IPC-7095C-2013.pdf - 第159页

9.4.7 Cold Solder Joint 9.4.8 Incomplete Joining Due to Land Contamination 9.4.9 Deformed Solder Ball Contamination 9.4.10 Deformed Solder Ball Possible Cause The ball contacts have not completed wetting at the attach- m…

9.4.3 Evidence of Dewetting

9.4.4 Mottled Condition

9.4.5 Tin/Lead Solder Ball Evaluation

9.4.6 SAC Alloy

Possible Cause

Dewetting of the solder at the contact interface may be due to

excessive oxidation on the land, organic contamination. Poor

plating can contribute to this condition as well. ENIG comes in

a number of systems, i.e., hi P and low P systems. Dewetting

of ENIG is due to oxidation of Ni barrier not excess P on sur-

face.

Potential Solution

Develop process effect controlled experiment to determine

which attribute contributes most to dewetting.

Possible Cause

The surface condition of the solder ball is likely the result of

overheating during the reflow solder process or excessive/

repeated exposure to temperatures above liquidus.

Potential Solution

Evaluate reflow process in order to determine proper ball char-

acteristics.

Possible Cause

Reflow of solder paste should form a proper ball geometry.

Potential Solution

Maintain process effects standardization.

Possible Cause

Slightly mottled appearance of the tin-silver-copper alloy.

Potential Solution

Determine paste and ball characteristics through experimenta-

tion.

IPC-7095C January 2013

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9.4.7 Cold Solder Joint

9.4.8 Incomplete Joining Due to Land Contamination

9.4.9 Deformed Solder Ball Contamination

9.4.10 Deformed Solder Ball

Possible Cause

The ball contacts have not completed wetting at the attach-

ment sites. Condition may be due to poor solder paste printing

or contamination on the attachment site that cannot accept

wetting.

Potential Solution

Check stencil and printing process to determine sufficient sol-

der paste deposit.

Possible Cause

Organic contamination or oxidation of the PCB land can nega-

tively compromise the uniform and complete joining of the sol-

der ball and PCB land surface. PCB land was not sufficiently

clean to promote proper wetting prior to application of solder

paste.

Potential Solution

Test for cleanliness as part of process. Implement proper PCB

storage and handling procedures to prevent contamination and

exposure to conditions which promote oxidation.

Possible Cause

Solder ball deformation can occur due to the component mov-

ing during the reflow soldering process (package warp or board

warp) and/or when the land pattern geometry is not correct.

Potential Solution

Avoid overheating which causes quality disparities of the inter-

poser.

Possible Cause

Ball deformation (column shaped) can result from temporary

warping of the substrate during reflow soldering. The package

substrate corner, in this case, moved upward at the higher

temperature, away from the board surface. While in this condi-

tion, the solder alloy cooled to a solidus condition resulting in a

column shape. This is known as dynamic warping because the

warping increases along with the reflow temperature. As it

cools, the package would return to its original shape if the

solidified solder was not preventing it from doing so.

Potential Solution

This is caused by CTE mismatch of the materials in the pack-

age or board. Though elimination of this condition is outside the

control of the SMT process, the effect can be minimized by

avoiding overheating of the interposer and the board.

January 2013 IPC-7095C

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9.4.11 Insufficient Solder and Flux for Proper Joint

Formation

9.4.12 Reduced Termination Contact Area

9.4.13 Solder Bridging

9.4.14 Incomplete Solder Reflow

Possible Cause

The solder ball suspended in air is due to the lack of solder and

flux. This condition is due to a solder skip during the stencil

printing process. In evaluating the solder ball interface at the left

it appears that the two materials did not reach a fully liquidus

condition.

Potential Solution

Check stencil and solder deposition as well as flux contained

within solder paste.

Possible Cause

The condition may be due to package warping upward in the

area shown. The three center connections have extended into

a column while the adjacent contacts remain somewhat spheri-

cal.

Potential Solution

Movement during BGA ball solidification as well as overheating

within the reflow process.

Possible Cause

Solder bridging between contacts is likely due to the transfer of

solder paste residue during the solder printing process or

because the stencil did not seat securely to the board surface

during the process.

Potential Solution

Check stencil opening and avoid excess solder paste deposi-

tions.

Possible Cause

The solder ball on the substrate and the solder paste on the

board did not reach a fully liquidus condition during the reflow

soldering process.

Potential Solution

Determine reflow profile in order to validate solder paste used

in attachment.

IPC-7095C January 2013

146

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--`,,```,,,,````-`-`,,`,,`,`,,`---