PCB Repair/Rework Service

BGA Replacement

In modern electronics components there are numerous reasons why a BGA may need to be replaced on a circuit board. This requires that a BGA replacement process, otherwise known as “remove and replace”, needs to take place. A BGA replacement may need to take place because the wrong component was initially installed on the PCB. In some cases a replacement BGA may need to be placed onto the PCB due to the actual failure of the component. Finally the BGA may need to be swapped in cases where the alloy needs to be changed. 

The first and most obvious step in the replacement of the BGA process is to make sure that the right component is being placed on to the correct location on the PCB. Not only must this be in the right location but the component must be in the correct orientation. This is confirmed by matching the part orientation designator, usually a notch or a tick on the part, to the silk pattern of the PCB. 

The next step in the BGA replacement process is to pick the right process given the device at hand, the board it is being placed on, the skill level of the operator and type of rework equipment it is being processed on. There are numerous methods for attaching the replacement BGA but the processes can be divided in to the flux and solder paste attachment methods. There have been numerous articles and papers describing the difference in first pass yield between using ”tacky” flux and solder paste in the BGA replacement process.

stencilquik

As a last step the device needs to be inspected in order to insure that the BGA replacement process has been done properly. The inspection criteria normally used rely on the IPC A-610 standards, the IPC-7095 BGA processing guidelines or an internally-generated customer-specific specification. By following these steps a good outcome can be assured for BGA replacement.

Solderquik Preform | BGA Reballing Kit

Solderquik Perform

There are several reasons that either BGAs or CSPs would need to be reballed. These include the need to reball a device after the device has been removed from the PCB and the exact same device needs to be placed back onto the PCB. In other instance, the device package has the incorrect solder alloy balls on it which means that the device balls need to be removed or deballed and replacement balls need to be placed back onto the device package. In still other instance, a new size solder ball may need to be placed onto the device in order for further processing  requirements.

 

 

In such reballing cases for low volume reballing requirements less than a few hundred pieces the rework technician will typically use a solder reballing preform.  The solder reballing preform has solder balls embedded in which correspond to the ball size, number and pattern of the device. After the balls are removed from the existing package and the pads are wicked or prepped otherwise as low and as flat as possible the package pads have solder  paste flux applied to them. The solder reballing preform whether the solderquik preform or the EZReball preform is then placed with the device on top of the preform and is reflowed. Post reflow the preform remnants are removed , the device cleaned and inspected.

The solderquik preform has been around for many years and  is well-suited for some applications. It consists of the solder balls embedded in a water soluble paper which after reflow is dissolved in DI water. The SolderQuik Preform is a stamped out design which means that any new patterns require some new tooling to be developed. This requires tooling charges and extended lead times for the solderquik preform to get in to the users’ hands.

There are several disadvantages inherent to the solderquik preform. One of them, citied above is the extended lead time and tooling cost associated with any of the new patterns. In addition, the mechanical tooling does not allow for very tight spacing in the solderquik preform design. In fact, pitches below 0.4mm are not currently available in the Solderquik preform.

 

Related Topics

Reballing BGA 

Ball Grid Array Repair

Solder Reballing

BGA Solder Reballing

Ball grid array, chip scale packages as well as other device packages with solder balls may require the solder reballing process to be performed on the package.

If the area array balled device needs to be removed from the printed circuit board it will need to have “fresh” balls placed back on to the package if the device will be re-used. In this solder reballing process the device, after removal from the PCB will have uneven deposits of solder left on its pads. After cleaning up and inspecting the device the pads need to have the remnant solder removed form them. This process is deballing. Deballing can be accomplished either through the use of a solder excavation machine, a mini way sold soldering fountain or through the use of solder wick and paste flux aided by a  soldering iron. After removal of the remnant solder, solder reballing calls for inspection of the devices. Solder balls can now be re-attached using fixtures and loose solder balls, solder preforms or through semi or fully automatic solder ball attachment machines. There is a variety of reflow ability for re-attachment of the solder balls including hot air, infrared, and vapor phase reflow techniques.

