Reballing BGA Components Using Replacement Balls & a Special
the method for reballing BGA components using replacement
balls and a special fixture.
Ball Grid Array Rework
Tools and Materials
Refer to Circuit Technology Center specific component reballing
instructions for machine operation, spacer construction and
For plastic or tape (generally metal
covered components) the process will be to add flux paste first
then apply solder balls.
Standard Reballing Flux is:
EFD, FluxPlus 6-411-A Paste Flux. This may be changed upon customer
Standard Solder Paste is: EFD SolderPlus
63 RMA-A. This may be changed upon customer specification.
Printed Board Type: R/F/C | Skill Level: Advanced |
Conformance Level: High | Rev.: A | Rev.
Date: 26 January 2006
devices are sensitive to the affects of moisture absorption.
Proper baking according to industry moisture sensitive device
(MSD) guidelines is critical to ensuring re-balling and subsequent
BGA rework success.
- Turn on the oven and preheat to 350° Fahrenheit
(176° Celsius). Allow approximately 20 - 30 minutes
for temperature to settle between 338° to 356° F
(170° to 180° C). Ensure the FR4 baking platform
(.125) is out of the oven. This platform will need to be
at ambient temperature so that component placement is simple
and smooth preventing ball disruption. Place a thermocouple
at an appropriate location near the component in order to
properly monitor ball temperatures.
- At the Re-balling Machine turn on the machine vacuum.
Align the ball stencil. If there is slight misalignment
between the flux / solder paste stencil and the ball stencil,
typically it is more important that the ball stencil be
precisely aligned than the flux stencil. Flux deposition
does not require the precision of the ball on the component
pad. The stencils are basically held in place and alignment
is done by moving the component within its nest. In the
instance that flux deposition requires absolute precision
utilize specified CTC stencil adapters (in-house machined)
to ensure fixture height, depth and width exactly conform
to reballed part dimensions.
ball stencil may be a combination of two or three stencils
stacked on top of each other. Look through a microscope
and ensure the stencils are properly aligned. There are
locating pins that are placed to do this but the stencils
may slip off the edge of the pins.
- Place Flux screen over component. Verify screen alignment
under a microscope. Screens are not held fully rigid at
- Brush flux onto the component pads through the screen.
It is important to get flux on every single pad. When flux
is not applied the pad will not hold the solder ball when
the balls are dropped into place. Additionally, a dry pad,
even if it holds a ball in place, will not properly wet
to the solder ball during reflow. On the other hand avoid
applying too much flux as excess flux on the component will
potentially gum up the solder ball screen preventing proper
ball drop onto the component. Once flux is brushed over
the screen holes use a stainless steel squeegee to press
the flux into the apertures.
- Lift the screen. Inspect under a microscope. If any
pad is missing flux, apply a small amount with an Xacto
- Apply solder balls over the hole locations.
more balls that are accurately placed initially the quicker
the process and the fewer balls will roll free on the screen.
An excess amount of free balls placed on the screen may
make lifting the screen clear and removing excess balls
difficult. Excess balls may spill onto component.
- Once the balls are on the screen, the ones that are
not in holes may be placed with a shortened acid brush (cut
down to about .25" length). Lift the screen once all
balls are in place. Excess balls may be collected by lifting
the screen and tapping the balls into an ESD protective
Balls that stick with the screen must be replaced on the
component surface. Make extra balls available on a convenient
surface. These balls may be placed on the component pads
by touching a minute amount of flux paste flux to the tip
of an Xacto blade, lifting a replacement ball (using the
surface tension of the flux) and laying it in place on the
- Once all balls are in place the component may be gently
propped up with an Xacto blade then the spatula placed under
the component to lift. Gently slide the spatula under the
component and keep the component angle as low as possible
while lifting. Once lifted, place the component on the FR4
- Turn the oven off momentarily (Preventing the distraction
caused by the heat and air flow of the convection oven).
Open the oven door and gently place the Baking platform
in the oven. Close the oven door. Inspect the component
balls with a microscope through the glass oven door. If
any balls have been dislodged they will have to be put back
in place. The balls do not have to be perfectly centered
on the pads as surface tension will center them during reflow.
- Turn the oven on at 500° F (260° C). On restart
the oven air will be at about 240° F (115° C). It
will ramp up to reflow temperature in about 2-3 minutes.
The part itself will heat up relatively slowly and will
take about 5-7 minutes to reflow. The balls will not reflow
until the oven temperature reaches about 448° F (231°
Celsius). Testing has demonstrated that using this procedure
the component temperature will not exceed 205° C (401°
The re-starting temperature of the oven can vary widely
due to different times taken to place components. Testing
on component temperatures indicates that the most aggressive
placement of the components (placing in the oven when the
oven temperature is 240° F (115° C) ) results in
a slightly greater than 1° C per second rise in temperature
for the first minute. After the first minute the ramp rate
BGA component may also be reflowed using an appropriate
reflow cycle at a BGA rework machine or run through a bench
top reflow oven.
- Once the component temperature reaches about 5 degrees
short of 361° F (183° C) observe the balls closely.
When reflow begins clock 30 seconds. After 30 seconds turn
off the oven to begin temperature down ramp. Very gently
open oven door by two or three inches to facilitate an appropriate
cool down ramp. Place the small deionizing fan on high about
two inches from the opening to promote even cool down of
the oven chamber.
cool down temperature ramp of the air will occur relatively
rapidly (still less than 2° C per second in the first
minute). At 130° C the components may be taken from
the oven to ambient air to cool.
- Using gloves remove the package from the oven at about
266° F (130° Celsius). Allow components to cool
in ambient temperature for three minutes to ensure package
thermal stability prior to component movement.
- The component balls should be perfectly aligned and
lustrous in appearance. If this is not the case, stop the
project and consult with project engineer.
- Inspect the body of the component for deformation. Also
inspect for dings and nicks in the substrate, potting compound
or die cover. Notify engineering of any defects.
- Inspect the underside of the BGA for cleanliness, flux
residue and debris left over from reballing process. If
the BGAs are not perfectly clean, inform engineering for
This document has been prepared by Circuit Technology Center,
Inc. The purpose is to ensure repeatable, high quality rework
of BGA components, and to assure conformity to the highest industry
standards and specifications.
covers procedures and guidelines specific to BGA component rework
conducted by the staff at Circuit Technology Center, Inc. Organizations
using this information may need to make modifications, or other
changes, to accommodate their own particular needs.
Links to Related