Measurement of effective cure shrinkage of epoxy‐based molding compound by fiber Bragg grating sensor using two‐stage curing process

Abstract

Cure shrinkage accumulated only after the gel point is known as effective cure shrinkage (ECS), which produces residual stresses inside molded components.The ECS of an epoxy-based molding compound (EMC) is measured by an embedded fiber Bragg grating (FBG) sensor. Under a typical molding condition, a high mold pressure inherently produces large friction between EMC and mold inner surfaces, which hinders EMC from contracting freely during curing. A two-stage curing process is developed to cope with the problem. In the first stage, an FBG sensor is embedded in EMC by a molding process, and the FBG-EMC assembly is separated from the mold at room temperature. The molded specimen is heated to a cure temperature rapidly in the second stage using a constraint-free curing fixture. Several technical issues have to be taken into considerations to ensure that (1) EMC does not pass the gel point before it reaches the cure temperature, and (2) EMC cures uniformly around the FBG during measurements. The ECS of an EMC with a filler content of 88 wt% is measured by the proposed method, and its value is 0.077%. The repeatability of the proposed method is corroborated by the results of a duplicate test.

Electronic Packaging Enhancement Engineered by Reducing the Bonding Temperature via Modified Cure Cycles

“…Figure a shows the thickness change of the EMC in CCC measured by TMA to analyze the ECS of the EMC. The average ECS was approximately 0.02%, according to eq , which is similar to values in the other works dealing with cure shrinkage of EMC. , Figure S1c shows the actual EMC/Cu bi-layer package fabricated in the CCC, and the curvature in the convex form appears at room temperature. Figure b shows the measured curvature of the EMC/Cu bi-layer package fabricated in CCC according to temperature and the comparison of zero-curvature and bonding temperature of the EMC/Cu bi-layer package from Timoshenko theory w/o and w/ ECS, and the experimental results are summarized in Figure…”

“…The average ECS was approximately 0.02%, according to eq 1, which is similar to values in the other works dealing with cure shrinkage of EMC. 44,45 Figure S1c shows the actual EMC/Cu bi-layer package fabricated in the CCC, and the curvature in the convex form appears at room temperature. Figure 4b shows the measured curvature of the EMC/Cu bi-layer package fabricated in CCC according to temperature and the comparison of zero-curvature and bonding temperature of the EMC/Cu bi-layer package from Timoshenko theory w/o and w/ ECS, and the experimental results are summarized in Figure 5 The curvature occurred in a convex form until the zerocurvature temperature because the CTE of the Cu was larger than that of the EMC, and the zero-curvature of the EMC/Cu bi-layer package appeared at approximately 107.5 °C.…”