Solder reballing also can be used to change the alloy of the solder balls residing on the balled package. This occurs in cases where  legacy lead bearing solders are used or in applications where the reliability has not yet been done using a different alloy or in cases where a unique alloy is required. In some cases, the assembly may need to meet regulatory guidelines and the alloy needs to be changed out.

Solder reballing when done properly has been shown to not have a detrimental effect on the long-term reliability of the printed circuit board assembly. While each assembly is different the impact of reballing has shown that while growing the IMC of the solder joint, in most all cases studied up to 3 reballing attempts did not negatively impact the reliability of the assembly. The unique nature of each assembly along with the end use operating environment will determine what type of testing will be required to test the impact of solder reballing.

Whatever the need BEST can be your outsourced service provider with respect to solder reballing services.

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BGA reballing services

Reballing BGA

Grid Array Rework | BGA Rework Process

The BGA rework process described herein is generic in nature to the type of heating system used. The experience BEST has gained in reworking thousands of BGAs on hundreds of different customer PCBs. BEST has expertise on stacked package (PoP) rework as well.

However Ball grid array rework is the operation of removing and then replacing with either existing or new a replacement device. This typically occurs when an upgrade is required, the device has failed or has been improperly placed ion to the PCB. By emulating the original controlled manufacturing process the replacement device can be properly seated on to the PCB.

Prior to removal to beginning the removal of the BGA, PCB preheating is necessary. This is especially true in the case of lead free PCBs as the required temperature difference across the package during device reflow is supposed to be very tight. By heating up the bottom side of the PCB, then applying top side of heat to the component to be removed, the heat becomes localized at the component and not distributed throughout the thermally conductive material of the PCB. This help reduce the possibility of the PCB from becoming warped.

By monitoring the PCB at several points on near and within the package the proper profile can be developed. External thermocouples (TC) are used as standard practice to monitor these temperatures. When heating the component from the top side, the generated heat should remain localized at that site until the solder goes in to the liquid state. The BGA component in this part of the BGA rework process can then be lifted from the PCB using vacuum.

After component is removed, the next step in the ball grid array rework process is site cleaning which is referred to as residual solder removal. This process can be done in a multitude of different fashions. One of the methods is with an operator using a hand soldering iron and copper braid. With lead-free solders entering mainstream manufacturing a few years ago, the increased melting point of the solder complicates this process further. Damaging the solder mask, lifting BGA pads during device removal and the damage of solder mask with excessive and uncontrolled heat are just some of the potential problems if the ball grid array rework/repair process is not done correctly.

Once the device has been removed and the site prepped the ball grid array must now be re-soldered to the location. This step is similar to removing the device from the PCB on that the replacement device is subjected to a controlled time-temperature characteristic curve. Prior to placement solder paste can either be re-printed on to the site location or paste flux can be used for attachment.

In any case a well-developed ball grid array rework process needs to be in place to insure a high first pass yield.

SMT Rework | Rework Stencils

SMT rework is the operation of bringing the printed circuit board back into compliance with the original inspection criteria using the original materials and processes. The objective of a removal and replacement of a component onto the PCB is to emulate the original manufacturing process albeit in the location only.

SMT rework generally consists of the following process:

Removal of the existing component

Preparation of the site where the device has been removed

Cleaning of the site

Inspection of the site

Replacement using a new device

Cleaning of the site (if necessary)

Inspection of the device

In the removal process, the existing component needs to be removed without damage to neighboring parts. Depending on the location this may require the removal of other neighboring components.

In site preparation the solder and perhaps other coatings or flux residue needs to be removed prior to replacement of the device. Here the SMT rework technician must be careful to not damage pads or solder mask.

Site cleaning is important so that the proper BGA site inspection can take place.

Inspection of the now cleaned site requires that the SMT rework/ repair technician should be well-versed in the inspection standards. Many times the site is re-inspected by a different operator after the completion of the rework process.

The replacement of the component or components is to be such that it emulates locally the profile of the original manufacturing process.

After placement, cleaning may be required depending on the flux chemistry required. No clean flux chemistries require no cleaning processes but water soluble flux chemistries require a water wash and others perhaps with a saponifier added  into the wash cycle.

