IT3/IT5
Connector System
T
IPS FOR
SMT
A
SSEMBLY
Document Number:
ETAD-F0458
Revision 3.10
Page
54
of
73
Bad Gasketing:
Poor
gasketing
is the root cause of many printing problems . If the
edges of
the
stencil aperture
ca nnot
seal against the PWB pad
, s older paste gets squeezed through the
resul ting gap and can cause a va riety of defects.
G
a
sk
e
ti
n
g
P
ro
b
le
m
s
Possible Cause
Suggested Action
Poor Boa rd Support
Check and improve PWB support
Alignment
See section on Alignment below
Solder mask hi gher than pads
Check solder mask hei ght and compa re to
specifi ca tion.
Stencil apertures a re larger than
PWB pads
Measure apertures and pads and compa re to
specifi ca tion.
Hot Ai r Solder Level (HASL)
Fi nish crea tes uneven printing
surfa ce
Consider more planar, non-HASL finishes .
Consul t wi th PWB fabri cator on improvi ng
doming effect of hot air leveling.
Labels , inks, or other surfa ce
features crea te a gap between
s tencil and PWB
If defects occur nea r surfa ce fea tures, consider
changing placement of those fea tures, or hal f-
etch s tencil from underside to allow clea rance
for feature.
Bad Alignment:
An
alignment error of up to 50 microns is typical
a nd usuall y a cceptable,
depending on tolerances in other pa rts of the assembl y process . If alignment of pas te deposits
and pads cannot be maintained at less than 50 mi crons , correcti ve a ction should be ta ken.
A
lig
n
m
e
n
t
P
ro
b
le
m
s
Possible Cause
Suggested Action
Poor Boa rd Support
Check and improve PWB support
Printer alignment error
Check printer fiducial reading errors
Stencil mesh torn or tension too
loose
Check s tencil’s mobility i n frame. Look for
movement a t beginning of print s troke.
PWB or s tencil posi tional error
Check corner-to-corner alignment of apertures
and pads . If they ca nnot be aligned, s tencil
should be s caled to compensa te for error.
Nov.1.2022 Copyright 2022 HIROSE ELECTRIC CO., LTD. All Rights Reserved.
