action

innovation-best-icoBEST Innovation

listen-imgListen to BEST
Fanfare