Inspection after SMT rework may require automatic optical inspection depending on the severity of the rework with manual inspection taking place based on the inspection criteria.

SMT rework generally is accomplished by soldering techs with more experience and a higher degree of skill than the assembly line soldering technicians. The reasons for this is that the boards, by the time they require SMT rework to be performed on them, are near their highest. The work itself generally requires a higher degree of skill as well as requiring that the rework operator be familiar with and skilled in using a variety of different tools. Some of the tools of the SMT rework trade that the technician should be familiar with include hot air rework stations, micro tweezers, x-ray systems, endoscopic inspection equipment and other specially-configured equipment. Many times the SMT rework technician is also skilled in some basic troubleshooting techniques.

BGA Inspection and Courses

ipc-solder-training

BGA s are difficult to rework as they require a pretty deep knowledge of the original manufacturing process, knowledge of the chemistries involved in the original manufacturing process, the thermal profiles of the various processes as well as an experienced eye in terms of BGA inspection.

In terms of BGA inspection, while the IPC-A-610 standard indicates that the inspection of BGAs can be confirmed from a process standpoint via x-ray, it is imperative that the tools of visual inspection, endoscopic inspection and x-ray be used for proper BGA inspection.

Visual BGA inspection on the edge of the BGA package and the geometries of the depiction is very limited and is a function of having access to the periphery of the device. Many times the operator will have to be able to articulate the board underneath the microscope. This also assumes that the edge of the board is not interfered to the edges of the device.

Endoscopic inspection is similar in scope and in its limitations to the visual inspection process. The endoscopic mirrors are placed in vicinity to the edge of the BGA so that BGA inspection can occur. The magnification of the inspection instrument is such that unlike optical inspection, the periphery of the BGA ball interface can be seen.  The ball to package interface is important because this part of the BGA inspection can determine if the wetting of the ball to the package is sufficient. The interface of the ball to the PCB also determines what the solder joint of the ball to the board looks like. Here, again the inspector looks at the wetting of the interface of the ball to the board. What is particularly critical is the board corners. If collapse and ball shape is confirmed at the corners in the BGA inspection process then it is generally assumed that the rest of the ball interfaces will be acceptable.

X-ray inspection of BGAs gives the processor many details of the outcome of the BGA rework or original assembly process. Not only is the ball size and it’ s uniformity a reflection of the consistency of the reflow process but other parameters can be determined from the x-ray. In addition to the ball collapse the uniformity any shorts can be pointed out through the examination of the x-ray image. The x-ray image in a BGA inspection process can also determine if anomalies such as the flowing of solder down the “dogbone” pattern of the contact to the via  disturbed.

Related Topics:

PCB x-ray inspection
BGA x-ray inspection

BGA inspection

PCB Rework/ Repair Service

Rework is one of the most unpredictable and variable parts of the PCB assembly process. In fact, no other single function in the assembly process negatively affects profitability more than rework. The equipment, training and engineering support required are costing electronic assemblers millions, not to mention the damage/scrap that is being generated.

Our Contract Rework/Repair Division has the ability to provide expert rework, repair, and ECO modifications to your PCBs, as well as prototype runs. BEST has performed rework/repair services for projects ranging from 1 board to 175,000 boards and guarantees that 100% of your boards will be returned to you without damage. We have saved our customers millions of dollars by assisting them with the rework/repair process and providing fast reliable service.

All rework and repair is performed in accordance with IPC-7711/7721, guidelines for Rework, Repair, and Modification of Printed Boards and Electronic Assemblies. All boards are inspected in accordance with IPC-A-610, Acceptability of Electronic Assemblies.

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EXAMPLES OF REWORK PERFORMED:
  • Plated Thru-Hole
  • BGA Reballing
  • SMT (QFP, PLCC, Chip Style, LCC, SOP)
  • SMT Fine Pitch, Ultra Fine Pitch
  • PBGA, CBGA, Micro BGA
  • Flip Chip
  • Pin Grid Arrays
  • Connectors
EXAMPLES OF PCB REPAIR PERFORMED:

Contact Us

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Rolling Meadows, IL 60008
Phone 847.797.9250
Fax 847.797.9255

Website: https://www.solder.net